Cost and Benefits of Fitting Trickle Ventilators

Costs and benefits of fitting trickle ventilators in replacement windows

BD2625

community, opportunity, prosperity Contents

Executive summary ...... 4

Costs and benefits of fitting trickle ventilators in replacement windows Introduction ...... 8 Costs (BSRIA)...... 8 Benefits – pollutant modelling (UCL) ...... 8 Benefits – health (LSHTM) ...... 9 GGF leaflet (UCL)...... 9 Conclusions ...... 9

Appendix 1 Costs ...... 11

Appendix 2 Pollutant modelling ...... 18

Annex 2a Moisture ...... 32

Appendix 3 Health effects ...... 34

Annex 3a Temperature ...... 63

Appendix 4 GGF leaflet ...... 65

Annex 4a Interview schedule ...... 70

Annex 4b Replacement window survey – householders ...... 72

Annex 4c Replacement window survey – bulk purchasers ...... 77

Annex 4d Figures...... 80 4 | Costs and benefits of fitting trickle ventilators in replacement windows

Executive summary

1 This study addresses the costs and benefits of fitting trickle ventilators in replacement windows (windows replaced in all habitable and wet rooms).

2 As requested, the modelling of health effects associated with the installation of replacement windows was carried out for the selected pollutants explicitly addressed by Approved Document F (ADF) – carbon monoxide (CO), humidity/mould, nitrogen dioxide (NO2) and volatile organic compounds (VOCs).

3 We thus did not include assessment of, for example, the effect of changes in winter indoor temperatures, particle concentrations, radon concentrations and exposure to environmental tobacco smoke.

4 In addition, limitations of scientific evidence and the inadequacy of current models meant that humidity was considered only in relation to its effect on mould growth, and not through possible influence on house dust mite populations; and the potentially complex mix of VOCs was considered only in relation to formaldehyde, the evidence about the potentially long list of other VOC pollutants being viewed as insufficient for quantitative modelling.

5 As a separate element of the project, research was also undertaken to assess how/if the Glass and Glazing Federation (GGF) leaflet for potential window purchasers, Advice to consumers regarding ventilation when replacing windows in dwellings, is used in practice, and by how much it increases the voluntary take-up of trickle ventilators.

Costs (BSRIA)

6 The costs presented here reflect the costs associated with the number of vents that were simulated in the pollutant concentration modelling work, i.e. windows replaced in all habitable and wet rooms.

7 The study has made estimates of these costs under the proposed guidance as follows: (i) Total annual costs to customer for installing trickle vents: £56,770,094 (ii) Total annual costs for alternative ventilation measures and poles: £5,297,039 Total annual costs for these measures (Cost A): £62,067,133 Executive summary |5

8 The cost given in 7(i) above is the cost to the customer for having trickle ventilators fitted, and it includes an element of profit for fitting trickle ventilators for the window supplier. However, it is recognised that a separate figure for the costs of supply and installation of the trickle ventilators would also be useful and hence a breakdown of these costs is provided below: (i) Total annual cost of supply and installation of trickle vents under proposed guidance: £25,889,909 (ii) Adding costs of poles and alternative ventilation measures, total annual costs for these measures (Cost B): £31,186,948

Benefits – pollutant modelling (UCL)

9 EnergyPlus and CONTAMW simulations have been undertaken for eight dwelling permeabilities. As requested, we built separate models of a house and a flat. As per the proposal, this work involved three moisture production rates, and three windows scenarios (old windows, new windows with no vents, new windows with vents). The results of the simulations were then passed to LSHTM for analysis in the next stage of the work.

Benefits – health (LSHTM)

10 In order to ensure that the results from this work would be suitable for informing a Regulatory Impact Assessment, we met with Europe Economics on 4/2/09. We agreed that our work would determine the incremental cost-effectiveness ratio (r) of the intervention. This is calculated as:

where: c (£) is the total cost of the intervention h (Quality Adjusted Life Years – QALYs) is the total health gain due to the intervention.

11 If (£ per QALY) is the ‘willingness to pay per unit increase in health gain’ threshold then the intervention is considered to be cost-effective if:

r ≤

Otherwise, it is not cost-effective.

12 As per the proposal we have taken 10 and 20-year time horizons. 6 | Costs and benefits of fitting trickle ventilators in replacement windows

13 Our estimate of the baseline total number of QALYs, for a 10-year time horizon, saved by fitting windows with trickle ventilators vs windows without trickle ventilators is: CO 0 Humidity/mould 538

NO2 0 TVOC 78 Total 616 QALYs

14 For a 20-year time horizon the estimate is doubled.

Conclusions

Cost benefit work

15 Relative to Cost A (cost to the customer), the trickle vents are cost-effective at about (‘willingness to pay per unit increase in health gain’) = £101,000 per QALY for a 10-year time horizon.

16 Relative to Cost B (cost of supply and installation), the trickle vents are cost-effective at about = £51,000 per QALY for a 10-year time horizon.

17 For a 20-year time horizon the values of above are halved.

18 To put the value of in context, the National Institute for Health and Clinical Excellence, for example, appears to use a value between £20,000 and £30,000 per QALY for cost-effectiveness in the NHS.

Uncertainty 19 There is considerable uncertainty in both the health benefits and the costs which makes it difficult to determine the cost-effectiveness of trickle vents precisely. The uncertainty in the health benefits is very approximately estimated. It is at least ± 25 per cent when taking into account parametric uncertainty (i.e. uncertainty in the relative health risks and exposures) only, and, at least, between –51 per cent and 34 per cent when taking into account structural uncertainty (uncertainty related to some of the assumptions that were made regarding the type of dwelling, moisture production schedules etc) only. The overall uncertainty in health benefits is a function of both, and is at least wider than either. Costs are also uncertain within ± 20 per cent. Executive summary |7

GGF leaflet (UCL) 20 The study indicated that individual consumers and bulk purchasers are not, in general, accessing the GGF leaflet. The findings indicate that it is probably only used by the industry ‘when needed’, i.e. if there is resistance by consumers to having trickle ventilators installed in situations where this is recommended by ADF 2006.

21 It seems unlikely that the leaflet is having any significant impact on the voluntary take-up of trickle ventilators.

Limitations of study 22 In this small-scale project we have made significant advances. We have developed a suitable and transparent methodology for estimating the health impacts of this intervention and undertaken a detailed cost benefit analysis as per the proposal.

23 However, it has been impossible to address fully every aspect of relevance. For example: – As per the proposal, only one house and one flat have been modelled – within the context of this small-scale project we have not been able to model explicitly the variation inherent in the entire stock. This is noted within the report and some relevant sensitivity analysis is undertaken. – A lack of epidemiological evidence makes it impossible to address every possible impact on health.

24 We note again that, as requested, the modelling of health effects associated with the installation of replacement windows was carried out only for the selected pollutants explicitly addressed by ADF.

25 While we have clearly set out what it has been possible to achieve and the assumptions that we have made, we stress that the work has inevitably been limited and further studies will be required to deal fully with this issue.

26 The findings of the study should be interpreted in the context of these limitations and also the considerable uncertainty associated with the health benefits and costs as noted above. 8 | Costs and benefits of fitting trickle ventilators in replacement windows

Costs and benefits of fitting trickle ventilators in replacement windows

Introduction

1 This study addresses the costs and benefits of fitting trickle ventilators in replacement windows (windows replaced in all habitable and wet rooms).

2 In the 2006 edition of Approved Document F (ADF), Communities and Local Government originally recommended that all replacement windows should be fitted with trickle ventilators. The purpose of this was to insure that good indoor air quality was maintained after window replacement.

3 However, the cost of introducing this guidance was underestimated, and when more realistic costs were established it appeared that the costs were likely to exceed the benefits. As a result of this, Communities and Local Government had to withdraw the guidance.

4 This current study was then commissioned in order to address the costs and benefits of fitting trickle ventilators in replacement windows.

Costs (BSRIA)

5 We have established the realistic cost of fitting trickle ventilators in replacement windows. There are some situations where trickle ventilators cannot be fitted, and these have been identified and fitting an alternative method of ventilation has been costed.

6 For full details of this work, please see Appendix 1.

Benefits – pollutant modelling (UCL)

7 As per the proposal, the typical changes in ventilation rate and indoor air quality that result when old windows without trickle ventilators are replaced by well-sealed windows, either with or without trickle ventilators, have been investigated by the use of computer simulation.

8 For full details of this work, please see Appendix 2. Costs and benefits of fitting trickle ventilators in replacement windows |9

Benefits – health (LSHTM)

9 The relevant health effects have been estimated and a cost benefit analysis undertaken.

10 For full details of this work, please see Appendix 3.

GGF leaflet (UCL)

11 We assessed how/if the Glass and Glazing Federation (GGF) leaflet for potential window purchasers, Advice to consumers regarding ventilation when replacing windows in dwellings, is used in practice, and by how much it increases the voluntary take-up of trickle ventilators.

12 For full details of this work, please see Appendix 4.

Conclusions

Cost benefit work

13 Our estimate of the baseline total number of QALYs, for a 10-year time horizon, saved by fitting windows with trickle ventilators vs windows without trickle ventilators is 616 QALYs.

14 For a 20-year time horizon the estimate is doubled.

16 Relative to Cost B (cost of supply and installation), the trickle vents are cost-effective at about = £51,000 per QALY for a 10-year time horizon.

17 For a 20-year time horizon the values of above are halved.

19 There is considerable uncertainty in both the health benefits and the costs which makes it difficult to determine the cost-effectiveness of trickle vents precisely. The uncertainty in the health benefits is very approximately estimated. It is at least ± 25 per cent when taking into account parametric uncertainty (i.e. uncertainty in the relative health risks and exposures) only, and, at least, between –51 per cent and 34 per cent when taking into account structural uncertainty (uncertainty related to some of the assumptions that were made regarding the type of dwelling, moisture production schedules etc) only. The overall uncertainty in health benefits is a function of both, and is at least wider than either. Costs are also uncertain within ± 20 per cent.

20 In this small-scale project we have made significant advances. We have developed a suitable and transparent methodology for estimating the health impacts of this intervention and undertaken a detailed cost benefit analysis as per the proposal.

21 However, given the available resources, it has been impossible to address fully every aspect of relevance. While we have clearly set out what it has been possible to achieve and the assumptions that we have made, we stress that the work has inevitably been limited and further studies will be required to deal fully with this issue.

22 The findings of the study should be interpreted in this context.

GGF leaflet work

23 The study indicated that individual consumers and bulk purchasers are not, in general, accessing the GGF leaflet. The findings indicate that it is probably only used by the industry ‘when needed’, i.e. if there is resistance by consumers to having trickle ventilators installed in situations where this is required by ADF 2006.

24 It seems unlikely that the leaflet is having any significant impact on the voluntary take-up of trickle ventilators. Appendix 1 Costs | 11

Appendix 1 Costs

John Sands and Richard Hillyard BSRIA

Basis of cost estimates

1 The basis of these costs and the assumptions made are given below, and this is followed by a detailed breakdown of the costs.

2 In order to enable the costs to be used in the cost benefit analysis, it is necessary to obtain the costs that relate to the number of trickle ventilators modelled.

3 Thus the costs presented here reflect the costs associated with the number of vents that were simulated in the pollutant concentration modelling work, i.e. windows replaced in all habitable and wet rooms.

4 The costs depend on: the proposed guidance in Approved Document F (ADF) 2010 (i.e. what has to be done), the size and nature of the market (i.e. number and types of replacement window installations), the cost of products, and the cost of installing these products.

5 The cost estimates were based on information obtained from discussions and face- to-face interviews with key stakeholders. These included: officials in a Government Department (Communities and Local Government) which is responsible for the regulations and guidance; operators of a competent person scheme for replacement windows for information on the nature of the market; a market research company for information on market size; equipment manufacturers/suppliers (two companies) for cost information; and window fitters (three companies) for cost information.

6 For this study it has been assumed that social housing providers will fit trickle ventilators in replacement windows even if not required to do so by the regulations. Thus only private sector dwellings are assumed to be affected by the proposed guidance in ADF. 12 | Costs and benefits of fitting trickle ventilators in replacement windows

Cost of supplying and fitting trickle ventilators

7 The market research company provided data from two 2008 reports that related to the 2007 market. Using these data as a basis, the total number of windows per year requiring trickle ventilators under ADF is estimated to be 3,128,460.

8 Using data from the report Cost benefit for trickle ventilators in replacement windows (produced for Communities and Local Government for the revision of ADF in 2006), it was determined that an average of 4.1 windows per dwelling would require replacement. Dividing this figure into the total number of windows requiring trickle ventilators under ADF (3,128,460) gives a figure of 763,039 dwellings.

9 The equipment suppliers provided the costs of trickle ventilators during the face-to- face interviews noted above.

10 The cost of trickle vents from the manufacturer to the window installers was found to be in the region of £1 to £2.50 per ventilator. One window installation company said it was charged £2 per trickle ventilator from its manufacturer as, like most installers, it no longer manufactures windows in-house, therefore a price is negotiated for the supply of the windows and trickle ventilators.

11 For the cost of installing trickle ventilators into the frame, a figure of £1.25 per ventilator has been used. This figure was obtained from the report, Cost benefit for trickle ventilators in replacement windows.

12 From the interviews conducted, the cost of a trickle ventilator to the customer is assumed to be £8 per ventilator regardless of its size.

13 For this study we have assumed one window per room. For habitable rooms, at least 5,000mm2 (equivalent area) is required per room. This can be met in one of two ways. a. Two 2,500mm2 trickle ventilators per window, and so the assumed cost per window for trickle ventilators will be £16 for habitable rooms. This is based on information provided that customers are charged the full £8 per trickle ventilator. However, the cost of the second trickle ventilator can be reduced because only about half the amount of work is required to install it, as the window unit is already in position to have the second hole routed. If a ventilator costs £2, and the full installation cost is £6, the second ventilator installation cost can be reduced to £3. The supply and fit cost is therefore £5 (£2+£3) for the second ventilator. This leads to a reduced price of £13 for the installation of two trickle ventilators per dry room window unit. b. After further consultation with a competent person scheme operator, it has been established that approximately a third (33%) of 5,000mm2 trickle ventilator installations will consist of just one 5,000mm2 trickle ventilator unit per window instead of two 2,500mm2 trickle ventilator units. The cost is £8 to the customer. Appendix 1 Costs | 13

14 The wet rooms require at least 2,500mm2 (equivalent area). The cost is £8 to the customer.

15 For hard-to-reach trickle ventilators, a pole is required and should be provided during the installation. It has been agreed with suppliers that the cost of the pole is £1. The 2006 report also recommends one pole per household which results in a cost of £763,039 for the supply of trickle ventilator poles.

Alternative measures to trickle ventilators

16 Costs for the most probable alternative ventilation solution where trickle ventilators are not possible/practical owing to technical considerations were also provided during the face-to-face interviews, as the same companies which make the trickle ventilators also manufacture the alternatives.

17 The average purchase cost for a circular acoustic ventilator, based on products from two different suppliers, was £40. This figure allowed for the manufacturers to upgrade their products to make them controllable, as recommended in ADF. Costs for installing the alternative ventilation measures have been provided by local tradesmen, as discussions during the face-to-face interviews showed that the window installers are unlikely to fit the other ventilation measures themselves as they would wish to limit their role to the window installation itself. As the assumed ventilation device can be fitted into a hole prepared with a core drill, the estimated time for installation was 0.5 hours. The labour rate of £20/hour was used, based on local trader costs and also feedback from a market study and other benchmarking activities. This gave a total cost to install a single unit as £50, and a cost per room, and hence per window, of £100.

18 This study was unable to determine the number of properties where trickle ventilators cannot be fitted owing to technical reasons (e.g. arched or circular windows). However, the number of such instances highlighted during the face-to- face interviews was very small, and so an estimate of 1 per cent of the total applicable market was assumed and used for calculating costs for this study. The relevant total market (private sector dwellings only) was obtained via data provided by the market research company and estimated to be 4,534,000.

Cases where alternative measures were already installed

19 From discussions with the equipment installers during the face-to-face interviews, the number of cases where a property already had alternative ventilation measures (normally air bricks) installed was estimated to be in the region of 10 per cent. This study has been unable to provide any documentary evidence to support this figure, but it was generally agreed by all those interviewed. Therefore, this figure has been used in this study for the number of replacement window installations that do not require additional ventilation. 14 | Costs and benefits of fitting trickle ventilators in replacement windows

Cases where trickle ventilators were already installed

20 Discussions during the face-to-face interviews with the equipment installers showed that the properties that already had trickle ventilators in the windows to be replaced were in the region of 10 to 30 per cent. This study has been unable to provide any documentary evidence to support this figure, but it was generally agreed by all those interviewed. Therefore, an average figure of 20 per cent has been used in this study. These windows are already required to have trickle ventilators when they are replaced so are not included in the costs here.

Detailed costs estimate

21 The detailed costs estimate was determined as follows. Number of dwellings The number of dwellings assumed each year to have windows replaced (from paragraph 8) is 763,039. The pollutant modelling work (see Appendix 2) assumed that these dwellings were split as follows: Number of ‘flats’ (20%) = 152,608 Number of ‘houses’ (80%) = 610,431

The modelled flat has five rooms (two wet and three habitable). The modelled house has eight rooms (three wet and five habitable). We used the ratio indicated in paragraph 13b to determine the modelled number of vents as follows: Number of vents in modelled flat

Wet rooms (2) Habitable rooms (3) Associated number of ‘single’ Associated number of ‘single’ 5,000mm2 vents: 1 2,500mm2 vents: 2 Associated number of ‘double’ 2,500mm2 vents: 2

Number of vents in modelled house

Wet rooms (3) Habitable rooms (5) Associated number of Associated number (average) of ‘single’ 5,000mm2 ‘single’ 2,500mm2 vents: 3 vents: 1.7 Associated number (average) of ‘double’ 2,500mm2 vents: 3.3 Appendix 1 Costs | 15

22 The estimates and assumptions described above are utilised as set out below. Number and sizes of trickle ventilators: Habitable rooms Single 5,000mm2 vents required: (1 x 152,608) + (1.7 x 610,431) 1,190,341 units Double 2,500mm2 vents required: (2 x 152,608) + (3.3 x 610,431) 2,319,638 units

Wet rooms Single 2,500mm2 vents required: (2 x 152,608) + (3 x 610,431) 2,136,509 units

Costs: Cost of single 5,000mm2 ventilators @ £8/ventilator: £9,522,728 Cost of double 2,500mm2 ventilators @ £13 for 2 ventilators: £30,155,294

Cost of windows/rooms requiring 5,000mm2 ventilation: £39,678,022 Cost of windows/rooms requiring 2,500mm2 ventilation @ £8/ventilator: £17,092,072

Total costs to customer for installing trickle ventilators in 763,039 dwellings under the proposed guidance: £56,770,094

Cost of alternative measures (45,340 units x £100): £4,534,000 Cost of poles for hard-to-reach trickle ventilators £763,039

Total annual cost of proposed guidance if windows are replaced and trickle vents fitted in all wet and habitable rooms in 763,039 dwellings – ‘Cost A’: £62,067,133

23 The above figure is the cost to the customer for installing trickle ventilators. However, it is recognised that a separate figure for the costs of supply and installation of the trickle ventilators would also be useful and hence a breakdown of these costs is provided here. Cost of the supply of trickle ventilators @ £2/ventilator: Single 5,000mm2 trickle ventilator: £2,380,682 Double 2,500mm2 trickle ventilator: £9,278,552 Cost of trickle ventilators for 5,000mm2 ventilation: £11,659,234 Cost of trickle ventilators for 2,500mm2 ventilation: £4,273,018 Total cost of the supply of trickle ventilators: £15,932,252 16 | Costs and benefits of fitting trickle ventilators in replacement windows

Cost of installation of trickle ventilators @ £1.25/ventilator: Single 5,000mm2 trickle ventilator: £1,487,926 Double 2,500mm2 trickle ventilator: £5,799,095 Cost of trickle ventilators for 5,000mm2 ventilation: £7,287,021 Cost of trickle ventilators for 2,500mm2 ventilation: £2,670,636 Total cost of the installation of trickle ventilators: £9,957,657

Using these costs of supply and installation (and the same figures for the costs of the poles for hard-to-reach trickle ventilators and the costs of alternative measures as in paragraph 22), the total annual cost of proposed guidance if windows are replaced and trickle vents fitted in all wet and habitable rooms in 763,039 dwellings – ‘Cost B’: £31,186,948

Conclusions and recommendations

24 BSRIA has provided expert opinion suggesting that a variance figure of +/– 20 per cent is appropriate to estimate the likely range of the total cost to the customer under these regulations. The same figure could be applied to the supply and installation costs, although in the case of the installation costs BSRIA has less confidence in specifying this value.

25 The figures arrived at by this study demonstrate the estimated total costs for implementing the measures to install trickle ventilators in all replacement windows where that is technically feasible, and to install other suitable ventilation measures where trickle ventilators cannot be fitted.

26 The costs incurred will not be borne by the industry as a whole. The costs will be carried by each installation project and paid for by the client. If trickle ventilators are a requirement, where it is technically possible, in all replacement windows, no single aspect of the industry will be at a disadvantage.

27 The study revealed that the single most dominant obstacle to the adoption of trickle ventilators in replacement windows has been the reaction of the customer. All equipment installers interviewed during the face-to-face interviews stressed the opposition they face from customers when told they must have trickle ventilators in their replacement windows as the windows being replaced were fitted with them.

28 This study has also shown that it has been difficult to gather authoritative data on the number of windows that already have trickle ventilators installed. Similarly, it has proved difficult, within the time and financial parameters of this project, to gather authoritative data on the number of instances where alternative ventilation measures (such as air bricks) are already installed. Appendix 1 Costs | 17

29 In-depth market research data are available for some aspects of the study, but at a cost in excess of that which is available for this study (approximately £6,000 for the full report).

30 Within the context of this project, the best available estimates of the following have been made: – the number of properties/installations where trickle ventilators are already fitted – the number of properties/installations where alternative ventilation measures are already installed.

31 However, it is likely that further dedicated work – beyond that possible within the constraints of this project – would improve the accuracy of these estimates.

32 The study revealed that the window replacement industry tends to work on averages, and not in great detail on a per unit basis. The drivers appear to be numbers of units with various elements then expressed as averages, i.e. the average cost of a frame, or the average cost of a trickle ventilator, etc. This appears to be possible as the product is fairly standard, within a relatively constant range of parameters.

33 The introduction of trickle ventilators to replacement windows would not have a cost to the industry as costs would be passed on to and met by the customer. It would not require the industry to re-tool as windows with trickle ventilators are already made. The study has shown that the cost of providing the trickle ventilators has not proved a barrier to sale. However, the work suggested that in some cases people might choose not to have the windows replaced, as their resistance to having trickle ventilators fitted may be so strong. 18 | Costs and benefits of fitting trickle ventilators in replacement windows

Appendix 2 Pollutant modelling

Ian Ridley and Mike Davies, UCL

Introduction

1 As per the proposal, the typical changes in ventilation rate and indoor air quality that result when old windows without trickle ventilators are replaced by well-sealed windows, either with or without trickle ventilators, have been investigated by the use of computer simulation. Hence three scenarios have been modelled: • dwellings with ‘old’ windows • dwellings with replacement windows (but no trickle ventilators) • dwellings with replacement windows and trickle ventilators.

2 Windows in all wet and habitable rooms are replaced.

3 The transient modelling, using both CONTAMW and EnergyPlus, has drawn heavily on the methodologies developed for project BD2523 (Investigation of Ventilation Effectiveness – Palmer et al, 2009) using the standard flat and house models.

4 A standard London TRY weather file, the same as in BD2523, has been used.

5 As requested, the simulations predict the hourly concentrations of the four main pollutants which are noted within Appendix A of ADF 2006: • nitrogen dioxide • moisture • total volatile organic compounds (TVOCs) • carbon monoxide.

6 The output of the computer simulations, namely the predicted pollutant concentrations, is passed on to the LSTHM team, and used to predict the health consequences of the inclusion or omission of trickle ventilators in replacement windows. Appendix 2 Pollutant modelling | 19

Dwelling types

7 As requested, two dwelling types have been modelled: • a mid-floor flat with two external façades, and • a detached house.

8 A key assumption was that the domestic building stock for England and Wales could be represented, in an approximate manner, by these two models, with 80 per cent (informed by ONS, 2009a) of the stock best represented by the house and the remaining 20 per cent by the flat. Some relevant sensitivity analysis was undertaken to investigate the significance of this assumption.

Mid-floor flat

9 The flat floor plan is shown in Figure 1, and the flat geometry is summarised in Table 1. All rooms have one external wall, with two external façades in total. The kitchen is accessed via a door from the living room.

Figure 1: flat floor plan. 20 | Costs and benefits of fitting trickle ventilators in replacement windows

Table 1: Flat (two bedrooms, mid-floor in a three-storey block, two external façades) – dimensions

Footprint 7.5m × 6m Number of floors 1 Floor to ceiling height 2.4m Envelope area 64.8m² Permeable envelope (internally impermeable) 36.0m² Room Hall Store Bathroom Kitchen Living Bedroom1 Bedroom2 Total Floor area [m²] 7.8 2.7 3.6 5.0 11.8 8.1 6.0 45.0 Volume [m³] 18.7 6.5 8.6 12.0 28.3 19.4 14.4 107.9

Detached house

10 Figure 2 shows the ground and first floor plans for the detached house, while the house geometry is summarised in Table 2.

Figure 2: Detached house – floor plan. Appendix 2 Pollutant modelling | 21

Table 2: Detached house (three bedrooms) – dimensions

Footprint 8m × 6m Number of floors 2 Floor to ceiling height 2.4m Envelope area 230.4m² Permeable envelope 230.4m²

Room Kitchen Living BedRm1 BedRm2 BedRm3 Landing Toilet Hall En-suite Bathroom Total

Floor area [m²] 18.6 16.2 12.6 12.6 6 9.6 1.8 11.4 3.6 3.6 96.0

Volume [m³] 44.6 38.9 30.3 30.2 14.4 23.0 4.3 27.4 8.6 8.6 230.4

Occupancy schedules

11 Tables 3(i), 3(ii), 4(i) and 4(ii) show the occupancy schedules that were assumed.

Table 3(i): Occupancy schedule, detached house, weekday

Location Occupancy Living room 1 adult 17:00 – 18:00, 18:30 – 19:30, 21:30 – 22:00 2 adults 19:30 – 21:30 2 children 17:00 – 19:30, 20:30 – 21:30 1 child 19:30 – 20:30 Bedroom 1 2 adults (asleep) 23:00 – 07:00 1 adult 07:00 – 07:45 2 adults 22:00 – 23:00 Bedroom 2 1 child 13 yrs (asleep) 22:00 – 07:30 1 child 13 yrs 07:45 – 08:00 1 child 13 yrs 21:30 – 22:00 Bedroom 3 1 child 12 yrs (asleep) 22:00 – 07:30 1 child 12 yrs 07:30 – 07:45 1 child 12 yrs 21:30 – 22:00 Bathroom 1 child 07:30 – 08:00, 19:30 – 20:30 En-suite 1 adult 07:00 – 07:30, 21:30 – 22:00 Kitchen 1 adult 07:30 – 07:45, 08:15 – 08:30, 18:00 – 19:30 2 adults 07:45 – 08:15 1 child 08:00 – 08:15 2 children 08:15 – 08:30 22 | Costs and benefits of fitting trickle ventilators in replacement windows

Table 3(ii): Occupancy schedule, detached house, weekend

Location Occupancy Living room 1 adult 09:15 – 09:30, 10:30 – 12:00, 13:30 – 16:30, 18:00 – 19:30, 21:30 – 22:00 2 adults 09:30 – 10:30, 12:30 – 13:30, 16:30 – 18:00, 19:30 – 21:30 2 children 09:30 – 10:30, 12:30 – 13:30, 16:30 – 19:30, 20:30 – 21:30 1 child 13:30 – 16:30, 19:30 – 20:30 Bedroom 1 2 adults (asleep) 23:00 – 08:00 1 adult 08:00 – 08:45 2 adults 22:00 – 23:00 Bedroom 2 1 child 13 yrs (asleep) 22:00 – 08:30 1 child 13 yrs 08:45 – 09:00, 21:30 – 22:00 Bedroom 3 1 child 12 yrs (asleep) 22:00 – 08:30 1 child 12 yrs 08:30 – 08:45, 9:00 – 9:15, 21:30 – 22:00 Bathroom 1 child 08:30 – 09:00, 19:30 – 20:30 En-suite 1 adult 08:00 – 08:30, 21:30 – 22:00 Kitchen 1 adult 08:30 – 08:45, 09:15 – 09:30, 12:00 – 12:30 18:00 – 19:30 2 adults 08:45 – 09:15 1 child 09:00 – 09:15 2 children 09:15 – 09:30 Appendix 2 Pollutant modelling | 23

Table 4(i): Occupancy schedule, flat, weekday

Location Occupancy Living room 1 adult 17:00 – 18:00, 18:30 – 19:30, 21:30 – 22:00 2 adults 19:30 – 21:30 2 children 17:00 – 19:30, 20:30 – 21:30 1 child 19:30 – 20:30 Bedroom 1 2 adults (asleep) 23:00 – 07:00 1 adult 07:00 – 07:45 2 adults 22:00 – 23:00 Bedroom 2 2 children (asleep) 22:00 – 08:30 1 child 08:30 – 09:15 2 children 21:30 – 22:00 Bathroom 1 adult 08:00 – 08:30, 21:30 – 22:00 1 child 08:30 – 09:00, 19:30 – 20:30 Kitchen 1 adult 08:30 – 08:45, 09:15 – 09:30, 12:00 – 12:30 18:00 – 19:30 2 adults 08:45 – 09:15 1 child 09:00 – 09:15 2 children 09:15 – 09:30 24 | Costs and benefits of fitting trickle ventilators in replacement windows

Table 4(ii): Occupancy schedule, flat, weekend

Pollutants

Total volatile organic compounds

12 The TVOCs have been modelled with the physical properties (molecular weight) of formaldehyde, as in BD2523. The background outdoor level of TVOC has been assumed to be constant at 35µg·m-3 (MRC, 1996).

13 The room-by-room emission of TVOC is based on an assumed constant emission rate of 300µg·h-1·m-2 normalised by floor area. This value was taken from Appendix A of ADF 2006. Appendix 2 Pollutant modelling | 25

Carbon monoxide from cooking

14 CO emission rate in the kitchen only of the house and flat: 18:00-19:00, 0.04 mg·s-1; 19:00-19:30, 0.70mg·s-1 (as in the value for CO used in BD2523).

15 The background level of CO was assumed to be constant at 0.5 mg·m-3 (as in the value for CO used in BD2523).

Moisture

16 The same moisture production schedule as used in BD2523 has been assumed. The daily moisture generated during a weekday is 5.8 kg/day which increases to 7.2 kg/day at the weekend. As well as modelling this normal moisture production rate, a high and low moisture production rate equal to 1.5 and 0.5 times, respectively, the normal production rate has also been modelled. The normal daily weekday moisture production rate in the flat is shown in Figure 3.

Figure 3: Weekday moisture production in flat.

Nitrogen dioxide

17 The production schedule of NO2 was based on the same cooking schedule used for CO production. The source strength of NO2 during cooking was taken from Dimitroulopoulou et al (2006). A value of 50µg·s-1 was used. The background level of NO2 has been assumed to be constant at 20µg·m-3. 26 | Costs and benefits of fitting trickle ventilators in replacement windows

Pollutant sinks

18 The models include pollutant sinks which lower the pollutant concentration in a zone; these sinks are intended to represent the action of the surface area of the building fabric and contents absorbing pollutants.

Moisture

19 The buffering effect of the building fabric and contents on moisture levels is taken into account. In EnergyPlus an EMPD model is used, while in CONTAMW a post- processing damping algorithm, as in BD2523, is used.

TVOC

20 A boundary layer diffusion model is used to simulate the storage, absorption and desorption of TVOC by the surface of the building fabric and contents. The method used is that described by Persily, in simulation of IAQ in dwellings (Persily 1998). The values used for the film mass transfer coefficient, the sorbent mass area, and the partition coefficient are 0.126m/h, 6kg.m-2 and 0.5kg-air/kg sorbent respectively. Note the models used in BD2523 did not include such a sink.

Nitrogen dioxide

21 The removal of NO2 is accounted for using a first order loss coefficient in which the rate of contaminant removal is as described by Persily (1998). Removal is proportional to room volume and a first order rate constant of 2.4 x 10-4s-1. As per Persily (1998), no re-emission is explicitly considered.

Window and internal door opening and extractor fan assumptions

22 In the heating season no window airing is included. We note that ADF 2006 assumes that some window opening may be necessary in spring and autumn to deal with moisture control.

23 All room doors are closed when occupied, otherwise they are open. The rooms that are accessible via other rooms, i.e. the en-suite, which is accessed via the master bedroom in the house, and the kitchen, which is accessed via the living room in the flat, will have the door closed when either of the spaces is occupied.

24 Extractor fans (with flow rates in compliance with ADF 2006) are assumed to be present in wet rooms and are used according to the schedules of BD2523. Appendix 2 Pollutant modelling | 27

25 Trickle ventilators are only included in the third scenario (new windows and trickle ventilators), no trickle ventilators are present in the first two scenarios (old windows, and new windows without vents).

26 For moisture, the RH was simulated for the heating season only as this is the period that is relevant to the mould relationships that are used. For the other pollutants, in order to produce annual estimates of pollutant concentration, additional simulations in CONTAMW were carried out to simulate summer conditions.

27 The results from the summer and winter simulations were combined to produce the annual files.

Additional data

28 Data on the number of dwellings undertaking window replacement each year were obtained from the BSRIA work described in Appendix 1 – the number of dwellings that have replacement windows fitted each year was estimated to be approximately 760,000.

29 The division of these properties into the eight permeability bands was informed via previous work undertaken by BRE (Stephen, 1998).

30 A study at UCL of 2,517 dwellings (Croxford, 2009) indicated that 66 per cent of dwellings have some sort of gas appliance in the kitchen. This figure is relevant for the proportion of dwellings that we considered to have sources of NO2 and CO.

31 Population data were sourced from ONS (ONS, 2009b).

Permeability

32 Additional work (in an extension to the plan in the proposal) has been carried out to increase the scope of the study. A much larger range and distribution of air permeabilities was simulated. The following permeabilities were modelled in both the flat and house: 3m3m-2h-1, 5m3m-2h-1, 7m3m-2h-1, 10m3m-2h-1, 15m3m-2h-1, 20m3m-2h-1, 25m3m-2h-1 and 30m3m-2h-1.

33 This range was chosen to be representative of the distribution of air permeabilities of the current UK housing stock.

34 The CONTAMW and EnergyPlus models used in BD2523 were modified to produce dwellings with the above permeabilities. The distribution and location of the gaps and cracks remained the same as in the BD2523 models. 28 | Costs and benefits of fitting trickle ventilators in replacement windows

Reduction in permeability due to window replacement

35 The following methodology was used to determine the reduction in permeability to be modelled in CONTAMW and EnergyPlus due to replacement of windows.

36 As requested, we drew upon previous work funded by Communities and Local Government (BD2425 – Ridley et al, 2006).

37 In this field study of ten houses the average reduction in seasonal infiltration rate in a dwelling after window replacement was found to be 0.23ach-1 (Oreszczyn et al, 2005).

38 Other work from a previous study (Ridley et al, 2003) also suggested that such a figure was a reasonable approximation: ‘A review of existing data suggests that replacing old leaky windows with modern sealed windows will reduce the background infiltration rate by the order of 0.1ach-1 to 0.3ach-1.’

39 Thus it was decided to set up the models such that a reduction in air change rate of approximately 0.2ach-1 was produced in a dwelling in which all windows were replaced.

40 In the previous study (Ridley et al, 2003), the theoretical reduction in winter air change due to window replacement was estimated analytically. Knowing the number of windows to be replaced, the volume of the dwelling and the flow coefficient of the old windows, the reduction in winter air change can be estimated from the ‘window replacement curve’ – see Figure 4.

0.005

Change in Infiltration ach

0.6 - 0.8 0.004

0.4 - 0.6 Co: Flow Coefficient of old window

0.2 - 0.4 0.003 0 - 0.2

0.002

0.001

Ratio N/V: Number of Windows to House Volume (m-3)

Figure 4: Window Replacement Curve. Appendix 2 Pollutant modelling | 29

41 The window replacement curve was used to estimate the range of flow coefficients of the old windows that would result in a reduction in air change rate of approximately 0.2ach-1, in the flat and house modelled in CONTAMW, assuming that five windows were replaced in the flat and eight in the house. The volume of the flat and house are 107m3 and 230m3 respectively. A flow coefficient of 0.002 was chosen to represent the old window to be replaced.

42 In the models, air permeability in an external wall is provided by two ‘cracks’, one at low level and one at high level. In a wall in which a window was replaced, the flow coefficient of each crack was reduced by 0.001, giving a total reduction of 0.002. If the flow coefficient was already less than 0.001 it was set to 0.

43 Upon testing the model it became apparent that the above methodology resulted in the predicted reduction due to window replacement (0.11ach-1 in the house and 0.13ach-1 in the flat) – while being in the range noted in the literature – being lower than the ‘target’ figure of approximately 0.2ach-1. That the figures should differ is unsurprising owing to the sensitivity of the output to the specific weather file used and exact details of crack placement and nature etc.

44 However, importantly, the 0.2ach-1 figure is based on data inferred from pressure testing (via the ‘divide by 20’ rule) and thus provides only an approximate guide in any case. 30 | Costs and benefits of fitting trickle ventilators in replacement windows

Trickle ventilators

45 For the baseline case we address the insertion of standard sized ventilators as per ADF 2006 guidance (5,000mm2 in habitable rooms and 2,500mm2 in wet rooms).

46 However, we also report on the impact of the insertion of ‘optimally’ sized trickle ventilators to allow a ‘perfect’ compensation for the reduction in air change rate due to the replacement windows.

Results – pollutant concentrations

47 The results of the simulations were then passed to LSHTM for analysis in the next stage of the work – see results in Appendix 3 (see Annex 2a for a note regarding the treatment of moisture).

References

BRE (2006) Cost benefit for trickle ventilators in replacement windows (produced for Communities and Local Government for the revision of Approved Document F in 2006).

Croxford, B. (2009) Private communication.

Dimitroulopoulou, C., Ashmore, M.R., Hill, M.T.R., Byrne, M.A., Kinnersley, R. (2006) A probabilistic model of indoor air pollution in UK homes. Atmospheric Environment, 40(33), pp. 6362-6379.

MRC Institute for Environment and Health (1996). Assessment on Indoor Air Quality in the Home: Nitrogen Dioxide, Formaldehyde, Volatile Organic Compounds, House Dust Mites, Fungi and Bacteria (Assessment A2).

ONS (2009a) www.statistics.gov.uk/census2001/profiles/commentaries/housing.asp. Accessed 31/3/09.

ONS (2009b) www.neighbourhood.statistics.gov.uk. Accessed 24/2/09.

Oreszczyn, T., Mumovic, D., Ridley, I. and Davies, M. (2005) The Reduction in Air Infiltration due to Window Replacement in UK Dwellings: Results of a Field Study and Telephone Survey. International Journal of Ventilation, 4(1), pp 71-77.

Oreszczyn, T., Ridley, I., Wilkinson, P., Hong, S.H. and The Warm Front Study Group (2006) Mould and Winter Indoor Relative Humidity in Low Income Households in England. Indoor and Built Environment, 15(2), pp. 125-135. Appendix 2 Pollutant modelling | 31

Palmer, J., Orme, M., Pane, G., Ridley, I., Davies, M., Oreszczyn, T., Lowe, R. (2009) Investigation of Ventilation Effectiveness – BD2523 – Final Report. Communities and Local Government, Building Regulations Division under the Building Operational Performance Framework series.

Persily, A. K. (1998) A modelling study of ventilation, IAQ and energy impacts of residential mechanical ventilation. NISTIR 6162. Building and Fire Research Laboratory, National Institute of Standards and Technology, USA.

Ridley, I., Fox, J., Oreszczyn, T., Hong, S.H. (2003) The Impact of Replacement Windows on Air Infiltration and Indoor Air Quality in Dwellings. International Journal of Ventilation, 1(3), pp. 209-218.

Ridley, I., Fox, J., Oreszczyn, T. (2004) Controllable Background Ventilation in Dwellings – The Equivalent Opening Area Needed to Achieve Appropriate Indoor Air Quality. International Journal of Ventilation, 3(2), pp. 147-154.

Ridley, I., Mumovic, D., Davies, M., Oreszczyn, T. (2006) Impact of Replacement Windows on IAQ of Occupied Dwellings – BD2425 – Final Report, Office of the Deputy Prime Minister, Building Regulations Division under the Building Operational Performance Framework series.

Stephen, R.K. (1998) Airtightness in UK dwellings: BRE’s test results and their significance. Building Research Establishment, BRE 359. 32 | Costs and benefits of fitting trickle ventilators in replacement windows

Annex 2a Moisture

1 The ‘Standardised RH’ (Oreszczyn et al, 2006) was calculated for each scenario. Standardised RH has been shown to be a good predictor of the occurrence of mould in a dwelling. A full description of the calculation process is given by Oreszczyn (ibid); the process involves the following steps. The hourly predicted vapour pressure excess is regressed against external temperature. The standardised VP excess at 5 degrees centigrade external temperature is then calculated. The hourly predicted internal temperature is regressed against external temperature and the standardised internal temperature at 5 degrees centigrade external temperature is then calculated. The standardised internal vapour pressure when external temperature is 5 degrees centigrade and external RH is 80 per cent, is then calculated. The standardised RH is then calculated using the standardised VP and standardised internal temperature. This process is carried out for both the living room and the main bedroom. The process was carried out for winter only.

2 The resulting predictions of standardised RH were then converted into the likelihood of a dwelling experiencing mould growth via relationships determined from analysis of data from a national study of England's Home Energy Efficiency scheme (Warm Front).

3 In the Warm Front study, each property underwent a detailed visual inspection on the occurrence and extent of mould on windows, walls and ceilings. The species of mould was not, however, identified. The mould condition in each dwelling was quantified as Mould Severity Index (MSI), described in the 1996 English House Condition Survey (EHCS, 2000). The mould condition is classified as ‘slight’ for MSI range of 1 to 2, ‘moderate’ for 3 to 4 and ‘severe’ for 5 and over. The equation below indicates that a dwelling will have an MSI of at least one if there is any mould growth in a single room. MSI = the number of rooms with mould growth + 1 if there is mould in either living room + 1 if the medium mould photograph is identified + 2 if the worst mould photograph is identified.

4 The calculation of MSI requires the quantification of the number of rooms with mould and a comparison of the mould severity against standard photographs showing three classes of mould severity ranging from slight, medium to worst. Annex 2a Moisture | 33

5 A relationship between standardised RH and the presence of mould (1,604 dwellings) was found. A very small risk of mould was seen even in dwellings with standardised relative humidity below 40 per cent, but above this there was a clear gradient of increasing risk, reaching, at 80 per cent standardised RH, around 40 per cent risk of having an MSI greater than one.

References

English House Condition Survey 1996 (2000) Energy Report. London: The Stationery Office.

Appendix 3 Health effects

Zaid Chalabi, Emma Hutchinson and Paul Wilkinson, LSHTM

1 As requested, the modelling of health effects associated with the installation of replacement windows was carried out for the selected pollutants explicitly addressed by Approved Document F (ADF) – carbon monoxide (CO), humidity/mould, nitrogen dioxide (NO2), and volatile organic compounds (VOCs).

2 We thus did not include assessment of, for example, the effect of changes in winter indoor temperatures, particle concentrations, radon concentrations and exposure to environmental tobacco smoke.

3 In addition, limitations of scientific evidence and the inadequacy of current models meant that humidity was considered only in relation to its effect on mould growth, and not through possible influence on house dust mite populations; and the potentially complex mix of VOCs was considered only in relation to formaldehyde, the evidence about the potentially long list of other VOC pollutants being viewed as insufficient for quantitative modelling.

4 For the remaining pollutants/pathways, the calculation of health impact was based on an adaptation of the methods used in the Home Health and Safety Rating System (HHSRS). The steps of the analysis are summarised below.

5 All baseline calculations were based on the comparison of the predicted distribution of indoor environmental parameters (CO, mould, NO2, VOCs) for dwellings with replacement windows without trickle ventilators vs dwellings with replacement windows with trickle ventilators. These distributions were derived from the work described in Appendix 2. • For each environmental parameter/exposure, health effects were described under four severity headings, described as ‘classes of harm’, as defined by the Home Health and Safety Rating System. • For each form of exposure and class of harm, the following evidence was derived: (i) the disease incidence or mortality rate of the relevant health conditions in the population (ii) the corresponding severity weighting(s) for the calculation of quality of life adjustments (iii) the relative risk of disease incidence/mortality for a defined level of change in exposure. Appendix 3 Health effects | 35

• In several cases, the health effects were assumed to apply only to susceptible subsets of the population (e.g. the elderly, children), and disease risks and exposure patterns were calculated accordingly. • Burdens of illness/mortality were estimated using the data for (i)-(iii) combined with data on the difference in exposure between dwellings with replacement windows without trickle ventilators and those with replacement windows with trickle ventilators. • The national total of disease burdens prevented by trickle ventilators was therefore calculated on the basis of an assumed annual number of window replacements (approximately 760,000) combined with exposure-specific assessments of the number/proportion of properties affected by the relevant exposure. • Although the intention was to calculate prevented cases of mortality/morbidity per year, the various health outcomes included in the analysis varied greatly in their time course and natural history. Individual decisions were therefore made as to the most appropriate measure of burden over time based on understanding of the time lag of disease onset and the variation in the subsequent time course to resolution or deterioration. • The health effects were summed across classes of harm using the quality adjusted life year (QALY) as the common unit.

Carbon monoxide

Approach There is evidence from epidemiological time-series studies of association between ambient concentrations of carbon monoxide (CO) and hospital admissions for myocardial infarction and other health endpoints. However, it remains unclear whether CO is the causal factor in this association, or is merely a marker for another agent, specifically fine particles, that is causal. Because of this, in its 2003 guidance, the Committee on the Medical Effects of Air Pollutants cautioned against using epidemiological studies of the effects of day-to-day changes in outdoor concentrations of CO and nitrogen dioxide in considering indoor exposure (COMEAP, 2003).

We followed this position and confined the analysis of CO effects to the well-described acute toxicity attributable to high level exposure, resulting in the formation of carboxy- haemoglobin and the consequent reduction in both oxygen transport and release.

It should be noted that the levels of CO needed to cause adverse effects are generally more likely to be a function of poor operation of the combustion device than of inadequate room ventilation. 36 | Costs and benefits of fitting trickle ventilators in replacement windows

In our modelling, we therefore assessed changes in indoor CO concentrations against World Health Organization guideline levels designed to prevent carboxy-haemoglobin (CO-Hb) levels from exceeding 2.5 to 3 per cent in non-smoking populations. The maximum concentrations are: 100mg.m-3 for exposure times not exceeding 15 minutes; 60mg.m-3 for up to 30 minutes; 30mg.m-3 for one hour; and 10mg.m-3 for eight hours.

Input data (1) Health outcomes by harm class: Population rate I. CO death ~ 10-6 II. Hospital admission with coma, 10-6 to 10-5 cardiac or other symptoms III. Impaired consciousness, Undetermined other symptoms (2) Relative change in risk per unit e.g. Feldman (1998) change in exposure (3) Number of affected dwellings All dwellings at potential risk. and occupants No. of dwellings with replacement windows = 760,000 (4) Assumed time course Acute or sub-acute effect with minimal time lag.

Method of calculation Number of affected residents = proportion of dwellings with supra-threshold exposure x average residents per household

Results Average CO levels (estimate of time-weighted exposure of kitchen, bedroom and living room concentrations) were marginally higher in dwellings with fitted windows without trickle ventilators compared with pre-window replacement dwellings, and appreciably higher than dwellings with fitted windows with trickle ventilators (Figure 1).

There was no exceedance of WHO guideline CO concentrations after fitting of replacement windows, with or without trickle ventilators, suggesting that the associated ventilation changes alone are normally insufficient to lead to clinically important change in CO exposure. Appendix 3 Health effects | 37

Figure 1. Indoor concentrations (mg.m-3) of carbon monoxide by permeability group in dwellings with old windows (blue), new replacement windows (green) and new replacement windows with trickle ventilators (brown): [A] flats, [B] houses. 38 | Costs and benefits of fitting trickle ventilators in replacement windows

Humidity/mould

Approach Although there is insufficient evidence to assume causal links, epidemiological studies suggest associations between significant visible mould and a range of respiratory and other symptoms such as wheezing, rhinitis, cough, nausea, vomiting and general ill health. In addition, fungal spores and mites are known allergens. The most vulnerable groups are young children, the elderly, allergy sufferers, and the immuno-compromised.

The main evidence used for the identification of health effects likely to be associated with the presence of visible mould was taken from a recent meta-analysis by Fisk et al (2007), and three overviews (Institute of Medicine (2004), HHSRS (2003) and IEH (1996)).

The Fisk review provided quantitative meta-analyses of the studies reviewed in the Institute of Medicine (IOM) of the National Academy of Sciences report plus other related studies, and suggested central estimates of odds ratios for respiratory health outcomes in the range 1.34 to 1.75. The authors concluded that building dampness and mould are associated with approximately 30 to 50 per cent increases in respiratory and asthma- related health outcomes. (i) Harm class II: hospital admission from respiratory causes (uncommon) (ii) Harm class III: asthma, respiratory symptoms (necessitating GP consultation) (iii) Harm class IV: more minor respiratory symptoms, including rhinitis, cough, and wheeze.

We further assumed that symptoms attributable to mould exposure would predominate in children, whose largely reversible airways disease would improve with time and as exposure diminishes. We therefore assumed persistence of symptoms only until 14 years. Appendix 3 Health effects | 39

Input data (1) Health outcomes by harm class: I. –– II. Hospital adm, resp. disease 1 per 103 children III. Asthma, respiratory disease 16 per 103 children IV. Rhinitis, cough, wheeze 93 per 103 children (2) Relative change in risk per unit Relative risk (RR) = 1.53 for outcomes in harm change in exposure classes II and III, and 1.83 for harm class IV (3) Number of affected dwellings No. of dwellings with replacement windows and occupants = 760,000 Proportion of dwellings with moisture level: High = 33% Moderate = 33% Low = 33% No. of children aged 14 years and under (the at-risk group) per dwelling = 0.34 Hence, affected population nationally in each of the three moisture bands = 760,000 x 0.33 x 0.34 (4) Assumed time course Damp/mould assumed to affect children only, who continue to exhibit symptoms until adolescence. No effects in adults.

Method of calculation Annual health benefits of vents reduce the number of children with respiratory symptoms living in flats with replacement windows and trickle vents compared to those living in flats with replacement windows but without trickle ventilators by harm class j (=II, III or IV):

where • Subscript f refers to flat • , , ,is the reduction in number of children with harm class j symptoms in flats with low (suffix L), medium (suffix M) or high (suffix H) moisture production schedule and permeability p • , , , is proportion of dwellings (flats and houses) with low ( ), medium ( ) or high ( ) moisture production schedule. (Note that ). 40 | Costs and benefits of fitting trickle ventilators in replacement windows

• , is the total reduction in number of children with harm class j symptoms in flats with replacement windows and trickle vents

The counterpart reduction of number of children with respiratory symptoms living in houses is:

where the subscript h refers to house.

If ßƒ is the proportion of all dwellings which are flats, then the total reduction of the number of children with respiratory symptoms is:

Class II:

Class III:

Class IV:

We assumed quality of life severity weights as follows:

Class II: 0.75

Class III: 0.9

Class IV: 0.9

Note that we assumed that children who move away from damp homes are replaced by other children, i.e. steady-state conditions.

Results The standardised relative humidity was higher in dwellings with fitted windows without trickle ventilators compared with pre-window replacement dwellings, and appreciably lower in dwellings with fitted windows with trickle ventilators (Figure 2). Replacement windows with trickle ventilators were associated with small reductions in the number of attributable cases of respiratory illness in children in both flats (Figure 3) and houses (Figure 4).

Over ten years, the number of quality adjusted life years (QALYs) saved by fitting windows with trickle ventilators versus windows without trickle ventilators is:

Z = 10 x ((1 – 0.75) x YII + (1 – 0.9) x YIII + (1 – 0.9) x YIV)

Substituting the values for YII, YIII and YIV yields an estimate of preventable disease burden (respiratory symptoms in children) of 538 QALYs. Appendix 3 Health effects | 41

Figure 2. Standardised relative humidity by permeability group at three moisture production schedules (low, medium and high) in dwellings with old windows (blue), new replacement windows (green) and new replacement windows with trickle ventilators (brown): [A] flats, [B] houses. 42 | Costs and benefits of fitting trickle ventilators in replacement windows

Figure 3. Health benefits expressed in terms of the reduction of number of children with respiratory symptoms in flats with replacement windows and trickle ventilators compared to those in flats with replacement windows but without trickle ventilators: [A] low, [B] moderate and [C] high moisture production schedule. Appendix 3 Health effects | 43

Figure 4. Health benefits expressed as the reduction in number of children with respiratory symptoms in houses with replacement windows and trickle ventilators compared with those in houses with replacement windows without trickle ventilators: [A] low, [B] moderate and [C] high moisture production schedule. 44 | Costs and benefits of fitting trickle ventilators in replacement windows

Nitrogen dioxide

Approach

The reasoning in relation to nitrogen dioxide (NO2) is similar to that for carbon monoxide. Although there is evidence from time-series studies of association between daily NO2 levels and a range of health endpoints, the Committee on the Medical Effects of Air Pollutants considered such evidence unhelpful ‘in considering indoor exposure… because the effects in these studies could be due to nitrogen dioxide acting as a marker for other components of traffic pollution rather than due to nitrogen dioxide itself.’

As with carbon monoxide, therefore, we did not apply exposure-response relationships derived from the epidemiology of outdoor exposure, but instead considered evidence, mainly derived from chamber studies, of the acute effects of exposure to high concentrations. Below 150ppb NO2, there appears very little risk of adverse health effect, and only moderate risk of some effect on respiratory symptoms at concentrations up to 400ppb. Above 400ppb, there is evidence for increased risk, especially among those with long-standing disease of the heart and lungs. This includes limited epidemiological evidence of increased risk of admission to hospital and of general practice consultation.

We therefore tabulated hourly indoor concentrations of NO2 exceeding 400ppb, and assumed attributable effects on (cardio-)respiratory symptoms applied only at levels above this threshold.

Input data (1) Health outcomes by harm class: Population rate I. –– II. Hospital adm, resp. disease 1 per 103 children III. Asthma, respiratory disease 16 per 103 children IV. Rhinitis, cough, wheeze 93 per 103 children (2) Relative change in risk per unit Imprecisely quantified; increased risk above change in exposure 400ppb (3) Number of affected dwellings No. of dwellings with replacement windows and occupants = 760,000 Effect assumed to apply to those with established cardio-respiratory disease (4) Assumed time course Acute, reversible effect without time lag

Calculation Number of affected residents = proportion of dwellings with exposures >400ppb x average residents per household x proportion of residents with cardio-respiratory disease Appendix 3 Health effects | 45

Results

Average NO2 levels (estimate of time-weighted exposure of kitchen, bedroom and living room concentrations) were lower in dwellings with fitted windows without trickle ventilators compared with pre-window replacement dwellings, and higher in dwellings with fitted windows with trickle ventilators (Figure 5).

There was, however, no exceedance of 400ppb one-hour average concentrations in dwellings with replacement windows with or without trickle ventilators, suggesting that the associated ventilation changes alone are normally insufficient to lead to clinically important symptoms from higher NO2 exposure. 46 | Costs and benefits of fitting trickle ventilators in replacement windows

Figure 5. Indoor concentrations (µg.m-3) of nitrogen dioxide by permeability group in dwellings with old windows (blue), new replacement windows (green) and new replacement windows with trickle ventilators (brown): [A] flats, [B] houses. Appendix 3 Health effects | 47

Volatile organic compounds

Approach VOCs (volatile organic compounds) are a complex mixture of chemicals and can be measured in terms of total VOCs (TVOCs) – with over 200 component chemicals typically existing in indoor air (IEH, 1996), or as individual chemicals. Most common are formaldehyde, benzene and polyaromatic hydrocarbons/benzo(a)pyrene (BaP). Potential health effects are highly complex. The biological effects are related to the mixture and vary according to its chemical composition, as well as to other environmental factors such as temperature and humidity.

For formaldehyde, exposures in the range 0.12 to 3.0mg.m-3 are associated with irritation to eyes and throat (Samet et al, 1988b, quoted in IEH, 1996). Although no causal link has been established, Mendell (2007) reports that several studies have shown an association with allergic and/or respiratory effects in children (0-16). Associations range from a 3 per cent increase in odds of asthma per 10µg.m-3 increase in formaldehyde concentration to a 10 per cent decrease in prevalence ratio for respiratory symptoms for a reduction in formaldehyde concentrations from 75µg.m-3 to 38µg.m-3. For allergy parameters relationships were in the range of 1.4 OR per 20µg.m-3 peak formaldehyde concentration (atopy). Evidence relating to the carcinogenic effects of exposure to low concentrations of formaldehyde is inconclusive. WHO’s air quality guideline is 0.1mg/m3 (100µg/m3) 30- minute average concentration.

In relation to benzene and benzo(a)pyrene, COMEAP (2004) concluded that the current state of evidence does not provide a secure basis for quantitative risk assessment, and COMEAP was not persuaded of the accuracy of the mathematical models to estimate health risks for exposure to low concentrations of genotoxic carcinogens. This, coupled with the limited evidence on indoor concentrations of benzene and benzo(a)pyrene, and uncertainties about their contribution to carcinogenic risk, led us to exclude consideration of their carcinogenic effects and to concentrate on the non-carcinogenic effects of formaldehyde alone.

For this we used the relationships published by Mendell (2007) and the WHO (2000), in conjunction with a conversion factor to estimate the proportion of TVOCs that is made up of formaldehyde. IEH (2000) has quoted an average annual mean concentration of formaldehyde in homes in the range of 23-25µg.m-3, and a TVOC concentration of 406- 415µg.m-3, as measured in a survey of 173 homes in the Bristol area by BRE in 1992. Based on this, we used a conversion factor of 0.05-0.06 to be applied to modelled results for TVOCs under various scenarios to derive a formaldehyde equivalent. 48 | Costs and benefits of fitting trickle ventilators in replacement windows

Input data (1) Health outcomes by harm class: Population rates of disease: I. (none assumed) II. 1 per 103 children III. 16 per 103 children IV. 93 per 103 children (2) Relative change in risk per unit 3 per cent increase in odds of asthma change in exposure per 10µg.m-3 formaldehyde (conversion factor TVOC: formaldehyde ~ 0.05-0.06) (3) Number of affected dwellings No. of dwellings with replacement windows = 760,000 No. of children aged 3 years and under (the at-risk group) per dwelling = 0.06 Hence, affected population nationally = 760,000 x 0.06 (4) Assumed time course Assumed to affect children under 3 years. No effects in adults.

Method of calculation

Assuming a conversion factor of 0.055 from TVOC to formaldehyde, then CF=0.055 × CTVOC where CF and CTVOC are respectively the concentrations of formaldehyde and TVOC.

Assuming also a 3 per cent increase in odds of asthma in children per 10µg m-3 increase of formaldehyde and a baseline rate of 16 children with asthma symptoms per 1,000, the attributable risk per N children for a change µg m-3 in formaldehyde is:

16 1.03 x N x exp x log –1 1,000 (( (10 )) )

Annual health benefits of vents: Reduce the number of children with respiratory Class III symptoms living in flats and houses by Appendix 3 Health effects | 49

where

• Subscripts ƒ and h refer to flat and house respectively

• WIII, ƒ (p): reduction in number of children with Class III symptoms in flats with permeability p

• WIII, h (p): reduction in number of children with Class III symptoms in houses with permeability p

• ßƒ proportion of dwellings as flats

• (1 - ßƒ) proportion of dwellings as houses

• WIII total reduction in number of children with Class III symptoms

We assumed quality of life severity weights as follows:

Class II: N/A

Class III: 0.9

Results Figure 6 shows the health benefits of trickle ventilators through effect on exposure to TVOCs by permeability band. Over ten years, the number of quality adjusted life years saved by fitting windows with trickle ventilators vs windows without trickle ventilators is:

U = 10 x ((1 – 0.9) x WIII) = 78 QALYs 50 | Costs and benefits of fitting trickle ventilators in replacement windows

Figure 6. Health benefits of trickle ventilators through effect on exposure to TVOCs by permeability band: [top] difference in concentration between dwellings with replacement windows without trickle ventilators and those with replacement windows and trickle ventilators, [middle] corresponding difference in formaldehyde, [bottom] reduction in number with children with Class III respiratory symptoms: [A] flats, [B] houses. Appendix 3 Health effects | 51

Summary

The baseline total QALYs for all exposures (for a 10-year time horizon) is: CO 0 Humidity/mould 538 NO2 0 TVOC 78 Total 616 QALYs

Uncertainty and sensitivity analyses

6 Uncertainty analysis can be divided into two main types: parametric uncertainty and structural uncertainty.

Parametric uncertainty

7 We mean by parametric uncertainty the uncertainty associated with the relative risks of adverse health events associated with exposures (outputs of the building physics models).

8 To quantify fully the parametric uncertainty in the health benefits of trickle ventilators would require performing comprehensive Monte Carlo (MC) simulations. This was outside the remit of this study. Instead, a very simple MC analysis is performed to provide a very approximate estimate of the parametric uncertainty in the health benefit.

9 The basis of the uncertainty calculations is as follows. The uncertainty analysis is carried out for one pollutant and scaled up for other pollutants. This is a rough approximation but it can be justified because the health effects of changes in the pollutant concentrations are assumed to be independent and linearly related to changes in these concentrations. Furthermore, the health effects are assumed also to be additive.

10 The uncertainty in the estimate of the health benefit (H) can be roughly approximated by the product of the uncertainties in the estimates of: • the change in the pollutant concentration (P) between the two scenarios (new windows and new windows + trickle ventilators) • the increase in the incidence of an adverse health event per unit increase in pollutant concentration (R). 52 | Costs and benefits of fitting trickle ventilators in replacement windows

11 We assume (via expert opinion) that the uncertainty in the estimate of P is at least ±10 per cent and that of R is also at least ±10 per cent, then the estimate of the uncertainty in H can be determined through MC simulations. Figure 7 shows as histograms the uncertainties in P and R obtained from MC simulations and in H, the health benefit. 105 random numbers were generated for each parameter, P and R (Figure 7A and 7B, respectively). The x-axis is the percentage uncertainty in the estimate which is assumed to be uniformly distributed between –10 per cent and +10 per cent. For simplicity of presentation the mean estimate of each parameter is centred at zero.

12 It is clear that the uncertainty in health benefit (Figure 7C) cannot be described by either a uniform distribution or by a normal distribution. However, it is much closer to the latter.

13 The variance of H is 33.24. If four pollutants are considered, then the variance of the total health benefit is 33.24 × 4 = 132.96 where 33.24 is the calculated variance of H. Assuming the histogram of H is very roughly normal, the mean estimate of the health benefit is between –1.96 × σ and +1.96 × σ with probability 0.95, where σ 132.96.

14 In other words, taking into account parametric uncertainty on its own, the mean estimate of health benefit is very approximately, at least, between –25 per cent and 25 per cent. Appendix 3 Health effects | 53

Figure 7. Histograms of P and R, and resultant uncertainty in H (i.e. the health benefit). 54 | Costs and benefits of fitting trickle ventilators in replacement windows

Structural uncertainty

15 We mean by structural uncertainty the uncertainty associated by the many structural assumptions made. Three types of assumptions will be tested via sensitivity analysis:

Dwelling types 16 A ratio of 80:20 (house: flat) has been used. This is in line with ONS data. However, there is a great variety in the types of real houses and flats and we have simply modelled a detached house and a mid-floor flat. The following ratios were also tested:

90:10 (S1)

85:15 (S2)

75:25 (S3)

70:30 (S4)

Moisture production schedules 17 We have assumed that the number of dwellings with each of the three moisture production schedules is equally split (i.e. 1/3 each). However, this is unlikely to be the case and hence the following ratios (low: medium: high) were also tested:

25:50:25 (S5)

0:0:100 (S6)

0:100:0 (S7)

100:0:0 (S8)

Permeability profile 18 We have assumed that airtight and leaky homes will similarly install replacement windows, whereas it could be expected that more of the airtight homes already have replacement windows. The following were also tested:

Exclude permeability 3 data (S9)

Exclude permeability 3 and 5 data (S10)

Exclude permeability 3, 5 and 7 data (S11)

Exclude permeability 3, 5, 7 and 10 data (S12) Appendix 3 Health effects | 55

19 The table below gives the results of the sensitivity analysis. It gives the QALY saved under each scenario and also the percentage change relative to the baseline scenario.

Sensitivity QALYs saved (% Change relative to baseline)

S1 –13

S2 –6

S3 6

S4 12

S5 2

S6 34

S7 7

S8 –41

S9 –1

S10 –17

S11 –29

S12 –51

20 Structural uncertainty gives a variation of at least between –51 per cent and 34 per cent around the baseline value.

A study of the ‘optimum’ trickle ventilator

21 The analysis below compares the health effects (negative) of replacing old windows with new windows without trickle ventilators. The purpose is to determine the impact of the ‘optimum’ trickle ventilator, i.e. the one that does not over- compensate for the installation of tighter windows. 56 | Costs and benefits of fitting trickle ventilators in replacement windows

Figure 8. Detrimental health effects due to moisture of replacement windows without trickle ventilators in flats expressed in terms of increase of the number of children with respiratory symptoms: [A] low, [B] medium, and [C] high moisture production schedule. Appendix 3 Health effects | 57

Figure 9. Detrimental health effects due to moisture of replacement windows without trickle ventilators in houses expressed in terms of increase of the number of children with respiratory symptoms: [A] low, [B] medium, and [C] high moisture production schedule. 58 | Costs and benefits of fitting trickle ventilators in replacement windows

Figure 10. Detrimental health effects due to TVOC of replacement windows without trickle ventilators expressed in terms of increase of the number of children with respiratory symptoms: [A] flats, [B] houses. Appendix 3 Health effects | 59

22 The total number of QALYs reduced is ~ 350. This is over-compensated by the QALYs gained (616) by placing trickle ventilators (sized as per ADF 2006) in new windows.

23 However, we noted in Appendix 2 that the predicted reduction in air change rates due to window replacement (0.11ach-1 in the house and 0.13ach-1 in the flat) – while being in the range noted in the literature – was towards the lower end of that range.

24 Thus the number of QALYs gained (616) by placing trickle ventilators (sized as per ADF 2006) in new windows is likely to provide a better approximation of the health effects associated with air change rates closer to the middle of that range.

Cost-effectiveness analysis

25 In order to ensure that the results from this work would be suitable for informing a Regulatory Impact Assessment, we met with Europe Economics on 4/2/09. We agreed that our work would determine the incremental cost-effectiveness ratio (r) of the intervention. This is calculated as:

where: c (£) is the total cost of the intervention h (Quality Adjusted Life Years – QALYs) is the total health gain due to the intervention.

26 If (£ per QALY) is the ‘willingness to pay per unit increase in health gain’ threshold then the intervention is considered to be cost-effective if:

Otherwise it is not cost-effective.

27 Let be the willingness to pay per QALY gained. Trickle vents are deemed to be cost- effective for that value of if: × (total QALYs saved) < Costs

28 The baseline estimated of the QALYs saved was found to be 616. The estimated costs are: • cost to the customer (Cost A) – £62,067,133 • cost of supply and installation (Cost B) – £31,186,948. 60 | Costs and benefits of fitting trickle ventilators in replacement windows

29 Relative to Cost A, the trickle vents are cost-effective at about = £101,000 per QALY for a 10-year time horizon.

30 Relative to Cost B, the trickle vents are cost-effective at about = £51,000 per QALY for a 10-year time horizon.

31 For a 20-year time horizon the above values of would be halved.

32 There is considerable uncertainty in both the health benefits and the costs, which makes it difficult to determine the cost-effectiveness of trickle vents precisely. The uncertainty in the health benefits is at least ± 25 per cent when taking into account parametric uncertainty (i.e. uncertainty in the relative health risks and exposures) only, and, at least, between –51 per cent and 34 per cent when taking into account structural uncertainty (uncertainty in the assumptions on the type of dwelling, moisture production schedules etc) only. The overall uncertainty in health benefits is a function of both, and is at least wider than either. Costs are also uncertain within ± 20 per cent.

33 The above cost-effectiveness analysis (CEA) is based on the concept of ‘willingness- to-pay’ which is the value that policy-makers or society are willing to pay per unit health gain. The measure of health gain that is often used in CEA is either a life year (LY) or a quality adjusted life year (QALY). Within the context of the NHS, the National Institute for Health and Clinical Excellence (NICE) seems to use a value between £20,000 and £30,000 per QALY gained for cost-effectiveness of new health technologies (Delvin and Parkin, 2004). This threshold value of cost- effectiveness was deduced from analysing decisions made by NICE. Outside the NHS, but within the context of health and safety, analysis was carried out to prescribe a threshold value for cost-effectiveness for non-health sector public health interventions such as the valuation of health benefits associated with reduction in air pollution (Chilton et al, 2004). The cost-effectiveness threshold in this case was derived from analysing the responses of a random sample of the population to a well-designed questionnaire using established methods in health economics. A threshold value around £31,200 per LY gained in normal health was deemed reasonable. It was outside the remit of this study to carry out such an analysis for valuing the health benefits of improving the indoor environment. Appendix 3 Health effects | 61

References

Chilton, S., Covey, J., Jones-Lee, M., Loomes, G., Metcalf, H. (2004) Valuation of health benefits associated with reductions in air pollution. London: Defra.

Committee on the Medical Effects of Air Pollutants (2003) Statement on the assessment of the health implications of concentrations of nitrogen dioxide and carbon monoxide – advice to HSE and DTI. London: Department of Health.

Committee on the Medical Effects of Air Pollutants (2004) Guidance on the effects on health of indoor air pollutants. London: Department of Health.

Department of the Environment (1994) Expert Panel on Air Quality Standards. Carbon Monoxide. London: HMSO.

Delvin, N., Parkin, D. (2004) Does NICE have a cost-effectiveness threshold and what other factors influence its decision? A binary choice analysis. Health Economics, 13, pp. 437-452.

English House Condition Survey (2008) 2006 Annual Report. London: Communities and Local Government.

The Eurowinter Group (1997) Cold exposure and winter mortality from ischaemic heart disease, cerebrovascular disease, respiratory disease, and all causes in warm and cold regions of Europe. Lancet, 349(9062) pp.1341-1346.

Feldman, R. (1998) Carbon monoxide. In: Feldman R, editor. Occupational and Environmental Neurotoxicology. Baltimore: Lippincott Williams and Wilkins, pp. 378-399.

Fisk, W.J., Lei-Gomez, Q. et al (2007) Meta-analyses of the associations of respiratory health effects with dampness and mold in homes. Indoor Air, 17(4), pp. 284-96.

HHSRS (2003) Statistical Evidence to Support the Housing Health and Safety Rating System, Vol II: Summary of Results. London: ODPM.

IEH (1996) Assessment on indoor air quality in the home: Nitrogen dioxide, formaldehyde, volatile organic compounds, house dust mites, fungi and bacteria.

IEH (2000) Volatile organic compounds (including formaldehyde) in the home.

Institute of Medicine (US), Committee on Damp Indoor Spaces and Health (2004) Damp Indoor Spaces and Health. National Academy of Sciences.

Mendell, M.J. (2007) Indoor residential chemical emissions as risk factors for respiratory and allergic effects in children: a review. Indoor Air, 17(4), pp. 259–277. 62 | Costs and benefits of fitting trickle ventilators in replacement windows

MRC Institute for Environment and Health (1998) Assessment on Indoor Air Quality in the Home (2): Carbon Monoxide (Assessment A5). Leicester. www.le.ac.uk/ieh/pdf/ExsumA5%20.pdf

Office for National Statistics (2007) Mortality statistics, England. London: ONS.

Wilkinson, P., Landon, M., Armstrong, B., Stevenson, S., McKee, M. (2001) Cold comfort: the social and environmental determinants of excess winter death in England, 1986- 1996. York: Joseph Rowntree Foundation.

Wilkinson, P., Pattenden, S., Armstrong, B., Fletcher, A., Kovats, R.S., Mangtani, P. et al (2004) Vulnerability to winter mortality in elderly people in Britain: population based study. BMJ, 329(7467), p. 647.

WHO (2000) Air Quality Guidelines for Europe. Second Edition. WHO Regional Publications, European Series, No 91. Copenhagen: WHO Regional Office for Europe.

WHO (2007) Housing, Energy and Thermal Comfort. A Review of 10 Countries within the WHO European Region. WHO Regional Office for Europe, Denmark. Appendix 3a Temperature | 63

Annex 3a Temperature

1 As outlined in the proposal, this project has concentrated on the costs associated with the installation of trickle ventilators and the health benefits of the resultant lowering of pollutant concentrations explicitly addressed in ADF.

2 The addition of trickle ventilators will also tend to lower internal temperatures during the heating season. If dwellings are maintained at the same temperature as prior to the installation of the trickle vents then additional energy is required. If not, then the temperatures will lower and, for the population as a whole, health impacts will occur.

3 This is not the core work of this project. Nevertheless, we highlight this issue to raise the fact that future work will be necessary in order to address fully this aspect of a wider cost benefit analysis. Such work presents great challenges in addressing the complex societal balance of additional energy use vs. reduced temperatures.

Commentary

4 The adverse effects of exposure to cold have long been recognised, and appear to be particularly large in the UK where there are approximately 40,000 more deaths between December and March than expected from the death rates in other months of the year. This seasonal fluctuation varies from year to year, is greatest for cardiovascular and respiratory mortality, and is larger in Britain than in many other countries of continental Europe and Scandinavia. Much of it is attributable to changes in ambient (outdoor) temperature, but seasonal infections and changes in behavioural patterns, air pollution levels and micro-nutrient intake may also account for some of the seasonal pattern. Although the evidence is uncertain, it is very probable that housing quality, specifically the energy efficiency of a dwelling, is an important determinant of vulnerability to cold.

5 WHO has recently concluded that there is sufficient robust evidence of a relationship between outdoor temperature and mortality, with ‘some studies showing that a substantial proportion of the excess winter deaths (suggested proportion 40 per cent) are related to inadequate housing conditions’. It advises that although the evidence is from the UK and Ireland, it is more than sufficient to justify actions by countries aimed at reducing population exposure to low household temperatures. WHO recommended indoor temperatures are 18 degrees centigrade for bedrooms and 21 degrees centigrade for living rooms.

6 There remains much uncertainty about the degree to which housing quality affects vulnerability to cold, but our own evidence based on linkage of mortality statistics to 64 | Costs and benefits of fitting trickle ventilators in replacement windows

the 1991 English House Condition Survey provides the most relevant quantification. Its evidence is broadly consistent with other published work, and shows that the magnitude of the winter excess is greater in people living in dwellings that have low winter indoor temperatures.

7 Specifically, there is evidence of the risk of excess winter mortality (EWM) and cold- related mortality in relation to adequacy of home heating as reflected by the standardised indoor temperature (SIT) – the indoor temperature measured when the outdoor temperature is 5 degrees centigrade. These relationships can therefore be applied to estimated changes in standardised indoor temperatures as a result of altered ventilation and other energy efficiency parameters. To compute absolute changes in mortality risk, the relative risk changes have to be applied to temperature profiles and mortality data for the population, supplied by the Office for National Statistics. There is less evidence regarding the relationship between housing characteristics and health impacts other than mortality. Appendix 4 GGF leaflet | 65

Appendix 4 GGF leaflet

Gemma Moore and Mike Davies, UCL

Introduction

1 The aim of this element of the project was to assess how/if the Glass and Glazing Federation (GGF) leaflet for potential window purchasers, Advice to consumers regarding ventilation when replacing windows in dwellings, is used in practice, and by how much it increases the voluntary take-up of trickle ventilators.

Methodology

2 To assess the usage and influence of the GGF leaflet from a range of perspectives (industry, bulk purchasers, individual consumer) a mixed-methodological approach was employed. This included: • a semi-structured interview with the Technical Director at GGF to provide background and context of the leaflet (see Annex 4a for full interview schedule) • telephone surveys with 50 consumers who had recently purchased windows, to gauge if and how the GGF leaflet is used in practice and how much it increases the voluntary take-up of trickle ventilators (see Annex 4b for survey template) • telephone interviews with five local authorities to understand the processes of window replacement for bulk purchasers, and the relationship between the installation of trickle ventilators and the use of the GGF leaflet (see Annex 4c for contacts and a summary).

3 FENSA (Fenestration Self-Assessment Scheme) provided the contact details of a sample of consumers who had recently purchased windows. The 50 consumers surveyed included households from all over England and Wales who had purchased windows from a range of companies, from small local suppliers to large, chain companies. The responses were reviewed throughout the data collection process and, owing to the results obtained, 50 respondents was judged to be an appropriate sample to understand if/how the GGF leaflet is being used in practice. Alongside this process, a list of local authorities was drawn up and contacted, until the target number of five interviews was reached.

4 The findings consider and compare the information collected from these three sources. 66 | Costs and benefits of fitting trickle ventilators in replacement windows

Findings

5 Context: Understanding the key factors considered when purchasing replacement windows is essential to recognise how ventilation fits into the wider context of window replacement. The majority of consumers (who took part in the survey) had purchased windows within the last three months (98%). The respondents ranged from having only one to all their windows replaced in their property (see Figure 1, Annex 4d). Each respondent was asked to state the main reason for replacing their window(s) – ‘maintenance’ was identified as the predominant reason. This incorporated issues such as seal deterioration, rotten frames and condensation within the glass.

6 Aesthetics, security, performance, energy efficiency and ventilation were all considerations for consumers when choosing replacement windows for their homes. However, cost and quality of the product were key determinants for the choice (Figure 2, Annex 4d). Thus the findings indicate that ventilation is only one component considered during the process of replacement and is not the priority for the consumer. Bulk purchasers (the local authorities interviewed) had a slightly different focus: for them, the priority is to ensure that the window complies with current building regulations. Nevertheless, Brent Housing Partnership stressed that replacement is not the first option – it would first explore if the window could be repaired. With over 600 properties undergoing window renewal during 2009, Brent outlined the organisational challenges involved in replacing windows on this scale (i.e. accessing homes, erecting scaffolding, informing residents, managing contractors), within restrictive budgets and time period.

7 Ventilation options: The different ventilation options considered when replacing windows were also examined. Within the consumer surveys, 60 per cent of respondents stated that their replacement windows did not have trickle ventilators, 28 per cent of those involved did (see Figure 3, Annex 4d) and 10 per cent reported that some of their replacement windows were fitted with trickle ventilators. When talking through different ventilation options available and the decisions made on their windows, none of the consumers surveyed commented upon a resistance to having trickle ventilators installed in their property. This is surprising since those working in the industry have experienced otherwise, as the quote below by the GGF Technical Director illustrates: ‘There is a huge resistance to having trickle vents installed, massive … When we had the short period where people thought that we had to put ventilators in, people turn away, they turned down the sale. The implication of that is not just one of my members losing a sale – commercial reasons – but we are trying to upgrade the thermal performance and efficiency of the existing housing stock, you got a single glazed window, and we want to improve it with a high performance one, and if we are not doing it because they have to put in a trickle vent and they [the consumers] don’t like it’. Appendix 4 GGF leaflet | 67

8 Within the local authorities interviewed trickle ventilators appear to be part of the standard specification for replacement windows. For example, Lambeth Housing has produced a brief for window renewal; it covers a range of issues including ventilation. It states: ‘Adequate ventilation shall be allowed for within the dwelling to avoid problems of excess condensation. Consider passive ventilation systems with humidity reactive vents, or mechanical ventilation systems with heat recovery, if part of a comprehensive improvement scheme. New windows to incorporate trickle ventilation to comply with the Building Regulations unless passive or mechanical whole house ventilation with controlled air inlets is provided’ (2005, p5).

9 Similarly, Herefordshire Housing Limited specifies trickle ventilators to all its new windows. The officer interviewed reported that they do not really consider any other ventilation options when replacing windows. However, they do try to educate tenants about ventilating their properties especially after having new windows fitted. They do also fit extractor fans to all kitchens and bathrooms where possible. With regards to other forms of background ventilation, 84 per cent of respondents of the consumer survey noted that they had forms of background ventilation in their home (illustrated within Figure 4, Annex 4d). Air bricks were the most common feature. However, many consumers stated more than one form of background ventilation in their home.

10 Guidance: The Glass and Glazing Federation (GGF) leaflet, Advice to consumers regarding ventilation when replacing windows in dwellings, was produced following the initial decision that trickle ventilators were to be installed in every replacement window, which caused an adverse reaction within the industry. The regulations were later amended, as the GGF notes: ‘We have this conflict, but we try to get as many positive things forward as we know there is a need to vent a room’.

11 This leaflet was produced alongside a factual, technical note for the industry that is incorporated within the Federation’s Glazing Manual (2007), which sets out the standards that all GGF members work towards. The leaflet has been disseminated within the industry.

12 Over three-quarters (76%) of respondents stated that they did not receive any advice regarding ventilation when purchasing/installing their windows (Figure 5, Annex 4d). Those who received advice were given either verbal guidance or literature from suppliers, installers or the salesmen. Out of the 50 consumers surveyed only 4 per cent (two respondents) had specifically seen the GGF leaflet. However, 18 per cent stated that they were not sure if they had seen that specific leaflet (mainly as they were given a lot of literature to read about various aspects of window replacement) (Figure 6, Annex 4d). Three respondents stated that the leaflet/literature they were given was useful in considering ventilation options for their property. 68 | Costs and benefits of fitting trickle ventilators in replacement windows

13 All local authorities interviewed spoke of providing information to residents, informing them of the process of window replacement. However, it appears that disparate guidance is disseminated, with each local authority producing/using its own literature. Only one local authority interviewed had seen the GGF leaflet (the London Borough of Hackney). The borough, however, pointed out that it does not use the leaflet in practice, as it has generated its own literature about windows which is mainly disseminated at road-shows/events to explain the process of refurbishment during renewal programmes.

14 Therefore there is limited evidence that the Glass and Glazing Federation (GGF) leaflet, Advice to consumers regarding ventilation when replacing windows in dwellings, is used in practice with window purchasers (both individual and bulk consumers). Although the GGF reports that the leaflet is ‘out there in the industry’, it is anticipated that in practice the leaflet is used in a bespoke way – only used when needed. The Technical Director of GGF was asked if he thought the leaflet increases the voluntary take-up of trickle ventilators. His response was: ‘I don’t know. I think it has, but it is a gut reaction, as they [installers] will say, ‘you need a ventilator in here as your house is so well sealed and why’. This does help with that process. Of course, if you tell a consumer that you need a ventilator, and they know what they are going to get and they say ‘ok’, then you wouldn’t have to bring that [the leaflet] out. It depends on if they feel it is required, so they recommend trickle vents for ventilation, if the consumer says that is fine, you don’t push it any further – you don’t need to say this and tell them that. A lot of consumers will have what they are told … but it is those that don’t want it, and, I don’t know, maybe only small percentage of market that there is a problem, but I get those you see’.

15 The leaflet provides a tool for this process and the findings indicate that it is probably only used when needed, i.e. if there is resistance to having trickle ventilators installed.

Conclusions

16 Trickle ventilators are, to some extent, being installed in replacement windows. The GGF felt that the installers are making this judgment and guiding the consumer on this process. However, as the GGF points out: ‘This industry has proven to be reliable, if they have the right guidance, which we have given them, they will use it correctly’.

17 Owing to the limited use of the leaflet in practice, it is unlikely that the leaflet influences consumers on voluntary take-up of trickle ventilators. It is more likely that the leaflet has influenced the industry. Appendix 4 GGF leaflet | 69

References

Glass and Glazing Federation (2007) Glazing Manual, Section 6.10, Guidance for Surveyors and Installers for the Provision of Trickle Ventilation and Other Forms of Ventilation for Replacement Windows within England and Wales.

Lambeth Housing (2005) Brief for Window Renewal: Sustainable Construction – Major Repairs Allowance. 70 | Costs and benefits of fitting trickle ventilators in replacement windows

Annex 4a Interview schedule

Introduction

Thanks for agreeing to be interviewed. As explained, I’m a researcher at the Bartlett School of Graduate Studies, UCL, working on a project which is exploring the impact of replacement windows on ventilation and Indoor Air Quality of dwellings. It draws on previous research undertaken by the Bartlett within the Building Operational Performance Frameworks. This project is funded by the Department for Communities and Local Government. It is anticipated that the findings of this project will feed into the consultation process to revise Part F of Building Regs, due to be undertaken in 2010. We are interested in finding out how the Glass and Glazing Federation (GGF) leaflet ‘Advice to consumers regarding ventilation when replacing windows in dwellings’ for potential purchasers is used in practice, and by how much it increases the voluntary take up of trickle ventilators.

General Background

Firstly, would you mind explaining the role of the GGF?

Can you describe your role in this organisation?

Leaflet Background

As you are aware, the GGF worked with DCLG to develop a guidance leaflet for potential purchasers of replacement windows. In your opinion, what were the aims of this leaflet? (I.e. what information was the leaflet meant to provide?).

Could you please describe how the ‘need’ for the leaflet was identified? Who, what, when?

Distribution & Use

From what you understand, how has/is the leaflet been/being used in practice (i.e. how is it currently being distributed and to whom)? How do you know this?

(If it is not being used) Why do you think the leaflet is not being used in practice? What do you think the key reasons are for this? Is this as planned? Was there an agreed process of distribution? Annex 4a Interview schedule | 71

Are different processes used to engage and inform installers, customers and bulk purchasers?

Impact

Do you feel the leaflet has met its initial aims? Do you think it has had the desired effect? Why, please elaborate on your answer. If not, how are consumers being informed on the options for ventilation?

Do you think the leaflet increases the voluntary take up of trickle ventilators?

Have you received any feedback (informal or formal) from users (either installers, bulk purchasers, customers)?

Finally

Do you find the leaflet useful? Why, please elaborate?

Is there any further information that you feel the leaflet needs to provide? If so, what?

How do you think the process of guiding consumers on window replacement could be improved?

Who else do you think we should be talking to/consulting on this matter? 72 | Costs and benefits of fitting trickle ventilators in replacement windows

Annex 4b Replacement window survey – householders

Name: Address:

Telephone: Email: Date of survey: Ref no:

Introduction

Hello. Can I speak to Mr/Mrs/Ms … My name is Gemma Moore I’m calling from University College London, on behalf of FENSA. We understand that you recently had the windows in your home replaced. We are working on a research project funded by the Department for Communities and Local Government which looks at the impact of replacement windows on ventilation and air quality in homes. We would like to ask you a few questions about your replacement windows.

The survey should take no longer than five minutes and the information collected will be treated as confidential. Annex 4b Replacement window survey – householders | 73

Background

1 When did you get your windows replaced? Less than one month ago Over 6 months ago Between 1-3 months ago Between 3- 6 months ago Don’t remember

2 Approximately, how many windows did you have replaced? All The majority (over 75%) Between 50-75% Half (50%) Between 25%-50% Under 25%

3 What was your prime reason for replacing your windows? Was it because of… (tick one only) Maintenance Security Aesthetics Noise Energy efficiency Other

4 What were the key factors you considered when deciding upon your windows? (tick max of three only) Cost Aesthetics Security Quality Performance/energy efficiency Ventilation Other 74 | Costs and benefits of fitting trickle ventilators in replacement windows

Ventilation Options

5 Do your replacement windows have trickle ventilators? Trickle ventilators are small adjustable ventilation openings, usually located at the top of the window frame, to provide controllable background ventilation. Yes Not sure No (go to question 6) Yes, but not on all the windows replaced If yes, or yes but, in what rooms do you have trickle ventilators? All Bedroom(s) Living room Dining room Kitchen Study Hallways/landings Bathroom(s) Other

6 Do you have any other forms of background ventilation in your home? Yes No (go to question 7) If yes, what type of background ventilation do you have? (tick as many as appropriate) Air bricks Stack ventilation Wall mounted ventilation Heat recovery fan units Night vents (two stage locking handles) Other Annex 4b Replacement window survey – householders | 75

7 We would like you to think back to when you decided upon your replacement windows: were you given any advice on the different ventilation options? Yes Not sure No If yes, what advice were you given?

If yes, who advised you? Friends/family Suppliers/ Installers Trade body (i.e. GGF, FENSA) Salesman Other

How were you given this advice? (tick as many as appropriate) Verbally Leaflets/literature Internet Other

8 The Glass and Glazing Federation (GGF) produced a short two sided leaflet entitled ‘Advice to consumers regarding ventilation when replacing windows in dwellings’ which aimed to help consumers consider the ventilation options. Have you seen a copy of this leaflet? Yes Not sure No (go to question 9)

If yes, did you find the leaflet useful? Yes No

Please elaborate on your answer 76 | Costs and benefits of fitting trickle ventilators in replacement windows

Specifically, did the leaflet influence your decision on having trickle ventilators installed? Yes No Please elaborate on your answer (how much did it influence/increase the voluntary take up of trickle ventilators?)

9 Dwelling details

Please describe your house type: House-terraced House-end of terrace House detached House-semi detached Bungalow Purpose built flat Converted flat

10 Approximately how old is your house? Consent We would like to pass the results of this survey on to UCL to use in their work. The information collected will be made anonymous and treated as confidential. Do you agree to this request? Yes No Annex 4c Replacement window survey – bulk purchasers | 77

Annex 4c Replacement window survey – bulk purchasers 78 | Costs and benefits of fitting trickle ventilators in replacement windows Key details Key Building control mainly deal with privately owned dwellings within the within dwellings owned privately with deal mainly control Building HHL do specify trickle ventilators to all their new windows, they don’t they windows, new their all to ventilators trickle specify do HHL owned Hackney in windows replacement every in installed are vents Trickle HHL base the requirements for ventilation on current building regulations. building current on ventilation for requirements the base HHL really consider any other ventilation options when replacing windows replacing when options ventilation other any consider really people to the building regs on the planning portal: www.planningportal.gov.uk/ portal: planning the on regs building the to people 22. Profile using windows replacement for specification Robert had not seen (or even heard of) the GGF leaflet. So did not use it in it use not did So leaflet. GGF the of) heard even (or seen not had Robert sheets and guidance technical own their produced have Camden practice. direct also They owners. property to regs the and control building explaining Part of the process of window replacement is to take the product to the to product the take to is replacement window of process the of Part it, use to how them show replaced, being are windows why explain resident, that seen has he this, Despite vents). the (including features the all explain priority the stressed he But, closed. or open vent the leave permanently people than rather property) per day one have (they time is jobs refurbishment for education. in it use not does however leaflet, GGF the seen have to claimed had He is which windows about literature own their generated have Hackney practice. renewal during refurbishment of process explain to shows road on out taken programmes. especially after having new windows fitted (which will hopefully perform a lot a perform hopefully will (which fitted windows new having after especially all to fans extract fit also do They windows). timber previous than better possible. where bathrooms and kitchens document, a such was there aware he was nor leaflet GGF the seen not has He a preparing be to going shortly is as up it looking be would he that stated but Borough Property Manager Property Borough Duty Surveyor Duty Herefordshire Housing Limited Housing Herefordshire Building Control, London Borough of Camdenof Borough London Control, Building building the with comply undertaken improvements if checking borough: http://www.camden.gov.uk/ccm/navigation/environment/building-control/ regulations. Hackney Home Repairs. 0208 356 3691356 0208 Repairs. Home Hackney properties. Asset and Partnering Team. 01432 38405701432 Team. Partnering and Asset properties their ventilating about tenants educate to try do they however Date of surveyof Date Contact 08/08/08Parton, Robert 22/08/08Williams Steve 22/08/08Maan, Sing Baldev Annex 4c Replacement window survey – bulk purchasers | 79 Key details Key Jon has not seen the GGF leaflet. GGF the seen not has Jon Lambeth Housing have produced a brief for window renewal: window for brief a produced have Housing Lambeth Not seen the GGF leaflet in question. in leaflet GGF the seen Not Not all windows are replaced: the first option Brent would look at is repairing repairing is at look would Brent option first the replaced: are windows all Not ‘Adequate ventilation shall be allowed for within the dwelling to avoid to dwelling the within for allowed be shall ventilation ‘Adequate (Page 5) (Page vents in all replacement windows: this is the standard spec. They also specify also They spec. standard the is this windows: replacement all in vents the with comply also windows The ventilation). night (for openings lockable regulations. FENSA other cost The properties. 600 around in windows replacing be will they year Next putting with issues – realise people most than more is this of organization and homes. accessing and scaffolding up problems of excess condensation. Consider passive ventilation systems with systems ventilation passive Consider condensation. excess of problems if recovery, heat with systems ventilation mechanical or vents, reactive humidity scheme. improvement comprehensive a of part Building the with comply to ventilation trickle incorporate to windows New with ventilation house whole mechanical or passive unless Regulations provided’. is inlets air controlled Property Services Property Environment Development Manager Development Environment Brent Housing Partnership. 0208 937 2490937 0208 Partnership. Housing Brent trickle specify do They it. replace will they then repair beyond if window, the Lambeth Housing. 0207 926 3572 926 0207 Housing. Lambeth Date of surveyof Date Contact 22/08/08Lissmore Jon 22/08/08Patel, Ranjit 80 | Costs and benefits of fitting trickle ventilators in replacement windows

Annex 4d Figures

Figure 1. Percentage of windows replaced in the home.

Figure 2. Factors considered for consumers when choosing replacement windows (number of responses). Annex 4d Figures | 81

Figure 3. Prevalance of trickle ventilators.

Figure 4. Details of other background ventilation (number of responses). 82 | Costs and benefits of fitting trickle ventilators in replacement windows

Figure 5. Details of whether advice is given on ventilation options available during the process of window replacement,

Figure 6. Details of whether the GGF leaflet is used. Cover price £25.00

ISBN: 978 1 4098 2332 2