Condensation in Loft Spaces: Myths and Realities

Journal of Building Survey, Appraisal & Valuation Volume 3 Number 2

Condensation in loft spaces: Myths and realities

Phil Parnham Received (in revised form): 22nd April, 2014 BlueBox Partners, Westgate Chambers, 3 High Street, Chipping Sodbury, BS37 6BA UK E-mail: [email protected]

Phil Parnham is a Chartered Building Surveyor INTRODUCTION and a director at BlueBox partners. He has Increasing energy costs, concerns about cli- many years’ experience organising and deliver- mate change and threats to Europe’s energy ing a range of professional and training services security are all factors that have pushed for those working in the residential property energy efficiency towards the top of the sector. Phil has also published a number of nation’s agenda. European and national books. government responses range from energy labelling (energy performance certificates or Abstract EPCs) through to more focused initiatives Both European and national governments see the such as the UK’s Energy Company insulation of the existing housing stock as an effec- Obligation (ECO) and the ‘Green deal’, a tive method of reducing energy use across the UK financing scheme designed to encourage and the EU. Although the proportion of insulated homeowners and landlords to improve the ‘hard to treat’ properties remains low, a variety of efficiency of their own buildings. government initiatives has resulted in the insula- Policy-makers and commentators debate tion of a high proportion of accessible lofts and the effectiveness of these initiatives but cavity walls. In relation to the insulation of lofts, homes in the UK are clearly beginning to anecdotal feedback from residential surveyors indi- change. According to government figures, cates an increase in condensation problems in loft increasing numbers of dwellings have been spaces. Although this problem has been described insulated in recent years, but many are still and solutions proposed in a variety of publications, below building regulation standards.1 For the defect is still misunderstood by many in the example, in 2013 it was estimated that: surveying and contracting sectors. In this paper the author draws on a range of published guidance and •• 16.2 million homes have loft insulation of research and separates the myths from reality. The at least 125mm (68 per cent of homes paper discusses the factors that cause condensation with lofts); in loft spaces; describes how condensation can be •• 7.4 million homes with lofts have less distinguished from other forms of dampness and than 125mm of insulation. Of these, outlines how loft space condensation can be reduced around 1 per cent have no loft insulation to manageable levels. at all; Journal of Building Survey, •• 13.4 million homes have cavity wall insu- Appraisal & Valuation Vol. 3, No. 2, 2014, pp. 112–123 Keywords: loft space condensation; loft lation (70 per cent of homes with cavity © Henry Stewart Publications 2046-9594 insulation; loft ventilation walls);

Page 112 Parnham

•• 5.3 million homes with cavity walls are not spoken at over 40 residential conferences, insulated. Most of these are classified as workshops and seminars attended by over ‘hard to treat’ and require further building 1,800 residential surveyors. The clear, albeit work to make then suitable for insulation; anecdotal, feedback is that condensation •• there are 0.7 million homes with ‘easy to problems in roof spaces are on the increase. treat’ standard cavities that are not Water droplets on the underside of roofing insulated; felt, damp thermal insulation and, in the •• only 3 per cent of the 7.9 million homes worst cases, stained ceiling finishes and wood with solid walls are fitted with solid wall rot have all been reported. insulation. This paper considers loft spaces above habitable rooms where the ceilings are Statistics are always open to interpretation horizontal and fixed to the ceiling rafters. but in the author’s opinion, the most straight- ‘Room in the roof’ arrangements are not forward insulation work has already been considered. done. Insulating the remaining stock is likely to be technically challenging and costly. CONDENSATION IN ROOF SPACES: MYTHS AND REALITIES IMPACT ON HOUSING CONDITIONS Condensation is a dynamic phenomenon and Anecdotal feedback from residential survey- understanding how it occurs is an important ors confirms this changing picture. Double- part of the diagnostic process. Despite numer- glazing, draught stripping, thick layers of loft ous publications clearly explaining the sci- insulation and condensing boilers are com- ence behind this process, the causes of monly encountered. Although less numer- condensation are still widely misunderstood. ous, most surveyors have inspected some For example, the increase in condensation properties with either external or internal in roof spaces has caused a number of organ- wall insulation. isations to review their practices. The NHBC Where thermal improvements are part of stated that increases in thermal insulation in a properly designed scheme, these changes roof spaces to modern standards greatly can be beneficial, resulting in lower fuel bills, reduces the amount of heat passing through increased thermal comfort, and positive the ceiling and ‘this can increase the risk of effects on occupant health. For example, condensation because the surfaces in the roof Age UK estimates that 1.7 million older remain cold’.4 This view is partly shared by people in the UK cannot afford to heat their the Building Research Establishment (BRE) homes, and over a third (36 per cent) say who state ‘in a cold pitch roof . . . there is a they live mainly in one room to save money.2 risk of condensation on the underside of the Where insulation is piecemeal or poorly roof; the thicker the insulation layer, the conceived, internal environmental condi- greater the risk of condensation’.5 Although tions will become unbalanced and result in these publications set these statements in a condensation and mould growth.3 In the broader context, they reinforce a common worst cases, it can result in deterioration of misconception across the sector — that the building fabric, affect occupants’ health increased levels of thermal insulation and a and if the property is rented, expose the drop in loft space temperatures are the sole landlord to legal challenge. causes of condensation. This paper will focus on just one aspect of Jeff Howell, the Sunday Telegraph’s prop- this complex and interrelated problem: loft erty advice columnist, further reinforced this insulation. Over the last year, the author has misconception. In response to a reader’s

Page 113 Condensation in loft spaces: Myths and realities

enquiry, Howell stated that the only solution felt). Assuming the level of water vapour to a post-insulation condensation problem in remains the same (at 0.85 kPa), to get the a loft was to ‘let a bit of heat escape into the RH down to a ‘safer’ level (say 65 per cent roof space, by reducing the thickness of insu- RH — point 2 in Figure 1) the air tempera- lation, or leaving the loft hatch ajar’.6 ture in the loft would have to be raised to It is interesting to note that a year earlier around 10.5°C. In an uninsulated roof space, David Snell, another Telegraph columnist, such a temperature rise would require a advised one of his readers that the best way considerable input of energy — far more to solve a roof-space condensation problem than the heat that a ‘half-opened’ access is to ‘make sure there is no leakage of moist hatch could provide. A partially open access air from the house below’.7 He went on to hatch would not only let heat into the loft say ‘Pay particular attention to the loft trap, but also water vapour. Vapour pressures in making sure that the lid sits on a draught occupied habitable spaces can be as high as excluder or a rubber beading.’ With this level 1.6–2 kPa at peak times and this will result in of inconsistency, it is no wonder homeown- a vapour drive from areas of high vapour ers adopt a number of different solutions. pressure to low.3 The amounts of water The reality is somewhat different. vapour in the loft would quickly rise unbal- According to the BRE, condensation is ancing the conditions and resulting in more caused where the amount of water vapour in condensation not less. the air (in the form of an invisible gas) The moisture content of roof timbers in a exceeds the amount that air can hold at any ventilated roof space was measured in one given temperature.3 When this limit is study.5 This found during the colder, wetter reached, the air is said to be saturated. This winter months (September to March) that saturation point varies with temperature — the higher the temperature, the greater the amount of water vapour it can contain. When saturated, any extra water vapour will be deposited in the form of condensation. Consequently, condensation can be caused by an increase in the moisture content of the air, a fall in the temperature of the air, a fall in the temperature of adjacent surfaces or a combination of all three. A psychrometric chart from BS 5250 shows the relationship between temperature, relative humidity and vapour pressure (the amount of water vapour in the air) graphi- cally.8 Using a theoretical case (see Figure 1), assume the temperature of the air in the loft space is 5°C with a relative humidity (RH) of 95 per cent (point one in Figure 1). The left-hand axis shows the vapour pressure to be approximately 0.85 kPa. Many commentators may consider 95 per cent RH in a roof space too high and condensation on colder adjacent surfaces could be expected (for Figure 1: Psychometric chart from BS5250 example, on the underside of the roofing

Page 114 Parnham

the moisture content of roof timbers is likely •• moisture levels in roof timbers will be to rise as they absorb moisture from the high higher during the winter months; humidities from the roof. However, this •• warm and moist air that leaks into the loft moisture will quickly re-evaporate ‘and will have a much bigger impact on con- safely escape outside during the warmer densation levels than any reduction in months’. This same report goes on to say roof space temperatures. that during winter months, the conditions within a cold pitched roof insulated at ceiling level closely reflect the temperatures, vapour REDUCING THE CONDENSATION pressures and relative humidities of the exter- PROBLEM nal environment, and where the moisture Before specific advice is given, a review of content of roof timbers attains a level of 24 some of the broader issues is necessary. The per cent for a period of three months or following matters may assist in this more, ‘the retrofitting of ventilators should understanding. be considered’. In the author’s opinion, this highlights the Well-sealed ceilings dynamic nature of environmental conditions Research into roof space condensation led in roof spaces and for relatively long periods, to an amendment of the British Standard the moisture levels of roof timbers will be 5250 (2002) ‘Control of condensation in above those considered acceptable in habit- buildings’.8 This document accepted that a able areas. As many residential practitioners completely air and vapour-tight ceiling will use conductivity moisture meters to assess be difficult to achieve and introduced the timber components in roof spaces, relatively concept of a ‘well sealed’ ceiling as part of a high moisture meter readings may result in strategy of reducing condensation problems unnecessary recommendations for further in lofts. investigations. The Standard describes the function and Another BRE report considered conden- purpose of vapour control layers (VCL) sation and airflow in pitched roofs and found and identifies three main types used in that moisture produced by the normal activ- ceilings: ities of a household raises temperatures and water vapour pressures in the habitable parts •• a separate membrane within the structure of the dwelling above those of the outside (for example, a plastic sheet between the air.9 Some of this heat and moisture (20 per plasterboard and ceiling joists); cent of the total) leaves the house by way of •• a lining board with an integral membrane the loft and passes through the ceiling by a (foil backed plasterboard); combination of conduction, diffusion and •• a suitable coating applied to internal air leakage. These studies further revealed surface of the element (vapour control that 80 per cent of the water vapour that paint). does get into lofts gets there by air leakage through gaps around the loft access hatch, Whatever the choice, it is important that the light fittings, service pipes and so on. VCL is placed on the warm side of the To summarise this brief review of some of insulation. the myths and realities associated with con- The Standard also reminds the reader that densation in loft spaces: more moisture gets into lofts by air leakage than diffusion through the ceiling and •• increased levels of thermal insulation in recommends that more attention be paid to lofts does not by itself cause condensation; reducing air leakage paths. Some of the more

Page 115 Condensation in loft spaces: Myths and realities

important characteristics of a well-sealed ceiling include:

•• all gaps and cracks are sealed wherever possible; •• no access hatch or door should be posi- tioned in bathrooms or kitchens because of high water vapour pressures in these spaces; •• a well-sealed, purpose-provided access hatch with third party evidence of low levels of air leakage should be used; •• penetrations for services and other fittings (especially downlighters) are sealed with proprietary products; •• any wall cavities or spaces behind dry lin- ings are sealed to prevent air movement into the loft.

Sealing the ceiling is not the only action Figure 2: Above this ceiling, the loft insulation required. The British Standard also has not been pushed up to the back of the wall recommends: plate and taken over the head of the wall. Condensation and mould growth has formed on •• overall moisture levels in the dwelling the resulting cold areas. This is still visible should be controlled through appropriate despite being cleaned with diluted bleach ventilation strategies and techniques; •• the roof space is ventilated to ensure any water vapour that does get through is Fitting 250–70mm thickness of thermal dispersed. insulation at the junction of the rafters and ceiling is difficult especially between trussed This advice is not unique and is reflected in rafters with a lower pitch. Kingspan Insulation current guidance for contractors who insu- solutions investigated this problem and found late cold lofts as part of projects carried out that:11 under the various government schemes.10 •• omitting the second layer of insulation Cold bridging and loft insulation from the eaves so that the ventilation is High levels of water vapour is not the only not blocked could double the U value of cause of problems in loft spaces as the ceiling and significantly affect thermal discontinuities in thermal insulation can performance; also cause localised condensation. Often •• butting the insulation up to the underside called ‘cold bridging’ or ‘thermal bridging’ of the eaves ventilation tray could degrade it occurs where part of a structure has lower the U-value by 500 per cent because of thermal resistance components. This can compression of the material; result in cold surfaces on which condensa- •• even at low wind speeds, air movement tion, mould growth and/or pattern staining through ventilated eaves could further can occur.8 Figures 2 and 3 show a typical reduce the thermal performance of the example. eaves insulation.

Page 116 Parnham

Figure 3: This is the view of the same ceiling shown in Figure 2 but from within the loft space. The insulation is approximately 75mm thick and upgrading this to 250–70mm while maintaining roof space ventilation would be a challenge

Kingspan’s solution was to use a sealed, a pre-formed, insulated section rather than breathable sarking membrane with insulated ‘simply relying on placing quilt insulation dry lining plasterboard on the underside of into this area’.5 the ceiling joists. Kingspan claims this solu- In the author’s opinion, these publications tion can reduce the need for loft insulation highlight the difficulty of avoiding cold to 150mm between the joists. bridging when lofts are insulated to current A similar issue is highlighted by the standards. The more sophisticated solutions Energy Saving Trust.12 Although cavity wall outlined above are clearly described in sev- insulation is the focus of this guide, it eral standard setting publications but, in the identifies a number of cold bridges including author’s opinion, it is rare to find this atten- at the top of older walls where a course of tion to detail in practice bricks closes the cavity. The guide points out that getting the loft insulation over the wall The influence of roof covering head to resolve this problem is likely to be underlays difficult and suggests a deep insulated coving As the thermal regulations have brought internally. in higher standards, manufacturers have The BRE also acknowledges this problem responded with a number of innovative and has suggested that in order to provide products. Microporous or ‘breathable’ roof- sufficient ventilation and to accommodate ing felts have become a common sight in loft insulation, it may be more appropriate to use spaces to both newly constructed and

Page 117 Condensation in loft spaces: Myths and realities

existing homes. Manufacturers of these •• loft hatches must incorporate effective products claim up to 25 per cent of the heat compressible draught seals; lost through a conventional roof system is by •• the rooms below the ceiling must include air leakage through the ceiling and from the provision for the dispersal and rapid dilu- loft space to the outside air. They claim that tion of water vapour, including extractor because these ‘breathable’ felts allow water fans in kitchen and bathrooms; vapour to permeate through, purpose pro- •• all water tanks must be covered with a vided ventilation to the outside air is not tight fitting cover; required. •• any vent pipes should be arranged so that British Standard 5250 provides detailed they do not discharge water vapour into guidance about the use of different underlays the loft space; and identifies two types for pitched roofs:8 •• cavities are closed at plate level to stop vapour transfer to roof space; •• Those with high water vapour resistance •• recessed spotlights and down lighters must (Type HR). These include traditional be sealed in accordance with the appro- bitumen-based sarking felt or the newer priate BBA/BRE certificate. meshed reinforced plastic underlays. To reduce the condensation potential with Even where this standard is achieved, some this type of underlay, cross-ventilation is manufacturers still require ventilation at high vital. level so it is important to check the BBA •• Those with low water vapour resistance certificate for the particular product. (Type LR). These include the fleece-type Building control authorities will often underlays. Where the ceiling is ‘well require ventilation with breathable felts in a sealed’, some Type LR roofs may not number of other situations: require roof space ventilation but this has to be confirmed by third party certifica- •• If the roof fitted with the breathable tion (for example, a BBA certificate). membrane is linked to an existing roof fitted with traditional felt or a roof space These breathable roofing felts present a num- that is already vented. ber of advantages especially to designers aim- •• If the breathable membrane is fitted tight ing to create highly insulated and low energy across the rafters with no counter battens. buildings. However, increasing numbers of This reduces the ventilation above the breathable felts have been affected by con- underlay and so could affect performance. densation and many authorities have reviewed Normally a ventilated gap of 25–50mm their guidance. For example, a building con- between the surface of the LR underlays trol department issued new guidance for and the underside of the roof tiles is breathable felts and pointed out that they are required. not simply a replacement for conventional overlays, they must be considered holistically It is clear to the author that breathable felts do from ceiling to roof tiles.13 Following recom- not provide a ‘quick fix’ to the condensation mendations in BS 5250, many building con- problem but have to be part of a moisture trol departments will now only allow management system that encompasses the unventilated roof spaces if the following con- whole property. ditions are met: Lofts and storage •• all penetrations into the roof space are Traditionally, ceiling joists are designed to properly sealed; support the weight of the ceiling construction

Page 118 Parnham

with an allowance for access for essential straightforward to spot. The main visual maintenance. In reality, homeowners often characteristics include: see the loft space as useful storage area. When thermal regulations were less stringent, it Water droplets on the underside was possible to fit boarding over 75–100mm of the roofing felt thick insulation without too much compres- This could range from a general misting to sion and loss of thermal value (although heavy water droplet deposits that fall away overloading of the ceiling often resulted). when touched. These surface deposits will Now that the typical thickness of insula- be more common during the late autumn tion is 250–300mm, using the loft for storage through to early spring. Even within this purposes becomes impractical. Where home- ‘condensation period’, the amount of con- owners lay boarding over the top of such densate can vary even within a 24-hour deep insulation, the thermal insulation value period because of changing external and will be decreased and the additional pressure internal conditions. The level of deposit is on the ceiling below could result in damage likely to be highest in the early morning. or even collapse. Under these circumstances, occupiers need to accept that loft spaces are Damp or wet insulation and stains no longer places for informal storage and sur- to the ceiling finishes veyor’s advice should reflect this. The exception is for access walkways for In thickly insulated lofts, the condensate maintenance purposes. Lofts can contain may be held within the insulation without water tanks, boilers and control gear associ- affecting the ceiling below especially if the ated with photovoltaic panels to which upper and lower rolls of insulation are laid operatives will need access. Where these fit- perpendicular to each other. Where the tings are further than 1m from the hatch, an condensate does affect the ceiling, the stains access walkway will be required. Although can be diffuse and spread over a broad area. specifications for these walkways vary, most The staining and damage is usually less standards require a minimum board width of intense than that caused by roof or plumb- 300mm fixed directly to the joists. The ing leaks. Where foil-back plasterboard is walkway should be fully insulated beneath used, the staining may follow plasterboard and the thicker insulation stopped at the joints. edge of the boards.10 Wet and/or rotten timbers Features on the underside of the roof can ASSESSING LOFT SPACES FOR concentrate the flow of the condensate and a CONDENSATION PROBLEMS typical example is the underside of valley Where loft space condensation is found, it is gutters. The saturation of timber compo- important for surveyors to identify the nents can cause wood rot. problem, highlight the most likely causes, and put forward effective but practical solu- Mould growth tions. Care should be taken when interpret- Mould can grow on the underside of the ing readings from conductivity moisture roofing felt, roof timbers and on stored meters especially during the colder months. possessions. Although this will be more obvi- Judgments should not be based solely on ous during the colder months, the mould moisture meter readings but placed in growth will still be evident during the sum- context with the signs listed below. In mer period allowing a diagnosis outside of the most cases, condensation problems are condensation season.

Page 119 Condensation in loft spaces: Myths and realities

IDENTIFYING THE CAUSE are becoming a common sight in many Although the visual evidence may strongly lofts. These can be from extract fans to a suggest the cause, it is important to eliminate bathroom or more sophisticated whole other possible causes. For example: house systems. If these are poorly fitted and the flexible ducts fall away from the Built-in moisture ventilators, the appliance can deliver large This is water enclosed within the structure amounts of warm and moist air into the during the building process and is often a loft (see Figure 4). problem during the first few months after the •• Flues from boilers and other heating appli- construction has finished (both new build and ances: Fanned balanced flues allow boilers larger refurbishment schemes). This may to be located centrally within a dwelling result in more generalised condensation in the with the flue taken up through the loft to roof space during the first heating season but terminate above the roof covering. Faults it should disappear as the building dries out. If in the flue can result in warm moist com- the problem returns, look for another cause. bustion gases affecting the loft space and create dangerous conditions. Roof leaks Faults in the roof covering are usually more Blocked ventilation to the roof space localised and related to a physical problem This is particularly common where the that can be seen from the outside or inside of property has been recently insulated with the the roof. insulation taken over the ventilation route. Replacement PVC fascias and soffits can Plumbing leaks have a similar effect. Leaking water and overflow pipework can result in similar signs but like roof leaks, they GENERALISED LOFT SPACE are usually more concentrated and associated CONDENSATION PROBLEMS with a particular source of water. The underside of cold water tanks can be affected by Once the other possible causes have been condensation causing similar damage to the eliminated, condensation caused by a general ceilings below but more restricted in extent. movement of water vapour from the dwelling below may become the primary suspect. Specific water vapour sources For descriptive purposes, the author refers to Specific faults in and around the roof space this type of deficiency as ‘generalised loft can result in high levels of water vapour. space condensation’ to distinguish it from the Typical examples include: other causes described above. Dwellings affected by generalised loft •• Water tanks without lids: Most common space condensation are likely to have the fol- with feed and expansion pipes from hot lowing characteristics: water tanks and/or heating systems. Warm and sometimes steamy water from expan- •• HR underlays (bitumen or plastic) beneath sion pipes can produce large amounts of the roof covering. Original slate and tiled water vapour and be the cause of the roofs without the benefit of an underlay problems. This is usually indicative of a are not usually affected by this problem; fault with the heating system requiring an •• breathable underlays (type LR) that are urgent repair. tautly fixed across the rafters with no •• Ducts from extract fans and other ventila- space between the underlay and the tion systems: A variety of flexible ducts underside of the roof covering;

Page 120 Parnham

Figure 4: This flexible duct should connect the extract fan from the bathroom to the ventilating tile in the eaves of the roof. Because the wrong ducts have been used, it is impossible to join these effectively allowing warm moist air to get into the roof space

•• original lath and plaster ceilings — espe- —— the equivalent of a continuous 25mm cially those that are cracked and in poor strip to each ‘long’ side of the roof to condition; provide cross ventilation; •• plasterboards that are not foil backed; —— the equivalent of 5mm continuous •• a high number of ceiling penetrations for strip at the ridge to provide high level services (especially downlighters) that are ventilation especially if the roof pitch not properly sealed; is greater than 35°. •• the dwelling does not have extract fans in the bathroom and or kitchen and/or a The construction of many existing roofs lack of background ventilation to other may prevent the installation of a continuous rooms (for example, trickle vents in the ventilation strip and in these cases individual windows or air bricks through the wall); roof tile ventilators may be used. These should •• poorly sealed loft hatches and/or the loft give the same equivalent ventilation area, be hatches in the ceilings over bathrooms equally spaced and located as close to the and kitchens. Larger access hatches with eaves and ridge as possible. ‘pull down’ ladders are particularly difficult to seal especially if they are used regularly; SOLVING THE PROBLEM •• lack of sufficient loft space ventilation. If any single cause has been eliminated and Although it will be impossible to assess the dwelling presents many of the above this accurately, a robust rule of thumb can characteristics, it is reasonable to assume that provide a good starting point: the problem is due to ‘generalised loft space

Page 121 Condensation in loft spaces: Myths and realities

condensation’. As previously discussed, this cracks and holes in the existing ceiling with type of problem is likely to be caused by a flexible filler; the ceilings lined with a thick number of interrelated deficiencies and so lining paper and painted with a vinyl-based the solution is likely to be complex requiring paint suitable for kitchen and bathrooms. a number of actions.14 These include: Although this will not stop all diffusion through the ceiling construction, it is likely Seal all service penetrations to reduce it to manageable levels. This typically includes using suitable collars around larger pipes and ducts, purpose made Insulate cold bridges non-combustible hoods or boxes over down- Where the loft insulation cannot be laid over lighters (proprietary hoods are available) and the cold bridge, provide alternative solu- expanding foam around smaller cables and tions. This could typically include deep pipes. Please note: the foam should be com- insulated covings; use of insulation with patible with the cables.10 higher thermal resistivity where conventional loft insulation cannot be accommo- Seal or replace loft access hatches dated; or the dismantling of the eaves/soffit Where these are in bathrooms or kitchens, construction to allow insulation over the they should be removed and resited. Where wall head. the existing hatches are in low humidity areas, they should be sealed by filling gaps around the frame and the ceiling with CONCLUSION expanding foams, insulating the back of the Avoiding dampness in buildings in all its hatch lid to the same standard as the rest of forms is about attention to detail and resolving the roof space, fitting good quality, compress- condensation problems in lofts is no different. ible draught stripping between the lid and Loft insulation is no longer a desirable, the frame and making sure that the lid is kept unskilled building operation carried out by in place with an appropriate fastener (light- well meaning DIY enthusiasts. Instead, it is weight lids can lift during windy weather). one part of an integrated strategy designed to improve the energy efficiency of a dwelling. Provide loft space ventilation This approach should look at the property as Where missing or inadequate, provide loft a whole so a balance between ventilation, space ventilation to the outside air. heating and thermal insulation is maintained and condensation problems are avoided. To Install extract and background achieve this balance, the level of design and ventilation to the dwelling specification will exceed the conventional This should meet the requirements of the expectation of many advisers and owners. It current building regulations and the occu- is also likely to result in more extensive and pants advised how to use the system. costly building work. Enhance the vapour resistance of the ceiling References Older ceilings are unlikely to have an effec- (1) Department of Energy and Climate tive vapour barrier. It is the author’s experi- Change (2013) ‘Estimates of home ence that property owners are unwilling to insulation levels in Great Britain’, July. replace the existing ceiling to allow a (2) Age UK (2014) ‘Spread the warmth conventional VCL to be fitted. A reasonable campaign’, available at: www.ageuk.org.uk compromise could include the filling of all (accessed 15th March, 2014).

Page 122 Parnham

(3) Garrett J. and Novak F. (1991) ‘Tackling one. Code of practice for the control condensation: A guide to the causes of, of condensation in buildings’, London: and remedies for, surface condensation and BSI. mould growth in traditional housing’, (9) BRE (2006) ‘Airtightness of ceilings — BRE Report 174, London: BRE. energy loss and condensation risk’, BRE (4) National House Building Council (2011) IP 4, Watford. ‘Condensation in roof spaces: Your guide to (10) Construction Industry Training Board understanding and controlling condensation (CITB) (2013) ‘General requirements and in your roof space’, HB2217 08/11. guidance for the installation of cold roof (5) Stirling, C. (2002) ‘Ventilated and loft insulation. Version 2’. unventilated cold pitched roofs’, BRE (11) Kingspan Insulation Solutions (2006) Good Building Guide, 51, London: BRE. ‘Mineral fibre loft insulation, cold (6) Howell, J. (2010) ‘Jeff Howell’s DIY bridging, ventilation and heat loss at eaves. advice: Wet roof spaces’, available at: A white paper’, July. http://www.telegraph.co.uk (accessed 28th (12) Energy Saving Trust (2007) ‘Good practice March, 2014). guide. Cavity wall insulation in existing (7) Snell, D. (2009) ‘Property advice: housing’, CE 252, London. Loft condensation’, available at: http:// (13) Charnwood District Council (2010) ‘Use www.telegraph.co.uk (accessed 28th of breathable roofing felts’, Loughborough: March, 2014). Building Control Department. (8) British Standards Institution (2005) (14) Energy Savings Trust (2005) ‘Improving air ‘BS 5250 2002 Incorporating amendment tightness of dwellings’, GPG224, London.

Page 123