St Athan Affordable Housing Development, File Type

Case Study 10 St. Athan Affordable Housing Development

Owner/Developer: Project Description the use of renewable and low Wales & West Housing The Wales & West Housing carbon technologies, in addition to the requirements and challenges Association Association (WWHA) developed 16 affordable housing units on the of meeting the CSH Level 4. Residents’ experiences of utilising Architect: site of a former church to help meet the strong demand for affordable the low carbon technologies were Powell Dobson homes for local people in the area monitored by WWHA in order Architects, Welsh of St Athan. The project was one of to accumulate knowledge and School of Architecture the Welsh Government’s first Code experience for future projects. (design research unit) for Sustainable Homes Pilot Projects, Key features requiring the new homes to achieve Code for Sustainable Homes (CSH) • Air Source Heat Pump (ASHP); Location: • Mechanical Ventilation with Heat St Athan, The Vale level 4. This standard entailed a 44% reduction in CO emissions Recovery (MVHR); of Glamorgan 2 over 2006 Building Regulations • High energy efficiency systems; Part L guidance. and Building Types: •Underfloor heating. Residential Key Drivers The core driver was for the WWHA to build a community of CSH level 4 dwellings to be utilised as affordable rented accommodation. This was a pilot scheme where sharing learning experiences and knowledge gained through the entire process were particularly important. Standard affordable housing units in St Athan The scheme presented an housing development. opportunity to experiment and Reproduced with permission of WWHA learn about offsite construction Renewable & Low technologies to discover their Carbon Technologies specific advantages and disadvantages. Other learning • Air Source Heat opportunities were gained through Pumps

Case Study 10 – St Athan Affordable Housing Development Procurement Welsh Government for the scheme, The WWHA chose to develop worth £1.9m. The remainder of the scheme under a negotiated the total scheme cost was funded Design & Build contract with by WWHA. contractor Lovell, who is on the Technology selection WWHA’s framework. The project Architects, Powell Dobson Architects, process worked in collaboration with Before any renewable or low carbon the Welsh School of Architecture technologies were considered, (WSA), who were undertaking a the design team used an energy Knowledge Exploitation Fund project hierarchy approach of ‘fabric investigating Modern Methods of first’ to make each building type Construction (MMC) from a Welsh as thermally efficient as possible. perspective. The WSA assisted For instance, triple glazed windows “We are very proud in providing a basis for design were selected, which improved the principles of the properties and thermal performance of the building of this scheme knowledge of MMC applications and provided an extra noise which reflects for the St Athan development. reduction benefit to residents. innovative design One of WWHA’s preferred suppliers Following implementation of and construction of heating systems are Worcester an energy efficiency building fabric, the most suitable renewable methods and a Bosch from whom it was possible to source an Air Source Heat Pump and low carbon technology was willingness to look (ASHP) that was appropriate in chosen through numerous refined beyond the usual terms of long term maintenance SAP calculations. and performance specification. concepts to help the Standard Assessment Other factors that made Worcester Welsh Government Bosch suitable for this project Procedure (SAP) achieve its target included their post installation SAP provides a simple means of reducing carbon support and participation in of reliably estimating the energy the Design Stage and post efficiency performance of dwellings. dioxide emissions.” handover stages. SAP ratings are expressed on a scale Anne Hinchley of 1 to 100, where better ratings Scheme Costs and Finance: WWHA equate to higher numbers. SAP is Excluding land purchase and calculated by predicting heating, demolition, the total build (contract) and hot water costs, which depend cost of the scheme was £2.25m, on the insulation and air tightness equating to £1,228/m². of the house and the efficiency and control of the heating system. The total cost of the ASHP The calculation uses the Building (including capital, installation and Research Establishment’s Domestic commissioning) was approximately Energy Model (BREDEM). £9,100 per unit. This included the cost of underfloor heating which The SAP calculations also allowed was used on the ground floor of combinations of renewable and low the houses in conjunction with the carbon technologies, including PV ASHPs had at £1,350 per dwelling. and solar thermal, to be investigated for the St Athan development. Funding for part of the project was However, due to the capital cost partially sourced from a Social and carbon saving target necessary Housing Grant obtained from the to achieve the ENE1 part of the CSH

Case Study 10 – St Athan Affordable Housing Development for CO2 reduction, the SAP process Level 4 the DER for the St Athan eventually indicated that an ASHP development made, on average, was the most suitable and cost a 47% improvement on the Part L1A effective low carbon technology. 2006 TER. ASHPs work well in conjunction Monitoring and operation with underfloor heating, due to the Following completion, the WWHA lower output heating temperatures adapted its handover process to compared to those associated ensure housing managers and with a traditional radiator system. tenants were comfortable with Installation of underfloor heating the systems and technologies at the St Athan development used in their homes. This included improved the ASHP coefficient contractors demonstrating to the of performance (COP), which is tenants how the ASHPs and MVHR the ratio of the energy transferred systems worked. for heating to the input electric energy used. The tenants were provided with energy meters to help them The development utilised an understand their energy costs. advanced construction method A dedicated Environmental Officer comprising of a pre–fabricated was available to act as a point structurally insulated panel (SIPs) of contact to assist residents in system. This enabled a much higher reducing their energy bills. level of airtightness to be achieved compared to Building Regulation Part of the energy monitoring system standards, at 3m3/m2.hr at 50 Pa involved a survey of residents at compared to 10m3/m2.h. regular intervals; after six months, one year, two years and three years, Airtight dwellings require to obtain longer–term feedback on mechanical ventilation to maintain the performance of their homes. adequate indoor air quality. As part To date the results have been of a number of low energy, high positive, with residents generally efficiency systems, the St Athan happy with their properties and development utilised mechanical WWHA continue to work with them ventilation with heat recovery to ensure they are getting the most (MVHR). MVHR warms fresh from them. incoming air using ‘waste’ heat extracted from outgoing warm air Following the first set of monitoring, via a heat exchanger e.g. from the resulting actual electricity kitchens and bathrooms. bills were actually somewhat higher than expected by the Part L1A 2006 of the Building residents, although still considered Regulations stipulated a Target reasonable. The ASHPs did not Emission Rate (TER), measured perform as well as indicated 2 in kWh/m , which describes the by the original SAP calculations maximum allowable CO emissions 2 due to differences in occupant for a Part L compliant dwelling. behaviour between the theoretical In order to achieve CSH Level 4, design calculation and the actual the CO emissions of a dwelling 2 inhabitants, in addition to an (the Dwelling Emission Rate (DER) abnormally cold winter during had to make a 25% improvement the first year of operation. on the TER. When compared against the benchmark for CSH

Case Study 10 – St Athan Affordable Housing Development Lessons learnt Occupant Involvement Technological Issues • Allowing members of the project • The Code of Sustainable Homes team to ‘Buy in’ to the scheme assessor has a crucial role to play gave many people a personnel and needs to work closely with commitment and involvement to the design team, guiding and the project; advising where appropriate. • Positive support from locals for the scheme was a benefit in the Financial Lessons context of this project; and • Early involvement of the contractor • Housing managers and tenants within the design team prior to were trained in the use of the planning stage enhanced the ‘new’ systems within the homes, value engineering potential; and reducing problems when • Contractor knowledge of products occupants moved in. “This development and willingness to provide solutions (in particular relation to Awards and Achievements is just one example the Code for Sustainable Homes) • Awarded Exemplar status of a whole range can be an important benefit. by the Building Research of initiatives which An example was the Euro clad Establishment and Constructing roofing system which ensured Excellence Wales; we are undertaking a long term maintenance free • Code for Sustainable Homes organisation–wide solution and integrated well within Level 4; the scheme. • Silver Considerate Constructors in order to reduce National Award; and our carbon footprint, • Short listed by Constructing make all our homes Excellence Wales Awards (in the 2009 Innovation category and and the communities in the 2010 Integration and in which we operate Collaborative Working category). greener and more cost–effective, and make the most of the opportunities which new technologies afford.” Anne Hinchley WWHA

Case Study 10 – St Athan Affordable Housing Development References and Further Information Acknowledgements Social Housing Grant, Paul Wyatt Welsh Government Wales and West Housing www.wales.gov.uk Association BRE & CEW Award descriptions www.cewales.org.uk/cew/wp– content/uploads/St–Athan–case– study–web.pdf

These case studies are presented to show examples of how buildings can be designed and built to be low carbon and incorporate renewable and low carbon technologies. This case study is part of a Practice Guidance series of case studies supporting Renewable and Low Carbon Energy in Buildings a separate practice guidance document on low carbon buildings. For further information see 1 Introduction

Case Study 10 – St Athan Affordable Housing Development