Data analysis shows that the nine criteria of the Code, as tabled in Chapter Two, Table 2.7, have varying degrees of impact on the design of Smith Lane, summarised by participants at the second Workshop at Appendix 4.1. The architect’s Code for Sustainable Homes checklist for Smith Lane (included at Appendix 4.2), noting Code 4 as ‘difficult’ (compared to Code 3 as ‘easy’ and Code 5 as ‘expensive’) is used to summarise the impact of the Code on the design of Smith Lane and relevant extracts related to Code 4 are listed in Table 4.1, showing the additional credits that need to be generated above those required for Code 3. These are considered below on the basis that the optimal generation of credits is needed to achieve a minimum calculated total of 68 points for Code 4 for Smith Lane within the dual constraints of a social housing grant regime and the contractor’s financial model.
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Table 4.1 Extract from the architect’s checklist of Code 4 credits
Ref. Element Code 3
credits
Additional credits for Code 4 Ene 1 DER over TER – 44% improvement 5 +3
Ene 2 Building fabric (HLP14) 1 1
Ene 7 Low carbon technologies - 1
Mat 2 Key building elements - 3
Mat 3 Finishing elements - 1
Hea 1 Daylighting 1 1
Eco 1 Improvement of ecological value 2 2
Elements which have generated innovation within the design process are discussed in detail in Section 4.12 and noted as such within the text that follows. Otherwise, detail from the analysis is included below.
4.2.1 Ene 1 - DER over TER - 44% improvement
The aim of Ene 1 is to limit CO2 emissions from the ‘operation of a dwelling and its services’ (DCLG, 200a:21). Ene 1 measures the percentage improvement in the CO2 Dwelling Emission Rate15 (DER) and Code 4 requires a mandatory 44% minimum improvement over Target Emission Rate (TER) as determined by 2006 Building Regulations, for which 8 credits are available, rising to 13 for an 89% reduction (DCLG, 2008c:40). The architect and contractor spent some time working through a range of possible options to meet the 44% target and these are discussed in Sections 4.12.1 and 4.12.2.
4.2.2 Ene 2 - Building fabric
The aim of Ene 2 is to limit the heat loss of the building envelope, promoting the efficient design of homes and the increase of levels of insulation and airtightness. A maximum of 2 credits are given for the Heat Loss Parameter measure, calculated from the external surface area,
14 HLP – Heat Loss Parameters 15 DER – ‘the estimated CO
2 emissions in kg per m 2
arising from energy use for heating, hot water and lighting for the actual dwelling’ (DCLG, 2008a:21).
114 construction insulation value and airtightness. A key part of the Smith Lane project was the negotiation between the architect and the contractor to generate a building envelope solution that would achieve an appropriate HLP measure for 1 credit. This process is identified as innovative and is discussed in detail in Section 4.12.1.
4.2.3 Ene 7 - Low carbon technologies
This element relates to the local generation of energy by, for example, photovoltaic panels and ground source heat pumps for individual homes. Credits are awarded for the resulting potential percentage reduction in CO2 emissions (1 credit for a 10% reduction, 2 credits for a 15% reduction). Again, the use of low carbon technologies as a contribution to the reduction of CO2 emissions in the design of the Smith Lane homes is identified as innovative and discussed in Section 4.12.2.
4.2.4 Synthesis of Ene 1, Ene 2 and Ene 7.
These three elements generate a possible 5 credits, representing half of the additional credits needed above Code 3 to achieve Code 4 with a minimum calculated 68 points. Although noted separately above, they also operate in conjunction with each other to achieve the mandatory minimum 44% CO2 reduction target for Ene 1 to achieve a Code 4 certification. The design of Smith Lane’s homes, by the architect and the contractor within the client’s Design Guide and the HCA’s requirements includes all three elements as a complex product and reflects a complex innovation process.
4.2.5 Mat 2 - Key building elements
Mat 2 encourages the specification of responsibly sourced building materials and credits are awarded, up to a maximum of 6, where 80% of assessed materials are responsibly sourced, using ‘auditable third party
115 certification schemes’ (DCLG, 2008a: 36) for the eight key building elements16.
The impact of this element of the Code on the design of Smith Lane is limited, analysis showing that the architect preferred traditional rather than timber frame construction to achieve Mat 2 credits, with materials specified from the BRE Green Guide to Specification (2002). This choice was not assessed as innovative because the guide was in current use.
More generally, the contractor noted the impact of the ‘chain of custody’ for, for example, timber needing sustainability accreditation from a company who ‘can monopolise a bit on the Code’ and charge a premium which pushes up build costs.
4.2.6 Mat 3 - Finishing elements
Mat 3 is similar to Mat 2 for finishing elements17, up to a maximum of 3 credits. Analysis for this Code element for Smith Lane showed that its impact for the design team was minimal, with the exception of the contractor, as the only member of the team whose role included the sourcing of finishing elements, noting the amount of time spent in defining a chain of custody for, for example, minor finishing elements such as a washing line as part of the Code accreditation process.
‘...you can lose weeks trying to get things sorted, on top of our normal job – can you send me a specification of the washing line...you can get really bogged down in the details’ (Contractor).
16 Eight key elements – frame, ground floor, upper floors, roof, external walls, internal
walls, foundation / substructure, staircase (DCLG, 2008a).
17 Eight finishing elements – stairs, windows, external and internal doors, skirting,
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4.2.7 Hea 1 - Daylighting
The aim of Hea 1 is to reduce the need for energy to light the home thereby improving ‘quality of life ... through good daylighting’. Additionally, good daylighting and ‘solar gain’ works with thermal efficiency (Ene 2) to provide heat during winter. Credits are given up to a maximum of 3 when all main rooms (excluding bedrooms, corridors, bathroom and WC) achieve a minimum average daylight factor and a percentage of the ‘working plane’ for these rooms receives direct light from the sky (DCLG, 2008a: 49).
For the contractor’s standard house design, there is a tension between the generation of credits to achieve the daylighting standards for Hea 1 and the ‘housebuilders not putting enough windows in’, expressed as the preference of purchasers for smaller windows.
‘People don’t want big windows, they just want enough light and to be able to see out, but to get the daylighting credit a percentage of light has to hit the middle of the room’ (Contractor).
The architect notes a saving of 5 to 10% on heating costs with larger windows. However, for north-facing windows where there is minimal solar gain, windows need to be bigger to meet Hea 1:
‘...in the Code, there are minimum lighting levels for rooms that face north and that’s a conflict, it’s a nonsense ‘(Architect).
Thus a three-way tension is expressed between the daylighting credits, the additional cost of larger windows and solar gain compromise for north- facing windows. Additionally, the HCA, in specifying a minimum Code 3 for housing developments in receipt of NAHP funding, requires windows that are large enough to meet Code 3’s Hea 1 standards within their Housing Quality Indices (HQIs). Although this element is not mandatory, it generates an additional credit for Code 4, where others may have been
117 even more problematic. The resolution of this tension was not noted as innovative for the research analysis.
4.2.8 Eco 1 - Improvement of ecological value
Although listed by the architect as Eco 1 (defined as ‘Ecological site value’ and aimed at encouraging development on land with an inherently limited value to wildlife, using a range of criteria and generating a maximum of 1 credit) it is possible that this element is Eco 2 ‘Ecological enhancement’ which aims to enhance the ecological value of the site with the advice of a ’suitably qualified ecologist’ (DCLG, 2008a: 61) for a maximum 1 credit.
For Smith Lane, the impact of this element is the early contractual involvement of an ecologist to support this single credit, noted by the contractor as ‘easy’. The architect’s layout at Appendix 4.3 includes the planting locations of 195 trees and shrubs (and further layouts show tree and shrub species and their 4 alternative tree-staking details). Appendix 4.3 also shows the location of 4 log piles, 8 bat and 8 bird boxes in house gables and 2 reptile refuges (marked at XX B B and R respectively).
4.2.9 The impact of the Code on the design of Smith Lane
The impact of the Code as the generation of additional credits to achieve Code 4, as summarised by the architect, addressed the detail of those Code criteria that were noted by case study participants and did not specifically involve an innovative response and referred to analysis for Research Question Two for those that provoked an innovative solution.
The following sections extend the analysis and discuss the general impact of designing to meet Code 4 across the sector evidenced by case study data at organisation and sector levels.
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