The UK’s aspiration for zero carbon new homes from 2016 moves a step closer with the publication of recommendations on the most appropriate ‘carbon compliance’ tool, assumptions and related regulations - the parts of the carbon compliance regime that together provide the mechanism for testing designs against the zero carbon definition.
The report, ‘Carbon Compliance for Tomorrow’s New Homes’, presents the findings from a six-month review of existing compliance modelling tools and their suitability for the future. The work was carried out by a cross-industry Task Group of experts drawn together by the Zero Carbon Hub and identifies areas where development is needed to ensure the compliance tool will deliver new homes that meet low energy / zero carbon design expectations, and achieve comfortable living standards in a warming world.
With this early identification of challenges that face the compliance process, and by indicating the areas for immediate attention, the Zero Carbon Hub is aiming to ensure that timely decisions can be made by Government with the support of the wider house building sector.
The report recognises that although the current compliance tool (SAP) was developed to assess the efficiency of a ‘typical’ house, the space heating demand predictions for low energy homes were still broadly consistent with the range of models tested.
Areas identified for further development included treatment of overheating, the calculation of hot water use and the role that an assessment regime plays in reducing any gap between design and as built performance.
David Adams, Task Group Chair and Director of the Zero Carbon Hub said:
“With low energy homes we are moving into a world where space heating no longer dominates the regulated energy use and other demands, such as hot water and potentially cooling, become more significant. Furthermore, the implications of a warming climate and decarbonisation of energy will increasingly influence technology choices. Any difference between the design and actual performance would become increasingly apparent. These changes require a fresh look at the carbon compliance regime.
“The wider house building industry needs a clear picture of the future to engender the confidence to invest the necessary time and money to prepare itself for the introduction of low energy / zero carbon homes from 2016. This report identifies a series of important and very timely recommendations to address these issues.”
Michael Black, Group Development Director of Bovis Homes said:
“The launch of this important and informative report is the result of positive collaboration between industry, the scientific and academic sectors and government departments. It considers and proposes the basis upon which carbon compliance should be expressed and measured, and the assumptions necessary to define the tool industry should use to design and demonstrate carbon compliance.
“This report I believe is a critical examination of issues that must be considered and will be useful in assisting government in its deliberation on the definition of zero carbon homes for the future.”
Dr David Strong, Chief Executive of Inbuilt Ltd said:
"The methodology used to check that new homes are genuinely low or zero carbon must be capable of not only discriminating between design options, but also ensure that there are no serious unintended consequences, such as overheating in the summer, or unhealthy indoor air quality."
The report concludes with a proposed timetable for implementation of these recommendations, which have critical links with the significant changes required in 2013 as well as the delivery of the fully operational compliance process, linked to Building Regulations Part L at 2016.
The Overview report ‘Carbon Compliance for Tomorrow’s New Homes’ is available to download at the Zero Carbon Hub website.
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Notes to Editors
1) Funding of this review
The independent review was jointly funded by: Communities and Local Government (CLG), Department of Energy and Climate Change (DECC) and the Zero Carbon Hub. NHBC Foundation sponsored the dissemination phase of this work, including the preparation of this report series.
2) Supporting technical reports
The review is made up of seven reports. As well as the Overview report published today, five individual technical reports (listed below and shortly to be published by the Zero Carbon Hub) have been prepared by specialist Topic Work Groups. The seventh report gives details of the modelling undertaken to support the work of the Task Group and Topic Work Groups.
Topic 1 – Carbon compliance tools considerations – key characteristics of the different modelling tools currently available.
Topic 2 – Carbon intensity of fuels – implications and responses to changing carbon intensity of fuels.
Topic 3 – Future climate change – affects on energy demand by changes in local and national climates.
Topic 4 – Closing the gap between design and built performance – how the tool could accommodate and reduce any performance gap.
Topic 5 – How the performance standard should be expressed – what terminology could be used to express carbon compliance.
3) Key Recommendations include:
- Provided an improved simplified test for overheating can be developed, we recommend that SAP, updated as recommended in the report, should continue to be used as the carbon compliance tool for new homes.
- An appropriate funding mechanism should be found and guaranteed to maintain and develop the compliance tool, consistent with the timetable for taking forward the other recommendations in the report.
- Regulation should require overheating to be migrated using passive or active means. Or, as an alternative, if an overheating risk is identified the compliance tool should assume that active cooling will be used, even if it is not provided. In both cases it should be included within carbon compliance and the primary energy limit.
- An absolute limit should be set for predicted carbon emissions per square metre of floor space in new dwellings (kgCO2/m2/yr), with different limits for different types of dwellings.
- Emission factors for the carbon compliance regime should include upstream emissions and carbon equivalents for other greenhouse gases including emissions from refrigerant leakage from cooling systems using HFCs.
- Emission factors used for carbon compliance should be based on the combined marginal approach. This should be implemented as a 15-year rolling average and updated annually for information. Factors for 3-year periods up to 15 years ahead should be published (from year 7 onwards in the form of a range). The 3 –year factors should be subject to review at 3-year intervals, but at each updating should be revised within the previously published range.
- A primary energy limit should be introduced. The metric should be reported by the compliance tool significantly in advance of it being introduced as a limiting regulation.
- The carbon compliance regime for zero carbon should incorporate confidence factors (for design, systems, build and post construction testing), scaled so as to provide an incentive for industry to improve its processes and to participate in an accredited scheme.
- Whole house post-construction fabric and services audit tests should be developed and implemented on a sample basis as part of accreditation.
- As a matter of some urgency, research should be undertaken to compare the carbon and energy performance of a national sample of newly completed dwellings with their design performance. The findings should be widely published and mechanisms put in place to gather performance data on a continuing routing basis.
- The compliance tool should model, more closely than SAP currently does, the factors affecting hot water demand, including system losses.
- The carbon compliance tool should incorporate appropriate tests for air quality and daylighting. The daylighting factor should be output for information, and consideration given to including in regulations later
- There should be a structured continuing programme of monitoring, starting immediately, to test and refine the compliance tool, including a full review of assumptions.
4) Related work
This report builds on the work of a previous Zero Carbon Hub Task Group which developed the Minimum Energy Efficiency Standard for zero carbon homes. The recommendations and implications of this report will be used to support the development and review of the 70% Carbon Compliance level and the Allowable Solutions when this work is undertaken.