Key principles of AECB CarbonLite
CarbonLite Programme STEPS
To help promote Passivhaus design in the UK, the AECB's CarbonLite Programme has developed three STEPS to improved building energy performance – STEPS One, Two and Three. Houses built to CarbonLite standards would be extremely cost-effective to build, would require very little energy to heat and could cut energy use by between 70-95% compared to the UK average.
STEP 1: Silver
- Useful space heating energy: 40kWh/m²yr
- Primary energy consumption: 120kWh/m²yr
- CO2 emissions: 22kg/m²yr
- Reduction in primary energy compared to UK average: 70%
- Reduction in CO2 emissions compared to the UK average: 70%
STEP 2: Passivhaus
- Useful space heating energy: 15kWh/m²yr
- Primary energy consumption: 120kWh/m²yr
- CO2 emissions: 15kg/m²yr
- Reduction in primary energy compared to UK average: 80%
- Reduction in CO2 emissions compared to the UK average: 80%
STEP 3: Gold
- Useful space heating energy: 15kWh/m²yr
- Primary energy consumption: 58kWh/m²yr
- CO2 emissions: 4kg/m²yr
- Reduction in primary energy compared to UK average: 85%
- Reduction in CO2 emissions compared to the UK average: 95%
* Energy and CO2 performance achievable in a typical newbuild dwelling for each of the three CarbonLite Steps - expressed as a combination of limits on space heating energy consumption, primary energy consumption and CO2 emissions. They can also be expressed as the percentage saving in energy and CO2 relative to the same building type in the existing building stock.
Whole Building Energy Performance
CLP’s three energy targets are all expressed in kWh/m2/yr. This is because building occupants receive energy bills expressed in kWh for all their energy use and can use this measure to understand how their building is performing against real world benchmarks. The CLP Steps apply at the whole building level, including not only the energy for space and water heating but for lighting, appliances and cooking too. The reason for this is that, if we are genuinely interested in reducing CO2 emissions from buildings, we cannot ignore the 30% associated with electronic goods, where usage is growing most rapidly.
Post-occupancy monitoring
As part of its requirements, the CLP encourages designers and developers to commit to delivering two years’ worth of post-occupancy data, either from basic utility bills or through smart metering technology. Setting out on the road to ‘zero carbon’ homes will be meaningless unless we measure the energy used of the homes we build. The CLP team is developing a database of UK buildings with measured energy use enabling people can plug into an extensive range of existing buildings to see the materials and techniques used in successful examples.
Case studies
STEP 1 (Silver)
The STEP 1 Silver Standard relates to the best performance currently possible in the UK using readily available technology. It achieves very good energy and CO2 performance without the addition of renewables or other ‘bolt-on’ equipment. A number of buildings already built in the UK have already achieved performance close to the Silver Standard, including the Elizabeth Fry Building, University of East Anglia. This building achieves a measured space heating use of 25-30kWh/m2yr, a total heat demand from boilers of 24Kw (two domestic wall mounted boilers) and no mechanical cooling, serving a building of 3000m2 used by up to 850 people. To achieve this, a number of ‘passive’ design strategies were employed including: use of building structure as an energy store; mechanical ventilation and heat recovery; super-insulation of the building envelope; airtight construction; and minimized thermal bridging.
STEP 2 (Passivhaus)
CarbonLite Programme’s Passivhaus standard corresponds to the best international practice in the design of building envelopes. There are thousands of Passivhaus buildings in Germany, Austria and Switzerland, including houses, offices, blocks of flats and schools. The standard has not yet been widely applied in the UK, but a number of projects are underway, some involving Registered Social Landlords.
STEP 3 (Gold)
One building already exists in the UK which can help illustrate the CLP Gold Standard. The award-winning £1m Pines Calyx ecological conference centre in St Margaret’s Bay Kent was designed to meet the highest energy standards in Europe, with the benchmark of attaining the CarbonLite STEP 3 (Gold Standard) for energy performance. The use of rammed chalk, excavated directly from the site, has created 650mm thick walls providing thermal mass. Thermal insulation levels are high and consequently heating is only necessary at very cold times, with hot water provided by solar thermal panels. The design target for energy consumption of the Pines Calyx is 35kWh/m2yr - the lowest of any commercial building in the UK. An independent energy monitoring programme is due to commence in Spring 2008 which will be able to verify whether the building has attained CLP’s ‘Gold’ standard level of performance.
The way forward
The AECB believes the CarbonLite Programme offers the rigorous approach required for the UK to achieve genuinely low carbon buildings by 2016. According to Liz Reason, Director of CLP, “We hope CLP will influence the current debates about 'zero carbon' buildings and for its standards to be widely adopted in the UK. CLP offers a comprehensive package of training and design guidance and is working with the supply and manufacturing industries to deliver the high performance products and building elements required for CLP buildings.” Access to CLP web-based materials is free to AECB members, with AECB membership costing as little as £60 per annum. www.carbonlite.org.uk