Speed is of the essence in the move towards zero carbon
Grant Shapps, minister for housing and local government, recently reaffirmed the government’s commitment to zero carbon homes by helping to define what zero carbon might look like. Now it’s time to start developing consultation documents for the changes to Part L in 2013 and 2016.
Previous approaches to defining zero carbon took carbon emissions from household appliances into consideration. But Shapps now accepts that the use of appliances, such as computers or televisions, is not influenced by the design or structure of the home and is therefore beyond the control of the architect.
He said: ‘Asking architects and housebuilders to put in place measures to reduce the emissions from appliances is unfair; we have decided therefore that the regulatory threshold for zero carbon should be set to cover only those emissions which are within the scope of the Building Regulations, such as those from heating, ventilation, hot water, fixed lighting and building services.’
He also said that the government would look again at the right level for carbon reductions on the site of the home itself, known as carbon compliance. The Zero Carbon Hub has led a review of evidence gathered from within the industry as well as from green groups and other experts, which the government intends to use in setting the maximum level of onsite carbon dioxide emissions. This will provide a starting point for a consultation on revisions to current Building Regulations, now just over two years away.
A more important issue is the ever-increasing performance gap between zero carbon theory and what is delivered in practice by housebuilders. To this end, Shapps said that he is looking to move towards an approach based on ‘real world’ carbon savings, rather than a modelled reduction in emissions. This is a bold step forward that will encourage innovation in order to deliver new and
better technologies and construction methods. This approach is likely to be based on the Zero Carbon Hub report (Carbon Compliance: Setting an Appropriate Limit for Zero Carbon New Homes – Findings and Recommendations, February 2011) which includes a number of detailed recommendations on technical matters that could be incorporated into the 2013 and 2016 revisions to the Building Regulations. It can be found at www.zerocarbonhub.org.
The report accepted that heat generation, for both room and water heating, is the most significant use of regulated energy in the home. Various technologies are available to provide low and zero carbon (LZC) heat. However, as we approach the requirements of the 2016 zero carbon homes regulations, it becomes increasingly difficult to comply simply through LZC heat generation. LZC electricity generation may also be needed, for which there is a smaller range of options.
In practice, the mainstream technology currently available for a variety of individual dwellings and locations is photovoltaic (PV) panels. Other options, such as wind turbines and CHP, are only appropriate in some situations and their use should not therefore be the basis for setting a national regulatory limit. The report indicated that a requirement for roof-mounted solar technologies equivalent to 40 per cent of the ground floor area would be the likely starting point for future regulation.
The Zero Carbon Hub also noted that at least one gas and one electric heating option should be available. For houses, it recommended these be individual rather than shared or communal systems. For apartments, options shared within the block should also be considered. The favoured electric option is an air-source heat pump because it is more efficient than instantaneous electric heating and more widely deployable than a ground-source heat pump. In the case of gas heating, the recommended choices are gas condensing boilers for houses and gas condensing combi boilers for apartments.
These technologies are not cheap. A semi-detached dwelling without access to a gas supply for heating, using an air-source heat pump and PV, would bear the net additional cost penalty of zero carbon, beyond what is required by 2010 Regulations (assuming an electric panel heater), which would be £10,300 at 2010 prices.
Alternative technologies using very low carbon fuels such as biomass may also be an option at the levels being considered. However, biomass is a finite resource for which there are competing demands, making its availability and price uncertain and therefore unlikely to be relied upon as the basis for 2013 or 2016 models.
The report highlights the need for change within the house building industry so that it achieves the required regulatory standards, and the necessity to ensure that built performance matches designed performance. This will have an impact on every aspect of the house building process including planning, design, modelling tools, construction and energy products, construction skills and quality assurance. The challenge is likely to be greatest for smaller architects and housebuilders. For this reason, the government needs to make prompt decisions that drive innovation and give industry sufficient time to respond.
Geoff Wilkinson is managing director of WilkinsonConstruction Consultants who are Approved Inspectors