The Code for Sustainable Homes is a sustainability assessment tool for new built housing. It considers a number of topics in nine different categories. Of these categories the one on energy use can be considered as the most important category: it accounts for more than 35% of the total score. Scoring well in the energy section is therefore essential to gain a good Code for Sustainable Homes rating. In this article I review the credit requirements and discuss how feasible it is to meet each these.
The Code for Sustainable Homes is a sustainability assessment tool for new built housing. The tool is developed by the UK government and is used to set minimum sustainability standards in government sponsored residential development. In addition to this many local planning authorities are using this tool to set benchmarks for private and commercial residential development projects as well.
The Code for Sustainable Homes considers a number of topics in nine different categories. Of these categories the one on energy use can be considered as the most important category: it accounts for more than 35% of the total score. Scoring well in the energy section is therefore essential to gain a good Code for Sustainable Homes rating. In this article I review the credit requirements and discuss how feasible it is to meet each these.
Dwelling emissions rate
The first issue in the energy category regards the energy performance of the building. This is considered in relation to the national building regulations. The national building regulations set minimum requirements for the energy efficiency of a building in terms of carbon dioxide emissions.
The dwelling emissions rate issue is the biggest contributor to a good score in the energy category. A total of 27 credits are available in the energy section and there are a maxi,mum of 15 credits available in the first issue. The minimum improvement over the building regulations that is awarded with one credit is a 10% improvement. The maximum of 15 credits is available for what is referred to as a "Zero Carbon Home". In addition to reduce the regulated carbon emissions from the building with 100% over the requirements in the building regulations a number of additional requirements are put on a building to qualify for the title Zero Carbon Home. This includes a minimum standard for the Heat Loss Parameter and a requirement to prevent carbon emissions from energy used for appliances in the building. Clearly the higher reductions of carbon emissions can only be achieved when using energy generated though the use of low or zero carbon technologies. Issue 7 of the energy categories deals with low and zero carbon technologies and I will discuss this in further detail in that section.
Aside from the way energy is generated,
the energy performance of the building envelope is by far the largest contributor to the energy efficiency of a building and the focus should therefore be directed to improving the energy performance of the building envelope. Improving the building performance is achieved through the use of materials that reduce the heat loss of a building. This means that materials with a large insulating value should be employed for the construction of roofs, walls and exposed floors. In addition windows that achieve a rating of the British Fenestration Rating Council in band C or better and glazed doors with U-values better than 1.5 should be used. Efficient boilers for space heating and hot water should be specified. Studies by the Carbon Trust and the Energy Saving Trust have demonstrated that a 25% reduction in the carbon emissions can readily be achieved using high specification materials that improve the energy performance of the building envelope.
A 25% improvement of the carbon emissions is awarded with 5 credits. This improvement is also a minimum requirement to achieve a total Code for Sustainable Homes rating of level 3. It is possible to achieve better than the score outlined here. For instance homes that are build to the "PassivHause" will score significantly better.
Building fabric
The Code for Sustainable Homes also awards credits for the energy performance of the building envelope directly in the second issue of the energy category. There are two credits available. When the strategy as discussed in the previous section is followed at least one of these credits and in many case both credits will be achieved.
Internal lighting
Two credits are available encouraging the use of energy efficient internal lighting. When 75% of the fixed internal fittings are dedicated energy efficient fittings both credits will be awarded. Clearly this is a simple and straightforward way to improve the CSH score.
Drying space
The fourth issue in the energy category requires the provision of an internal drying space for laundry. One credit can be awarded when there is 4 or 6 meter of drying line available. Again this is a relatively simple and low cost measure to implement.
Energy labelled white goods
Two credits are available when energy efficient white goods are installed. The energy efficiency of the appliances is taken from the EU Energy Efficiency Labelling Scheme. To qualify for the two credits the following minimum standards apply:
- Fridges and freezers or fridge-freezers A+
- Washing machines and dishwashers A
- Washer-dryers or tumble dryers B or information about the scheme when not provided
There is of course a slightly higher cost associated with better performing white goods. This would only be in the order of a few hundred pounds. Otherwise these credits are straightforward to achieve.
External lighting
Two credits are available when external space lighting and security lighting are designed for energy efficiency. Again it is relatively easy to achieve these credits at low cost.
Low or zero carbon technologies
Under issue 7 in the energy category, the Code for Sustainable Homes awards up to two credits when low or zero carbon technologies are implemented in the scheme. Because implementing these technologies will also have a significant effect on the carbon emissions of the building as described under the first issue (ENE 1), the actual gain in credits will be higher. In many cases another 2 credits will be awarded through the improvement in issue ENE 1.
To be eligible for the credits a study into the feasibility of the various technologies needs to be carried in or before RIBA stage C. In addition the low or zero carbon technologies need to contribute to a carbon emission reduction of at least 10% for one credit and 15% for two credits.
When a building design includes a high energy performance of the building envelope a significant source of the energy demand of a house lies with the need for domestic hot water. Providing a solar thermal system is a relatively cost effective way to provide about 50% of the energy required for hot water. This often accounts for a carbon reduction of more than 10% in energy efficient houses. Further improvements can be made using other technologies. It depends on the nature and the location of the project what technologies would be best suited to achieve these further reduction in carbon emissions. It is worthwhile to mention that in the UK photovoltaic cells to generate electricity will likely become much more cost effective from April 2010. From that date the new system of Feed-In-Tariffs will go live. The UK government will set minimum rates that electricity companies will pay for energy generated from small-scale installations. It is proposed that electricity generated with photovoltaic cells will receive up to 36p per kWh.
Cycle storage
There are two credits available when sufficient and dedicated space to store cycles is provided. This credit is relatively easy to achieve in detached and semi-detached houses, although more challenging when considering terraced housing or flats.
Home office
The Code for Sustainable Homes awards one credit when dedicated space is made available for the use as a home office. Although in principal this is a relatively easy and low cost credit to achieve, there is one element that requires careful consideration. The room that is chosen to be adapted to allow its use as a home office is required to have a day-lighting factor of at least 1.5%. Whilst this is not an overly onerous requirement to meet, not all rooms will necessarily meet this criterion in all new homes.
Conclusions
Focusing on the energy performance of the building envelope is an important element in a strategy for a good score within the energy category of the Code for Sustainable Homes tool. It will provide good credits in its own right, but also makes it easier to achieve the credits associated with the provision of low and zero carbon technologies. Combining these two topics should enable a project to achieve eight to ten credits. In addition to these credits, the remaining issues are usually straightforward and cost effective to implement. This would achieve another eight to ten credits. Achieving more than 70% of the available credits in the energy category is therefore feasible without having to resort to advanced methodologies for most residential development proposals.
