Ecohouse: 'Sustainable Construction' codes explained

Date:

Saturday 17th April 2010

Show House, the UK's best read trade magazine for housebuilders, has launched its first ever eco supplement, Ecohouse, to help more housebuilders in their attempts to build more green-friendly zero carbon new homes, with a raft of outstanding sustainable construction solutions now competing in the market. John Cave explains each level of the zero carbon Code for Sustainable Homes, facing new home developers today.

Sustainable Homes

Legislation on ‘Sustainable Construction' has only just begun and is not going to stop anytime soon. For those new home builders looking to secure future business, an understanding of the requirements and demands of the CfSH, and energy efficient/low carbon building in a wider context, is crucial.

Many new home developers working in the social housing sector are now very comfortable with Code Level (CL) 3 buildings as they have been mandatory for some time and those housebuilders who have been reading the recent consultation documents on Part L Building Regulations will have noticed they are moving to line up with many of the requirements of CL3.

By 2012, social housing will have moved on to CL 4 and the target of 2016 for CL 6 is still firmly in the political sights. There has been much debate on whether the new homes sector will be able to effect wholesale change in such a short time, but even if the target slips by a few years and the CfSH changes some of its requirements, the new homes sector as a whole still has to change dramatically.

Code Level 3
The ‘simple' headlines for compliance are:

• 25% reduction of building CO2 emissions relating to energy in the home over 2006 Building Regulations.

• Internal potable water use restricted to 105 litres per person per day.
There are other mandatory requirements for all code levels relating to materials, water run-off and site waste.

The key construction aspect that new home developers need to remember with most code levels is the performance of the building envelope and CL3 is no different.

An understanding of air tightness, which is largely reliant on attention to detail on site, will help ensure the operational energy use is reduced.

There are also a number of products that have been developed to address some of the more difficult areas of airtightness.

The code works on a points system, with many areas where new home builders can ‘pick up' points. For a CL3 house new home developers need to comply with the minimum standards, the headline requirements and achieve 46.7 points in total.10.3 points are awarded as a base level for the headline points of CO2 reduction and water usage.

The points come from a massive range of areas including:
• Providing cycle storage and drying space
• Energy Efficient Lighting
• Providing a home office
• Reducing water run-off
• Use of environmentally friendly materials
• Ecology reports

New home developers need to work with a qualified Code assessor to ensure the points are correctly allocated and to sign off the completed project.

Code Level 4
The headline requirements for CL4 are:

• 44% CO2 reduction of building CO2 emissions relating to energy in the home over 2006 Building Regulations.

• Internal potable water use restricted to 105 litres per person per day.
The same mandatory requirements in materials, water run-off and site waste are required.

The 44% reduction target really starts to challenge the way that new home developers are used to building. As mentioned under CL3, air tightness is crucial to ensure that the energy that is produced stays in the home. Over 60% of the energy produced in buildings in the UK goes straight through the walls.

There is a lot of confusion over air tightness in the UK. Air tightness is a separate issue to ventilation. All new homes need to be ventilated, but our walls are not designed to carry out that function. Another separate issue is breathability, which is all to do with moisture and not air.

Insulation is also an important factor, which the new homes sector is getting to grips with.
The CO2 reduction calculations are derived by using a tool called SAP. Standard Assessment Procedure involves the assessor working out a Target Energy Rating (TER) for the new home. The next step in the SAP report process sees the assessor calculate the Dwelling Emission Rate (DER). If this is equal to or less than the TER, then the SAP rating shows a pass and the SAP calculations are complete.

For a CL4 house new home developers need to comply with the minimum standards, the headline requirements and achieve 54.1 points in total. In CL4 13.9 points are awarded as a base level for the headline points of CO2 reduction and water usage.

Code Level 5
The headline requirements for CL5 are:

• 100% CO2 reduction of building CO2 emissions relating to energy in the home over 2006 Building Regulations.

• Internal potable water use restricted to 80 litres per person per day.
The first question is usually - what does 100% reduction actually mean? The key to this is the Building Regulations. Building Regs cover emissions relating to heating, hot water, ventilation and lighting. Other energy uses in the home such as appliances are not part of this calculation.
In effect this 100% increase means emissions in these areas should be zero. This can only be achieved by the use of renewable technology.

Renewable technology could fill a number of articles and the Government has now introduced the feed-in tariff to make these technologies more attractive. Whether they are the real answer to the energy problems in the UK is also the subject of much debate.

For a CL5 house new home developers need to comply with the minimum standards, the headline requirements and achieve 60.1 points in total. In CL5 23.9 points are awarded as a base level for the headline points of CO2 reduction and water usage.

Code Level 6
The headline requirements for CL6 are:

• Zero Carbon Home

• Internal potable water use restricted to 80 litres per person per day
This is the standard which the government wants to achieve by 2016. The definition of Zero Carbon has also been a subject of much debate and the government launched a consultation last year to resolve this.

A zero carbon home is one whose net carbon dioxide emissions, taking account of emissions associated with all energy use in the home, is equal to zero or negative across the year. The definition of ‘energy use' will cover both energy uses currently regulated by the Building Regulations and other energy used in the home.

There is still much debate on how this can be truly achieved by new home developers, but again the use of renewable technologies is the only way of compliance.

For a CL6 house you need to comply with the minimum standards, the headline requirements and achieve 64.9 points in total. In CL6 25.1 points are awarded as a base level for the headline points of CO2 reduction and water usage.

There is a long way to go, and the mechanism for getting there will undoubtedly evolve, but there is no question that the age of sustainable new homes construction has begun.

John Cave is sustainable materials manager for EH Smith, one of the UK's largest independent distributors of building materials. www.sustainablebuildingmaterials.co.uk