Ask an Architect: What is the Code for Sustainable Homes?

Friday, September 19, 2014

Richard from Richmond asks, “I’m considering a self build and I’m trying to familiarise myself with building regulations. I’ve discovered my borough uses the Code for Sustainable Homes. Just getting to grips with basic regs had been hard enough – can you clear up CFSH for me?”

The Code for Sustainable Homes sits separately from the building regulations as a national standard for sustainable design in new domestic builds. While it is technically voluntary, many local authorities have integrated CFSH into their planning approval process, with levels 3 and above commonly required.

Why have councils decided to add another layer on top of already complex building regulations? The standard regs may seem exhaustive, but they’re only focused on the quality of the structure itself, while CFSH tackles a broader range of issues critical to modern development. CFSH is measured across nine criteria:

Energy/CO2, water, materials, surface water runoff, waste, pollution, health and well-being, management, ecology.

Each of the nine categories has a certain number of potential credits, the total of which are added for your final score from level 1 to 6.

Generally, the categories can be mixed and matched to achieve the desired level but sometimes high performance will be required in a specific category depending on the site. For example, water runoff will be crucial in a flood zone, while ecology and pollution will be heavily scrutinised in a rural environment.

Beyond what may be required by your local authority, a high CFSH level is also a valuable tool in swaying a contentious planning application. For example, building on a greenfield site is less likely to face opposition if you present a design that is sustainable, efficient and has minimal ecological impact – which is exactly what levels 4 and above display.

For us, CFSH is a challenging puzzle. With the help of expert consultants we need to develop tailor made solutions to hit the required CFSH level by taking advantage of the opportunities of the site and working around the restrictions, all without compromising our client’s vision or bursting their budget.

The first step is to score points from low hanging fruit. Designing a home with future flexibility, installing security systems, cycle and waste storage are all relatively easy to achieve. There can be some surprisingly simple ways of gaining credits. In a recent build, we pushed ourselves over the required level by installing a cheap rainwater harvesting tank on the garden shed.

Following that, we detail the building fabric. Heavily insulating the walls, roofs and floors; using top quality building products such as elegant, efficient and cost effective windows, doors and rooflights; exhaustively detailing the design to avoid cold spots and thermal leakage. The more efficient the building fabric is, the less we have to offset with expensive renewable energy sources.

It may surprise you to learn that installing renewable energy sources won’t always save you money – even in the long run. Solar panels and ground source heat pumps will reduce energy usage of the property, but the initial capital expenditure and running costs can add up to more than they save you.

The current costs of renewable energy sources are not set in stone and advances in technology may change their viability. While you may not want to install them now, we can design a home that can easily have renewable added at a later date.

Regardless of whether or not they cut your costs, some form of renewable energy source needs to be installed in order to pass CFSH level 4 or above. Which type depends on the restrictions of the site: a ground source heat pump won’t fit in a dense, urban environment while a structure without south facing surfaces won’t benefit from solar panels.

Finally, we tackle the categories that apply during  and after construction, such as site management and ecology. This involves sharing our construction plan, details on our trusted contractors and using expert ecologists to prove that the build will have minimal impact on surrounding life, whether human or wild.

Of course, all our meticulous planning would be for nothing without high quality, trusted contractors. If corners are cut in construction you may be left with a build riddled with air leakage problems and a poorly managed site, undoing all the hard work on the drawing board and leaving you with potentially crippling penalties.

All of this may make you see CFSH as a burden rather than a benefit, but such standards ensure that Britain’s new builds are high quality and will stand the test of time. Achieving a high CFSH requires expertise at every stage, and is a seal of quality for current owners, future buyers and the local authority to feel confident in the value of the home.

CFSH also removes a great deal of risk, as inexperienced architects and corner-cutting contractors simply won’t be able to achieve the required levels. When you’re considering starting your project, ask whoever you’re bringing on board for their experience in building to the Code for Sustainable Homes.

If you have any questions of your own, send them to [email protected] with the title “Ask an Architect” and they could be featured right here in our blog.

By Michael Gwynn