Photo: Marieke McBean
Self builders are an adventurous, determined bunch, so it’s no surprise that they’ve long been at the vanguard when it comes to adopting green measures into their homes.
Building a new house gives you the perfect opportunity to not only put your own stamp onto the place you live, but also to insulate yourself against spiralling energy bills. In doing so, you’ll enjoy a comfortable, tailor-made home with low running costs. So what’s involved in building a sustainable eco home?
What the regulations say
As the government gears up towards hitting its carbon emission targets, so Building Regulations are becoming ever more stringent in the drive to make the UK’s housing stock more efficient.
Approved Document L (conservation of fuel and power) of the regulations sets out the minimum standards all new housing has to hit. It was last updated in 2010, when the requirements were broadly brought in line with Level 3 of the Code for Sustainable Homes (CSH).
The CSH is a set of criteria against which a building’s eco credentials can be measured. The CSH is measured on a scale of 1 to 6, with 6 indicating the highest performance.
Level 3 basically equates to a 25% improvement on energy efficiency in comparison to the standards laid out in the 2006 iteration of the Building Regulations. The key measure of this is U-values, which indicate how much heat is lost through the main elements of the house (such as walls, roofs, floors, windows and doors).
The Building Regulations are set to be updated again in 2013, at which point they’re expected to move in line with Level 4 of the CSH – a 44% improvement on the 2006 standards.
Depending on where you’re self building, you may already be subject to stricter requirements than those defined in the Building Regulations. For example, some local authorities already require you to hit Level 4 of the CSH, and will set this as a condition of your planning approval.
The Building Regulations will continue to be ramped up over the coming years, with a so-called ‘zero carbon’ target set for 2016. The result would be a fundamentally efficient house that produces no more carbon in use than is saved through the offsetting – though only in terms of the areas covered by Building Regulations, such as heating, ventilation, hot water, fixed lighting and building services.
A ‘fabric first’ approach is the best approach to creating an eco home. That means prioritising elements such as insulation and air tightness in order to deliver a structure that won’t leak heat.
Once you have a suitably efficient building fabric in place, you can begin to look renewable energy sources, such as heat pumps and solar technology. There’s no point in specifying these systems in a house that’s not up to standard as you won’t be able to maximise their potential (you may even end up paying more to run them than you would for conventional alternatives).
So what are key areas to focus on when planning an eco home?
Insulation Put simply, the more insulation you can incorporate into the major structural elements of your home (such as the walls, roof and floor), the more heat it will retain and the more efficient it will be in use.
Air tightness Fewer gaps in your home’s structural envelope mean less heat lost to the outside world. Prefabricated systems, such as closed panel timber frame and structural insulated panels, tend to offer good air tightness off the shelf. With others, such as brick and block, high-quality workmanship on site is essential.
Thermal mass Materials such as brick and concrete can absorb warmth from the sun’s rays during the day and release it into the home as external temperatures drop – helping to maintain a comfortable internal environment. Used correctly, this thermal store can help to reduce energy consumption.
Natural light Maximising the amount of natural light in your home – through good use of windows, rooflights, sun pipes, etc – will help to reduce your need for artificial lighting. However, glazing is much less insulating than conventional walling, so your house designer will need to strike the right balance.
Materials There are various ways to ensure the products and materials you use are as green as possible. One option is to source locally, for example, while another is to consider natural products, such as sheep’s wool insulation. If you’re buying wood, always look for proof that it’s been sustainably sourced, for instance through FSC or PEFC certification.
All construction systems can be adapted to meet good levels of energy efficiency, but some lend themselves more immediately to hitting the highest standards.
Closed panel timber frame and structural insulated panels (SIPs) are two popular options, offering a straightforward route to a well-insulated, highly airtight structure. That’s largely thanks to their large degree of prefabrication, which minimises the potential for human error on site. Find out more about timber frame.
One of the advantages of SIPs is that the system involves a continuous layer of insulation, with no breaks for studwork. That makes for extremely low levels of thermal bridging (where internal warmth can find a path to escape to the exterior). Find out more about SIPs.
If you’re looking for a masonry solution, insulating concrete formwork could be worth a try. This involves using expanded or extruded polystyrene blocks as the formwork for a structural concrete pour. This formwork stays in place after the build, providing a continuous layer of high-quality insulation. Find out more about ICF.
That’s not to rule out an old favourite, brick and block. Masonry walls can now be built with ultra-wide cavities to accept plenty of insulation, and they offer the benefit of plenty of thermal mass. Find out more about brick and block.
A variety of other systems have been developed with energy efficiency and sustainability in mind. These include modern methods, such as externally-insulated solid walls, as well as traditional or natural options, such as straw bale building - which was the technique behind the Grahams' hands-on homebuilding project pictured above.
Eco-minded self builders and renovators have led the way in terms of adopted renewable technologies, and their efforts could help you pick the right options for your home.
Among the most popular technologies are solar photovoltaic panels, solar thermal panels, biomass boilers and stoves, and ground-source or air-source heat pumps. Other options include rainwater harvesting systems and boilers that generate electricity as a by-product of their heating cycles.
Find out more about renewable energy sources