Our building legislation contains many sustainability standards to be met. But for many self-builders these are merely the starting point rather than the finish line.
Passive House advocates, for instance, argue that the sole focus on carbon emissions, rather than energy use, is a fatal flaw in how we approach the idea of a more sustainable home. John Stapleton, head of external affairs at Sustainable Homes, a not-for-profit consultancy, identifies the self-build community as critical innovators in sustainable house construction:
“Innovation is key to the sector and it’s always good to mix things up. Sustainability is about much more than energy efficiency, and the self-build element in itself could be a sustainability aspect.”
So, what steps can you take if you are looking for the ultimate, eco-friendly self-build?
The production process involved in cement is extremely carbon intensive: search as hard as you like and you will not find any truly environmentally sustainable cement products.
Timber, however, is extremely environmentally friendly, as long as the wood is sustainably sourced. As a form of biomass, as long as the trees are replanted and managed sustainably, there should be very little net carbon emissions as a result.
2. Heat Recovery
According to The Renewable Energy Hub, a mechanical ventilation and heat recovery system (MVHR) in a domestic property can save up to 50 per cent on energy bills, although this will vary significantly depending on the building itself.
Best suited to a house designed to be a highly insulated and airtight home, MVHR works by extracting stale air and replacing it with filtered fresh air. Heat is extracted from the stale air and this is used to warm the incoming filtered air, thus keeping the air fresh and the internal temperature comfortable and stable.
The most efficient MVHR units, such as Zehnder’s ComfoAir Q range, can recover up to 96 per cent of the heat from extracted air that would have otherwise been exhausted to the atmosphere.
Less heat is wasted meaning less heat is required: but it’s not just heating costs that benefit. MVHR also extract toxins, excess moisture and harmful compounds from the air, offering clean fresh air of the highest quality.
At the heart of Passive House designs is insulation. These buildings require very little, if any, heating, as a result.
There are some excellent environmentally responsible products, such as sheep wool that can be used for your roof and wall insulation. The u-values you can achieve with this are comparable to those given by the carbon-intensive production of rigid board insulation or fibreglass.
When you are designing your property from scratch, it’s so much easier to incorporate a lot more solar capacity than a standard house. This larger solar input, combined with air-tight, insulated construction, can be used to run an efficient electric heating system, like an air pump or heat pump.
Heat pumps offer much lower running costs than traditional heating systems. They also run on electricity and, if powered using green electricity (such as solar PV), can be 100 per cent renewable.
If your home is well insulated, they are the most obvious heating solution: their relatively low installation costs are currently heavily government subsidised by the domestic Renewable Heat Incentive Ofgem scheme (RHI).
Ground source heat pumps are even more efficient than air-based pumps, due to the stable ground temperature used as their heat source. Their installation costs, however, are higher, but they do also attract equally generous grants.
If you have the space on the plot of land you have purchased, biomass is an increasingly attractive eco-source of heat. It’s a bit pricey to install, but, with funds available again from the RHI, most systems will have covered the installation costs within seven years.
Solar thermal is the most sustainable way to heat your hot water, and you can also benefit from the RHI to fund this.
5. Rainwater harvesting
While the cost-savings on heat can be massive, water is a cheap utility here in the UK.
Yet, costs to the environment remain high, thanks to the carbon emissions and energy used to produce and supply it.
It is simple to incorporate a rainwater harvesting system into your self-build, as long as it is planned in at the early stages. This can be used to flush your toilets, do your washing, water your garden and clean your car.
The sustainable self-build
The sustainable self-build is an investment in your wealth, in your family’s health and in the future. There is a misconception that Passive House is an expensive option when it comes to self-build, but according to Passivhaus Trust, the UK’s Passive House organisation, Passive House builds can be achieved on a range of budgets and bring a 90 per cent reduction in the energy needed for heating requirements, which equals savings from year one.
From the initial outlay, sustainable self-build is money well spent.