Sustainable Buildings: Raise high the green roof beams

Constructing homes sustainably, i.e using materials, technologies and practices that have the minimum possible impact on the earth’s resources, is an exponential growth industry. From what was perceived as a minority ‘fringe’ world only a decade ago (how we laughed at Prince Charles’ green assertions in the 1990s – who’s laughing now?) it’s now mainstream, and worth billions to the global economy. But what does constructing homes sustainably actually mean?

In short, it’s perceived as lots of different things to a great many people with different convictions, agendas and interests. To some it’s all about preserving natural resources e.g. if you chop down one tree for lumber, then the sustainable thing to do is to plant another. For others that doesn’t go far enough. The tree should only be used locally because to transport it has a high ‘embodied energy’ cost i.e. it uses an abundance of fossil fuels – oil (petrol), gas etc to get it to its destination.

At the heart of this argument is the belief in the science of climate change i.e. that through the release of green house gases (CO2 and methane being the primary two, which is primarily brought about through the burning of fossil fuels: coal, oil and gas) the planet is heating up to a level beyond which humanity, fauna and flora cannot survive. En route to the apocalypse, sea levels will rise, drowning cities, famine will ensue, and civil conflict will break out. Some predictions argue that this will occur if the planet’s temperature rises 4 degrees above the current level.

Ok, so how do our homes impact on the domesday scenario? Well, almost 50 per cent of CO2 emissions are attributed to the built environment – residential and commercial buildings. In the UK the residential sector accounts for 27 per cent of CO2 emissions. This

is affected by a combination of newly built dwellings – including the embodied energy of e.g. making the brick that the house is constructed from and the energy required to get it to site e.g. on lorry – and the emissions from our existing homes.

Because 99% of our electricity and heat generation domestically in the UK is from fossil fuel based sources, our homes have a huge carbon footprint. The average household in the

UK emits 6 tonnes of CO2 annually; in the US it’s higher than 10 tonnes. We can reduce or CO2 emissions through a combination of using less electricity and gas, and by generating the fuel we need to light, power and heat our homes from renewable energy sources e.g. the sun, wind and water, which are carbon neutral and emit little or no CO2 when they are used to create electricity and heat.

So, in essence, that’s why building our new homes – there is a huge housing shortage of quality housing in the UK as well as elsewhere in the world – needs to be undertaken sustainably. It also explains why we need to what’s called ‘retrofit’ our existing homes: to make them more energy efficient which means beginning with air-tightness – in the UK the majority of heat (and CO2) is lost through un- or poorly insulated roofs and walls (in hot countries where there is an over-reliance on energy hungry air-con the homes need to be better built to remain cooler naturally).

Increasingly, new homes (spearheaded by those built by the members of Sustain Worldwide, a membership organisation of global sustainable developers) are being built sustainably. Such homes are significantly powered and heated from renewable energy e.g. solar PV and solar thermal panels, or ground source heat – all of which have a heavily reduced carbon footprint over conventionally heated and powered homes. Many of the homes are built using locally sourced building materials e.g. timber from a local forest that is sustainably managed.

These homes are also being built with an awareness to conserve water e.g. through the installation of aerated shower heads and taps; some have inbuilt grey water systems which once cleaned recycle tap and bath water to be used in the toilet and washing machine. Waste reduction measures are implemented – both to minimise building waste during construction – but also provisions are made to sort, reuse and recycle, where possible, once people are living in the homes.

Reduce, Reuse, recycle is not a bad motto to build solid foundations upon.

This article was contributed by Gordon Miller, sustainability and communications director of Sustain Worldwide. +44 (0)20 7754 5557 http://www.sustainworldwide.com/