What's the carbon footprint of ... building a house
New homes require far less energy to run than older properties, but building them generates plenty of CO2
• New houses such as these ones in south Derbyshire take lots of energy and resources to produce. Photograph: Rui Vieira/PA
The carbon footprint of a house:
80 tonnes CO2e: A newbuild two-bed cottage
The carbon footprint of building a house depends on all kinds of things – including, of course, the size of the house and the types of materials chosen.
The estimate of 80 tonnes given above is for the construction of a brand-new cottage with two bedrooms upstairs and two reception rooms and a kitchen downstairs. It's based on a study that I was involved in for Historic Scotland. The study looked at the climate change implications of various options for a traditional cottage in Dumfries: leave it as it is, refurbish, or knock it down and build a new one to various different building codes. We looked at the climate change impact over a 100-year period, taking into account the embodied emissions in the construction and maintenance as well as the energy used and generated by those living in the building.
Unsurprisingly, the worst option by far was to do nothing and leave the old house leaking energy like a sieve. Knocking down and starting again worked out at about 80 tonnes CO2e whether the house was built to 2008 Scottish building regulations or to the much more stringent and expensive Code for Sustainable Homes Level 5 that demanded 'carbon neutrality'.
Here's how that total broke down for the carbon-neutral option:
Eighty tonnes is a lot – equivalent to five brand-new family cars, about six years of living for the average Brit or 24 economy-class trips to Hong Kong from London. But a house may last for a century or more, so the annual carbon cost is much less – and for all the new-build options, the up-front emissions from construction work were paid back by savings from better energy efficiency in 15–20 years.
However, the winning option was to refurbish the old house, because the carbon investment of doing this was just eight tonnes CO2e, and even the highest-specification newbuild could not catch up this advantage over the 100-year period. Once cost was taken into account, refurbishment became dramatically the most practical and attractive option, too.
If this one study is representative, the message for the construction industry is clear. Investment in the very highest levels of energy-efficiency for new homes is, even at its best, an extremely costly way of saving carbon. Investing in improvements to existing homes is dramatically more cost-effective.
• This article draws on text from How Bad Are Bananas? The Carbon Footprint of Everything by Mike Berners-Lee
