The Citu Home and the Climate Innovation District that it will be part of have been designed from the outset to massively reduce CO2 emissions, both during construction and over its life time.
The Citu Home is built from timber, which stores carbon, rather than bricks, concrete or steel, which require huge amounts of carbon to produce. This means every time a Citu Home is built instead of a typical new build masonry house, it saves 50 tonnes of CO2 on average.
That’s a lot of CO2, but it is just the start. The envelope of the Citu Home is extremely well insulated, so the walls, floors, roofs and windows transmit far less heat than they would in a typical new build house. In addition, we build our houses to be ten times more air tight than typical new build houses. Since most heat in homes escapes due to airflow, this massively reduces heating requirements.
Homes still need a constant flow of fresh air of course, so the Citu Home usage a mechanical ventilation heat recovery system to bring take warm moist air out of the property and bring in a flow of fresh air. The clever bit is that it transfers over 90% of heat from the exiting stale air to the incoming cooler fresh air, meaning you get a constant flow of fresh air but the heat stays within the home.
All these features mean that the Citu home has heating requirements over ten times lower than typical UK homes of a similar size, and around five times less than a typical new build home. This means the average Citu home prevents the emission of around well over 2.3 tonne of CO2 every year due to its lower heating requirements, because an average new build house emits 2.3 tonnes of CO2 from burning gas for heating each year.
But it’s not just the design of the house that makes it low carbon- it’s the design of the place as well. By sharing all solar power generated across the Climate Innovation District from the site’s solar panels, and by setting up a community energy company that will buy renewable energy in bulk to generate savings for residents, the small heating needs of the Citu home can be supplied via renewable energy.
All Citu developments are also designed to encourage low carbon transport options – particularly walking and cycling. Because we only build on brownfield sites in or near city centres, our residents can easily commute on bike or on foot rather than in polluting cars. We’re also providing electric car charging as standard in the Climate Innovation District, so for those who do still need a car can easily switch to an all-electric vehicle. Because of this, we’re predicting that two thirds of our residents will switch from communing via car to using lower carbon transport options such as walking, cycling, public transport or an electric car. We’ve assumed that people will continue to use cars for other activities, so this will reduce the emissions the average households emits due to road travel by 25%. We hope it will be even higher than this, but a 25% reduction in CO2 emissions from cars owned residents is a great start.
Using this as a fairly conservative scenario for how big an impact moving to a Citu home will have on a household’s carbon emissions, we can make projections about how much CO2 will be saved by the Climate Innovation District and if the Citu model was adopted more widely.
We estimate that the Climate Innovation District, including both phases, will prevent the emission of over 55,000 tonnes of CO2 by 2050, compared to building the same number of homes in same way as most UK housebuilders do. You don’t need me to tell you that is a lot of CO2!
But what if all the new houses in the UK were built on the Citu model, rather than the current industry standard? We calculated that if all 300,000 homes that the government wants to be built every year were built to our standards it would prevent the emission of 551 billion tonnes of CO2 by 2050 Vs building the same number of homes in the traditional way.
That’s more than half a trillion tonnes, and hard to get your head around. But it is four times the CO2 emissions of Leeds City region over the same period, so building all new homes in the UK on the Citu model would be the equivalent of making four UK cities the size of Leeds completely zero carbon.
So there you have it, to save half a trillion tonnes of CO2 by 2050 you just need to get the housebuilders to stop building the old-fashioned way and start building to the low carbon standards that we need to meet to be in with a chance of avoiding dangerous levels of climate change. Changing the whole industry won't be easy, but you can do your bit to force them to make the change by choosing sustainably designed homes over old-fashioned ones.