We build our houses to be over 10 times more airtight than building regulation require, for one simple reason: it means they require several times less heating than a traditionally built home.
Why is that? Well, airtightness is the most crucial ingredient for retaining heat. Imagine building a house with well-insulated walls, but no roof. All the hot air would just waft straight out, and your heating would never keep you warm.
That’s the extreme case, but it’s the exact same principle with all houses. You can have a really well-insulated house, but if it’s not at all airtight then all the heat will just drift out as the air changes.
But don’t you need fresh air? Yes, of course. The Citu Home is built to be extremely airtight, but it also has a mechanical ventilation heat recovery system. This brings in a constant flow of fresh air and pumps out stale air. So there’s never a build-up of moisture that could cause damp. Here’s the clever part: the MVHR system transfers 90% of the heat from the warm stale air leaving the house onto the incoming cooler fresh air. That means you need many times less heating than a traditional house. In fact, when combined with its excellent levels of insulation and triple glazed windows, a Citu Home’s heating needs are up to 10 times lower than an average UK home of a similar size.
Investing in our own air testing kit
To achieve our goal of providing ultra-efficient homes that help tackle climate change at scale, we’ve invested in our own air testing kit. This is unique in the industry because no one else in the UK is building houses this efficient on this kind of scale.
This allows us to test all of our homes at different stages to ensure all are up to scratch when it comes to airtightness. And when we say up to scratch, we mean achieving some properly tough targets.
The average new build home in the UK achieves an airtightness level of about 5 air changes per hour. That means when the home is pressured to 50 pascals, 100% of the air inside changes 5 times per hour.
The Citu Home is built to achieve an airtightness of 0.6 air changes per hour, almost 9 times better than the industry standard, and 10 ten times better than UK building regulations require.
That’s not easy. So we need to make sure we can test all our properties to ensure they are performing to the high standards we set.
We’ll always have an external body conduct the final airtightness test before we hand over the plot. So you can be sure you’re Citu Home will perform as we say, and we’re not marking our own homework. But by having our own air testing equipment means we can test at every stage, so faults are never passed forward.
For example, if we only discovered that a plot wasn’t managing to achieve an airtightness of 0.6 air changes per hour once it was complete, then we’d have to take all the plaster boarding and fittings out to find what was causing the problem.
Now, because we can test before the plaster boarding starts, we can check that the airtight membrane is doing its job before adding the plasterboard.
But doesn’t the plasterboard add another layer, thus increasing the airtightness? Well yes, but to ensure every plot is up to scratch, we make sure it achieves the right level of airtightness before the plasterboard is added, not after. That means if you decide to drill lots of holes in your plasterboard to hang pictures (Using 35mm screws or smaller to ensure you don’t breach the airtight membrane) the performance of your home won’t take a dip.
Getting the right gear to realise our big idea
This new air test kit is just one part of what we need to build ultra-efficient homes that require so little heating that they can be kept warm with 100% renewable energy. We’ve invested millions in our state of the art production facility to create our timber framed panel system, and we’ve got a pipeline of over 1,000 homes to build across Yorkshire.
Everything we do at Citu is working towards one huge goal: to accelerate the transition to zero carbon cities. Because when you know climate change is real, and a threat our future, then you’ve got to step up and act. If you feel the same way, come join us.