An eco retrofit has many positives, which include prolonging the life of existing building stock and reducing carbon usage. So, rather than build from scratch, we’ve chosen to retrofit our existing home.
However, one big disadvantage is that new builds are exempt from VAT — whereas, perversely, retrofit is rated for full VAT. Another, if you’re already living in the house, is disruption.
Getting your thermal and airtightness strategies right while minimising the amount of disruption you’re willing to bear – without having to vacate the house for the duration of the build – is difficult to say the least.
We started with a ‘minimal disruption’ strategy — adding an external airtight and thermal layer would allow us to stay put during the works. It would also mean we could make our mark on the appearance of the existing building, as well helping us to unify any extensions.
However, the party wall kept throwing up risks for this strategy that I couldn’t overcome without intrusive investigations. We’re architecturally one of a pair and drastic changes to our house made our adjoining neighbours understandably nervous.
So we’ve ended up with a ‘maximum-disruption-do-everything-internally’ retrofit approach. We do have to be more conscious of moisture risks with internal insulation, and we have a few more thermal bridges with internal walls breaking the insulation line.
For the extensions we are putting wood fibre insulation boards on the outside of the timber frame to minimise condensation risk; the construction becomes more vapour open towards the outside. The structural board that stiffens the frame is then on the inside and is vapour and air-tight; doubling its function.
Paul and his family have had to move out of their home while works commence
I’m also using some materials that we haven’t tried before and this will be our first EnerPHit project (the Passivhaus standard designed for retrofit projects).
This isn’t about financial investment; it’s highly unlikely we’ll get close to recouping our capital investment in the short-term, but our house will be futureproofed and won’t need further measures down the line.
Most crucially, though, it also means we have to move out for the duration of the works. We could stay but the works would be slower and, ultimately, much more expensive.