What I learned from having external insulation fitted

One of my current projects is to try and get our 1920s terraced house an A rating for energy efficiency by the end of 2020. Some of my plans haven’t worked – underfloor insulation was thwarted by a complicated and only partially accessible crawlspace. Solar heat storage came to nothing because we don’t have the physical space to fit it in. One thing we have been able to tick off is the biggest job of them all – replacing the leaking front porch and cladding the house with external insulation.

This is an important one, because cavity walls were fairly novel when the house was built, and so it has solid brick walls. The easy option of filling a wall cavity with blown foam wasn’t available. It’s not a very big house either, so internal insulation would have sacrificed quite a lot of space. The best way to improve the heat retention of the building was always going to be the most awkward and expensive, and that’s to clad and then render the external walls.

With that now done, here are some things I’ve learned.

First, eco-builders are hard to find. I hunted high and low for a builder in our region with experience of eco-builds. I couldn’t find one. The expertise in your local construction pool will vary. In places that have deliberately encouraged high environmental standards, such as Exeter or Norwich, builders will skill up. You’ll have a bigger selection in cities of course. And part of it is that builders that are willing to travel generally want larger jobs than the front of my little house. I don’t have any complaints about the guys who did our work, but there’s no doubt that things could have been better on waste and natural materials in particular.

On that point, better materials will be available eventually. When researching home renovation, I’ve been to the Ecobuild conference and talked to companies producing insulation panels made of jute or wood, or post-harvest agricultural waste. When it comes to actually using any, it’s either not on the market yet, has to be imported from Germany, is only available to the trade or is fiendlishly expensive. With a bigger budget or a well connected builder, there might be ways around this. As it was, we fitted polystyrene with a slightly heavy heart. It’s efficient and affordable, theoretically recyclable and it will have to do. Hopefully the huge demand for retrofitting in coming years will drive investment in the alternatives.

Not everyone will do it well. One of the reasons I wanted a builder with experience of eco-homes is that there is some science to fitting insulation. I’m no expert, but I do understand the theory of creating a building envelope. The subcontractor doing the walls didn’t. At one point I came home to find they had cut off the insulation flat above the sloping roof, rather than bringing it down to the tiles. There are times when you might do it this way, but in this context it would have left a cold stripe across the middle of the house and dramatically reduced its effectiveness. The fitter insisted it was always done this way, until I walked him round the corner to see a local house where it has been done properly.

This highlights a broader problem – the building trade will be vital to the transition to a sustainable future. At the moment it is not fit for purpose, and that won’t change in the near future. One of the main reasons that I am sceptical of zero carbon targets for 2025 or 2030 is the skill level of the construction industry. Builders from Eastern Europe tell me that the British industry is 20 years behind the times. Retrofitting to zero carbon standard is specialist, and I don’t see how it would be possible to train enough people to deliver those retrofits and then carry them out in such a short time frame. The sooner we start working on this the better, and that will need regulation, upskilling and higher standards that at the moment look politically unlikely.

Finally though, the external insulation does work. We feel the difference, particularly the way the house holds its heat better through the night and isn’t as cold in the mornings. The heating has been on less, and that will bring down our carbon emissions. It’s been a job with lots of compromises, but it’s a step in the right direction of a sustainable home.