One of our favourite rooms in our home is our little office. It’s where I do most blog related work, but the thing I love most is that it allows me to peek down the street and have a nosy at what’s going on in the world around me.
And there’s one shock horror thing that I’ve been observing with dread over the last months – everyone seems to be having cavity wall insulation pumped into their houses. There have been at least 7 houses in the last week alone!
But isn’t it a good thing to be insulating your home I hear you shouting?
Well, yes and no.
We’ve insulated every possible last bit of our home – under the floors, the loft, pipes – you name it, we’ve done it, but there are areas where insulating your home is a bad idea that can cause you severe problems in the future. Retrofit cavity wall insulation is one of these problem areas.
So, what actually is cavity wall insulation?
Retrofit cavity wall insulation is essentially an insulating material that’s injected into the gap between the outer and inner brickwork layers of your external wall. Filling the gap with an insulating material is meant to reduce the amount of energy that you will lose through your walls.
How does insulating your walls work?
The company carrying out the work (this really isn’t a DIY job) turn up with a big van. Within a matter of a few hours, they’ve drilled a load of holes into the outer layer of your brickwork and pumped millions of little polystyrene balls (they’re actually called EPS balls) into the gap between the two brickwork layers. Then they fill the holes in your wall and are off again.
This is what the little balls look like.
So why insulate everywhere else but not install cavity wall insulation?
Well, it’s simple really. By filling the gap between the two layers of brickwork you will inevitably create a bridge between the outer and inner layers and the gap is there for a reason! It creates a barrier between hot (inside your home) and cold (the outside temperature) and between the wet outside and dry inside of your home.
If water enters the gap, it’ll run down the outer layer of your brickwork and dry out (which is why airbricks are important). If you have retrofit cavity wall insulation the water should run down through the non-absorbent insulation balls and out at the bottom. That’s the idea anyway.
In reality, especially if you live somewhere as wet as we do, that may not always be possible. If it’s wet and windy, the exposure to rain may not give the cavity time to dry and therefore the moisture could transfer to the inner wall and into your home.
Also, the installers are essentially blind as to how they’re filling the gap. Yes, the do drill a lot of holes and pump in the insulating balls till the gap seems full, but it may not be completely full and you may be left with pockets in your wall where there’s no insulation!
Not only does this not help you keep in the heat, it can also cause a thermal bridge which is essentially a weak spot in the insulation that allows hot and cold air to meet. The big difference in temperature that’s created through the bridge will cause condensation and could therefore also result in damp issues.
Overall it’s something that I personally wouldn’t do – ever, but especially if (like us) you have a cavity that’s less than 5cm wide – don’t do it!
That’s of course not to say that the technology won’t change in the future, but at the moment it’s just worth the risk to us.
I would even go so far as to say that I would consider not buying a house that has retrofit cavity wall insulation. I know that this sounds extreme, especially when you consider the state our home was in when we bought it, but for us, it just comes with too many risks and is too difficult to put right.
What if I’ve already had retrofit cavity wall insulation installed?
If you’ve already had retrofit cavity wall insulation fitted, you could consider having your house surveyed with an infrared camera. It’ll allow you to see if the insulation is evenly distributed throughout the wall and at least help you determine if you have any gaps that will need filling to avoid thermal bridging problems.
We’d also recommend checking your pointing and gullys to make sure that everything is well maintained and therefore hopefully avoiding any penetrating moisture as far as possible.
If you’re already having issues with cavity wall insulation or would like advice you can check out the cavity wall insulation website.
This, of course, isn’t the case for every house with retrofit cavity wall insulation and you may never have problems, but if you do decide to have cavity wall insulation installed and start to experience condensation, damp or mould don’t say we didn’t warn you! Overall be careful and do your research!
Do you have cavity wall insulation? We’d love to know if you do and if you’re happy with it or if you’ve encountered any problems!
PS. I just came across this article in the Telegraph that covers possible issues with retrofit cavity wall insulation.