I am thinking about cavity insulation.
As i understand it, it is forced into the cavity under pressure.
How is that done so as not to bridge the damp-proof course, both laterally and vertically?
What about the top of the wall? Surely it would pour out of the top?
Anybody have experience of this? And is it cost effective anyway?
TIA
The materials should be designed/treated to not transmit moisture.
It only spreads so far from the injection holes. IIRC ours was drilled on a grid pattern about every metre, horizontally and vertically, so the uppermost holes were just far enough from the top to fill without overflowing. They put "bottle cleaners" in the open edge of the cavity at each ventilator, to prevent escape there. BTW, if you have your electricity cupboard indoors and it is single brick, with the cupboard taking up the space of the cavity and the inner skin (as ours does), make sure that they don't drill into the cupboard from outside - they had to vac out ours after they accidentally, completely filled the cupboard!
Incidentally, the holes for ours were drilled in the mortar lines and only just caught the edge of the brick. It is so unobtrusive that we have had people knock at the door to sell us cavity wall insulation and not believe at first that we already have it.
I have no idea about cost effectiveness, as about the time we had it done, we also had the first of our three children, so we were using much more heating and hot water and re-did our central heating, so efficiency would have changed there at the same time.
Urea/formaldehyde foam insulation was injected into the cavity of this late 1950's bungalow in the 1970's when my mother owned it. In one or two places, rugby-ball sized 'balloons' of foam came up the cavity into the loft space, but nothing serious. They eventually became brittle and could be removed easily.
I was a little concerned by reports that I'd seen that U/F foam could deteriorate over the years, but recently I've had a doorway cut through an exterior wall and the insulation that was exposed is perfectly OK after 50 years, and rather more fibrous in appearance than the balloons in the loft.
I have no idea about cost-effectiveness though. It just seemed a good idea at the time, and everyone was being encouraged to do it. I guess it very much depends on the structure of your house.
Have a read of this:
I don't know if this method was on that site - don't have time to read it. My rockwool insulation seems to be ok (~1950 semi, standard brick) and I know that it's filled the walls as I see it in a couple of places in the loft and also when I drill through the wall. Came across this:
I don't think it is suitable for properties exposed to strong wind and rain.
seen lofts full of it due to wallhead cavity not blocked off
suckers
yes but rockwool is built in and is laminated to stop water ingress
That's why we didn't do it. We get strong winds and salty rain on the north coast of Scotland. There is thick insulation under the plasterboard, though.
Mould on the wallpaper but didn't plug in a dehumidifier. How daft can some people be.
If you're in a situation where damp is a risk, you can always use unglued polystyrene bead. It's easy to remove later, possible too easy. Take care that all holes are sealed.
Our cavity wall has polystyrene beads. If they ever had glue on them, it's long since become ineffective. That isn't much of a problem until you have new windows and patio doors. As soon as the old ones are removed, the stuff comes pouring out and gets everywhere, particularly on a windy day. Our double-glazing installers can vouch for that!
It's not so easy to replace, either, when the original holes in the brick mortar have long since been covered over with render and paint.
Of course it is. Ether r an impervious foam is used, in which case the water stops at the insulation, or the cavity blown full of breathable fibres. And remains somewhat porous
It as no different to having a single brick wall lined with kingspan or a layer of rockwool
That's their one downside. But in situations where there's a risk of causing damp, loose bead is the go-to option, as they're easy to remove.
It's almost trivial. Drill your holes on the inside, then you can make them vanish afterwards. Drilling outside is a bodge.
Just had the whole place decorated. Some furniture is built-in. Inside drilling strikes me as unlikely to be popular. I was hoping to hear from readers with personal experience that might be encouraging. :(
Was that with foam or bead?
Rockwool here too, done 35 years ago, and all remains fine. It certainly works.
Fibre.
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