Internal insulation

[321purple]

We need to get an wall in our living room insulated. The rest of the walls are have filled cavities, but this wall in solid brick and gets very cold and damp.

We don't want to lose too much space in the room, but don't want to spend a fortune on superthin insulation, while also having the room well insulated. How can we achieve this balance?

Is it better to get separate insulation and plasterboard or is insulated plasterboard good?

Work will be carried out by a tradeperson.

 

[John D v2.0]

I assume you've discounted external insulation for whatever reason?

Thinnest reasonable solution would be dot and dab insulated plasterboard (kingspan or whatever) then skim the lot. Don't go for too thick as you can get condensation through the joints to the wall, which could rot any timber in the area. You'd also have to have a solution for any sockets currently on that wall. Personally I'd (re)move them to another wall if it's easy enough to do without.

If you want to go for super insulation e.g. 100+mm celotex, you'd want to put in a better vapour barrier, so you're looking at something like insulation, then VCL with taped joins, then 25mm battens, fix through the lot into the wall, and then screw your plasterboard to the battens. Or something similar. But then you have thermal bridging to deal with at the internal walls.

 

[321purple]

Got a quote for external a few years ago and it was nearly £5k. we've since had the wall insulated inside when we redid the kitchen, but had more room to play with there.

What thickness of insulated plasterboard would be best? Does that stick straight to the wall? Does is need a vapour barrier?

Thanks for the response and sorry for more questions!

 

[John D v2.0]

For insulated plasterboard the skim is the vapour control layer. And the best thickness is probably about 50mm, too thick and you lose space and have condensation risk. Even 20mm is a massive gain in thermal terms!

There are handy condensation risk calculators and u value calculators online if you need them.

 

[321purple]

That's nice and thin. I was thinking it'd need to be 100mm. Glad that it doesn't!