External and Internal Insulation?

Daith

Hi all,

I've got external insulation wrapping around the house which has made a big improvement. The house is north/south facing and I was going to repair/replace the interior north facing plasterboards in three room. I was thinking of using insulation boards, as they really don't get much sunlight or warmth in.

Would there be an issue with having some internal insulation, it would just be one side of each room as well as external insulation. There is an air vent already, so it should be supplied with fresh air.

But I'm probably missing something.

Thanks

MicktheMan

But I'm probably missing something.

So your external walls are finished to the inside with plasterboard and I doubt the block work at the back of the pb is rendered. If so then you likely have a heat loss issue due to air leakage through your wall block work because un-rendered block work is porous to air. This heat loss can be significant and should be understood / addressed first rather than blindly adding more insulation.

If you are removing the pb, then make sure to render the block work (normal sand/cement render is good) and apply air tight tape to the wall to floor junction as well as around the window reveals to the window frames. This will likely make a big difference to the heat loss and also have the added benefit of increasing your thermal mass.

If you're not sure about this, you could opt to have a heat loss survey done first which, amongst other things, will test for air tightness, pinpoint where the issue are and offer various options to address.

Daith

That sounds exactly like the issue with the plasterboard and walls. It does sound like getting these walls rendered would be the best option.

Because I'm not a DIY person at all, is this a standard job that a plasterer would do?

Thanks for the detailed response btw. It's really helpful

MicktheMan

Because I'm not a DIY person at all, is this a standard job that a plasterer would do?

The plastering, yes; the taping, no so would need to find someone to do this. It's not very difficult to do once he/she knows what they are doing and why they are doing it.

Daith

Thanks, very useful. Appreciate it

hesker

Just in case it wasn’t clear I’m pretty sure Mick was saying to apply plaster to the blockwork not to fit plasterboard and then plaster that.

And to your original question, no point in using insulated plasterboard.

Daith

Thanks all. Appreciate the advice.