Hi everybody I have a single storey extension on my house with a solid brick wall that has been dot and dabbed internally with regular plasterboard. The room is cold in comparison to the rest of the house and I wondered if there was any reason why I shouldn’t drill a hole in the plasterboard and insulate between the brick and plasterboard using expanding foam? Grateful for any advice.
It would likely be a patchy process at best, add very little insulation value, and would also risk bowing out the plasterboard if excessive foam were squirted in. Other than that, fill yer boots If you are certain that it's the wall that's to blame for the coldness, then it might be worth biting the whatsit and going 'grrrrrr'; hack off that board and D&D some insulated p'board on in its place. Or, if you don't mind a slight extra loss of internal space - an extra inch - then just D&D right over the existing boards - much less work. Even the thinnest TLB will give huge gains. I have a room with a single skin block wall and the thinnest TLB - 35mm thick. It's well cost and easy to heat.
Always the risk of popping off the board. As the wall is solid I would have gone for a stud wall/bearer on wall, would then allow you get insulation in, plus use insulated plasterboard. Other causes possible for coldness.
Is the room damp? Damp air is much more difficult to heat than dry air, the dampness may be due to penetration from outside as the insulation backed boards are not so good at moisture penetration resistance as they have no real vapour barrier. Bring in a de humidifier for a couple of weeks and see how much water you pull out.
Bob, all the insulation backed I have used has had a foil vapour barrier. Certainly the siniat GTEC thermal PIR I have used recently has, and advertises that fact https://www.siniat.co.uk/en/products-and-systems/products/internal-boards/gtec-thermal-pir