Insulating wall with Celotex

Lewis_Gerolemou

I want to insulate the bedroom walls of my oast. They are feather edged boards outside with fibreglass insulation between the studs and plasterboard inside. I intend to temporarily glue the celotex to the wall and then fix the plasterboard through the celotex onto the studs. I am unsure as to whether or not I should in fact fit battens first so as to create an air gap. I am aware that condensation can be a problem. Any advice would be appreciated. Thanks

designermatt_2

I dont have a clue what an oast is but assuming it is just any other house type building. The air gap that Celotex or anyone else would recommend is to take advantage of the low emmisivity foil layer. Essentially when the foil layer on the Celotex is adjacent to an unvented air gap of 25mm or more, it helps to retain the heat and will do so more than without the air gap. If you are placing the Celotex straight over the studs or ontop of battens on top of the studs or existing plasterboard, Celotex will advise taping all joints. This will provide you with a vapour barrier and stop any moisture passing into the construction thus stopping any interstitial condensation. If the water vapour can not get out it will condense on the next coldest surface.. usually your windows. The way to avoid the build up of humidity is to ventilate! If you have night vents or back ground vents, use them. If not you could provide an air vent or grill through your wall. Your whole construction might not be that 'tight' and you have enough air leakage anyway so you may find you don't need to do this. Occasionally an air gap would be advised in something like a garage conversion, and this would help with penetrating damp through a single skin wall, in addition to the low emmisivity values of the foil face but not really interstitial condensation.

Essentially, you may get condensation inside the room, if you do, ventilate, and insulate the next coldest element. Condensation occurs when the humid air condenses against a cold surface, essentially lowering the air temperature in that location lower than the dew point of the air at that humidity. Stop breathing, or insulate and ventilate. These are the only real solutions for condensation.

Lewis_Gerolemou

Thanks Matt, an oast is an oast house. A farm building used for drying/storing hops. From what you say I do not need to use battens. I'm having the windows replaced, I will make sure they have night vents.