Garage conversion insulation how to attach to walls

[Ivor Windybottom]

Hmmm. Not sure, lots of this stuff is theoretical risk

A warm roof has timbers in free air, not encapsulated in foil-backed plastic insulation.

 

[robinbanks]

The timber will be colder than the room

No

 

[Ivor Windybottom]

Yes

Sorry forgot caps lock. YES.

I win. Unless you can explain how the laws of physics don't apply in this situation.

 

[noseall]

A warm roof has timbers in free air, not encapsulated in foil-backed plastic insulation.

It matters not. The critical factor is that the timbers are separated from the externals with a robust continuous layer of insulation - thus deeming them room temp'.

 

[Ivor Windybottom]

You seem to think that celotex somehow knows it is insulation, and the wood knows that it isn't.

The reality is that there's a gradient of temperature between the interior of the room and the outside world. The wood insulates - less than celotex, but it still insulates, so its edge facing the outside world will be colder than its inner edge. Not as cold as the outside world, as there's celotex beyond it, but definitely colder than the room. So there's potential for moist warm air from the interior reaching the back edge of the porous wood, condensing and collecting there.

It needs a barrier between the room and the colder wood.

 

[freddiemercurystwin]

Is this thread going round in circles, I'm not really keeping up with it but for the avoidance of any doubt you should always fit a vapour barrier (that is an impermeable membrane) immediately behind the plasterboard be that foil backed plasterboard or an independent membrane if non foil backed plasterboard is used.

 

[Ivor Windybottom]

Agreed. I'd add a third option, which is to foil tape over the timber, forming a continuous seal across it between the sheets of celotex.

Once everything's silver, put the plasterboard up. Screw through the tape into the timber.

 

[robinbanks]

Is this thread going round in circles

Just Ivor going round the same nonsense assertion that a piece of timber inside a room at 20 degrees will somehow magically endothermically maintain a temperature of 14 degrees and have condensation form at its core unless a bit is sticky tape is attached to it

I've stopped taking an interest