Warm deck Roof

[topman870]

Hi,

I've got a warm deck roof which which was a garage conversion 20 years ago... ever since the bedroom has always been freezing cold and I cannot seem to figure out the root cause. The outer walls all have 100min insulation cavity walls aswell as external wall insulation which is 50mm so I've ruled that out. Recently I added 30mmm insulation on the floor and laminated over it but the room is still cold and the last spot I'm thinking has to be an issue in the roof.

The roof has 100mm Kingspan and is a warm deck so has a air gap throughout.. should the plasterboards be a vapor barrier or not as they have used standard.

I don't see any mould on the ceiling or the walls throughout, room on stay warm whilst the heating is on and cools down very very quick... I can only think the heating is somehow escaping through the ceiling as height rises..


Any tips would be helpful..

Thanks

 

[DiyNutJob]

Get an infrared thermometer and point it at each room surface and see which is the coldest. If the room has a window, check for air leaks.

 

[martygturner]

An air gap ? Is the roof made up as below ? If so did they upstand the sides

 

[topman870]

So from the bottom up you see the joists then ferrerings, then 18mm plywood, then 100mm insulation, then 18mm OSB board which has EPDM rubber on it.

I can't see any vapor barrier and the plastered board is standard as in not foiled back....

 

[martygturner]

The ply looks stained but that could be the light....it does look damp though . however it does look like there is no vapour barrier, so you could have a sweaty roof and hence a cold roof,

You have two choices, Hybrid roof...not ideal or the lot up ouch. You could just add a vapour control layer under the joists as a basic fix to stop the moisture build up on the ply.

If it was me add a 50mm insulation between the joists batten backed to stop them drifting up, vapour barrier under the joists then cross board with 25mm insulation / plasterboard or just used insulated plasterboard. Make sure the soffits are insulated. I personally like the cross board with 25mm foiled insulation..you can foil tape it to add a second vapour control.

The question of ventilation is a consideration, seen quite a few mushroom domes venting supposed warm roofs, I would trickle ventilate the space personally...

 

[topman870]

Thanks for the reply.

Would it be okay to put insulation plasterboard from inside and be done with it?

Thanks

 

[catlad]

Vapour barrier won't make any difference to the temp, my guess if its leaking heat it will be around the wall cavities and fascia's. As someone as already mentioned a thermal imaging camera will be a good place to start.

 

[martygturner]

Condensing water transfers a considerable amount of heat as it forms droplets, its taken a lot of energy to get that water into vapour, and when in condesens it gives up that stored heat to the surface in condenses against. Essentially you are making the ply deck into one large heat sink.