Insulation advice.

[p4rky86]

Hi newbie here. Not sure if this is in the right area or not.

I do have some diy experience but I’m looking for some advice on insulating the roof of my house. Last year I had foam put in the loft which is shown by the red lines. Problem is the rest of the roof has no insulation as the foam didn’t get sprayed that far down. I was tempted to get them back and do the job but it was over a year ago now and it’s only after putting a socket in I have seen and felt the cold in the yellow area.

I was thinking of the following options as it is stud work and room in roof style.

Pir board cut and siliconed in place on the vertical part and the try and put some on the sloping roof part or do I go for mineral wool, but then it may fall out of the vertical part?

I am conscious to keep the air flowing as the soffits are vented.

Any opinions on what’s best? I have an 8 month old baby and want the room to be warm for him.

 

[theknobs]

I have gone with PIR board all the way down the slope on mine. You need a 50mm ventilation gap above it so put in board that is the right thickness to lie flush with the underside of the timbers, then, if you want more, lay some completely under the timbers. If you cut them fairly tidily they will wedge in without any adhesive, then use foil tape at the joins and under/round any timber to seal any tiny gaps and create a reflective surface.

 

[piglet11]

The jury is out on sprayed in foam insulation, especially directly under the tiles and felt.

A better solution though longer and more expensive, would have been rigid foam under the rafters.
Look up "warm roofs" and "sarking". If you have a traditional "cut" roof i.e. rafters and purlins put together on site as opposed to off site trussed roofs, then a warm roof is very straight forward. A trussed roof is just more of a pain in the backside.

There are huge advantages in warm roof spaces. For starters, you get a warmer drier space. Ventilation of roof timbers is not compromised.

What your room in the roof really needs is all round insulation.

You didn't mention the insulation on the ceiling of the room. Surely that would have been done when it was built.

If you safely get up into the voids, you could have a good look at what has been done.

Ventilation around the timbers is really important.

I've seen roof spaces insulated by professionals who ignored the ventilation and one householder ended up with what looked like a tropical rain forest with very wet fibreglass insulation, all condensation.