Insulating a wall

[KeenToLearn]

Hi everyone,

I use my attic as a small stuff workshop- it is boarded and the rafters are covered internally in a couple of layers of double airtec and shiplap- has been like this for 20+ years and gets nice and warm up there with a heater on and is completely dry. I want to insulate the end wall- the brickwork is not flat so am thinking celotex not suitable therefore. So should I put fibreglass insulation against wall between battens, then vapour barrier on inside face of that then plasterboard or should I be using breathable roof felt? See so many conflicting ideas....

Thanks in advance for any advice you can offer.

 

[Katomi woodsmith]

Banquet do a loft insulation that is made of plastic no nasty glass fibers
That and the vapour barrier then board it

 

[KeenToLearn]

Banquet do a loft insulation that is made of plastic no nasty glass fibers
That and the vapour barrier then board it

Yes, I didnt mean fibreglass, I meant whatever the non itch type stuff is sorry.

 

[MikeJhn]

What is on the other side of the end brick wall?

 

[Ozi]

+1 for Banquet. Although I keep it away from electrical fittings in case there is a fire risk but so much nicer to work with.

 

[ChaiLatte]

If you use mineral fibre insulation in a vertical application, you have to give some small thought to retaining it in place as it can sag. The Rockwool cavity insulation slabs are a little stiffer than the stuff that comes on a roll and can be cut generously and jammed in between studs.

If you are going to plasterboard it, the back of whatever the plasterboard screws to needs to be flat irrespective of how wonky the wall is. So just make the batten thickness at the most-projecting part of the wall equal to a celotex sheet thickness and then the celotex will work.

 

[KeenToLearn]

What is on the other side of the end brick wall?

It's the outside wall, so fresh air Mike

 

[Jameshow]

You could batten with 63mm cls then 50mm celotexinsulation.
Giving air gap against wall.
Celotex wouldn't need a vapour barrier.

 

[MikeJhn]

It's the outside wall, so fresh air Mike

Is it a cavity wall or solid brick/block, makes a difference to any recommendation to insulate the inside face.

 

[KeenToLearn]

Is it a cavity wall or solid brick/block, makes a difference to any recommendation to insulate the inside face.

Solid brick wall, 2 bricks thick

 

[pip1954]

The wall will probably get damp so air gap behind is way to go .
Would not use any fibre martial. You can make air gap by using small batterns inside you big timbers to make easy work and makes sure insulation stays of the wall ,very easy to use with celotex .

 

[KeenToLearn]

The wall will probably get damp so air gap behind is way to go .
Would not use any fibre martial. You can make air gap by using small batterns inside you big timbers to make easy work and makes sure insulation stays of the wall ,very easy to use with celotex .

Thank you. Would the air gap need to be vented? As if I did that as it is currently, it would be a sealed box with the insulation on the inside then air gap then brick wall

 

[Lard]

Batten and multifoil for me

 

[pip1954]

Ideally yes vent .

 

[RobinBHM]

As Mike says, it depends on whether there’s a cavity or not

As you’ve said there isn’t, if you insulate tight against the wall, there’s nowhere for any damp ingress to disperse.

I think if it was me I’d put up a stud wall with a gap to create a cavity, then insulate that…..you can put some spacers in so you can still fix at a few points to strengthen the studwork so if you only want to go say 63 x 38 CLS you can.

 

[trvlr]

How would one air vent the cavity created in say a room with an outside wall, or in a shed/garage with an outside wall?

And would each space between battens or studs need to vented?