Stud wall in garage & insulation

[datadiyer]

Hi all, (sorry about duplicate posts, I have reported myself)

Wonder if I could ask a couple of questions on my insulating garage project:

It's a detached garage.
I bought a load of 50mm Celotex insulation and have enough to put either 100mm in ceiling and 50mm in-between stud walls (3"x2") or vice versa. Bit of a mess in there at mo so excuse the pics.

1. Which is the best place to put the 100mm (ceiling or walls?)
2. What centers should I use between studs? (450mm to be able to wedge batts in-between?)
3. I guess I don't need a vapour barrier as the batts are foil faced?

Hope someone can answer there for me, much appreciated as always.
Datadiyer.

 

[noseall]

When you mention stud wall, is it your intention to line the walls with studs etc?

Also, how you use the garage will determine how you go about the whole design spec. Have you considered vapour barriers and moisture migration?

My guess is that the roof/ceiling abutment will be the most vulnerable. But it will be more about usage and cold spot vulnerabilities, if you intend spending large amounts of time in the garage.

I take it that is a flat roof?

 

[datadiyer]

Hi,
Sorry, should have specified more. Yes, I mean line the walls with a stud wall, it's a flat roof and I will be using it as a workshop and keeping tools in, (I'm hoping my tools won't rust once it's insulated!). I've read that as the insulation is foil based then a vapour barrier isn't required? (I will be taping up all the joints). So I won't be spending a whole lot of time in there. My thoughts are that the ceiling would be more vulnerable as you say but thought i'd check with you more knowledgeable people.
Thank's in advance,
Datadiyer.

 

[noseall]

I'd go with 50mm between studs and ceiling joists and 50mm across also. Help banish any cold bridging.

 

[datadiyer]

Thanks Noseall,

Yeah, that would be my preference also but I only have enough to cover 100mm on either ceiling or walls (the other would be 50mm). I could buy some more but as it's only a workshop I can't justify (or at least my wife won't) buying more. I think i'll go with 100mm between ceiling joists and 50mm between stud walls unless anyone can give me reason not to. Also if I tape the joins up well enough, would I need a vapour barrier? I'm not too familier with insulation techniques (as you can tell).
Thanks,
Datadiyer.

 

[datadiyer]

Ok, different but similar plan. 100mm Kingspan/celotex in ceiling joists and 50mm + these 25mm in the walls (totalling 75mm in wall):

http://www.diy.com/departments/jablite-3728502025-insulation-board-l1200mm-w450mm-t25mm/26830_BQ.prd

Anyone have any experience with these? I can only find B&Q stocking these, or does anyone know any other supplier?
Also, I wanted to centre the studded lined walls at 450mm to be able to wedge in the 1200mm x 450mm batts, will that work out ok?

Cheers,
Datadiyer.