Garage insulation?

[blanko]

A quick Google came up with this https://www.boards.ie/b/thread/2057334577

Is it ok before you cover it up.

With that type of non breathable membrane it may be best to have a vented gap between the insulation and the membrane. 50mm is often recommended, but 25mm minimum should be ok. But this relies on having continuous ventilation along the eaves and ridge.

Otherwise, again you could full fill the roof with insulation tight up to the membrane - and in this case no gaps anywhere are even more important. The concept is to stop any moisture getting into the roof via damp air, and condensing on the cold membrane.

In both cases tap all joints and across the rafters.

Good find, thanks! I googled the full "minitex 20 P" and that didn't come up...

Air gap then, or it will end up like that! That's why I'm asking so many questions, insulation is so confusing! Even builders I had out to quote for it said different things, that's why I'm looking to do it myself now... so celotex between the rafters with a 50mm air gap and taping required.

The roof is sound, I've lived here four years and the garage was built in the late 90's and apart from a guttering issue, everything is fine.

 

[blanko]

Fireproof wall and ceiling linings, i.e. plasterboard, have obvious advantages in a garage, and may be required by building regs.

I want to hang a lot of things from the walls, hence the OSB. It won't be habiited, just a workshop

 

[cjard]

Moisture is produced everywhere

What activities are you envisaging in this guy's garage, that will generate a problematic amount of moisture?

 

[Johnpaul Manning]

If you are going to stud out the wall your best to use either a high density fiberglass like knauf frametherm as it is breathable or if you want to use Celotex GA4075 or Celotex GA4050 you will need to leave at least a 25mm air space between the wall and the celotex insulation as it could sweat over time. This air gap should run from the floor right up to the underside of the rafters. You will also need to ensure you have ventilation coming in from the soffit or via vent tiles as this will enable a cycle of fresh air.

After that slab away and your fine. No need to over complicate the job.

 

[blanko]

If you are going to stud out the wall your best to use either a high density fiberglass like knauf frametherm as it is breathable or if you want to use Celotex GA4075 or Celotex GA4050 you will need to leave at least a 25mm air space between the wall and the celotex insulation as it could sweat over time. This air gap should run from the floor right up to the underside of the rafters. You will also need to ensure you have ventilation coming in from the soffit or via vent tiles as this will enable a cycle of fresh air.

After that slab away and your fine. No need to over complicate the job.

Ok thanks a lot for the info.