Floor Slab Insulation - 2 x 100mm or 1 x 200mm

[SBMS]

We are looking at PIR insulation on our slab and are looking at 200mm insulation. Has anyone put this much down, and if you did, would you advise doing it as 2x 100mm boards, or a single 200mm board?

[Thorfun]

I'm no expert but there have been many threads about this subject and I believe the majority think that 2 x 100mm is better as you can stagger the joints to reduce the potential of gaps allowing cold through. Also, many have stated it's easier to cut 100mm PIR than 200mm so that's another bonus.

 

 

[JohnMo]

We put 200mm PIR in our floor.  100mm X 2 is what we did, with staggered joints.  To be frank cutting 100mm was a pain, 200mm would be a really big pain.  When cutting you want to eliminate any gaps to not let the heat escape through an easy route.

[Olf]

2x100mm : on top of what already mentioned handling of 100mm thick is manageable by 1 person, 200mm tough. Also (but this may be seasonal/regional) 200mm thick  may cost more than 2x100 due to lack of popularity, and so may come with extended leadtime.