PIR Strips - 1200mm x 600mm

[NandM]

I'm hoping to have our roof built next week, using 600mm centers and was looking at blown-in cellulose or mineral wool - but budget is getting tight!

 

I was having a look on seconds & co and so this size of boards which in theory should just slot into place. Does anyone have experience with these pre-cut strips? (I'm looking at a saving of just under 2K)

[garrymartin]

I've no experience of the boards, but if you have 600 mm centres in your roof, then the gap to be filled will be less than 600mm and you'll have to cut a small amount from the width of every board.

[JohnMo]

2 hours ago, NandM said:

looking at blown-in cellulose or mineral wool -

Then for the same u value use a decent high density mineral wool batts. 

[NandM]

1 hour ago, garrymartin said:

I've no experience of the boards, but if you have 600 mm centres in your roof, then the gap to be filled will be less than 600mm and you'll have to cut a small amount from the width of every board.

 

Yeah, I have a bad feeling about that. The information available is scarce, with some mention of them being made for 600mm centres - but then pictures show then boards as being 600mm wide! 

 

I'll see if anyone local has them...but even then, I wont know if seconds will have something different.

[NandM]

30 minutes ago, JohnMo said:

Then for the same u value use a decent high density mineral wool batts. 

My bad, I meant bats - currently looking at Nyrock 32 and have a decent quote from SIG that is almost £2K cheaper than a cellulose quote I've had!

 

So the pir I mentioned is 1.5K cheaper than the bats, and they in turn are almost £2k cheaper than cellulose (waiting on other quotes). 

[JohnMo]

Have you priced up Frametherm 32?

[saveasteading]

10 hours ago, NandM said:

the pir I mentioned is 1.5K cheaper than the bats, and they in turn are almost £2k cheaper than cellulose

So keep looking. It's truet that the pir market is very competitive. But so should be bats.

I got a better price fir PIR from the local than from online, incl from "seconds". And it meant I could order for no waste and get more if necessary.

 

The trouble with pir is that your  roof will not be standard cc.  600cc +/- 2? Deduct 45mm width +/- 1. Then allow for twists in the timber.

Builders end up cutting small and putting squirty foam in.

 

A pragmatic solution for 150mm fill is 50mm pir, with some gaps, then 100mm mineral wool bats, which push in tight.

[NandM]

9 hours ago, JohnMo said:

Have you priced up Frametherm 32?

I think I will do now. I focused of Nyrock as it comes in 150mm, so two layers would nice fill the 300mm rafters. 

[NandM]

54 minutes ago, saveasteading said:

A pragmatic solution for 150mm fill is 50mm pir, with some gaps, then 100mm mineral wool bats, which push in tight.

 

That's a good point and something that I thought about yesterday. If I go for a mix then I can gain some decrement delay/noise insulation benefits.

[saveasteading]

The pir is horrible to squeeze in when 100 or thicker. Very much easier at 50mm.