Should you compress glasswool insulation?

[wonderwire]

I have 160mm joists in my loft floor.

It appears you can't buy 160mm depth glasswool insulation. So should I insulate with 150mm glasswool and have a gap, or 170mm glasswool and compress it slightly?

I've read compressing can reduce insulation's performance, but would it be below that of the 150mm option?

Which is the most efficient option? Pricing appears to be the same for each.

Thanks

 

[JohnD]

use 150mm

the cumulative improvement of another 10mm is imperceptible

the 170mm rolls are shorter

 

[wonderwire]

Thanks @JohnD, do you also know if compression of 10mm affects the thermal efficiency?

 

[JohnD]

10mm will probably also be imperceptible.

Generally, compressing insulation brings no benefits, and brings the risk of making the ceiling bulge.

 

[^woody^]

150mm of quit is not 150mm deep. It will fill 160mm

 

[datarebal]

compress and efficiency is reduced