Compressing fibreglass insulation

[Lex Foutish]

I've heard that compressing fibreglass insulation reduces its insulating properties. Is this true? If so, any idea why?

 

[eamonn123456]

Yes definitely.

Because its the trapped air that acts as insulation as well, so if you compress it you have effectively a much thinner layer of insulation.

 

[theengineer]

I agree, you should not compress

 

[Lex Foutish]

Thanks eamonn and engineer - for the explanation and the advice.

 

[eamonn123456]

I had my attic insulated recently with 300mm blown rockwool ie well above the joists, and one of the guys doing it told me if I wanted to put boards down to just throw them on top, the rockwool would compress nicely

I told him that I didn't think that was a great idea!

Just shows that even the 'experts' can be quite ignorant of the product they are selling.

House lovely and warm now with the nice thick insulation layer, and I won't be compressing it!

 

[Lex Foutish]

I had my attic insulated recently with 300mm blown rockwool ie well above the joists, and one of the guys doing it told me if I wanted to put boards down to just throw them on top, the rockwool would compress nicely

I told him that I didn't think that was a great idea!

Just shows that even the 'experts' can be quite ignorant of the product they are selling.

House lovely and warm now with the nice thick insulation layer, and I won't be compressing it!

Thanks Eamonn. Sounds toasty! I went looking at fibreglass insulation today and the best I could find was 200 mm. Do you know if a thicker one is available and if any of the big DIY stores or builders suppliers sell it?

 

[sas]

Thanks Eamonn. Sounds toasty! I went looking at fibreglass insulation today and the best I could find was 200 mm. Do you know if a thicker one is available and if any of the big DIY stores or builders suppliers sell it?

I don't know if it comes in rolls thicker than 200mm but you're better off laying it in 2 layers anyway. 1 layer running with the rafters, 1 layer across the rafters.

 

[Lex Foutish]

I don't know if it comes in rolls thicker than 200mm but you're better off laying it in 2 layers anyway. 1 layer running with the rafters, 1 layer across the rafters.

Good idea sas. Thanks.