Loft Floor Insulation Foil backed PIR

[tvrulesme]

I need to replace some old glass mineral wool insulation in my loft. I have very reduced head height (approx 1.2m) and being a listed building I am not allowed to insulate between the rafters. 

 

I have a load of left over foil backed PIR which I was going to stick on eBay. Is there any reason not to use it between the joists on the floor? All searches seem to show PIR between the rafters and rockwool on the floor but I can't find anything which says this would be a bad idea.

 

The loft is very well ventilated and I'll make sure I don't cover any soffit vents etc.  

 

 

[Conor]

You'll get condensation on the face of the boards unless you have a vapour control barrier underneath. Last thing you want in an old building.

[JohnMo]

Sell your left over PIR then go to B&Q or Wickes and buy the right stuff.

[tvrulesme]

46 minutes ago, Conor said:

You'll get condensation on the face of the boards unless you have a vapour control barrier underneath. Last thing you want in an old building.

Thanks Conor. Right you are, hands and knees over the itchy stuff it is. 

[JohnMo]

If don't mind spending a little more b&q do a recycled plastic bottle insulation - not itchy 

[tvrulesme]

55 minutes ago, JohnMo said:

If don't mind spending a little more b&q do a recycled plastic bottle insulation - not itchy 

Thanks @JohnMo yes I did see that in my local B&Q the other day. Impressive product, I'm sure if you give it a few years there'll be more and more of this. 

 

I just can't justify the £10 m2 in comparrison to £2.77 m2 for Knauf Space. I've a whole load of chipboard in the garage so I think I can probably add some boards to crawl on and still come in cheaper

Edited August 20, 2023 by tvrulesme

[TonyT]

I use a site hoover while doing insulation in the loft. Collects air borne particles, saves having to wear a mask and the breathing issues with a mask 

[ETC]

I wouldn’t put PIR in a floor.