Lft insulation

[Jim Lyon]

Hi!
I'm fitting a floor to my loft (not a complete one , & have a question about insulation - I've just had some of that yellow glasswool fitted, & am wondering how much insulation to leave beneath the floor when I fir it (well most of it as it's impractical to go right out to the eaves - & probably best not to, in order to let it breathe). So, is it OK to compress the existing 9" of glasswool into 5" of floorspace? I know physically it can be done, but will that reduce the insulation effectiveness of the glasswool by reducing its airspace? - Or to word that differently, is there a ratio (of insulation to minimum space) for working out minimum acceptable effectiveness?
If that's a problem, would I be best to remove a layer before fitting the floor?

Cheers,
Jim

 

[str]

As i understand it, if you compress the insulation, you will lose most of its effectiveness.

the correct way is to lay further joists at 90 degrees to the existing to bring up the level of the finished flooring, and that we the insulation can still run un-impeded.

However, you might have to think about loads/weight of all this on the existing joists

 

[Jim Lyon]

As i understand it, if you compress the insulation, you will lose most of its effectiveness.

JL - That's what I suspect, but lacking confirmation, that's why I started this thread.

the correct way is to lay further joists at 90 degrees to the existing

JL - That seems to imply that the layers of insulation should be laid in a "cross ply" pattern (like the layering of tyre carcasses ) in order to be most effective?

to bring up the level of the finished flooring,

JL -I'm already thinking of using 2"x2" in order to raise most of the floor from 3" to 5" in order to level it off. - Which brings me to my next comment,

and that we the insulation can still run un-impeded.

However, you might have to think about loads/weight of all this on the existing joists

JL - If I were to raise the floor in order to bring it up to the level of the insulation (i.e. left free standing), I'd have to raise it by 6", & that weight might not be desirable?
Given that, might I not ne better to compromise by laying in the extra 2"x2" @ 90 deg. as you suggest (to get a cross ply patern, & slightly reduce the level of insulation in order to make it more effective?