under floor insulation

[Bylough]

I am in the same situation with u/f insulation. and would like to know what this rot proof netting is? Also does loft glass wool insulation do ok-100mm thick? (I am like a duck popping up all over while I'm on this job)
You may take a pot-shot!
Thanks for any replies.

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hi jacked from this post

 

[Mr Winston]

Also does loft glass wool insulation do ok-100mm thick?

100mm quilt is not enough

90mm celotex/kingspan insulation would meet the u-value

If using quilt it would be 250-300mm at a guess (not sure exactly without calculating it but i know that 100mm is inadequote)

 

[Bylough]

Many thanks, Mr.Winston.
Could I ask further- Is celotex self supporting, and 'breathable' ?
Or could you suggest how would it be suported ?
(Apologies to jose the space for my worming in!)
Thanks again all.

 

[Mr Winston]

Many thanks, Mr.Winston.
Could I ask further- Is celotex self supporting, and 'breathable' ?
Or could you suggest how would it be suported ?
(Apologies to jose the space for my worming in!)
Thanks again all.

First of all im assuming that your insulating a suspended timber ground floor like jase the space.

Its not breathable- you will need a 150mm clear gap below the joists with air bricks.

rest the celotex on top of nails or clips or battens fixed to the side of the joists

 

[Bylough]

Many thanks Mr Winston, That method sounds more straight forward.
My joists are 75mm*100mm, so the 90mm celotex is ok to fit hard against the floorboards underneath (I have about 1/3mtr air depth under the joists- but, the central heating pipes are suspended (and insulated) directly under the joists- so some heat will rise on occasions I think.
I wonder could this cause condensation maybe on the length of 4mtr?
Also, as celotex is 'airtight'- is it worth the risk of rot setting in over a long period?
I have some obstructions to airflow- ie two long rooms 35 foot in all, long. two hearth slabs, a concreted kitchen beside room needing new floor (no side air flow) and next doors extension near to one of my airbricks.
I worry that there is no track record of insulating suspended u/f insulating.
You can see that after all the good help and advice, the worm might turn- a sad day for environmental green stuff. Thanks again man.
(Sorry jase- I'll get it right next time!)