Using excess loft insulation under floorboards??

17 Oct 2015
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United Kingdom
hi all and happy new year
I live in an early Victorian house with suspended timber floors which can be very cold and draughty... In my loft I have 6 or 7 unused rolls of insulation, I was simply going to spend one afternoon rolling them out in the loft as an extra layer but then wondered if they could be used under the floorboards to warm the place up a bit?
I've looked online and it says that I'd need to staple netting to the joists etc but I just wanted to check that loft insulation if safe to use under the floor in the void of my house ? Or do I need a special treated insulation to stop it from getting damp and smelly??

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Totally fine.
It won't get damp - that's why the space under the floor is cold and draughty, just like your loft should be.
Yes you can. It will muffle the draughts, which are more of a problem, since there is no heat convection through the floor. Pay special attention to the edges of the room, where there will be gaps under the skirting. While working, take the opportunity to clear away all rubbish and unblock the airbricks, which may be choked with dust and cobwebs, and insulate all underfloor pipes.

If you have bare boards with no carpet, treat the whole underfloor. There must be no obstruction to airflow through the airbricks and under the floor.
Thanks for your replies. Looks like I've just given myself another job to do then!
Will garden mesh/netting stapled between the joists do the job??
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A small mesh will be less likely to let it bulge through.

Mineral wool will stuff into irregular gaps without needing precise cutting, and prevent cold draughts blowing up through the gaps.

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