Which insulation in loft floor/bedroom ceiling?

[Ian H]

Can anyone recommend an insulation to go in the loft floor/bedroom ceilings to reduce noise?

My joists are 200mm and I'd like to get something that's a good mix of performance v's price.

Cheers.

 

[endecotp]

Either an acoustic mineral wool, or wood fibre batts.

 

[Doggit]

The wood fibre bats are better, but thinner, so you'd need to check the specs, but I've used 170mm of rockwool in 200mm joists between a pair of flats, and it cut the noise down dramatically. I lifted about every 6th floorboard, cut the rockwool into bats to fit beween the joists, and pushed them in under the floorboards.

 

[Ian H]

Is there any point filling the full 200mm?

The thickest acoustic stuff seems to be 100mm so I wondered if I should double it up.

 

[endecotp]

What noise are you concerned about?
Is there anything there currently?
Is the loft unheated? If it is, the thermal performance is probably more important.

 

[Ian H]

We are converting the loft and it will be mine and my missus's room with kids below.

I'd rather not be able to hear music/TV/talking from one room to another.

 

[endecotp]

OK so thermal doesn't matter.

I think building regs require only 25mm of normal mineral wool inside a stud wall between bedrooms, for soundproofing, though they do also need 15mm plasterboard. Or maybe it's 50mm. In any case, 100mm of wood fibre or acoustic moneral wool is plenty more than that. I think that once you've got that much then other routes of sound transmission will dominate, in particular downward transmission of footsteps though the solid elements. I.e. make sure there are no squeeks when you fit the floor, and get a carpet.

 

[Doggit]

You can't fill the gap completely, as you need to allow the electric cables to dissipate heat. You might be better off just putting in the 100mm, and then using a sound deadening material under the carpet. The bats will reduce air transmitted noise, but still allow vibrations though the joists and the floor. If you want to go for broke, then you could add sound deadening plasterboard on the kids ceiling.

 

[endecotp]

I've looked up the building regs requirement; it's section 5.23 of approved doc E, and it requires 100mm of material with a density of at least 10 kg/m^3.

 

[Ian H]

Ok, thanks very much for the advice. I'll stick to 100mm and board the ceilings with the blue boards

 

[Ian H]

Does the 100mm acoustic in this listing seem the right stuff for the right price? It looks 1/3rd cheaper then anything else I can find.

https://www.ebay.co.uk/itm/162382054377

URSA LOFT ROLL & ACOUSTIC PARTITION ROLL

 

[endecotp]

"Lightweight" doesn't sound like what you want for an acoustic insulation material.
See if they can supply a datasheet with numbers that you can compare to other products.

 

[Ian H]

I've googled and it's listed as 2.2kg per M2, surely can't be 22kg per M3?

 

[endecotp]

Yes it can be 22 kg/m^3.

Steico flex wood fibre is 50 kg/m^3.

I note that those specs don't mention the acoustic performance.

 

[Doggit]

There's a lot of uncertainty in that advert. It's made from sand that's abundant, yet may be made from up to 80% recycled glass - and as endecopt says, advertised as an acoustic product, but doesn't mention any acoustic properties. I'd avoid it, as it may well be the old fashioned glass fibre insulation.