Insulating between joists

barrowvian

Hi,

We have a 1950s house which unfortunately doesn't keep the heat or sound in particularly well.

We're having the carpets replaced upstairs so we're taking the opportunity to insulate the floor between the ground floor and the first floor. I've read that accessing this from beneath is best, however, because we're not replacing the plaster boards this isn't any option. We have wooden floor boards upstairs and I can remove these easily enough and work my way around.

To note; there are some electrical wires and central heating pipes between floors.

I was thinking of either fibre insulation like Rockwool, or board insulation like Celotex. Either of these would do the job of insulating against heat loss but I'm guessing neither would do much good against the sound problem. Does anyone have any experience of either of these? Or any other recommendations? I'd read that adding battens slightly above the plasterboard (from the ceiling underneath) would create an air gap and prevent the buildup of condensation and would also prevent the electrical wiring from getting too hot.

With regards to the sound proofing. I was thinking maybe something that could be laid over the top of the joists and insulation, but underneath the wooden floor boards. Does this sound like a realistic approach? Really trying to cover all the bases with this so any advice would be greatly appreciated. Thank you.

Grenage

I will shortly be working from the top down in our house, and plan on using this stuff:

http://www.noisestopsystems.co.uk/acoustic-insulation/100mm-dfm-acoustic-insulation

!!! long as there is some space around the electrical cables, you should be fine. Condensation should not really be a concern internally.

FreeBear

Grenage wrote: »

I!!! long as there is some space around the electrical cables, you should be fine. Condensation should not really be a concern internally.

I used Knauf Ekoroll (170mm) this summer to do exactly the same as the OP - Can't say if it has made any difference WRT soundproofing. Also took the opportunity to lag the CH pipes and plug a few draughts.

Condensation shouldn't be a problem as both rooms are heated. Interstitial condensation is only really a problem when one side of the insulated partition is cold (i.e. outside walls or roof space).

TheCyclingProgrammer

I always thought there was very little value in insulating between floors - most of your heat losses are going to be out of the roof and the walls. Is your loft well insulated?

If you want to insulate for sound proofing purposes, its a bit more complicated than just putting some insulation in as sound can pass through walls too.

Grenage

TheCyclingProgrammer wrote: »

I always thought there was very little value in insulating between floors - most of your heat losses are going to be out of the roof and the walls. Is your loft well insulated?

If you want to insulate for sound proofing purposes, its a bit more complicated than just putting some insulation in as sound can pass through walls too.

It can make a pretty big difference when you're trying to keep heat in downstairs rooms. A co-worker filled his first floor void with rockwool, and says the difference when people are walking around is staggering.

There are definitely benefits, especially if you're redecorating and can easily pull up the floor.

jamesperrett

Insulation will do nothing to stop sound passing through although it can deaden the sound if it is bouncing around (much as furniture and carpets do to an empty room). If you really want to prevent noise passing through the ceiling you will have to remove the underside of the existing ceiling and build yourself a new ceiling underneath. You should also use the correct materials for it (multiple layers of different thickness acoustic plasterboard).

Gloomendoom

A friend of mine has a large country house with Georgian additions. The floors in the "new" parts are insulated with sea shells. Apparently, they are very effective for blocking noise.

Grenage

I can believe that; anything that adds mass will help deal with hollow footsteps above.

FreeBear

Grenage wrote: »

It can make a pretty big difference when you're trying to keep heat in downstairs rooms. A co-worker filled his first floor void with rockwool, and says the difference when people are walking around is staggering.

There are definitely benefits, especially if you're redecorating and can easily pull up the floor.

Agreed - The room where I insulated the ceiling is noticeably warmer without the CH running - Some 3-4°C warmer than the rest of the house. Any sound reduction (and there will be some) is a small bonus. For the cost of a couple of rolls, it is a minimal expense that does deliver an improvement in my opinion.

Norman_Castle

Grenage wrote: »

It can make a pretty big difference when you're trying to keep heat in downstairs rooms. A co-worker filled his first floor void with rockwool, and says the difference when people are walking around is staggering.

Did he use acoustic rather than thermal insulation? Has it reduced airbourne noise such as voices from travelling up through the ceiling?

glasgowdan

Doesn't insulating the floors make the upstairs rooms colder?