Between-floor insulation - quick and easy method?

[Dougal2345]

In order to fit some pipes and cables in my house, I've lifted some of the floorboards upstairs.

The boards are T&G chipboard, below there is an 8" gap then the plasterboard of the downstairs ceiling, with no insulation between.

I've only lifted one strip of board, from the front to the back of the house perpendicular to the joists. So if I stick my head into the gap I can see under the floor from one side of the house to the other.

I don't want to lift too much more as the chipboard panels were laid before the stud walls were erected upstairs - in other words, it would be a pretty big job.

So is there any way I can get some kind of (thermal) insulation into the space? It would need to be something solid-ish that I could feed through the gap and shove along until it reached the side walls.

But I've read that insulation needs to be suspended above the plasterboard ceiling, using netting, for some reason? I obviously couldn't do that without lifting more floorboards.

Is there anything worthwhile I can do, insulation-wise, while I have the boards up, or should I leave well alone?

 

[mointainwalker]

Insulation doesn't have to be suspended above the p.b. What you have read is advice for insulating ground-floor joists where there is nothing to stop the insulation falling through.

Your idea of pushing insulation in, is not very practical in my opinion, and not very safe,

Even if you could push it in, you would have no idea if you had caught any electrical cables and were stretching them or even breaking the connection,

That apart the standard advice is not to bury cables under insulation to prevent overheating and fire-risk although this is more important for power circuits than lighting-circuitc,

 

[Dougal2345]

Thanks for this!

Most of the cables are quite neatly threaded in bundles through large holes in the centre of the joists, or tacked along the centre line of the joists, at about 4" high, so if I could find some 4"-thick "solid" insulation it could, maybe, be slid into place underneath the 'cable level'.... my house is not all that wide, so with a torch I can see most of what's going on under the floorboards....

Although in fact the cables present do include the ring mains for both upstairs and downstairs so it is quite "busy" under there.

 

[Dougal2345]

I was looking at some "Jablite" sheets in B&Q the other day:

http://www.diy.com/diy/jsp/bq/nav.j...0647758&fh_view_size=10&ecamp=aff-p9-awin-001

Would 50mm-thick sheets of this, laid on top of the plasterboard of my downstairs ceiling, be worthwhile?

Or are there other 'rigid' products that would be better, or cheaper?

As I'd have to slide this in from one side, it would not always be fitted particularly tightly, and indeed there would sometimes have to be gaps of a cm or two between joist and Jablite - would this dramatically reduce the insulation potential, or just have a slight effect?

 

[mointainwalker]

What you propose would, in ideal circumstances , improve insulation. however trying to push sheets of 50 mm PS through a void would probably break it.

This apart, why do you want to insulate between floors ?

The heat will otherwise heat the floor above ( bedroom-level as I read it ), and unless this is unused, is a sensible path to allow .

 

[Dougal2345]

What you propose would, in ideal circumstances , improve insulation. however trying to push sheets of 50 mm PS through a void would probably break it.

This apart, why do you want to insulate between floors ?

The heat will otherwise heat the floor above ( bedroom-level as I read it ), and unless this is unused, is a sensible path to allow .

In fact two of the three bedrooms are mostly unused, and I only switch the heat on in the one I use when it's especially chilly.

Whereas the rooms downstairs - kitchen, dining room, living room - all are heated much more frequently.

So in my case, between-floor insulation may be of more importance than loft insulation.... hence my keenness to find a good solution!

 

[Deluks]

Mineral wool slabs might be easier to push about and will have the added benefit of improving sound and fire insulation between floors. These come in different thicknesses so maybe 60-75mm would suffice?

In any case don't ignore the loft insulation.