Insulating my cellar ceiling

moneysaver1978

Disclaimer: I am not experienced like the other folks' posts above to take my suggestion with a big grain of salt!

If you are not bothered about the cellar or have a renovation project for the cellar in near future and want to keep it as cheap as possible with minimal disruption and mess.

Why not just purchase some ceiling nets with hooks and some rock wool insulation?

Chickereeeee

Incidently, as the source of warmth is from above, there will be little in the way of convection currents. Static air is an extremely good insulator (e.g. fiberglass loft roll gets all its insulation value from trapped air!) so if you can eliminate drafts, the type of insulation used is almost immaterial!

ThisIsWeird

GDB2222 said:

https://forums.moneysavingexpert.com/discussion/5950847/spray-foam-insulation-for-underfloor-areas-of-the-house

Maybe worth a look. 

As I suggested, a 'bit too controversial to consider, alas', but I cannot see it being any sort of problem in a vented underfloor situation like this - and it should provide the best insulation and draught-proofing. No idea how much it costs to do, tho', and I'm not going to 'recommend' it in any case due to the emotive aspect.

I would happily have it under my floorboards, tho'. :-)

Bluey87

I am considering converting all 5 cellar rooms as it happens but that’s the difference between me doing a couple of days with a mate and removing the existing coverings and then getting someone in who will charge me in the region of £1500 or spending £85,000 to convert a large cellar to add to an already large house. 

You may think, 85k, that’s a lot and whilst it is I’ve always fancied a cinema room made up like your old style red velvet cinemas of the 60s etc so that won’t be a cheap job. 

GDB2222

Once you convert the cellar, you will presumably heat it and draught proof it. Then you would not need to do the insulation?

Bluey87

Yes but that’s a long way off if I do so would be happy to spend a relatively small amount to improve the comfort of the treat of the property. 

FreeBear

GDB2222 said:

Once you convert the cellar, you will presumably heat it and draught proof it. Then you would not need to do the insulation?

If rockwool or fibreglass batts were used, it would improve fire resistance of the ceiling/floor - Something that can't be said for spray foam. The insulation would also help to absorb sound which would be an advantage for an entertainment room.

ThisIsWeird

The main issue to address from any suspended floor is almost certainly draughts. Not just the seep through every board joint, but - usually especially - from under the skirting boards, where the floor boards below stop well short the wall, leaving an impressive air gap to the chilly below.
The easiest way to tackle this would be to lift whatever floor covering you have - carpets or 'solid' - and to first lay 'paper', whatever the correct stuff is - I'm sure there are products designed for this. And then seal the gaps between the skirting boards and the floor - either firmly press in a foam strip, or just use cheap frame sealant. 
Is the under-skirting gap large - 5+mm - or will you be updating the interior at some point, where the skirtings will come off? If so, use foam strip. 
If, however, you are liking your bare boards, then you may instead need to tackle this from below. Or, use some flexible sealant - not sure which is best - to seal along each board joint. Again, there are bound to be products for this.
From below, I guess cut strips of the 'paper'/vapour-control barrier membrane slightly wider that the joist gaps, and find some way of sticking it up in place against the boards.
That should cut the under-draughts to near zero, and make a huge difference.
You understandably want to go further, and add insulation down there too. As I'm sure you've sussed, the choice of what to use will mainly need to address the technical challenge or keeping the darned stuff in place, as oppoosed to 'which one is best'. Ie, getting the darned stuff to stay put, snugly up against the board undersides. I think you'll struggle with the loft Knauf, for example, juggling holding it in place with one hand, whilst you staple mesh to hold it with the other.
I guess you could begin stapling the mesh at one end where the joist ends are, and staple up enough mesh that will still allow you to easily shove the insulation in the gap full depth, before stapling another step along and repeat?! Realistically, how far can you 'stuff' each time? 500mm? A bit more? 
Or, you use a firm insulation block like the fibrous slabs/batts, which can presumably be trimmed to slight oversize, and make even stay in place whilst timber noggins are added? But, again, what a palaver.
Clearly, this is a job much easier done from above!
I'd love to know what the best/easiest solution here would be.

When you come to convert - or even if you plan to 'board the ceiling now - if you use insulated p'board, even 1" stuff, that will make the whole caboodle very cosy.

Oohmaaagaaawd, I think I've just had an inspired. When you take down your old ceiling, keep all the lath and cut them into joist-width-plus-a-few-mm lengths. As you push-and-hold whatever insulation up against the floorboards, take these lath-braces and push them up between the joists so's they bend to fit in, press them snugly against the insulation, and they should stay in place as tensioned arches.