drylining and insulating walls

[mcmook]

I am renovating a shop. Its probably never been heated but isn't damp. The front shop is victorian and lined with the original wood panelling, which we'll keep. The back section of the shop about 7m x

5m I was intending to dry line.

my questions

is there any point insulating only a part section of outside wall (probably about 40%) ie the part in the back section of the shop - it has a window in it, and the external wall is in a vennel so its not at all exposed

the walls are about 12" thick stone with a lime plaster on the inside

- does this need to be removed before i dryline? was intending to build a timber frame attached to floor and ceiling about 2" away from the wall on which to attach plasterboard.

since these walls are probably breathable (lime/stone etc) am i likely to introduce problems by using a vapour barrier?

(also a suspended timber floor so i imagine there may be an airflow here)

thanks

[meow2222]

Yes, that will cut wall losses by nearly 40%. The more you can insulate the better of course. Stone walls are quite bad performers thermally.

no

well, it is a risk, but in most cases its ok. If you dont use a vapour barreir you'll get condensation in the insulation, so a VB is the thing to do. Its only a minority of buildings that go on to have damp probs.

thats another place you could insulate then, under the wood floor. If you wanted to.

Making sure theres good ventilation down there will at least maximise what wall evaporation surface is available below the floor.

NT

[The Natural Philosopher]

yes. Every little helps

No.

was intending to

Good.

No. Quite the reverse I would say. You will be reducing moisture flow to the inside of he wall..what moisture gets in will be via rain on the outer wall and any rising damp.

As long as that can get OUIT to teh outside, all will be well

If it bothers you shove a plastic sheet behind the studwork so that even if the wall DOS get damp, it wont rot the wood.

Then use foil backed plasterboard. as well.

Lift it, insulate and seal it, and refit.

[mcmook]

... good advice thanks.

It would be a major undertaking to insulate the floor (I doubt whether the floorboards would lift undamaged) but if i did I would have about

6" to play with - do I need an airgap or could insulation be packed into the full depth - and which would be better rockwool or rigid boards celotex/kingspan. there is no dpc as such but there is a layer of tar over the solum which i'm assuming has the same effect - could i use loose fill? Warmcell (which would only allow 150mm rather than the recommended 250mm) - but would mean i could only lift sections of the floor and pack it in.

i was intending to sand the floor boards as the final finish so minimum disturbance would be best and i don't have a limitless budget!

or if i do go to all this trouble insulating the floor then maybe underfloor heating would be the way to go? ...to many options??

[fred]

In article , [e-mail] writes

Underfloor insulation is generally a lot of work for little return, heat loss through floors is estimated to be one quarter of that lost through ceilings so it is generally an issue of comfort level.

I have insulated my own floors (with 150mm of fibreglass over a hardboard sub-floor) and I welcome the benefit but this was a situation where there was a deep and well ventilated underfloor with baltic winds howling through so I felt obliged to put in some sort of barrier.

You have a limited space underfloor which is less likely to have a howler blowing through. In your place I'd be inclined to fully draught proof the floor (sorry not an easy option with bare sanded boards) apply taped and sealed hardboard followed by substantial underlay and carpet (or dense insulation and lino if commercial) and leave it at that.

On no account poor in loose fill or do anything to compromise air circulation or you'll be looking at rot in the long term.

[The Natural Philosopher]

Umm. Not really. Once your walls are done and your ceiling is done, it becomes the dominant path....a typical slab has a U value over 1.5..

True enough.

In the end its the OP's call. there is no doubt in my mind that once you do a pukkah job on the walls, the floor remains a very real source of heatloss.

Whether you then go insulation and UFH and a thin surface, or a bloody great shag carpet and radiators, is personal choice.

For bare boards i would always use UFH.

[fred]

Of course, when you start plugging the leaks in an old bucket the last hole will always be responsible for 100% of the loss ;-)

Btw, this is boards, not a slab.

Go that route and you'll definitely need top notch floor insulation but that means lifting the floor which was the step I had hoped to save the o/p. A recent post (which I haven't checked for accuracy) suggested that a minimal (12mm?) thickness of celotex on a solid (or was it cavity) double brick wall was enough cut the heat loss in half. Given that I'd be inclined to forgo lifting the floor and add a thin but dense insulator with a ply sub-floor (if anything).

[mcmook]

ok i've done a little bit more investigating and i've almost convinced myself it would be a good idea to lift the floor, lay 18mm ply subfloor and then T&G bamboo planks. this way i can get a better finish, be confident about draught proofing and i can probably use the old boards upstairs... so under the floor i have 6" joists resting on bricks on a tar solum (i presume the tar was an old method of DPC) no sign of any damp/rot in the areas already lifted.

... i'm wondering is this enough space (only about 7") to fit any insulation that would have a worthwhile effect (25mm/50mm? - rigid board type) - without comprimising airflow? the floor is 70m2 and is vented at the front only.

(ps a shag pile carpet is not in the equation - this will be a coffee shop and gallery - and i want it to be warm because we're trying to promote biomass heating by installing a wood pellet stove boiler...)