What thickness of insulation?

DonnyDave

cyclonebri1 wrote: »

Just a couple of things to add, without offending anyone I really would not involve building control with this 1. I think that's taking thing 2 far. IMHO of course.

No, I won't be doing this!

cyclonebri1 wrote: »

There will be no issue with condensation, that only happens on the hot side of a cold wall/ceiling. All you need do is seal around the edge of every sheet, I'd go 50 celotex or similar, and seal each sheet to each other and to the roof and floor. All just to ensure no warm air reaches any voids left behind.

That's interesting. How might I seal it?

I'm looking at putting aluminium tape on the rear of the battens, then fitting the pre-cut insulation on top and then putting aluminium tape over the top of the battens to join the two pieces of insulation. The insulation will be pushed as far up as possible (to touch the ceiling and there will be another 100mm of insulation inserted at the bottom (as floor-to-ceiling is 2.5m and the insulation is only 2.4m).

How about the plasterboard? I will get tapered edge, but as it's also 2.4m I will need to join a bit — will I need to taper the edge or will the fact that it'll be behind the skirting board mean that it won't matter, so long as the plasterer puts some plaster on it so as to give the skirting board a flat surface to butt up to.

ic

I'm intending to install internal insulation in my bathroom when I refit it next year. I came across this set of instructions, which talks about using expanding foam around the edges to ensure there are no gaps. Most of the insulation boards I've found tend to suggest that using tape on them will ensure a vapour seal. I also intend on using treated timbers for the battens, and moisture resistant boards which I will tape and lightly skim the joints before fixing tiles floor to ceiling.

Furts

cyclonebri1 wrote: »

Just a couple of things to add, without offending anyone I really would not involve building control with this 1. I think that's taking thing 2 far. IMHO of course.

There will be no issue with condensation, that only happens on the hot side of a cold wall/ceiling. All you need do is seal around the edge of every sheet, I'd go 50 celotex or similar, and seal each sheet to each other and to the roof and floor. All just to ensure no warm air reaches any voids left behind.

Sorry to disagree, but 50 Celotex is not enough.

100 Celotex goes under a floor slab, but heat rises and this is where adequate insulation is definitely required. IIRR Building Regs required me to put 100 Celotex around some light shafts a couple of years ago. And the timber structure had to be insulated to prevent thermal bridging. The Regs have since tightenned up.

50 Celotex is often inadequate for use in a cavity wall, and that is when used in conjunction with an aircrete block.

cyclonebri1

Furts wrote: »

Sorry to disagree, but 50 Celotex is not enough.

100 Celotex goes under a floor slab, but heat rises and this is where adequate insulation is definitely required. IIRR Building Regs required me to put 100 Celotex around some light shafts a couple of years ago. And the timber structure had to be insulated to prevent thermal bridging. The Regs have since tightenned up.

50 Celotex is often inadequate for use in a cavity wall, and that is when used in conjunction with an aircrete block.

I know what you are saying but 4" is 1 heck of a lot to lose of the wall, and given he has a door up to that wall I think 4" plus plasterboard may well intrude into the door opening.

Of course I get the BR aspect, it's important to such as yourself when providing a service, but for a DIY application like this, well I'm sure you know what I'm saying.

To put it another way, is the OP better off with nothing due to not wanting to involve BC?, or adding 50mm and having the house a lot warmer than it was for limited cost?


OP, I'd simply use a non silicone sealant, polyurethane, on the underside and as said earlier a gap filing foam to address any gaps top/bottom and sheet to sheet.