Vapour membrane > T.Frame walls.

[PeterW]

Yep spot on ..!

[zoothorn]

6 minutes ago, PeterW said:

Yep spot on ..!

 

Ok good that's a plan then- great helps progress having clarity on the next job.

 

In the meantime I'm mostly thru my top room foil-taping job. But some Q's..

 

I've done the vertical timbers, but left the last two that join the house old wall (the end of my house, as it was): here its quite in-out with gaps between timber & old orig wall face, so Ive foamed the gap. So Ive got about 1" of timber left not foiled, then a foamed gap, then my old wall.

 

Do I foil around > just onto my old wall? or just over a bit to just cover the foam?

 

 

[PeterW]

You can foil any of it . Have you left the old wall exposed ..? That may be a candidate for insulation backed plasterboard to stop any cold bridging from the exposed areas. 

[Onoff]

Will those Spotclips give the 90mm clearance above the fitting? Saying that they do do different heights.

 

Again worth reading the manufacturers instructions that came with the lights.

 

They also have a version of the Thermahood they call Spotbox but again its install from above. Meant really for when trying to maintain (near?)air tightness in passive esque builds.

[zoothorn]

On 09/03/2020 at 23:10, PeterW said:

You can foil any of it . Have you left the old wall exposed ..? That may be a candidate for insulation backed plasterboard to stop any cold bridging from the exposed areas. 

 

Hi PeterW.. just back doing this job, flat-out (paid) work deluge.

 

Ok yes- left the old wall (old outside of house) exposed. Idea is to see how warm room is.. & if this wall's a huge 'cold radiator, then I'll line it later. I hope not to tho (may even sand-blast the render off to expose the stone if warm enough).

 

Re. the foil: what's best to do in the reveals? foil > (sheet) > pB? or try & somehow line them.. prob is, I've only got very limited window frame area to put 1" max insulation > then pB. I'm inclined to do without PIR here, if I'm allowed to.

Edited March 13, 2020 by zoothorn

[zoothorn]

Been foil taping mad. Done top room reveal: builder left me with not enough either side of window, to line the reveal (sides) with even 25mm PIR > pB over. So my plan is cut a 25mm PIR in half (tricky) > foam fix it to the foiled reveal sides > pB with long drywall screws, thru PIR, into timber.

 

Is this a good plan?

 

I just can't deal with plastic-lining the upstairs room, let alone both (its a job too much for just me).. so tried to foil really well instead. Foil job alone took me 2 days. I did look at one screwfix sheet roll but couldn't see it properly, so couldn't guage how tricky the job might be.

 

 

[zoothorn]

On 09/03/2020 at 21:43, PeterW said:

If he wants just insulation clearance then spot clips will do it easily. Just cut the hole and shove it in - they grip the edge of the boards and the pressure from the insulation holds them down. 
 

eBay is one source 

 

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F322439800094

 

Hi PeterW.. about to buy some clip jobs today (you suggested after Onoff's reading of '90mm clearance'). So just going over my led instructions, to concur with Onboff's 90mm clearance figure.. to ask clip seller what clearance each might give me.

 

I've just spotted the last tiny point on the 'warning' list (after "min 50mm from joist etc".. "minimum ceiling void depth 90mm")..

 

"The fitting is suitable for covering with thermal insulation".

 

So, are these are ok for my insulation to sit ontop of in fact.. or am I missing something? (maybe Onoff interpreted the ceiling void min depth, as the needed clearance from light > to insulation).

[andyscotland]

Looks good. I think it would probably have been quicker and easier to sheet it than foil tape but it's done now. You can probably get away without doing both but maybe do a final check over the surfaces of the boards and tape over any obvious cuts/scratches in the foil coating.

 

For the reveals you can get insulated plasterboard as thin as 27.5mm for the combined insulation/plasterboard which would work out much easier and probably cheaper than trying to foam fill all the gaps in a hand-thinned board.

 

You can also get slightly thicker (e.g. 29.5/32.5) if you can accommodate a little more - but check the insulation material. Some of the 30ish mm ones are polystyrene so won't actually increase the insulation over 27.5mm PIR-backed.

 

If you do have to hand-cut PIR then I think planing/sanding it down with a surform will be easier and more even than trying to cut with a saw but you will need to manage the copious dust.

 

Bear in mind if the plasterboard will be clamped solid against insulation under the whole sheet then you don't need 12.5mm, 9.5 or even 6mm would be fine.

[zoothorn]

Hi @andyscotland I thought the idea was to foil -and also- placcy sheet, a belt & braces plan?

 

I'll be very relieved if what I've done is even a fairly-sufficient barrier, & I've negated the need to placcy sheet it. Can you confirm this?

 

Re. the reveals.

 

Ok I've got 2sqM of 25mm of PIR left from kitchen job. So instead of buying costly insulated-pB.. which I'd need a full sheet of just to effectively do 4 reveal sides).. & the fact that I can literally only get 12.5mm IE half thickness of any PIR in (+12.5mm pB offcuts to use up too, makes sense = 1" total material, MAX, due to my builder not giving me much room L&R).. so I was  thinking foam-stick my PIR cut halves (only 20cm wide of course, so cutting w'breadknife doable).. then screw-on my pB.

 

I can't think how else to line these sides, with at least some insulation, if its even needed, to max 25mm total material.. without doing my plan.

[dpmiller]

I got a few sheets of 10mm XPS to do the reveals, but I've only done the bathroom windows and think I'll do the kitchen ones but don't really see the need to do the rest.

[zoothorn]

12 minutes ago, dpmiller said:

I got a few sheets of 10mm XPS to do the reveals, but I've only done the bathroom windows and think I'll do the kitchen ones but don't really see the need to do the rest.

 

I was wondering if I even need to line the reveals at all. I mean they're all "lined" with 100mm of timber as it is being a TF build, plus a sandwiched 25mm PIR layer I put in next to this 'frame' around the window, then another 50mm timber stud outside of that. The window would look 'correct' if I could just put pB directly onto the timber sides. I could then just PIR line the top/ btm with a full 25mm.

 

Surely timber has thermal properties itself of a sort, or big log houses wouldn't be inherrantly warm.. chalet I was once in switz was warmest house Ive ever known.. just one skin of big logs afaik.

[andyscotland]

On the vapour control, I would have gone for sheet instead of taping, but I don't think you need both if the taping is thorough.

 

On the reveals I guess depends on the value of your time/sanity. You may need more expanding foam than you think but if you have that spare as well then probably the cheapest option.

 

If you need to get to a total thickness of 25mm then maybe make a little jig with a channel of 25mm batten or similar? Put the plasterboard in the bottom, the PIR on top, then you could run the saw/knife flat along the battens either side to get a fairly even cut?

 

 

[zoothorn]

Just now, andyscotland said:

On the vapour control, I would have gone for sheet instead of taping, but I don't think you need both if the taping is thorough.

 

On the reveals I guess depends on the value of your time/sanity. You may need more expanding foam than you think but if you have that spare as well then probably the cheapest option.

 

If you need to get to a total thickness of 25mm then maybe make a little jig with a channel of 25mm batten or similar? Put the plasterboard in the bottom, the PIR on top, then you could run the saw/knife flat along the battens either side to get a fairly even cut?

 

 

 

Ok great I'm gonna call the vapour box TICKed.

 

Andy do I even need to PIR line the reveals, at the sides?? could I just do top/ btm with a full 25mm PIR, pB on top.. sill on lower (I have enough room to do this, its only the sides I'm restricted due to narrow width). Then the window will all sit symmetrically 'correct' to the walls around it.

[andyscotland]

I'm not sure... I would if I could, I suspect it would potentially be ok without. Timber does have some insulating properties (more than masonry for sure) but not enormous.

 

I can't picture the makeup/layout of the studs/existing 25mm PIR you mention above, can you share a pic/sketch?

[zoothorn]

2 minutes ago, andyscotland said:

I'm not sure... I would if I could, I suspect it would potentially be ok without. Timber does have some insulating properties (more than masonry for sure) but not enormous.

 

I can't picture the makeup/layout of the studs/existing 25mm PIR you mention above, can you share a pic/sketch?

 

You see the thing was, my builder used so much timber 'packers' (horizontal layers top & btm of room) Ive got alot more studs going on than I should. Seemingly around the window/ door too.. alot of timber going on.

 

 

[andyscotland]

Ah, OK. So the 25mm PIR between those studs will help with the overall room temperature/heat loss, but won't affect the "point" heat loss/temperature of the plasterboard where it meets the window which is the main reason for insulating the reveal. The plasterboard at the "room" end of the reveal will be pretty much the same temp as the room / rest of the internal walls, but as it gets nearer to the outside wall it will get progressively colder. That increases the probability of getting condensation on the wall near the window.

 

The impact of that will be somewhere on the scale of nothing - a bit of mildew/black mould - plasterboard softening and disintegrating. Exactly how bad depends on a lot of variables including relative temperatures, indoor humidity, etc. But you would almost certainly see the mould developing before anything fundamental went wrong. And there are loads of existing houses around with a bit of mildew round the windows...

 

If you can get even a thin layer of something in there it will reduce the risk / severity. Or you could just board it and keep an eye on it, it wouldn't be the worst job in the world to redo the reveal with a bit of insulation down the line if it was necessary. But you might have no issue, or you might just need to give it an occasional wipe down with a bleach / fungicidal spray as you would in an old house.

 

If you leave the insulation out then I would foil tape the timber in the reveal right up to the window and then put some silicon to seal it up to the window frame. That should avoid any moisture getting into the timber so if you do get condensation any damage will be limited to the plasterboard rather than anything structural.

[zoothorn]

@andyscotland

 

thanks for that info/ post Andy. Understand a bit more about 'cold bridging' now. I have it in abundance in my house as is.

 

Ok so I will try & get my cut-down halves of 25mm PIR to line this upper window then after all.

 

I'm still doing this damn foil job.. but I've been scuppered to progress/ do my french door reveal areas, by finding alot of condensation on the -inside- of both the glass -and- mostly at the very corners where I've put some foil (to be continued to complete the job). So the inside areas are soaking wet, water streaming down the foil tape.. & I can't complete the job as more tape won't stick on it.

 

I'm finding this condensation situation infuriating. Not only I can't see out the doors as its satuated on the outside.. but now I find it in abundence on the inside too. I've no idea if this is a structural fault, something to be expected/ me to solve/ something I've introduced. What it seems is the silver metal foil tape's cold surface has introduced this condensation.

[zoothorn]

Surely if I were to now put on a huge placcy sheet over the whole silver inside surface (a job to much for me/ I cannot deal with the prospect of doing this) this condensation will be trapped under the surface/ between these two layers, on top of the timber.

 

I am just not understanding this situation/ what to do/ how its meant to be at all.

[andyscotland]

1 hour ago, zoothorn said:

@andyscotland

 

thanks for that info/ post Andy. Understand a bit more about 'cold bridging' now. I have it in abundance in my house as is.

 

Ok so I will try & get my cut-down halves of 25mm PIR to line this upper window then after all.

 

I'm still doing this damn foil job.. but I've been scuppered to progress/ do my french door reveal areas, by finding alot of condensation on the -inside- of both the glass -and- mostly at the very corners where I've put some foil (to be continued to complete the job). So the inside areas are soaking wet, water streaming down the foil tape.. & I can't complete the job as more tape won't stick on it.

 

You either need to get the heating on, or get the doors and windows open, or both. The condensation is due to moist air inside (possibly timber / flooring that was delivered with a bit of moisture content acclimatising to your house, possibly any screed / plaster / other "wet" trades curing and drying.

 

You can dry off with a towel to get the worst of it off, but warmth and fresh air will be the only way to get it totally dry.

 

1 hour ago, zoothorn said:

 

I'm finding this condensation situation infuriating. Not only I can't see out the doors as its satuated on the outside.. but now I find it in abundence on the inside too. I've no idea if this is a structural fault, something to be expected/ me to solve/ something I've introduced. What it seems is the silver metal foil tape's cold surface has introduced this condensation.

 

The surface of the foil tape is the same temperature (for all practical purposes) as the material it is stuck to. Potentially however it's making the condensation more visible because it can't soak into the timber - that's of course the foil tape's job, and is a good thing. It will likely clear up as the building materials acclimatise and you get the space heated. Likewise once you get the reveals insulated to reduce the severity of the "cold spot" where the wall meets the window.

 

1 hour ago, zoothorn said:

Surely if I were to now put on a huge placcy sheet over the whole silver inside surface (a job to much for me/ I cannot deal with the prospect of doing this) this condensation will be trapped under the surface/ between these two layers, on top of the timber.

 

I am just not understanding this situation/ what to do/ how its meant to be at all.

 

Correct - one reason why I said I'd do one or the other. You generally want to have the most effective moisture barrier nearest the room, and then let materials get progressively more permeable to the outside so that moisture has somewhere to go.

 

You will be fine.

[zoothorn]

@andyscotland

ok that's reassuring.. but there's no way anything inside (including the render fully dried after 3+ months now) has any moisture content that's causing the condensation/ everything is bone dry. Today there wasn't as much (not as cold last night) so only the french doors had the condensation in the corners not the window reveal: evidently to me its due to cold outside getting in at the weakest point, the sides of french doors.

 

If I line the door reveals (& top) with 30mm insulated pB.. which I will buy monday, 1 sheet will do the doorway/ window reveal below/ & the window area of this pesky too-narrow window upstairs.. I assume I'll stop this cold ingress/ condensation here. But this leaves the doorway sill. I don't think this PIR pB stuff is correct to line the sill, as full weight is stepped on here & pB isn't the right stuff anyway.. so what am I meant to do here? or is it a Q of just having one weak spot/ junction, & at least I've 'done/ lined' as much as I can.

[PeterW]

Your concrete slab will take 6 months or more to cure and will continue to give off water vapour too. If you put a piece of heavy plastic on the floor about a foot square, cover it with an offcut of PIR and leave it a day and you’ll come back to a damp patch under the plastic. 
 

Big industrial dehumidifier from a tool hire place will dry stuff out in a week or two, and they make it a bit warmer too. 

[Onoff]

You can buy a cheap humidity meter off of Amazon etc for about a fiver to give an indication of where you are now with regards to it. Similarly it'll show it reducing if you do hire a dehumidifier. Amazing the amount of water they suck out of thin air!

[zoothorn]

33 minutes ago, Onoff said:

You can buy a cheap humidity meter off of Amazon etc for about a fiver to give an indication of where you are now with regards to it. Similarly it'll show it reducing if you do hire a dehumidifier. Amazing the amount of water they suck out of thin air!

 

@PeterW thanks chaps- I had no idea at all about this, sure am learning as I go along. Ok good more reassurance on the condensation.

 

Could either of you advise on my french doors sill:

 

I asked builder to push the doors up 50mm. Why? bc A) he produced such a low set my head was almost hitting the frame.. yet another thing very not as per plan. And B) to scrimp every 50mm of height for my balcony [bc of his build height cockup] so doors will skim the deck).

 

So its made it in cheap timber @ 50mm H. 240mm D isn't a good step for my size 11's.. so thinking I add a bit inwards/ easy. Tried to take up the OSB surface to whack in some PIR, but screws too hard.  Its what to put on this timber sill is my Q. Or is it fine as it is?

[Onoff]

There is no heating in my refurbed bathroom. I do get some condensation on the inside of the original double glazed, upvc window. I really sealed up the 4 sides also. The window is in the outer leaf which doesn't help!

 

 

 

Saying that, the shower is used +4 times a day and the extractor doesn't seem that good. Must take the door off and trim up to a definite 10mm gap.

 

 

 

 

 

 

 

[zoothorn]

@Onoff My bathroom is appaling for this (walls so cold) & my backdoor worst: here I have so much black mould all around periphery the plaster's rotting. Anyway my only weak point is my french door sill.. can you advise on my door sill?

 

Another Q.  Any reason I can't put polystyrene offcuts as "fill" between my pozi joists? (got two useful 1m x100mm packing 'batons'). I mean only in a ~1m section. My rockwool won't quite reach you see.. so I'll have a 1.2m vacant section I can fill up with this + some 25mm PIR chopped up to make 75mm. 

 

So my joist will be filled tmrw with 140mm rockwool, with a 1m gap left (under doorway, directly above I think best) here filled up with PIR & polystyrene all wedged & foamed in. Prolly fill up over half the joist gap minimum, about as much as the rockwool will.