Cold Extension - Insulation Issues?

[EinTopaz]

Hi all,

i've been looking for some guidance to help troubleshoot and solve a cold extension we've got and this forum felt a good place to ask.

 

It's a single story gabel extension (6meter x 5 meter, vaulted ceiling) done about a year ago, we noticed this Winter that something isn't right regarding it's temperature and comfort levels. At this point i'm not sure whether it's due to draughts or something else contributing to the heat not being retained well , but it's notably colder in this room than any other, which has struck me as odd as the rest of the property is 1950's; suspended floorboards and not the biggest cavities in the world etc, where as this new room is the only room in the property that's been built to modern standards(tm), yet it's a good 3degrees cooler than the other rooms.

We specced 5kw of radiators in there, and a 7kw gas fire for good measure. It gets warm at a reasonable rate, but the issue is once the heating goes off, the temperature rapidly falls. I.e last night it was dropping maybe a good 2degrees an hour at the worst. 


It doesn't just feel cold either, I have noticed pretty strong draughts when i've removed sockets or wall/ceiling light fixtures which I found alarming. With that in mind, i'm becoming concerned that the coldness and amount of draughts in this room may be an issue stemming from when it was constructed, so I figured it'd be good idea to put some images up of the construction stages to see if anyone can notice anything that may be contributing to, so i'll put some images below. From memory the insulation was all PIR and 100+50mm in the roof, 100mm in the walls and 100mm in the floor.

 

 

 

 

I've got some thermal images I can share too but i've hit my limit for this post so i guess before I do, What do you guys think of the build? Anything stand out as looking bad? thoughts very welcome and appreciated, i'm at my witts end with it and open prepared to go as far as necessary to get this fixed.
 

thanks all,

G

 

 

 

 

 

 

 

 

 

 

 

 

[FuerteStu]

That's a lot of glass.. 

 

That's my gut feeling. What's the detailing around them and their spec? 

[EinTopaz]

54 minutes ago, FuerteStu said:

That's a lot of glass.. 

 

That's my gut feeling. What's the detailing around them and their spec? 

 

It is alot of glass and i'm fine to upgrade to something better thermally if I need to, though I guess that wouldn't explain the draughts. 

Spec wise, they're standard 28mm double glazed units, from memory spec was U value of 1.3 or so. Though I believe one of them has failed. It's showing much colder on the inside, and transmitting more heat from the outside when you view via thermal cam. Images below.

 

 

Edited February 15 by EinTopaz

[JohnMo]

Strong suspicion the insulation details around the steelwork leave some thermal bridges. It's a big bridge if not correctly detailed.

 

The steel at the top of the roof, could also be an issue as you have lots of gaps in the roof insulation at that area.

 

PIR in cavity walls is easy to do badly and difficult to do well.

 

Suspect you have a lot of small detail issues that all stack up.

 

Window size shouldn't give you issues.

 

But post your thermal images.

 

Around windows, around all steels, floor to wall intersection, the walls and ceiling.

[Andehh]

Insulation looks pretty good all considering. Even some thermal bridging is fairly average. Could just be the fact it's 30sqm space with high ceilings and lots of glass!

 

We have a room(s) similar and whilst it doesn't actually loose heat that fast, it does feel chilly due to significantly above average glazing and high ceilings.

 

Check for strong drafts with a candle... And see if Windows need adjusting.

 

If its connected to the rest of the house, could the warmth be drifting through the rest of the house?

 

All else fails fit bigger radiators, adjust the heating schedule, and accept big glazed rooms feel colder then small windowless spaces!

 

The price for extra heating... £25 more a month vs the cost of that extension.... For the couple months a year when it's properly cold.... Ya can't win everything!

Edited February 15 by Andehh

[MikeGrahamT21]

Dot and dab plasterboards on wall by any chance?

[EinTopaz]

1 hour ago, JohnMo said:

Strong suspicion the insulation details around the steelwork leave some thermal bridges. It's a big bridge if not correctly detailed.

 

The steel at the top of the roof, could also be an issue as you have lots of gaps in the roof insulation at that area.

 

PIR in cavity walls is easy to do badly and difficult to do well.

 

Suspect you have a lot of small detail issues that all stack up.

 

Window size shouldn't give you issues.

 

But post your thermal images.

 

Around windows, around all steels, floor to wall intersection, the walls and ceiling.

 

Interesting, I hadn't considered the steel. How much of an effect would that sort of bridge have if not insulated properly?

I suspect you are correct that it's a sum of the parts. I feel like i'm catching them one by one (i.e the wall light draughts) but they're not really notably improving the comfort/thermal levels of this room. Which is concerning me.

I'll likely have more images than this, but these ones cover a good swathe of the interior. 

 

 

 

 

 

 

Then on the Exterior, these were the most concerning areas I saw... Really no idea why so much warmth is coming out of that portion of the pitched roof. Surely that's not normal.

 

 

 

[EinTopaz]

58 minutes ago, Andehh said:

Insulation looks pretty good all considering. Even some thermal bridging is fairly average. Could just be the fact it's 30sqm space with high ceilings and lots of glass!

 

We have a room(s) similar and whilst it doesn't actually loose heat that fast, it does feel chilly due to significantly above average glazing and high ceilings.

 

Check for strong drafts with a candle... And see if Windows need adjusting.

 

If its connected to the rest of the house, could the warmth be drifting through the rest of the house?

 

All else fails fit bigger radiators, adjust the heating schedule, and accept big glazed rooms feel colder then small windowless spaces!

 

The price for extra heating... £25 more a month vs the cost of that extension.... For the couple months a year when it's properly cold.... Ya can't win everything!

 

I can feel the strong draughts with my hand. Every socket had them, every light fixture. I've plugged them all with rockwool now but any idea why that's happening? it felt like a gale wind blowing in my face in some of those openings. Really surprised so much air was getting in.

Could be warmth getting to the rest of the house but see the thermal images posted above. They do tell a different story, definitely warm air leaking out by the looks of it.

To be honest the rad sizes aren't a concern, its that that room when unheated is only a few degrees warmer than outside temp, and that can't be right surely.

[ProDave]

3 minutes ago, EinTopaz said:

Can you post a normal picture of this corner for context please.

 

something is making it very cold right in that corner.

[EinTopaz]

20 minutes ago, MikeGrahamT21 said:

Dot and dab plasterboards on wall by any chance?

 

on walls yes dot and dab,  for the ceiling the plasterboard was hardfixed to the roof. Can see the dabs on the thermal images posted above. 

[EinTopaz]

 

7 minutes ago, ProDave said:

Can you post a normal picture of this corner for context please.

 

something is making it very cold right in that corner.

 

Attached, I think I know what is causing that.

Before the extension was built there was an extractor fan vent there for the downstairs bathroom, when the extension was built the builders said they added on routed the ducting for it up and out one of the tools in the pitched extension roof. I've seen it from the exterior but haven't investigated how they ran it though the roof and how neat the connection is etc. Though I suspect it's gotta be that, as thats exactly where the duct would've been. 

 

 

 

 

Edited February 15 by EinTopaz

[MikeGrahamT21]

10 hours ago, EinTopaz said:

 

on walls yes dot and dab,  for the ceiling the plasterboard was hardfixed to the roof. Can see the dabs on the thermal images posted above. 

Chances are you’ve got a plasterboard tent then especially with how much air flow you are getting through your sockets.

 

it’s very hard to resolve this once it’s been fitted, you can try injecting flexible foam behind all around the perimeter at 100mm intervals, but it’s not easy to get a perfect seal.

 

either wet plastering the walls or having a properly airtight service void is the only true way of resolving this, but it would mean removing all of the wall boards and starting again.

[EinTopaz]

5 minutes ago, MikeGrahamT21 said:

Chances are you’ve got a plasterboard tent then especially with how much air flow you are getting through your sockets.

 

it’s very hard to resolve this once it’s been fitted, you can try injecting flexible foam behind all around the perimeter at 100mm intervals, but it’s not easy to get a perfect seal.

 

either wet plastering the walls or having a properly airtight service void is the only true way of resolving this, but it would mean removing all of the wall boards and starting again.

 

It was particularly bad on one socket the rest were ok, the one particularly bad one was on the wall adjoining the rest of the property and the cable to it is fed from the ventilated subfloor of the rest of the property where it's joined into one of the ring mains down there. So perhaps the draught was coming from there for the socket. The wall lights however are definitely fed from above, and they were very draughty.

 

I mean even with dot and dab should this much air be coming in? One thing I suspected was that the builders didn't insulate the eaves properly, where the wall insulation meets the roof insulation. When I did our loft and eaves I went through this myself and made sure everything tesselated and was taped up etc. Im not sure they've done that and whether that's contributing to just how cold/draughty this room is. Could that be worth investigating? 

[MikeGrahamT21]

54 minutes ago, EinTopaz said:

 

It was particularly bad on one socket the rest were ok, the one particularly bad one was on the wall adjoining the rest of the property and the cable to it is fed from the ventilated subfloor of the rest of the property where it's joined into one of the ring mains down there. So perhaps the draught was coming from there for the socket. The wall lights however are definitely fed from above, and they were very draughty.

 

I mean even with dot and dab should this much air be coming in? One thing I suspected was that the builders didn't insulate the eaves properly, where the wall insulation meets the roof insulation. When I did our loft and eaves I went through this myself and made sure everything tesselated and was taped up etc. Im not sure they've done that and whether that's contributing to just how cold/draughty this room is. Could that be worth investigating? 

It’s surprising just how little of a gap you need for a huge amount of airflow to come from behind plasterboard.

 

definitely investigate everything you can, that should be fairly easy to access without having to damage anything 

[EinTopaz]

35 minutes ago, MikeGrahamT21 said:

It’s surprising just how little of a gap you need for a huge amount of airflow to come from behind plasterboard.

 

definitely investigate everything you can, that should be fairly easy to access without having to damage anything 

 

With it being a vaulted ceiling and no 'loft' per sae, I assume the only way to see the join between the roof and wall insulation would be from outside? soffits & fascia off, or lifting some tiles? 

Edited February 16 by EinTopaz

[FuerteStu]

I think you have two problems here. 

 

A large room with a floor like a sponge for absorbing the heat. Once up to temp it might not feel like it drops too much, but it's going to take a while to get up to temp, not having underfloor heating in it. That seems to be the preferred method to most. 

 

The detailing around your insulation at the joints seems poor (see picture). Foaming up the gaps like this would have made quite a difference. 

 

I'm guessing the cold spots are from gaps like this, From there it will travel down the walls behind the plasterboard, and put through the sockets. 

 

[EinTopaz]

11 minutes ago, FuerteStu said:

I think you have two problems here. 

 

A large room with a floor like a sponge for absorbing the heat. Once up to temp it might not feel like it drops too much, but it's going to take a while to get up to temp, not having underfloor heating in it. That seems to be the preferred method to most. 

 

The detailing around your insulation at the joints seems poor (see picture). Foaming up the gaps like this would have made quite a difference. 

 

I'm guessing the cold spots are from gaps like this, From there it will travel down the walls behind the plasterboard, and put through the sockets. 

 

 

yeah good spot, I saw the gaps in that this morning when flicking through the images. As it has another 50mm kingspan between that gappy 10mm layer and the plasterboard will that still be a problem though? ie where the wall plasterboard meets the ceiling plasterboard, the draught would have to get past that 50mm layer too right? or am I being silly? 

 

 

Also i was reading this morning about the issues with draughts in the dot and dab plasterboarded walls being caused by "The board not being glued around the perimeter and then cold air can come down from above and chill the whole wall" ... Any idea what that means? if its related and what I can do to fix that now?

Edited February 16 by EinTopaz

[FuerteStu]

Dot and dab plasterboard should have a continuous line of adhesive at the top and bottom of the board, and around any sockets and windows. 

 

There are posts about this on site and discussions about rectifying it. 

 

 

[FuerteStu]

Actually that isn't the post that discussed dot and dab fail.. Memory fail.. 

[MikeGrahamT21]

2 hours ago, EinTopaz said:

 

With it being a vaulted ceiling and no 'loft' per sae, I assume the only way to see the join between the roof and wall insulation would be from outside? soffits & fascia off, or lifting some tiles? 

Just tiles, looking at the overhang of roof you may need 3 rows off to see the internal junction but it will give a good opportunity to see everything and fix what you find.

 

2 hours ago, EinTopaz said:

 

yeah good spot, I saw the gaps in that this morning when flicking through the images. As it has another 50mm kingspan between that gappy 10mm layer and the plasterboard will that still be a problem though? ie where the wall plasterboard meets the ceiling plasterboard, the draught would have to get past that 50mm layer too right? or am I being silly? 

 

 

Also i was reading this morning about the issues with draughts in the dot and dab plasterboarded walls being caused by "The board not being glued around the perimeter and then cold air can come down from above and chill the whole wall" ... Any idea what that means? if its related and what I can do to fix that now?

Quite likely, you can have really snug fitting PIR and you’ll still get air leakage through it.

 

with the tiles off you may be able to improve the issues. The problem with dot and dab even when installed as per manufacturer guidelines with continuous bead of adhesive, it only takes a bit of block shrinkage to create a new path for air leakage, lots of people use a parge coat on the blocks to get around this but for me wet plastering is the easiest way of achieving airtightness which you can clearly see long term is staying that way.

[EinTopaz]

3 hours ago, MikeGrahamT21 said:

Just tiles, looking at the overhang of roof you may need 3 rows off to see the internal junction but it will give a good opportunity to see everything and fix what you find.

 

Ok that's good, saw the price of replacement soffits and assume they're all nailed in and can't remove without damaging. So if it's possible to do with tiles that will save me some faff. I guess I only need to inspect a meter wide to see evidence, if confirmed I can take some more off and continue to fix. Time consuming but i dont mind if it will lead to an improvement.

 

3 hours ago, MikeGrahamT21 said:

lots of people use a parge coat on the blocks to get around this but for me wet plastering is the easiest way of achieving airtightness which you can clearly see long term is staying that way.

 

Forgive my naivety but parge coating as in a full sealing pass of the block before the plasterboard goes on? I assume it's too late for me now unless I remove all the plasterboard.

 

likewise for wet plastering, as in no plasterboard and plaster directly the blocks?

Edited February 16 by EinTopaz

[EinTopaz]

5 hours ago, FuerteStu said:

Dot and dab plasterboard should have a continuous line of adhesive at the top and bottom of the board, and around any sockets and windows. 

 

There are posts about this on site and discussions about rectifying it. 

 

 

 

The continuous line of adhesive im not sure whether it was done or not. But by "top" do you mean where the wall plasterboard meets the sloping roof plasterboard?

if so, could I, for example cut off the top 5cm of wall plasterboard thats there now, and seal across the bottom of the roof plasterboard, then reboard that section on the wall? Or is that a daft idea? 

[Onoff]

8 minutes ago, EinTopaz said:

if so, could I, for example cut off the top 5cm of wall plasterboard thats there now, and seal across the bottom of the roof plasterboard, then reboard that section on the wall? Or is that a daft idea? 

 

You could hide it with coving.....

[Onoff]

After this point, I'm assuming aside from not foaming the gaps, that they didn't then foil tape over the timber joists so that and the foil on the PIR became an airtight membrane?

 

[Onoff]

Did they use cavity closers around the windows?