Could this wall in the middle of our extension be the reason it's so cold?

[Andy-T]

Hi all,

 

First time poster, long time lurker. 😊

 

Our 3 bed detached house (built in 1970) has always been hard to keep warm, it seems to lose heat pretty quickly, particularly downstairs.

 

I think we have a few issues to tackle (insufficient/poorly located rads, poor insulation, maybe some thermal tenting etc.). We're looking to come up with a list to tackle as part of some general refurbishment works.

 

As I say, by far the coldest part of the house is downstairs, particularly at the back of the property which is a single story extension. This extension is to the kitchen and the lounge (kind of adding a dining room space).

 

When the extension was originally done (by the previous owner) it was left as a flat roof. However, we replaced this with a proper tiled pitched roof about 18 years ago.

 

We wanted to retain a flat ceiling in the dining room (to fit in with the lounge) but went with a vaulted ceiling with a Velux in the kitchen (as we wanted to improve light in what was a very dark kitchen).

One of the things I want to understand is the extent to which this choice might be contributing to the heatloss from the kitchen (where it's so cold).

 

I suspect the Velux isn't helping, but my concern is how the wall dividing the extension looks on a thermal camera. 

 

I'm sure the builders insulated above the ceiling in the lounge and the kitchen, but I suspect this wall between is losing a lot of heat to the cold roof above the lounge.

 

Interested in what people would do to investigate/fix this? Should we consider lowering the ceiling in the kitchen (to match the lounge) and then improve the insulation above the ceiling both sides of the wall? I'm not sure how well that could be done if we look to retain the velux?

 

If it's helpful, whilst it wasn't particularly cold last night outside, Tado says our heating went off at 8:50pm and 2 hours later the temperature in the lounge was about a degree cooler. The heatloss is probably worse in the kitchen, but I don't have data for there.

Anyway, thanks in advance for any pointers,

Andy.T

[Nickfromwales]

At 15.8° at that height, it’s time to get the padsaw out and cut some exploration holes. 

 

Borescopes are cheap on Amazon, which means only having to drill 10mm holes to go poking around.

 

Looks like cold airflow from the cavity into the roof, which is typical of this type of building ‘improvement’ work tbh.

 

Zero thermal detailing or prevention of draughts etc, just straight painted plasterboards which look nice but are used to hide laziness or sins. 

[Andy-T]

46 minutes ago, Nickfromwales said:

having to drill 10mm holes to go poking around.

 

Thanks Nick, that's great. What would I be looking to find out/establish?

 

The wall is dot and dab both sides I think (same as the external walls of the extension), and from that thermal image it almost looks to me (admitedly clueless) like they extended the internal wall with breeze blocks or similar? 

If so, what would some possible remedies be?

 

Do you reckon it'd be possible/advantageous to lower the kitchen ceiling so it's flat (like the lounge behind), so that it can take more insulation? Or would the Velux make that pointless or too complex?

 

And should the existing dot and dab inside the extension come off, and be redone in a more insulated/draughtproof way? I'm guessing you can't just fill behind the plasterboad very well without it all coming off?

[Nickfromwales]

8 minutes ago, Andy-T said:

 

Thanks Nick, that's great. What would I be looking to find out/establish?

 

The wall is dot and dab both sides I think (same as the external walls of the extension), and from that thermal image it almost looks to me (admitedly clueless) like they extended the internal wall with breeze blocks or similar? 

If so, what would some possible remedies be?

 

Do you reckon it'd be possible/advantageous to lower the kitchen ceiling so it's flat (like the lounge behind), so that it can take more insulation? Or would the Velux make that pointless or too complex?

 

And should the existing dot and dab inside the extension come off, and be redone in a more insulated/draughtproof way? I'm guessing you can't just fill behind the plasterboad very well without it all coming off?

The cold streak at the top of the wall is, imo, being caused by cold airflow coming from the cavity in the outside wall, and that’s being drawn up to the ridge by draughts / convection.

 

Dropping the ceiling (on the vekux elevation) would do very little afaic, as the thermal image doesn’t show this section to be adversely cold.
 

You pointed the IR camera at purple, but there’s black which will be colder again, and as heat rises in the room that should be the same surface temp as the ceilings, but it’s not.

 

You can use ‘tapping on the wall’ to located the dabs, plus possibly also the IR camera. You can then drill 6mm holes in the wall between dabs and inject expanding foam. This would fill voids without removing the PB.

 

This would need to be done well, right into the corners, and all the way down each side at the internal junction with the outside wall, in order to have any practical effect.

 

Skirting boards can come off and you can foam behind there too, if the issue is more persistent, as an additional way to attack this without doing major work.

 

The object would be to stop airflow (thermal tenting) behind the PB, which then sucks the heated air out of the room and blows it to the ridge and to the clouds (24/7/365).

 

The significance of the cold at the top of that wall suggests there’s a massive cold bridge, or there’s a LOT of cold air blowing a hooly through there.

 

Ventilation heat loss (blowing a hooly) is where my money would be.

 

The least intrusive way to see what going on at the top of that wall would be to remove some roof tiles, and peel back the membrane, and get in there from above. May just need some more rockwool stuffing in there, but it would need to be done carefully to not make it worse…..eg you stop the cold air flow but then the insulation bridges damp.

 

Hope that’s cheered you up!!  

[ADLIan]

That section of wall is effectively an ‘external’ wall, with some shelter from the loft space the other side. Do I see the pattern of blocks in the thermal pic? Would indicate no insulation in this wall (single skin of 100mm block?). Add thermal bridging and thermal bypass and you have a huge heat loss here!!

[Andy-T]

Thanks both, as Nick says, I can see roof tiles needing to come off to assess this properly.

Is there a reputable trade body for builders/installers who assess and retrofit insulation in this sort of scenario?

I want to get the external cavity walls assessed too, as I think that was bodged when we had it done as part of a grant about 20 years ago (which I gather was very much par for the course back then). But I'm guessing the businesses that would assess/fix cavity wall insulation wouldn't necessarily be the same as would do this sort of remedial work to internal walls etc.

[ProDave]

I assume there is on access to the loft space from the living room side?  That would answer a lot of questions.

 

But as already said this is basically an outside wall with cold loft air one side and your warm room air the other.  It clearly lacks insulation and / detailing allowing your heat to escape from this room into the cold loft space.

 

Correcting it, once you know what is wrong is going to be intrusive.