I've been following this forum for a while now, all through my self build. Now nearly completed, I've decided to add to the discussions.

Over the winter I "sensed" that some rooms seemed colder that others, even though UFH room stats all showed the same temperature. The insulation used was celotex @ 120mm with 50mm air-gap (inside 2 layers 4" blocks).

We didn't have carpets down then, and convinced myself it would be different when they were down. I bought a seek thermal camera and it didn't show up any difference either.

Then I had an Eureka moment and checked through the photo's I'd taken through the build and couldn't believe I'd missed it. Along with the architect, builder & building control.

Some internal double skin structural walls are only insulated on one side (not easy to understand I know - see attachment), so my study and utility room downstairs, and bathroom upstairs have missed out.

My question is, should they be? And if so, should I get it done retrospectively or am I worrying about nothing?

... why would you insulate internal walls?

Your diagram shows what appears to be an internal wall consisting of 2 layers of blockwork, an air gap and insulation. Is that correct?

There is no reason not t insulate them - and the mass structure is on the warm side anyway

Is there an air path into that cavity on the study side - that could well be loosing a lot of heat that is impeded from getting into cavity from the hallway but not from the study

I'm thinking the bathroom is above the study ? - and the cavity wall continues up to the underside of the roof level and connects with the ventilated void of teh roof make up ?

If that is the case then a lot of heat is going that way - sufficeinet that whilst all the output is warming the floor, it can't maintain comfort as the loss is greater (or that wall is colder and giving a cold radiant effect to the room)

Squirt it full of polybead might be a solution with least damage to the walls

Regards

Barney

Regards

I tried (& failed) to upload 2 pic's to help.

If you look at the links below, they should help to see better.

https://www.dropbox.com/s/7fl8y1zqp1gp53p/IMAG0392.jpg?dl=0


https://www.dropbox.com/s/nglsx9ij0q3xx6j/IMAG0638.jpg?dl=0

Thanks for all comments so far.

This looks a bit like a few of the situations in my house...

In my case they are caused when extensions were added through the history of the house, enveloping cavity walls, and the unfilled cavity opens into the loft space.

In your case it looks like the air gap could be the "cavity" that is opening. At 50mm though it's almost as large as the masonry cavities in my 1950s build! How is the air gap terminated at the top of the house?

Not sure I understand how the diagram relates to the photo though... the photos show a _|¯ while your diagram is ¯|_ . The reason I bring that up is because what you say about thermal imaging. If the diagram is inaccurate and the air gap runs the entire length of the study wall then there may not be as big a difference in temperature to stand out, compared to the external wall temperature. Dunno...

Looking at the photos, is the 'study' in the 'garage' section? if so, then it looks as if it has been thermally separated from the main dwelling?
Effectively the 'study' is in the garage?
The partial-fill cavity insulation does not seem to continue along the front of the 'study' from the photos!
So no surprise if it feels colder than the rest of the house?

Tony, you must have better eyes than me...

I would say that two thermally isolated heating zones have been inadvertently created. And there is a difference, however slight in temperature gradient between the two that your body can sense. This slight difference can be down to the way the two zones are used, occupancy and the equipment and appliances installed in each. Also might be that the garage door is losing heat from that zone. The UFH is also not acting evenly across the whole house.

Where is the thermostat located?

We have 200mm PIR under 40mm liquid screed (with UFH pipes in).

The garage door may not be the most heat efficient door, but it is a fire door, and it was fine during the blower test.

I've tried going through a few lists (Google, CIGA & the energy advice service), and there doesn't appear to be anyone in my area, S/W Wales, or within ~100 miles who still do cavity wall insulation.

I've read on other sites of some who have bought a few boxes of expanding foam and drilled multiple holes, and done it themselves, would this do the trick?

I'm 99% sure there's no other heat leakage in the house, and this is the only (if any) issue I have.

Oh, and what do the architect's drawings show as intended?

The thermal camera seems to be fine, it shows temperatures as well as colours, and did show up leaks around front door (now sorted) and when it was on, the UFH in the screed. I've also used an IR thermometer before buying the Thermal camera with the same result. It also helped me to make sure my thermal store in the garage was 100% insulated around all valves & pipes.

I have a MVHR system running continuously, the air into the rooms was all even when tested in the winter, although I know I have to finish insulating the pipework in the garage for that.

gravelld, this is the problem, there shouldn't be an air gap on internal walls. The space is there because higher up it isn't an internal wall (above the garage roofline). It should have been filled with rockwwool.

The drawings show the blockwork with 170mm gap, with no insulation detail for all walls.

Posted By: mikrtgravelld, this is the problem, there shouldn't be an air gap on internal walls. The space is there because higher up it isn't an internal wall (above the garage roofline). It should have been filled with rockwwool.

If there's nothing closing the cavity horizontally at the garage roof level then that's certainly a major cause of the coldness. But that should most definitely show up using either a thermal camera or a thermometer. There's something weird going on.

The drawings show the blockwork with 170mm gap, with no insulation detail for all walls.

If the drawing doesn't show it, there should be a reference to the spec. Else sue the architect! And somewhere in the drawings and spec there should be an indication of how the cavity is closed.

The drawings show the blockwork with 170mm gap, with no insulation detail for all walls.

That sounds like my experience of architects too unfortunately, minimal detail.

Posted By: djhIf the drawing doesn't show it, there should be a reference to the spec. Else sue the architect! And somewhere in the drawings and spec there should be an indication of how the cavity is closed.

BC didn't seem interested in that kind of detail, planning certainly didn't. Builder happy to work without it. Would be nice to have that kind of expert thought going into a design, but I do wonder how many times it does.

Posted By: tonyInsane design to have a cavity wall inside the house!

But likely to happen if the house does not have the same number of storeys throughout. Like Mikrt part of my build is taller than the rest (architectually interesting??), it is tough to avoid a cavity internal wall in that layout. I omitted the insulation and ensured the cavity was airsealed at the ground floor level - it is an external wall at 1st floor and isulated etc.

Fill with some kind of insulant if you can, although not easy retrospectively. Go squity foam if you can't get anything else.

Oh yeah, you can go crazy trying to think of a way to avoid the thermal bring such a layout creates. I have a layer of thermal block to help matters, haven't noticed any problems with an IR thermometer. A good eco design would avoid height changes like this, so if you haven't got planning permission yet chuck such a design back at the architect!! Too late for me and Mikrt of course, but split level designs mean inherent problems.

I have a gut feeling that Humidity has bearing on the sense of perceived temperature.
If you are getting the impression that 2 rooms of identical temperature feel different and there are no discernible air currents in either see if they have the same RH.

Easy to be wise after the event but EWI would have been a better use for that insulation as the structure within the insulation acts as a heat store and maintains a much more stable environment.