Cavity insulation...

JayBee66

The following two photos are from our IR imaging camera and show the outer walls of two bedrooms. They are indicative of the whole perimeter of our house.

The blue band, at the top of the photos, can almost treble in depth if the outside temperature is sub-zero.

Yes, these bedrooms are quite cold. It was daytime and the wood stove had not been lit. At night the rooms are about 16C.

The cavities have both white polystyrene slab and a later pumped bead insulation. The attic has roll insulation.

My questions is, what are the possible reasons for such a temperature drop at the tops of the walls?

1) The bead insulation doesn't go all the way to the top?

2) There is cold getting under the insulation roll at the extremities, where the ceiling meets the external wall?

3) Another reason for thermal bridging?

What can I do to insulate further?

1) Pump more beads in?

2) Insulate above the soffit (against the external wall) and continue the attic insulation onto this raft of new insulation. Remembering to provide new ventilation where the soffit vents are blocked.

Any ideas welcomed?

Three different BER Assessors have been to our property (for a variety of improvements,) not one of them had an IR imaging camera and yet our house is supposed to be B1!

sell9999

We had.the exact same problem a few weeks ago, very cold bedrooms.

The wall insulation was not our issue.

The attic insulation had not been laid out to the edge properly.

Issue sent away after the insulation was laid properly under the attic floor between the joists out to the very edge but not blocking the soffit vents.

I'd definitely start there if I were you.

sydthebeat

The reason is the thermal bridge caused by the blocks that are used to close the cavity at the eaves.

JayBee66

Thanks for your replies, I think you are both right. I shall insulate over and around those top blocks.

10-10-20

Just by way of illustration as this detail is tricky to find online when searching, the closer block is used in this way at the top of a double-leaf cavity wall:

(from: http://www.viking-house.ie/traditional-cavity-wall.html)

The more modern way of closing and insulating the cavity is as follows:

(from: https://www.kingspan.com/ie/en/products/insulation-boards/roof-insulation-boards/kooltherm-k7-pitched-roof-board/?s=d)

In your images you can just make out the defined line of what looks like the cavity closer, roughly 10cm's from the ceiling.

JayBee66

https://www.boards.ie/discussion/comment/120506875#Comment_120506875

Thanks for that information. I suspect, given who built the bungalow (a relative of a relative), it was the former method. I'll lift the insulation when I go into the attic, this summer, to lay a floor. Then I'll see what I can do.

In the summer, the same blue areas in the photos are bright yellow because heat is leaking in so it will be a matter of insulating against the heat in the summer to achieve the same for next winter with regards to the cold.

10-10-20

https://www.boards.ie/discussion/comment/120507500#Comment_120507500

What IR camera or attachment are you using, out of interest?

JayBee66

https://www.boards.ie/discussion/comment/120507564#Comment_120507564

A UNI-T UTi260B.

All my test equipment (apart from vintage valve and transistor "boat anchors") is from UNI-T.

MicktheMan

The best (and imo only) safe way of addressing this block cavity closer tb is to externally insulate (and go up past the soffit)

rustynutz

https://www.boards.ie/discussion/comment/120530230#Comment_120530230

Would an internal insulated slab work?

10-10-20

https://www.boards.ie/discussion/comment/120530256#Comment_120530256

Slab, meaning concrete floor? If so, we're talking about the opposite ends of the external wall here.

JayBee66

https://www.boards.ie/discussion/comment/120530230#Comment_120530230

My plan (open to change) is to attach PIR board (because I have it) to the outer wall, above the soffit.

Hopefully, that will keep the cold off that part of the outer wall above the soffit and allow me to put fibreglass roll out further over the cap and onto the PIR board. Alternatively, I will make an L-shaped arrangement of the PIR board on the wall and cut pieces of it to cover the cap too.

I'll do it for one room this summer. If it stops heat from seeping in (bright yellow on the IR camera) then it has probably stopped thermal bridging for next winter.

A colleague of She Who Must Be Obeyed has external insulation but it goes from the ground up to the soffit and no further. I looked at her walls through my IR camera and they are not a lot better than our walls. You can still see a blue band where the wall meets the ceiling. Not as bad but it's there, suggesting that the cap is not well insulated.

MicktheMan

https://www.boards.ie/discussion/comment/120530256#Comment_120530256

High risk of interstitial condensation / mould behind the insulated board, that’s why I mentioned ‘safe’.

MicktheMan

https://www.boards.ie/discussion/comment/120531447#Comment_120531447

If I understand you correctly you will not make much of a difference to the tb because of the outer leaf being still effectively uninsulated and thus a direct path still exists for unrestricted heat flow.

The colleague’s mistake with the ewi was not continuing it up past the soffit to wrap with the attic insulation.