insulation around window reveals

Rushy Fields

Hi
Anyone have any info on insulation around window reveals. i forgot to set back my block therefore i am looking for the best performing insulation/board and also as thin as possible.
Any information is very welcome. Please PM me if necessary to comply with boards rules. Thanks

Certified

nealger wrote: »

Hi
i am looking for the best performing insulation/board and also as thin as possible.

That would be Spacetherm. Mr google will be able to give you some suppliers names.

Doingit

Not sure if post is still open. I have the exact same situation with regards to the reveals around the window. Just wondering how you got on. What did you use?

domcq

I had a similar problem and used the thinnest sheet of Ballytherm insulated plasterboard I could get which was around 27 mm I think.

I cut these to fit around the window reveals and plastered over them. Where they joined the 82 mm insulted plasterboard on the wall, I cut away the insulation (a 27 mm slice all around) to allow the thinner sheets to sit flush with the plasterboard from the 82 mm board.

That way, there was only plasterboard visible all the way round which gave the plasterer a nice even surface to plaster to.

Doingit

Thanks for the reply domcq. That is exactly what I'm planning to do also but from time to time still wonder if it is the right way to go. Was your project a new build? My dilemma just now is the insulation in the cavity around the window. I had planned to get windows fitted (hopefully next week) without putting any insulation pieces around the cavity between the inner leaf and the damp course. I would then put the airtight tape around the inside of the windows and pump the cavities right up against the window frame. But I'm wondering, will this work? Will the pumped in beads just push the damp course around so that it isn't in position properly? The window installer wants to have the foam pieces in place in the cavity right around the window, he will install the window and then squirt in the expanding foam around the frame to seal it all up. We would then go around afterwards, cut away any excess foam and then apply the airtightness tape. What is the best practice here?

glashanator

What I did was have bigger frames around the outside of the window which can allow plenty of insulated plasterboard.there was plenty of glass pane so no biggie. But if your windows are measured up and on there way you're too late for that.

As far as pumped bead is concerned.... the bead is pumped in under pressure , so anything flapping around it may push thru.
Possibly anything you can poke your finger thru, the bead might force its way out.

Doingit

Thanks glashanator. Yes, windows on way - frame width is around 60mm. Really until they are in I'm not 100% sure how much depth I have left to play with, between the scratch coat, the slab and the final skim coat I'm guessing that will take up anything between 30 to 40mm. Can you remember what width was the outer frame of your windows?

glashanator

yeah it was 75mm

glashanator

Have you thought about just putting on plasterboard without any insulation on back of it. that would be 12.5 mm. would give you more to play with. the reveal wouldn,t be insulated as such but may help in relieving cold bridging at the window. The area of the reveal compared to the overall area of the wall would be small in comparison.....

You could take the small hit at the reveal and have a much better look.

You'll quickly forget there is no insulation on reveal....... but you will always see the windows.

Doingit

Yeah glasahanator, I had an airtightness guy price the job for me a couple of weeks ago and this is also what he suggested - just using a plain slab without the insulation. So basically, I am waiting for the windows to be fitted to see exactly what thinkness I have left and will then decide. Thanks for all the comments.

MicktheMan

glashanator wrote: »

You'll quickly forget there is no insulation on reveal........

You won't when the mould starts growing!

manufan16

I used as Certified suggested, aerogel/spacetherm backed plasterboard around my window and door reveals.

I think it was 9mm insulation with the option of 9mm or 12.5mm board attached.

Doingit

Manufan16, does that come as a single product - board with aerogel backing. If so what is it called??

BryanF

Doingit wrote: »

Thanks for the reply domcq. That is exactly what I'm planning to do also but from time to time still wonder if it is the right way to go. Was your project a new build? My dilemma just now is the insulation in the cavity around the window. I had planned to get windows fitted (hopefully next week) without putting any insulation pieces around the cavity between the inner leaf and the damp course. I would then put the airtight tape around the inside of the windows and pump the cavities right up against the window frame. But I'm wondering, will this work? Will the pumped in beads just push the damp course around so that it isn't in position properly? The window installer wants to have the foam pieces in place in the cavity right around the window, he will install the window and then squirt in the expanding foam around the frame to seal it all up. We would then go around afterwards, cut away any excess foam and then apply the airtightness tape. What is the best practice here?

You've essentially started 2 threads on this topic
> you need a cavity closer. Discuss this with your certifier.
> one method now is to offset the lintels and inner leaf to allow of a decent overlap of insulation.
> what width is the cavity?
> best practice is to have your certifier detail this and agre that detail with the window installer & main contractor.

dfader

nealger wrote: »

Hi
Anyone have any info on insulation around window reveals. i forgot to set back my block therefore i am looking for the best performing insulation/board and also as thin as possible.
Any information is very welcome. Please PM me if necessary to comply with boards rules. Thanks

Are you building your house off your planning drawings?

BryanF

dfader wrote: »

Are you building your house off your planning drawings?

Your replying to a 15 month old post

domcq

Mine wasn't a new build. The windows were double glazed and already in place but I had very little window reveal to work with so I had to take a hammer and chisel to it and trim back the plaster block to give myself some room.

I foamed up any gaps but didn't use airtight tape.

john f 4g63

MicktheMan wrote: »

You won't when the mould starts growing!

Just wondering how would he get mould growth as wouldn't you technically still have insulation just behind the slab anyway? Either with the pumped beads up against it or else the pir board which closes off the cavity and foam filled to the window?

MicktheMan

john f 4g63 wrote: »

wouldn't you technically still have insulation just behind the slab anyway?

You might have but relative to the rest of the wall, the reveal will be colder. Thus, if conditions are right, this is one of the first places for mould to grow.

Also, what technically is possible is a lot different to what happens on site!

I do a lot of thermal imaging surveys and window reveals as described above, without major thermal bridging are a rarity.

acehigh76

Doingit wrote: »

Yeah glasahanator, I had an airtightness guy price the job for me a couple of weeks ago and this is also what he suggested - just using a plain slab without the insulation. So basically, I am waiting for the windows to be fitted to see exactly what thinkness I have left and will then decide. Thanks for all the comments.

If the window haven t been fitted yet its not a huge deal to cut the reveals back. You didn t mention if the inside block is returned at the reveal , if not and you have 100mm cavity showing plug the gap with insulation,and dpc to the outside. Then put your 27 mm insulated slab against the reveal . Used to build for ruden homes in cork and this is how they wanted it. They always used inch isulation on the reveal

john f 4g63

MicktheMan wrote: »

You might have but relative to the rest of the wall, the reveal will be colder. Thus, if conditions are right, this is one of the first places for mould to grow.

Also, what technically is possible is a lot different to what happens on site!

I do a lot of thermal imaging surveys and window reveals as described above, without major thermal bridging are a rarity.

Ya that's true, so in your own opinion as you have obviously seen reveals finished differently do you think using a pir board is the best way to close a cavity at the reveals as a-posed to pumping the bead up to the window?

MicktheMan

john f 4g63 wrote: »

Ya that's true, so in your own opinion as you have obviously seen reveals finished differently do you think using a pir board is the best way to close a cavity at the reveals as a-posed to pumping the bead up to the window?

PIR board fitted properly is better combined with a thermally broken frame.

john f 4g63

MicktheMan wrote: »

PIR board fitted properly is better combined with a thermally broken frame.

The windows I am fitting are passive certified ones with 7 chambers so they are well thermally broken. I think I will use the pir board now to close the cavity as seems to be best option.
Can you tell me is 50mm ok to use or should I use 100mm pir board?

Carrickbeg

All this stepping back the reveals is great on paper but on site the straps get in the way of any really successful way of implementing this detail?