How to insulate top of cavity block wall

Atlantic1

If I externally insulate my cavity block house, I presume a lot of heat will be lost upwardly through the holes in the blocks. I've checked in my attic crawl space and I could easily put 100mm of rigid board insulation on the top blocks and still have a generous air flow space over them.

Two questions:-

1. How do insulating contractors deal with this issue?

2. How would they deal with the top blocks on the gable (A roof) end?

BryanF

Atlantic1 wrote: »

If I externally insulate my cavity block house, I presume a lot of heat will be lost upwardly through the holes in the blocks. I've checked in my attic crawl space and I could easily put 100mm of rigid board insulation on the top blocks and still have a generous air flow space over them.

Two questions:-

1. How do insulating contractors deal with this issue?

2. How would they deal with the top blocks on the gable (A roof) end?

in my experience:

1. they couldn't give a hoot! (the grant will pay out when its butted up to the soffit!)- its up to you or your specifier to detail and clearly specify how this is done
2. badly - same as above

Atlantic1

Thanks Bryan.

I was afraid that might be the case. A neighbour had hers done. A fine job but the top block wasn't sealed in any way. I don't think she's aware of it though.

Our houses have a heavy dash finish. Would I have a thermal looping issue if it didn't get a quick coat of plaster first?

I reckon that Rockwool would eliminate this problem but I wouldn't use it if I was having the house externally insulated.

BryanF

Atlantic1 wrote: »

Thanks Bryan.

1. I was afraid that might be the case. A neighbour had hers done. A fine job but the top block wasn't sealed in any way. I don't think she's aware of it though.
2. Our houses have a heavy dash finish. Would I have a thermal looping issue if it didn't get a quick coat of plaster first?
3. I reckon that Rockwool would eliminate this problem but I wouldn't use it if I was having the house externally insulated.

1. footings/floors, reveals/windows, threshold, eaves, gables etc all need to be considered by the cleint or his/her representative because the installers will not - and the seai grant doesn't pick this up - it barely picks up the need for wall vents
2. each insulation board should have its perimeter sealed between the board and dash - in reality this is down to site supervision and professionalism of the contractor.
3. i like the mineral wool option ('rockwool' is a brand name) - its slightly more expensive than EPS but cheaper than the PIR and its recyclable at its end of life... though the PIR offer the best insulation value for its thickness.

Atlantic1

Thanks again, Bryan.

1. Do Rockwool type products lose some of their insulating properties over time?

2. Would you regard PIR as phenolic? (Like Kingspan K5) Did it lose its certification?

3. Is it much more expensive?

I posted this here last week.......

My original plan was to go for external insulation. About 6 m2 of the front of my house is stone faced so I got a local insulation company out to give me a price for the whole hose, less the stone faced part. (I was going to go the insulated plasterboard route on the inside of that wall rather than applying for planning permission to change it. We're in a park of identical houses). It's a 3 bed semi. He quoted me €9000 to do it.

I spoke to a builder and he said that he could replace the stone front on the house at a reasonable cost and about 9 months later, I asked the same company to come back to give me a price for the whole house.

In the meantime, the insulation grant scheme had been introduced and his new price was €13800! The grant was €4000 at the time...............

BryanF

Atlantic1 wrote: »

Thanks again, Bryan.

1. Do Rockwool type products lose some of their insulating properties over time?

2. Would you regard PIR as phenolic? (Like Kingspan K5) Did it lose its certification?

3. Is it much more expensive?

1. no - feel free to provide peer review literature to disprove
2. Polyisocyanurate (PIR) not that I'm aware of - ill take advice though
3. maybe 20% + € for same u-value, ill take advice on that also

please don't change the colour, we can read fine in black thanks, and try the quotation tags cheers!

Andrew_Doran

Atlantic1 wrote: »

Our houses have a heavy dash finish. Would I have a thermal looping issue if it didn't get a quick coat of plaster first?

I reckon that Rockwool would eliminate this problem but I wouldn't use it if I was having the house externally insulated.

From talking with an EWI contractor I gathered that that the type of wool batts they used were very dense so I do wonder if they would conform to the dash finish any better than EPS. It hardly seems to matter if the lot is properly sealed as Bryan suggests.

Andrew_Doran

BryanF wrote: »

1. footings

It's disappointing that upstand/perimeter/skirt/whatever insulation doesn't seem to be more common with EWI as from (limited) experience it's surprisingly effective.

Atlantic1

Atlantic1 wrote: »

Do Rockwool type products lose some of their insulating properties over time?

BryanF wrote: »

no - feel free to provide peer review literature to disprove

I had to do some searching to find where I saw reference to Rockwool losing its thermal properties.

It's the 7th post (Hope I'm allowed to post this link from another website. Apologies if I'm not).

I don't know if it's his personal opinion or based on his experience......

please dont link to other forums thanks

Atlantic1

Andrew_Doran wrote: »

From talking with an EWI contractor I gathered that that the type of wool batts they used were very dense so I do wonder if they would conform to the dash finish any better than EPS. It hardly seems to matter if the lot is properly sealed as Bryan suggests.

That all makes sense.

BryanF

Atlantic
I dont mean to be harsh but, posting to another forums random punter musings is not 'peer review' literature to disprove mineral wools longevity