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Re: Possibly a bonkers idea - cavity wall insulation
Posted: Tue Jun 25, 2024 1:37 pm
by cojmh
Joeboy wrote: ↑Tue Jun 25, 2024 9:17 am
Could this be put up on the inside and the outside covered in a thinner layer EWI to more preserve the side access? Internal vapor movement being the big one , I didn't dig into it to see.
This is the issue I am butting up against.
No manufacturer has a calculator that allows us to calculate adding either or both EWI and IWI to the current cavity wall situation that is currently in place. I have looked in detail at both the Celotex and Kingspan calculators (and unless I am missing something) it just doesn't give a solution that we can show achieves the target for the purposes of the building control.
If someone knows of a calculator or organisation that can calculate this I would be very interested in speaking to them.
Re: Possibly a bonkers idea - cavity wall insulation
Posted: Tue Jun 25, 2024 1:52 pm
by NoraBatty
Havent read through all thr latest developments, but with an eye to monry saving, seriously consider looking at a place called
https://www.secondsandco.co.uk/?gad_sou ... NYQAvD_BwE
For insulation.
I am doing my underfloor insulation this year. In the last house we had rockwool installed held with netting. Results were extremely impressive but still had the odd draught.
This house, i want celotex underfloor, and am using gapotape to squish and hold it in place, but hace saved over 50% on the insulation by buying seconds.
These vary from oh my god how can anyone use that for £1 a sheet, to almost perfect.
Mine, barely have blemishes on them.
Some are perfect but only need a foil face glueing on. For a fraction of the rrp.
They also do IWI insulated plasterboard, and i highly suspect they do EWI if you have a look.
Re: Possibly a bonkers idea - cavity wall insulation
Posted: Tue Jun 25, 2024 2:00 pm
by Countrypaul
cojmh wrote: ↑Tue Jun 25, 2024 1:37 pm
Joeboy wrote: ↑Tue Jun 25, 2024 9:17 am
Could this be put up on the inside and the outside covered in a thinner layer EWI to more preserve the side access? Internal vapor movement being the big one , I didn't dig into it to see.
This is the issue I am butting up against.
No manufacturer has a calculator that allows us to calculate adding either or both EWI and IWI to the current cavity wall situation that is currently in place. I have looked in detail at both the Celotex and Kingspan calculators (and unless I am missing something) it just doesn't give a solution that we can show achieves the target for the purposes of the building control.
If someone knows of a calculator or organisation that can calculate this I would be very interested in speaking to them.
Have a look a this site for how to calculate it yourself:
https://www.open.edu/openlearn/nature-e ... tion-2.2.6
My Quick and dirty attempt at your existing wall:
Existing Wall
U value
Ext face 0.04
Brick skin 0.132
50mm Poly beads 4
Brick leaf 0.132
13mm Plaster board 0.118
Internal face (wall) 0.13
4.304 0.232
At the IWI solution from your Architect:
Architects IWI soution
U value
Ext face 0.04
Brick skin 0.132
50mm Poly beads 4
Brick leaf 0.132
100mm PIR 5.7
50mm Air gap 0.18
37mm PIR 2.1
13mm Plaster board 0.118
Internal face (wall) 0.13
12.532 0.080
MIssing the 100mm PIR from above
Architects less 100mm PIR IWI soution
U value
Ext face 0.04
Brick skin 0.132
50mm Poly beads 4
Brick leaf 0.132
50mm Air gap 0.18
37mm PIR 2.1
13mm Plaster board 0.118
Internal face (wall) 0.13
6.832 0.146
Obviously needs checking by someoe more experienced, but all corrections welcome (needed?).
It does suggest that what you Architect proposed for IWI ignores what is present already, or mmaybe I just misunderstood his proposal. Just missing the 100mm PIR from his proposal would get you down to below 0.15 though loosing less than 100mm from the internal wall.
Re: Possibly a bonkers idea - cavity wall insulation
Posted: Tue Jun 25, 2024 2:19 pm
by AGT
NoraBatty wrote: ↑Tue Jun 25, 2024 1:52 pm
Havent read through all thr latest developments, but with an eye to monry saving, seriously consider looking at a place called
https://www.secondsandco.co.uk/?gad_sou ... NYQAvD_BwE
For insulation.
I am doing my underfloor insulation this year. In the last house we had rockwool installed held with netting. Results were extremely impressive but still had the odd draught.
This house, i want celotex underfloor, and am using gapotape to squish and hold it in place, but hace saved over 50% on the insulation by buying seconds.
These vary from oh my god how can anyone use that for £1 a sheet, to almost perfect.
Mine, barely have blemishes on them.
Some are perfect but only need a foil face glueing on. For a fraction of the rrp.
They also do IWI insulated plasterboard, and i highly suspect they do EWI if you have a look.
I did 2 layers of 100mm thick kingspan in suspended floor of my extension, did a layer, expanding foam around the perimeter and joins, did a second staggered layer, same foam and foil tape.
Also did the netting in the original house part, think it needs some kind of membrane underneath to prevent further drafts but haven’t looked into that further!
Re: Possibly a bonkers idea - cavity wall insulation
Posted: Tue Jun 25, 2024 2:52 pm
by MrPablo
I used this site for some of the calculations when insulating around my gambrel roof house. It's pretty basic, but good enough to get the U value numbers I needed.
https://www.changeplan.co.uk/u_value_calculator.php
Re: Possibly a bonkers idea - cavity wall insulation
Posted: Tue Jun 25, 2024 2:54 pm
by cojmh
NoraBatty wrote: ↑Tue Jun 25, 2024 1:52 pm
Havent read through all thr latest developments, but with an eye to monry saving, seriously consider looking at a place called
https://www.secondsandco.co.uk/?gad_sou ... NYQAvD_BwE
For insulation.
I am doing my underfloor insulation this year. In the last house we had rockwool installed held with netting. Results were extremely impressive but still had the odd draught.
This house, i want celotex underfloor, and am using gapotape to squish and hold it in place, but hace saved over 50% on the insulation by buying seconds.
These vary from oh my god how can anyone use that for £1 a sheet, to almost perfect.
Mine, barely have blemishes on them.
Some are perfect but only need a foil face glueing on. For a fraction of the rrp.
They also do IWI insulated plasterboard, and i highly suspect they do EWI if you have a look.
Thank you for the link - those prices are very very good and will certainly come in useful for underfloor insulation and the roof insulation.
Re: Possibly a bonkers idea - cavity wall insulation
Posted: Tue Jun 25, 2024 2:59 pm
by cojmh
Countrypaul wrote: ↑Tue Jun 25, 2024 2:00 pm
Have a look a this site for how to calculate it yourself:
https://www.open.edu/openlearn/nature-e ... tion-2.2.6
My Quick and dirty attempt at your existing wall:
Existing Wall
U value
Ext face 0.04
Brick skin 0.132
50mm Poly beads 4
Brick leaf 0.132
13mm Plaster board 0.118
Internal face (wall) 0.13
4.304 0.232
At the IWI solution from your Architect:
Architects IWI soution
U value
Ext face 0.04
Brick skin 0.132
50mm Poly beads 4
Brick leaf 0.132
100mm PIR 5.7
50mm Air gap 0.18
37mm PIR 2.1
13mm Plaster board 0.118
Internal face (wall) 0.13
12.532 0.080
MIssing the 100mm PIR from above
Architects less 100mm PIR IWI soution
U value
Ext face 0.04
Brick skin 0.132
50mm Poly beads 4
Brick leaf 0.132
50mm Air gap 0.18
37mm PIR 2.1
13mm Plaster board 0.118
Internal face (wall) 0.13
6.832 0.146
Obviously needs checking by someoe more experienced, but all corrections welcome (needed?).
It does suggest that what you Architect proposed for IWI ignores what is present already, or mmaybe I just misunderstood his proposal. Just missing the 100mm PIR from his proposal would get you down to below 0.15 though loosing less than 100mm from the internal wall.
Thank you very much .... that looks like it might actually help me solve the question of what I have and what I need.
I will check this in more detail this evening to see if it spits out what I need to do.
Many Thanks,
Re: Possibly a bonkers idea - cavity wall insulation
Posted: Tue Jun 25, 2024 4:16 pm
by NoraBatty
AGT wrote: ↑Tue Jun 25, 2024 2:19 pm
NoraBatty wrote: ↑Tue Jun 25, 2024 1:52 pm
Havent read through all thr latest developments, but with an eye to monry saving, seriously consider looking at a place called
https://www.secondsandco.co.uk/?gad_sou ... NYQAvD_BwE
For insulation.
I am doing my underfloor insulation this year. In the last house we had rockwool installed held with netting. Results were extremely impressive but still had the odd draught.
This house, i want celotex underfloor, and am using gapotape to squish and hold it in place, but hace saved over 50% on the insulation by buying seconds.
These vary from oh my god how can anyone use that for £1 a sheet, to almost perfect.
Mine, barely have blemishes on them.
Some are perfect but only need a foil face glueing on. For a fraction of the rrp.
They also do IWI insulated plasterboard, and i highly suspect they do EWI if you have a look.
I did 2 layers of 100mm thick kingspan in suspended floor of my extension, did a layer, expanding foam around the perimeter and joins, did a second staggered layer, same foam and foil tape.
Also did the netting in the original house part, think it needs some kind of membrane underneath to prevent further drafts but haven’t looked into that further!
Two layers is the plan for me. With limited arm mobility, and doing it all from the crawl space, i was loathing doing the same spray, cut flush and tape method.
When i found gapotape, i jumped at it.
More expensive than spraying and taping, but means significantly less time under the floor, which is worth its weight in gold to me.
Building regs also do not like the spray and foil method. Full compliance with the gapotape.
You get a snug friction fit every time, making sure there is the full insulation thickness at every join and seam and ut is forgiving to 1cm if your cuts arent great
We tested it out last winter with a removeable panel in front of the door to keep the heat in, instead of the usual curtain. Brilliant stuff.
I certainly have felt not having any insulation under the floor here.
Cant wait to get it in and have warm feet!
Re: Possibly a bonkers idea - cavity wall insulation
Posted: Tue Jun 25, 2024 4:19 pm
by NoraBatty
cojmh wrote: ↑Tue Jun 25, 2024 2:54 pm
NoraBatty wrote: ↑Tue Jun 25, 2024 1:52 pm
Havent read through all thr latest developments, but with an eye to monry saving, seriously consider looking at a place called
https://www.secondsandco.co.uk/?gad_sou ... NYQAvD_BwE
For insulation.
I am doing my underfloor insulation this year. In the last house we had rockwool installed held with netting. Results were extremely impressive but still had the odd draught.
This house, i want celotex underfloor, and am using gapotape to squish and hold it in place, but hace saved over 50% on the insulation by buying seconds.
These vary from oh my god how can anyone use that for £1 a sheet, to almost perfect.
Mine, barely have blemishes on them.
Some are perfect but only need a foil face glueing on. For a fraction of the rrp.
They also do IWI insulated plasterboard, and i highly suspect they do EWI if you have a look.
Thank you for the link - those prices are very very good and will certainly come in useful for underfloor insulation and the roof insulation.
Youre welcome.
Keep an eye out or call them. Stock changes constantly, and they do sell cavity slabs. They may be able to put you on a call list or something when a decent batch come in.
Re: Possibly a bonkers idea - cavity wall insulation
Posted: Tue Jun 25, 2024 4:20 pm
by richbee
Countrypaul wrote: ↑Tue Jun 25, 2024 2:00 pm
cojmh wrote: ↑Tue Jun 25, 2024 1:37 pm
Joeboy wrote: ↑Tue Jun 25, 2024 9:17 am
Could this be put up on the inside and the outside covered in a thinner layer EWI to more preserve the side access? Internal vapor movement being the big one , I didn't dig into it to see.
This is the issue I am butting up against.
No manufacturer has a calculator that allows us to calculate adding either or both EWI and IWI to the current cavity wall situation that is currently in place. I have looked in detail at both the Celotex and Kingspan calculators (and unless I am missing something) it just doesn't give a solution that we can show achieves the target for the purposes of the building control.
If someone knows of a calculator or organisation that can calculate this I would be very interested in speaking to them.
Have a look a this site for how to calculate it yourself:
https://www.open.edu/openlearn/nature-e ... tion-2.2.6
My Quick and dirty attempt at your existing wall:
Existing Wall
U value
Ext face 0.04
Brick skin 0.132
50mm Poly beads 4
Brick leaf 0.132
13mm Plaster board 0.118
Internal face (wall) 0.13
4.304 0.232
At the IWI solution from your Architect:
Architects IWI soution
U value
Ext face 0.04
Brick skin 0.132
50mm Poly beads 4
Brick leaf 0.132
100mm PIR 5.7
50mm Air gap 0.18
37mm PIR 2.1
13mm Plaster board 0.118
Internal face (wall) 0.13
12.532 0.080
MIssing the 100mm PIR from above
Architects less 100mm PIR IWI soution
U value
Ext face 0.04
Brick skin 0.132
50mm Poly beads 4
Brick leaf 0.132
50mm Air gap 0.18
37mm PIR 2.1
13mm Plaster board 0.118
Internal face (wall) 0.13
6.832 0.146
Obviously needs checking by someoe more experienced, but all corrections welcome (needed?).
It does suggest that what you Architect proposed for IWI ignores what is present already, or mmaybe I just misunderstood his proposal. Just missing the 100mm PIR from his proposal would get you down to below 0.15 though loosing less than 100mm from the internal wall.
It's quite useful that site / course - I worked through it when I was first looking at the ASHP heat loss calcs
