Block and Block with 180mm cavity instead of Isotex ICF

[Chanmenie]

So I designed and build my foundations to accept ISOTEX ICF Blocks, however you may have read the post about Insulhub going into receivership, my blocks should have been delivered this week but that’s not going to happen.

so I need to redesign my construction.

The foundation walls are 380mm wide so I’m considering using 100mm Celcon Aircrete blocks with 180mm cavities with 100mm PIR which I believe will give a U Value of .15W/m2K the same as the Isotex blocks would have given.

Has anyone built with large cavities and used PIR cavity insulation that can give me some pointers. 

[Mr Punter]

Can you narrow the walls down to 350mm?  Lintels, wall ties and cavity closers will be easier to source.

[Dave Jones]

slim down to a 150 cav, have a look at recticel tongue and groove insulation. superior than celotex sheets.

[Chanmenie]

Yeah have looked at recticel eurowall+ and Celotex thermocel which is the same thing.

if I reduce cavity to 150mm I’ll have 30mm of dense block uncovered that will be a cold bridge and could cause condensation.

I spoke to Celotex and recticel  and asked why their T&G boards could only have a residual cavity of 10mm and they both replied it was because of the BBA certificate was done on that basis. 
but if use the plain cavity boards I should have a 50mm residual cavity, yet both boards are made from PIR 

[ADLIan]

Why not 175mm mineral wool batt at 0.032 W/mK? Will give U=0.15 W/m2K with aircrete block inner.

[Nickfromwales]

6 hours ago, Chanmenie said:

So I designed and build my foundations to accept ISOTEX ICF Blocks, however you may have read the post about Insulhub going into receivership, my blocks should have been delivered this week but that’s not going to happen.

so I need to redesign my construction.

The foundation walls are 380mm wide so I’m considering using 100mm Celcon Aircrete blocks with 180mm cavities with 100mm PIR which I believe will give a U Value of .15W/m2K the same as the Isotex blocks would have given.

Has anyone built with large cavities and used PIR cavity insulation that can give me some pointers. 

Are you looking to get airtight and install MVHR?

[Chanmenie]

7 hours ago, Nickfromwales said:

Are you looking to get airtight and install MVHR?

Yes Nick

[Nickfromwales]

31 minutes ago, Chanmenie said:

Yes Nick

Ok, just anything other than EPS ( a-la Nudura etc ) it's a big PITA to get right in masonry or woodcrete. Woodcrete would be my last choice, but tbh I'd probably go masonry if woodcrete was the only remaining contender. Have you considered the XR35 Nudura block? I can recall the exact depth of block, but iirc its 100 - 150 - 100 so a 350 depth EPS to EPS.

You'll save money as even though the shell will be expensive ( but quick ) to put up, you'll save a lot on being instantly water-tight, and getting super-airtight is then child's-play. 

[Dave Jones]

57 minutes ago, Nickfromwales said:

Ok, just anything other than EPS ( a-la Nudura etc ) it's a big PITA to get right in masonry or woodcrete. Woodcrete would be my last choice, but tbh I'd probably go masonry if woodcrete was the only remaining contender. Have you considered the XR35 Nudura block? I can recall the exact depth of block, but iirc its 100 - 150 - 100 so a 350 depth EPS to EPS.

You'll save money as even though the shell will be expensive ( but quick ) to put up, you'll save a lot on being instantly water-tight, and getting super-airtight is then child's-play. 

 

its a false saving getting  watertight in weeks if you dont get a completion cert for another 12 months remember. Same as the expensive shed builds. Unless the trades are lined up to machine gun the build out in 8/12 weeks its burring cash for no reason.

[Nickfromwales]

Just now, Dave Jones said:

 

its a false saving getting  watertight in weeks if you dont get a completion cert for another 12 months remember. Same as the expensive shed builds. Unless the trades are lined up to machine gun the build out in 8/12 weeks its burring cash for no reason.

Complete and total bollocks, and yes I am blunt, and yes you should all be used to that by now.

 

If you're wanting to build through the winter, an exposed block build will be weathertight, far more than a woodcrete build would be, especially the Isotex block. If you want to get on with a completed interior it is 100% the way forwards. The woodcrete stays saturated for months, especially if you've had to wet coat the interior vs dry-line. and the shrinkage when this all dries out makes the walls look like a map of New York.

[Russell griffiths]

If you where going to build in icf then carry on, building with Cellini blocks is going backwards massively. 
calm down, stop for a week and talk to some other Icf suppliers. 
im sorry if you have lost any money, but not building with isotex will be a massive relief once you have found an alternative product. 

[Kelvin]

I agree to an extent on the expensive shed builds as you may as well stick build it. However getting to watertight quickly seems to be a good thing to achieve to this inexperienced self-builder which is part of the reason we went expensive shed. Plus it seems a bit easier to get it airtight etc

[Nickfromwales]

14 minutes ago, Kelvin said:

I agree to an extent on the expensive shed builds as you may as well stick build it. However getting to watertight quickly seems to be a good thing to achieve to this inexperienced self-builder which is part of the reason we went expensive shed. Plus it seems a bit easier to get it airtight etc

100%

[saveasteading]

I don't know these building systems in detail so please excuse any errors of understanding.

 

I like celcon type blocks in the right circumstances, but would use concrete blocks for footings. They are stronger, less likely to crack during construction or in service, and have better fixings pull-out resistance.

 

If they are to remain exposed they are also tidier and readily  take a coat of blackjack. 

Celcon will soak up water.

 

The insulation difference is trivial and can easily be recovered in other ways.

[Iceverge]

Rigid boards in a cavity. DON'T DO IT!! 

 

Lightweight blocks are good for the Bricky as they're light. Bad for everything else. Expensive, they crack. They're hard to fix to and render. The benefit to u value is tiny. 

 

Like @Russell griffiths says stop and take a breath. Nothing major lost yet (I hope you haven't lost money)  and you can still get an excellent building. 

 

AN alternative brand of ICF or a Stick build would be my choice. 

 

 

 

 

[Chanmenie]

5 hours ago, Nickfromwales said:

Ok, just anything other than EPS ( a-la Nudura etc ) it's a big PITA to get right in masonry or woodcrete. Woodcrete would be my last choice, but tbh I'd probably go masonry if woodcrete was the only remaining contender. Have you considered the XR35 Nudura block? I can recall the exact depth of block, but iirc its 100 - 150 - 100 so a 350 depth EPS to EPS.

You'll save money as even though the shell will be expensive ( but quick ) to put up, you'll save a lot on being instantly water-tight, and getting super-airtight is then child's-play. 

Hi Nick thanks for the suggestion but Nudura won’t fit on my footing as the 150mm concrete would sit partially over the cavity, I think the only other ICF would be Thermawall as they do a 50-150-100 or a 50-150-150 which because of the initial 50mm eps would fit on my footing.

[Chanmenie]

5 minutes ago, Iceverge said:

Rigid boards in a cavity. DON'T DO IT!! 

 

Lightweight blocks are good for the Bricky as they're light. Bad for everything else. Expensive, they crack. They're hard to fix to and render. The benefit to u value is tiny. 

 

Like @Russell griffiths says stop and take a breath. Nothing major lost yet (I hope you haven't lost money)  and you can still get an excellent building. 

 

AN alternative brand of ICF or a Stick build would be by choice. 

 

 

 

 

Yes I have lost money, my Isotex blocks were paid for.

so I need a system I can do myself, 

With DIY,  lightweight blocks and rigid PIR work out much cheaper than ICF especially when you factor in the cost of concrete and pump hire.  
I’m surprised you say they are hard to to fix to and render to, how are they any worse than EPS.

Edited April 7, 2023 by Chanmenie

[Iceverge]

15 minutes ago, Chanmenie said:

Yes I have lost money, my Isotex blocks were paid for.

so I need a system I can do myself, 

With DIY,  lightweight blocks and rigid PIR work out much cheaper than ICF especially when you factor in the cost of concrete and pump hire.  
I’m surprised you say they are hard to to fix to and render to, how are they any worse than EPS.

 

Sorry to hear that. That's a real PITA. I hope you'll get some money back. Were they on credit card or anything?

 

Using regular dense blocks is a better way for cavity walls IMO Vs lightweight. Get some prices and do some U value calcs and you'll see. Blockwork isn't too different but in my hands it's extremely slow for DIY.  EPS beads or full fill mineral wool and a 180mm cavity will get you to a respectable 0.17W/m2K.  Stainless steel cavity ties for up to 300mm cavities are easy to get here in Ireland. UK must be similar I imagine. 

 

For DIY only a stick frame would be my choice. As you've unfortunately found out there's a big plus in being able to walk into any builders merchants for materials. 

 

220mm stud full filled with cellulose.  11mm OSB racking, 50mm cavity and 100mm block facing would fit nicely on the 380mm foundation. A/T membrane to the inside and a 50mm insulated service cavity. U value about 0.14, quick to watertight and will perform excellently. 

[Chanmenie]

1 hour ago, Iceverge said:

Rigid boards in a cavity. DON'T DO IT!! 

 

Lightweight blocks are good for the Bricky as they're light. Bad for everything else. Expensive, they crack. They're hard to fix to and render. The benefit to u value is tiny. 

 

Like @Russell griffiths says stop and take a breath. Nothing major lost yet (I hope you haven't lost money)  and you can still get an excellent building. 

 

AN alternative brand of ICF or a Stick build would be by choice. 

 

 

 

 

Out of interest whats wrong with rigid PIR cavity boards if fitted correctly and taped ?

 

I'll look into stick built as you suggest thanks.

 

[Nickfromwales]

17 minutes ago, Chanmenie said:

Yes I have lost money, my Isotex blocks were paid for.

so I need a system I can do myself, 

With DIY,  lightweight blocks and rigid PIR work out much cheaper than ICF especially when you factor in the cost of concrete and pump hire.  
I’m surprised you say they are hard to to fix to and render to, how are they any worse than EPS.

The longevity of wet layers ( plaster / render ) over aerated blocks is dire, as they are dry as a biscuit and crack a lot through settlement etc.

Get the structure as your #1 focus, and don’t lose track of what can and can’t be retrospectively addressed / upgraded / altered. The structure is one such thing.

Have a look at this again, and defo stay focussed. 
 

22 minutes ago, Chanmenie said:

Hi Nick thanks for the suggestion but Nudura won’t fit on my footing as the 150mm concrete would sit partially over the cavity, I think the only other ICF would be Thermawall as they do a 50-150-100 or a 50-150-150 which because of the initial 50mm eps would fit on my footing.

Nudura offer a thinner system also, 67 - 150 - 67 iirc. The XR35 is their beefed up block.

Isn’t your cavity superfluous? 

[Russell griffiths]

2 hours ago, Chanmenie said:

Hi Nick thanks for the suggestion but Nudura won’t fit on my footing as the 150mm concrete would sit partially over the cavity, I think the only other ICF would be Thermawall as they do a 50-150-100 or a 50-150-150 which because of the initial 50mm eps would fit on my footing.

Why do you have a cavity if you were going with icf, just fill the cavity in and proceed with Icf blocks from there. 

[Iceverge]

14 hours ago, Chanmenie said:

Out of interest whats wrong with rigid PIR cavity boards if fitted correctly and taped ?

 

They cannot practically and cost effectively be fitted properly. 

 

The inner surface is too uneven even with really careful masons to avoid thermal bypass. It needs foaming. 

 

The cavity ties will create penetrations that need to be foamed. 

 

All joints will be need closed cell foam and be given the time to dry before being trimmed and taped. In reality this is happening outside in the rain with plenty of mortar droppings. It cannot be done easily which means it's never done right and mostly not even attempted. 

 

 

 

[Lisa Maggs]

I’ve heard Isotex Italy will be offering any customers affected a large discount 

we have been left with a house half built

so yesterday me and my Husband started building ourselves.   

[Brickie]

1 hour ago, Iceverge said:

 

They cannot practically and cost effectively be fitted properly. 

 

The inner surface is too uneven even with really careful masons to avoid thermal bypass. It needs foaming. 

 

The cavity ties will create penetrations that need to be foamed. 

 

All joints will be need closed cell foam and be given the time to dry before being trimmed and taped. In reality this is happening outside in the rain with plenty of mortar droppings. It cannot be done easily which means it's never done right and mostly not even attempted. 

 

 

 

100% agree. 
Never going to get the states U value due to the realities of installation,even if you had the most conscientious bricklayers in the world. The detailing at reveals & lintols would require surgical precision to be anything other than leaky. 

[Iceverge]

On 08/04/2023 at 07:40, Lisa Maggs said:

I’ve heard Isotex Italy will be offering any customers effected a large discount 

we have been left with a house half built

so yesterday me and my Husband started building ourselves.   

 

This is really a pain for all involved. Good to hear isotex are doing something. 

 

As you're new feel free to create a post and keep us informed. We're all pretending to be helpful just to excuse our nosiness!