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ICF and airtightness


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Following an afternoon of taping the VCL / airtight layer on my timber frame self build I'm thinking about things I'd do differently if we get permission on our second potential plot.

 

The main change I had considered would be using ICF instead of timber frame but I'm curious to know what the strategy on an ICF build is in terms of airtightness. I'd be keen to avoid any membranes possible as this build has annoyed me in that respect and all the membranes and tapes really add up cost wise. I know there are alternative ways of doing a timber frame but generally speaking I imagine there are more membranes in this type of construction than ICF - please correct me If I'm wrong.

 

Particularly interested in how internal services are run and the link between floor / wall / roof for the airtight layer in an ICF build (assuming it is done internally?).

 

Many thanks

 

 

 

Edited by bissoejosh
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The only membrane I will be using is on my ceiling internally, it will cover the entire ceiling and be taped to the walls at wall plate level. 

Obviously all windows will be taped to the window jambs. 

I have used nudura i know it can be a very different situation with other manufacturers. 

No external membrane needed either. 

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7 minutes ago, Russell griffiths said:

The only membrane I will be using is on my ceiling internally, it will cover the entire ceiling and be taped to the walls at wall plate level. 

 Obviously all windows will be taped to the window jambs. 

 I have used nudura i know it can be a very different situation with other manufacturers. 

 No external membrane needed either. 

 

What forms the window opening within the ICF - timber?  Presumably the concrete core is airtight enough by itself to not need any wall membranes then? It sounds ideal but as you mention I guess it depends on the chosen system.

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Funny you where asking this question as we where discussing the same question what we would do different on build 2 at tea break today !

 

I have only used tape at windows (inc velux) and doors. I have sprayed insulation covering full width of icf block to the ridge. Hoping this provides a respectable/good air tightness.

Edited by Alexphd1
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48 minutes ago, bissoejosh said:

 

What forms the window opening within the ICF - timber?  Presumably the concrete core is airtight enough by itself to not need any wall membranes then? It sounds ideal but as you mention I guess it depends on the chosen system.

This all depends on the make of icf, mine is all eps, including all cavity closers

i know some other makes are as porous as a weetabix. 

You pay your money and take your choice. 

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5 hours ago, Russell griffiths said:

98A83DC0-C574-40D3-A3E9-18ACA791C39E.jpeg.e3c18168757caac854ab7af15c0c66b3.jpeg2492909A-4E81-4B9F-86AB-5B4692BC1479.jpeg.ef5a216837b79a4ce18a498240a481f4.jpeg

cavity closer system for nudura. 

Tape the inside and outside and I cannot see a lot getting through there. 

Very neat - Nudura is definitely on the list for potential suppliers.

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18 hours ago, Russell griffiths said:

i know some other makes are as porous as a weetabix. 

this will be why that type(durisol +Isotex) always seem to suggest a parge coat on outside to seal  it up .if not using a membrane 

velox type would not need it as it is a conitnous wall of concrete --no webs

or hard plaster internally and chase wiring in to the walls ,same goes for poly types

 no big deal to use one of those stucco/tirolean  spray things  to fill up the surface on outside before final cladding 

I still think a VCL under the plasterboard if going that with service void, would be a good idea though ?

 

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I have spent last 9  months studying ALL ICF types I could find of the poly types ,but looks like i may be rebuilding an old house now instead-

 

my choice would be Isodom2000 or integraspec for poly type 

Isotex for woodcrete type 

all worth a look if you thinking of ICF 

I,m sure they all work fine is care is taken 

I certainly wouldn,t be put off using TF just cos you have to fit memebranes ,

sure there are a lots more boring things in any build job  you have to do 

 

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Another guy/gal on here build a TF then sprayed the whole house with open cell foam. He used nothing else apart from extra window/door details and achieved a good air tightness results. 

 

I am a big fan of ICF and tbh prob will use again on next build.

 

 

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