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ICF extra insulation and siding installation

ShoxEg | Posted in General Questions on
Hello everyone, 
I have been doing a lot of reading on this forum about ICF, so much so that i decided to build our dream home in ICF, Well i am using a local contractor… I am located in Ottawa Ontario, Climate zone 5A, we also have some pretty decent temperature fluctuation in the winter and summer. 
He uses IntegraSpec blocks, which are 2.5 and 2.5 inch foam 
My first question is about adding extra insulation on the main residence portion of the built. i was thinking of adding 3 inch (r12)  
My idea behind this is to better benefit from the thermal mass and have proper straping for exterior metal siding installation. 
According to a Local energy guru, the extra 3 inch of foam could possibly equal to an energy savings of 8%… which in the end i won’t necessarily get the return on investment in 20 years… unless it ends up performing better then anticipated 
Question 2, installing metal siding. i am currently looking at this product 
if i don’t add extra insulation can this be fassent directly onto the icf web of should i install strapping to leave an air gap 
Question 3
sorry one more, for installing stone veneer panels, like 
would i need to install, 1/2 ply with house wrap or can i go directly to the web of strapping 
Thank you everyone very much for your help 

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  1. jberks | | #1

    Hi Etienne,

    I personally think in whichever way you've described, you should do housewrap and furring strips before your siding.

    I'm not an icf contractor, but I have installed it for a foundation on my current build.

    For above ground, I would be thinking about moisture. You could probably get away with an interior vapour barrier and siding directly against the icf. But I imagine the siding will rust sooner than later with no ability to dry on the backside. Also the vapour barrier install would have to be top notch because it would basically have a sponge full of water (the concrete) constantly bombarding it.

    I'm sure someone with more experience on this can chime in.

    If it were my build, I'd do tyvek rolls to manage secondary water and allow wall moisture out. And 3/4" vertical furring strips screwed to the web of the icf with the siding overtop. This allows a path for moisture to get out.

    I know concrete can stay wet, it's not a structural issue like it is for wood structures. But you don't want any mold issues or possible premature failures. I'm an overcautious builder for things like this, but Tyvek and furring is relatively cheap. At $0.13 CAD per sqft for tyvek and roughly $0.25 CAD per sqft for the furring strips, plus labour, I think it's a cheap insurance.

    Just my 2 cents

  2. Expert Member
    Michael Maines | | #2

    Etienne, I don't use ICFs above grade because they have one of the largest carbon footprints of any building system, but if you are committed to using them, have you considered simply using higher R-value blocks, such as these or these The labor savings would probably be significant. The thermal mass effect is greatly overestimated; airtightness, R-value and good windows are all much more important.

    As Jamie says, Tyvek (or other WRBs) are a good idea, especially because they allow you to mechanically lap joints and flashing.

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