Say Goodbye to Moisture with These Foam Boards | InSoFast MAX 3.75 Panels

[@danslickers8166]

I do like the product. I really like the fact that it has “studs” built into it.
My fear is the amount of air it’s allowing through the drainage plain between the osb and the insofast. Zero Fahrenheit air coming in contact with 60 Fahrenheit osb temperature, and it will, is going to cause all sorts of problems.
What are your thoughts on this?
Grace and Peace
Slick

[@alldecentnamestaken]

My concern as well.

[@user-bm5fw5ef3e]

Doesnt insulation have to be touching the sheathing to provide maximum insulation value?

[@Gjehcyekcgev]

You get the full insulating value if the foam is continuous, that doesn't mean it needs to be 100% in contact with the sheathing.

[@Honeybadger_85]

You're going to get a convection effect. Hot air will rise and pull cold are in from the bottom.

[@user-bm5fw5ef3e]

@@Honeybadger_85 Thats what I thought. If there is space water to move, that means there is space for air to move. If there is space for air to move, shouldn't the insulation value go down?

[@Zorlig]

@@user-bm5fw5ef3e Based on what you've said, but your facts aren't quite correct. There is a minimum distance required for convection. For some idea of how big that is take a look at your windows. The glass panes will be a distance under that minimum.

[@dosadoodle]

How much air flow happens behind the insofast panels? What is the effective R-value with that consideration?
I'm not advocating for the other foam as better. Rather, I'm wondering if neither of these are the right solution. It seems like a vapor-open exterior insulation is preferable.

[@danslickers8166]

Problem with vapor open insulation aka mineral wool is the air moving through it.
It needs covered in a fluid applied wrb or a peel and stick wrb.
Grace and Peace
Slick

[@mefobills279]

Capillary action is due to evaporation around the foam panel, creating negative pressure directly behind the panel. Eventually, the Zip will dry, but why take chances? What I really like is internal webbing and its strength, along with no need for furring strips. To answer the critics, some testing data on R value for the entire wall assembly will satisfy them. For example, air movement through the grooves will likely have minimal impact. The entire wall assembly will be insofast recommended method. Personally, I think OSB then fluid applied, and then insofast might be a sweet spot.

[@dosadoodle]

@@danslickers8166 I've heard otherwise on air moving through mineral wool boards (though I had and still perhaps have some mild concerns about that as well). What I'd been advised was that I shouldn't think of the air flow like I'd expect from a hole in the building shell, where air is passing from inside to outside; it is dense mineral wool up against a flat air-impermeable surface, so supposedly very little air flow. (And I'd expect evaporating moisture to behave differently than static air, e.g. the vapor pressure would force some air movement to allow drying.)
Re: fluid applied or peel and stick -- referring to foam board? I don't think the fluid applied would work: many foam board shrink a little over time, so gaps would likely be present a year or two after install. I'm unsure how peel and sticks will hold up, e.g. if they'll lose their adherence to the foam or if they'd hold up and just stretch a bit at seams.
The approach I took to retrofit our house beyond the standard stud cavity: ZIP sheathing, larsen truss equivalent + mineral wool cavity insulation (~4" exterior insulation at ~R15), house wrap to hold things together / prevent cavity insulation from falling out, 1.5" rain screen (2x3s), and then siding.

[@gregoryfambro7592]

GREAT CONTENT

[@randyscrafts8575]

Yup. Just as I figured. The Zip wall is the problem.

[@kenttaylor2568]

if water moves behind your panel, air moves behind your panel and your insulation value is nil