We are building ICF in the St. Louis Missouri region. Mold is a huge concern in this part of the country and we want to make sure we do this correctly. How do I find a qualified HVAC engineer and installer? The architect that designed the house has done a lot of ICF so we were good with his designs. We plan on using spray foam in the attic with ridge venting in the attic. Any other helpful advice you can give us? We start pouring concrete in mid October.

If your spray foaming the attic for a sealed enclosure, you don't need ridge vents. Unless you are closing the underside of the rafters in so that the roof deck can breath. Can be done but costly and pain in butt. I'd recommend sealing it up best as possible. Always put a electronic damper on a humidistat in the attic to control that area. Most a/c guys get paid by the ton and don't want to waist time designing a system. Do your homework and get references. Don't oversize, best to undersize.

Is the architect not local? He may know some pros who have done a good job on his projects in the past. If he's no help then at least make sure the HVAC people know what a Manual J calculation is and actually perform one.

If you are using a vented attic, then make sure that there are soffit vents and ridge vents of enough area. And that the attic floor is well air sealed (as spray foam should do). Solar heating will cause enough temperature increase to keep %RH low on a regular basis (ie, no mold).

Don't put ducts in a vented attic.

Energy heel roof trusses deep enough to accommodate 18-20" of open-blown cellulose is a lot cheaper than code-min spray foam at the roof deck (vented or unvented.) Blower-door test the place prior to insulating, so that you can find & fix all of the air leaks ahead of time.

If you're insulating with foam with the idea that the foam is going to air seal the place, blower door verify the place on foam-day, before they start breaking down the foam spraying setup. It's WAY too easy to miss spots, and fixing it later is difficullt & expensive compared to fixing it while they're already suited up, with the chemistry already at the right operating temp. Don't let them spray open cell foam in lifts any thicker than 6", or closed cell at lifts thicker than 2", and allow the foam to cool for the manufacturer's recommended time between lifts. If you don't follow the protocol there is a short term risk of fire breaking out as the stuff cures (sometimes hours later), and a longer term issue with shrinkage & adhesion problems.

A better architect with ICF experience should be competent to run an aggressive ACCA Manual-J heating/cooling load estimate on the place. Don't leave that up to the HVAC people to run on their own, especially in an ICF house where they are even more likely to overestimate the peak loads. There is tendency for HVAC people to be too conservative, and if they model the ICF house correctly they might not believe the numbers, and tweak the inputs until it makes THEM more comfortable, but by oversizing the equipment it will result in you being LESS comfortable.

Thanks everyone for the speedy replies! We really appreciate your time and expert opinions!

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