love this forum that you can do a little diy advising! ok the mold in the supply boxes and on the grills probably isn't from the duct takeoffs @ the plenum. it takes a long time for mold to travel that far..and if there isn't moisture & food source it won't spread to that area. it isn't always mold..sometimes it is just dust. so mold/dust buildup at the ducts @ plenum is lack of proper air seal. mold in supply boxes & on grills is lack of proper air seal at the cut in the sheetrock ceiling where supply grill is attached to the box. nine times out of ten..you can solve the issue by sealing supply boxes to sheetrock. see attached picture. hardcast brand #1402 mastic tape is used to seal supply box to sheetrock. this tape is 3" wide. I split the 3" into 1 1/2" lengths. stick to sheetrock and fold into supply box. as the tape adheres to many surfaces you need to be careful to keep it within the area covered by the supply grill. once it sticks to the sheetrock..you'll lose paper if you try to move it. surfaces have to be clean & dry for tape to adhere. and once in place you'll want to press it in place as it is somewhat pressure sensitive. the tape is strong enough to keep the box tight to attic floor on the attic side when installing the supply grill. wash the dust off the grills, wipe inside the supply box & into the duct. reinstall the supply grill. oh and when you remove the supply grills..take a sharpie and mark what direction they faced (throw to window..dirveway side whatever note you need to put them back in same position) this way you'll put them back as they were. I've tried several other brands of mastic tape. hardcast 1402 is the best. the others are 2" width and mastic is thinner, resulting in less strength and useful life. why would I chose spray foam for my floors? I've sealed floors several ways, foam is the easiest albeit more costly, once prep work is done. there isn't enough room to physically install foam sheathing to the bottom of the floor joists. I'll seal any big holes..like under tub then do 3" foam. I've looked at froth packs like tiger foam..but having worked with so many foam companies locally, will just have them do my floor when they are in my area. the software is pricy. we lease it yearly. once upon a time we bought the cd..but too many people abused it. so now it is a download & upgrades to original install. a lot of mastic isn't always an indication of a good seal. it doesn't take a lot if you put it in the actual leaks. you can feel around the duct take offs on the plenum while unit is running and feel some of the leakage. also checking plenum connections to the equipment at the same time. I use mastic tape to connect plenums (after screwing them in place) much easier to seal under the plenum to equipment with tape than painting mastic upside down.

Here's a bit more info to give you a better idea. Zone 5B, Cold winters, hot summers (rarely humid but like this year...humid and hot summer!) My walls will be 2x6 with either dense fiberglass or mineral wool insulation (products readily available locally). My current debate among my thoughts is trying to decide about the WRB (MY HOUSEWRAP) and at what tier/level/plane to install it (Or even two). Windows are not permanent, and in a forever home (God willing), windows will need to be replaced in the same lifetime I live. Therefor, I don't want to choose some method that would hinder future upgrades/replacement. (Such as installing foam over a flange so it must be cut out, or installing a type of flashing that requires more of the foam wall or window box to be torn out to replace the next time around. I am debating between a quality house wrap to prevent moisture and also act as an *air* barrier not a *vapor* barrier. Basically, on a cool winter day with 50 MPH Wind, I don't want that wind (air) easily permeating through the house because I will a.) not be sealing the joints of foam b.) possibly not even taping the foam joints c.)not going to use any internal poly as a air or vapor barrier. I am not sealing the foam joints because foam shrinks and expands and those joints will not stay tight forever. If I have the luxury, I will install (2) layers of 1" thick versus (1) layer of 2" thick to provide staggered joints and prevent air from moving inwards that much more. There is a wealth of information on greenbuildingadvisor, but it seems to boil down to personal preference on two things. One being that I can opt for innie (windows set towards the OSB wall sheathing layer) or outie (windows that are at the most exterior plane as possible). And we all know that flashing a window opening is important for multiple reasons, and that the standard way includes integrating your house wrap (WRB) into the rough opening with multiple methods. I would like to use a flexible peel & stick flashing that will seal to/against the house wrap. My concerns for those who have rigid foam on the exterior are a.)where did you locate a house wrap (Or WRB)? and b.)in what fashion did you set your windows? It varies by foam thickness, but generally 1.5"+ of foam requires framing out a window frame/buck for window support whereas under 1.5" doesn't seem to need the additional support. And of course the other option is the fasten the window like standard construction, on the sheathing level right against the sheathing (osb in my situation) and into the studs. This would then mean I would either use the WRB at the same time to detail the window opening, or perhaps not. But also means I would have to design a custom flashing to cover the exposed foam around the window, since the window is set inside from the foam and siding. I am surprised house wrap (a WRB) seems to not be the norm. It is here...and it is something I do not want to overlook. My understanding is that in new construction with rigid on the outside, builders extend the window opening (like you said Mushcreek) to the same thickness as the foam, therefore that foam will not have an exposed edge. I read on GBA that instead people build plywood boxes for the windows the thickness of the foam + 3/4" and then use a 1x3 or 1x4 flat around the window opening fastened thru the foam into the window opening studs. Then the window flange is fastened to this flat 1x3 or 1x4 frame, and it also brings the window out the extra 3/4" so that 3/4" firing strips can be used to install siding. I do not think house wrap *over* the extended window frame would be as effective as if I just installed the windows flush with the foam level, allowing my flexible sticky flashing tape to easily fold over the opening and adhere to the foam. ---starting to think I should just not be so concerned about this detail. Turning my hair grey.

3650 PSF is equal to 25 PSI..... Their dricore products are just massively overpriced, at least in the US they are. I think it is better to put down a foundation wrap (DMX), then 1" XPS foam (25-30 PSI). Assuming that the floor is flat, you could probably get away with putting flooring (with a membrane) directly on top of it. If your floor isn't flat, you probably will need a dedicated subfloor. I'd also be sure to use some kind of flooring that is somewhat rigid and install it perpendicular to the foam boards, so that if the foam boards do try to lift or sink, the flooring will add some rigidity to prevent it from mattering.

We built all-ICF in upstate SC, and the performance is remarkable in our fairly mild climate. Given the same foam thickness, either method should perform about the same. The only big advantage I can see for ICF is that it has fastening strips embedded for attaching drywall and exterior siding, if desired. I think ICF does best in moderate climates, with performance falling off at the extremes of temperature. While building our house, I measured the core temperature during the coldest part of winter, and it was about 13 C. (55 F.). I imagine in a very cold climate, it would be much lower than that. Our small house has about 100 tons of concrete in the walls. I'd hate to try to heat that significantly. Here, our ground doesn't freeze more than a couple inches. Our winter design low is -7 C. (20 F.), and in the summer, it is often 34 C. (93 F.), occasionally much warmer, and rarely gets below -18 C. (0 F.) in the winter, and is almost always above freezing during the day. I read an article measuring the true R- performance of ICF in different temperatures. During the shoulder seasons, when temperatures are rather mild, it can perform as high as R-66, while the 'true' R-value is R-24. That's why you sometimes see inflated claims as to its performance. For a very cold climate, you'd want extra foam on the outside of the foundation, plus careful attention paid to isolating the concrete core from the cold ground temperatures. They do make ICF with different thicknesses inside and out.