SPF Residential Queastion - Condensation

I had 8" of SPF sprayed on the under-deck of our new home, and the contractor also created an insulated envelope in the attic by draping the rafters with cloth and insulatign them to form vertical walls to the sheetrock. Just moved in - we're getting heavy condensation in a bathroom A/C vent/register after a shower, and also condensation inside the clothes dryer.

Thoughts?>>>

8" of foam? I'm betting it is an open cell product then. Cheaper to apply and much less efficient than closed cell.

If the underside of the deck has been foamed, everything below that becomes conditioned airspace.

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I have reread the post and understand it a little better, but I still question the process!

If you want the attic and living space the same temperature, you will still have the warm moist air rise into the attic as this will be vapor. You will then have two different tempertures(living temp in bathroom and above attic space). If this is an enclosed room, you will depend on the fan to extract moist air. The vapor is too much for the fan to vent and will therfore seep into the attic. once the vapor comes in contact with the underside insulation, the temp will be colder at that location, thus creating your condesation.

2nd...If your fans are cover by insulation in the attic, it will also create localized condensation and drip from the fan.

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Roof Doctors USA Said: It all sounds kind of strange to me. I thought that by spraying to the rafters and making the attic air tight, the attic should be kept at the same temperature as the rest of the house and there should be no attic ventilation. You either need to try and keep the attic the same temperature as outside the house by venting it and insulation between the attic and the living space or keep it the same temperature as the living space by insulating under the deck and trying to keep the attic the same temperature as the living space. You will have condensation anytime there is a difference if temperature and humidity. If you insulate under the deck and vent it and bring in warm humid air from the outside (during the summer) and run a/c in the house condensation will happen. Youve got to keep the warm humid air out of the attic or youll have to void the under-deck insulation, put in old fashioned insulation bats between the rafters or trusses and properly vent your attic.

Not being a "foamer" I showed this thread to the PM of the SPF side here, who said exactly that, and that he had seen it many times before. He also pointed out that after three inches you reach a point of "diminished return" with regard to foam depth insulation on the inside.....just sayin'>>>

It all sounds kind of strange to me. I thought that by spraying to the rafters and making the attic air tight, the attic should be kept at the same temperature as the rest of the house and there should be no attic ventilation. You either need to try and keep the attic the same temperature as outside the house by venting it and insulation between the attic and the living space or keep it the same temperature as the living space by insulating under the deck and trying to keep the attic the same temperature as the living space. You will have condensation anytime there is a difference if temperature and humidity. If you insulate under the deck and vent it and bring in warm humid air from the outside (during the summer) and run a/c in the house condensation will happen. You've got to keep the warm humid air out of the attic or you'll have to void the under-deck insulation, put in old fashioned insulation bats between the rafters or trusses and properly vent your attic.>>>

If your dryar and bathroom are enclosed (no windows) you will have to run your fans more than normal...I have a timer that is connected to the fan that comes on automatically at certain times of the day in my W/D room.

I am concerned about the [contractor also created an insulated envelope in the attic by draping the rafters with cloth and insulatign them to form vertical walls to the sheetrock.] and the 8 inches of SPF? Is the condensation actually in the attic? With sprayed SPF, it may have blocked your intakes at the eaves. These particular rooms can create a lot of moisture and can seap into the attic space even with the fan running, without intake air to move the warm moist air to the ridge vents/AF-50 version of vents, the moist air will stay and thus become condensation once it hits the dew point.>>>

Sounds like your dryer vent and toilet room vent terminate in the attic space. Check to make sure they go thru the roof into the atmosphere.>>>

Does your exhaust vent have a flapper valve that opens up?, and does your roof vent have a flapper valve that opens up? I have seen them cancel each other out and one has to bee removed. Also how is the vent house installed? The more vertical the hose the less chance of condensation, and what kind of hose is it? Here we use an insulated hose>>>

Turn on the exhaust fan. It is not breathing. Open some windows and let the air pressures balance out. It is probably dangerous to breath the air in the house.>>>