Hi guys, while not quite HVAC - it is heat and ventilation related...
I've been in this new home now for going on 3 winters and so far it hasn't been a big problem but we got hit with ice dams this year. The attic just stays way too warm.
Here is the situation, the contractor used Icynene open cell foam on the attic floor to insulate (my choice) but apparently looks like they didn't put in enough depth to get a good R value. The attic has ridge vents (sort of a mesh stuff) and soffits but a lot of the soffits are partially blocked by the foam and given the design of the house we don't have 2:1 soffit to ridge ratio even if they were all wide open (its a cape with a perpendicular wing off the back). So I had a gable vent put in to see if a little more air flow might help and it didn't really. And its the only ventilation when a lot of snow is on the roof as the rear roof is low pitch so the ridge vent is useless. When there is snow on the roof, the attic stays a pretty constant 45 degrees (the ductwork is up there but R6 insulated and pretty tight).
Just after the ice dams last week when I broke down and put in a gable fan in the other gable (god they are loud) to help control temperature. It has helped some when its on but only gets the attic down to 38 or 39 degrees with snow on top insulating things when its even in the low 20's outside.
Even if I turn off the upstairs heat to rule out duct leakage/radiant heat, the temperature is still elevated with and without the fan on. So I need more insulation - I'm going to put in fiberglass batts on top of the foam and have them try to free up some soffits if they can.
But here is the dilemma, the attic also stays relatively humid, sort of a dewpoint between the inside and outside roughly - I'm not even running my inside humidifier - and only having the fan on brings that dewpoint down to the outside level. I'm afraid if the insulation works and I get it colder in the attic that it'll start to condense the atmosphere up there and get wet.
Is it that the open cell foam allows not only the temperature but the vapor to migrate into the attic? I guess if we'd gone low tech and used kraft faced batts it would have a vapor retarder. The other possibility is that my ceilings were just primed not painted...I hear just latex paint can be a vapor retarder - might painting the ceilings help?
Any ideas how you would deal with an attic like this? Thanks....