It's -25 outside today, -50 windchill. I've had this issue in the past, but more than at least a year ago. Getting a wet spot in the bathroom on the ceiling, and in the bedroom directly on the exact opposite side of the bathroom spot, so basically under each end of the same ceiling joist if that makes sense. ( bathroom window facing east, bedroom window facing west) I have a attic hatch that had some minor gaps around it( just sealed it off with plastic) after I saw the leaks. I don't want to open it to go up there to let all that heat in until it warms up outside. The roof has soffit vents and static vents, and a vent in the bathroom which we run all the time during showers and 30 mins after. My only thought is not enough insulation in those spots in the attic? I have no idea.... Why is this happening just now on a record low temperatures? The house is built 1986, 2 story...

Apologies if my terminology is a bit off here; I'll do my best to be as clear as possible. I have a hydroair zone in my house where the blower sits in an [u]insulated, but unconditioned utility closet[/u]. The blower unit stands upright and the feedstack comes off of the top and up into the ceiling to branch out into nearby rooms. The utility closet (5x15ft) is fully insulated but sits mainly at outdoor temperatures because it is not conditioned. Between heating cycles, the entire blower unit cools down to near outside temperature (southern New England) and also, cool air is leaking into the adjoining rooms, I suspect up through the ceiling where the feed stack enters. Along with using spray foam to seal off any leaks in the ceiling, I want to cut into the feed stack to add a small duct/vent with a manual damper. I think dumping some heat into this room will minimize lag time to getting hot air out of the registers and avoid the need to heat up the entire unit each time it cycles as it won't cool down to outside temperatures nearly as quickly. My questions: The feed stack is one of those large rectangular sheet metal ducks that is insulated. What is the best way to cut into this? Should I add a short run of duct-work away from the stack or just mount a damper/register right on it? Or, more importantly, is this a dumb idea and I shouldn't bother?