Latest Discussions : HVAC

BV024893

01:55PM | 04/14/21
First, thanks for reading! My apologies for the length. I know this is a common problem in vaulted ceilings, but I'm having trouble finding a person with experience who can provide a plan of action.

In our NC lake house, there's a consistent problem with moisture build-up near the peak of the cathedral ceiling along the length of the great room, one big rectangle w/ kitchen, dining, living, apprx 25' x 38'. There is a significant temperature change in the top 5'-6' of the 22' ceiling. Condensation is building up on the cardecking ceiling and exposed beams, to the point of causing dripping from the highest few feet of the ceiling.

A little more info ... this is a very "tight" 1994 house with apprx 12/12, 45 degree roofline; interior great room ceiling is painted cardecking, then foam board insulation, roof decking and brand new high quality asphalt shingles; soffits exist but questionable in function because there's NO ridge vent in roof. I've been told that there is very little space between those ceiling/roof layers where there should normally be space. There's accessible attic space beyond both great room end walls from apprx 10' up to peak of ceiling; one end is over beds/baths, one end is over screened porch, both have ceiling trap-door access. Hope that is a clear enough description from this lay person!

One thought is to mount some type of fans to circulate air in the peak downward to push hot air down, or upward to push cool air up. Should they be horizontal and as close to ceiling as possible? Or should they be vertical, mounted on end wall and/or on beam(s) and blowing air horizontally? Blowing toward returns? How many would I need?

Another idea is to use some type of gable attic fan (one on each end?) that could be connected to a thermostat to control the temperature 24/7 without supervision. Would this solution require ducting to soffits to prevent unintended problems in attic? Would that solution move enough air to make a difference?

A whole house dehumidifier system was installed 4 months ago, but already we have this problem and haven't lived through a humid summer yet. I would appreciate any help solving this problem before the summer heat arrives! Thanks in advance for any assistance...Monica
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