Drywall condensation
I live in south Louisiana with a recently purchased 90s home where there are several attic access areas- some small for storage & 2 just to house the hvac equipment. The previous owner stuffed r19 batts in the rafter bays, in the soffits and generally everywhere in some of these attic space/storage rooms. What little I know about attic venting made me think this was a bad move, not having any baffles.
So I opted to make my own baffles from 1″xps and run them up to the upper attic areas where there are exhaust vents and replace all the wall and rafter batts with rockwool.
My problem is that once I started removing the insulation on the walls which lead to the interior of the house the drywall was damp, the fiberglass batt facings were damp/wet. My question is without placing a dehumidifier in each of these rooms what are my options, I feel like what little duct leakage there is isn’t enough to keep these rooms cooler/dry.
Also checked another attic area which the rafters werent insulated and the soffits were clear and the backside of the drywall in there was wet also. So I’m having a hard time deciding if it’s more or less ventilation I need because too much of either seems to have the same issue
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Replies
You need to make the choice do you have a vented attic full of HVAC equipment or a conditioned attic that you are committed to keeping at more or less the same conditions as the rest of the home.
As the precious owner’s experiment has shown encapsulation is a recipe for mold and rot.
The way I see it the conditioned attic is marginally better but tends to use expensive, ungreen and risky spray foam and do not make a return on the large investment.
Consider making the HVAC as air tight as possible and burying the duct work in insulation https://www.energyvanguard.com/blog/buried-ducts-allowed-2018-building-code/
The new unproven idea that may apply in your climate is the vapor diffusion port.
Walta
I really appreciate the advice you have with the cost of converting the vented attic to conditioned and it not having a cost benefit, I feel like that's something Noone ever wants to say.
I would rather keep a vented attic because the house is massive, intricate roof design and gas mechanicals, foaming and making it conditioned to me seems like the cost would be enormous.
Explain to me what a vapor diffusion port is, I'm unfamiliar with this unless it's in reference to a conditioned attic.
Also- wirh the recommendation on sealing and insulating the ductwork - how would this mitigate my problem with condensation on the back side of my drywall?
Okay I looked up another post on here about vapor diffusion ports and it's used with either conditioned attics or unvented unconditioned attics which honestly Ive never heard of an unconditioned unvented attic.
Id rather not make my attic areas Conditioned because I don't think I could ever air seal those areas 100%
I have not seen your attic but to my ear it sounds like the previous owner blocked the attic vents and added insulation at the roof line while leaving the existing insulation on the attic floor. So now the attic is not vented or conditioned let’s call it encapsulated. The air in that attic is likely quite moist and quite cool in the winter. In fact, my guess is the dew point of the attic air gets above the surface temps for parts of the attic. Those surfaces condense water from the air and that is why the drywall is wet.
Walta
Yes, spot on. And I have another small room similar but it's not insulated at the roof deck and the drywall to the interior of the house is damp as well. So having one encapsulated completely I understand the moisture issue but the other I don't understand, so what could be the best way to correct this