Seal ceiling penetrations or have ridge vent?
We have a home in WI that has had moisture issues: wood casement windows with mold, ghosting on ceilings, dehumidifier running continuously from spring to fall. Our attic is unique as there are 4 separate cathedral ceilings and 2 separate true attic areas. We had Focus on Energy to evaluate our home. The Work done was adding insulation with baffles to open attic areas, sealing in several areas in the attic, sealing slatted wood wall, sealing rim joists, sealing entire HVAC.
Moisture is Still high in the attic but Improved on the basement level.
The roof of our home has box vents, even in the cathedral ceiling areas. Additional soffit vents were added being told there were too few. I am monitoring the attic which the humidity levels are now in the 70’s which the changing weather. I have noticed when the HVAC is on the house smells, but at rest it seems to fade.
The additional soffit vents seemed to increase the ghosting and possibly the odors – chemical like in the summer, musty in the fall.
Do I focus on more air sealing? Should some of the soffit vents be closed or should we look into getting ridge vents (requiring a new roof)?
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Replies
> dehumidifier running continuously from spring to fall
How many pints/day are being removed? Two dehumidifiers might well be needed. And old, dust filled dehumidifiers may remove very little.
Even a good vented attic will see periods of high humidity. I'd compare outside dew point to attic dew point to provide a better indication if there are other sources of moisture being added to the attic.
Thank you.
You don't need a new roof to put in ridge vents, ridge vents can usually be cut in with a circular saw without much trouble. I'm thinking they would help you, but I can't be sure. I don't think you want to seal up the soffit vents though. My first thought is that there may be more exhaust area compared to intake area with your attic venting, which would lead to a slight negative pressure in the attic and more air leak issues from inside the home into the attic.
Attic humidity levels will typically track with outdoor humidity levels, just keep in mind that %RH will vary a bit since your attic is likely to be a little warmer than outdoors (which means slightly lower %RH for the same water content in the air).
Have you thoroughly checked your basement to ensure you don't have any moisture issues down there anywhere? That's usually where moisture gets in with problems like this, unless you have a LOT of air leakage above grade in the home itself.
Bill
Since the rim joists were sealed and the HVAC system, the dehumidifier is running much less. Prior it was Spring through fall, now it is intermittent starting in June.
The soffit vents initially were 1 Soffit to 1 Roof. Sizes were 4x18”. Replaced 3 years ago with 1.5 Soffit to 1.0 roof vents. 4x18” were replaced with 8x18”. Reason for entertaining sealing the additional soffit vents, could there be too much positive pressure?
Had replaced all windows with Marvins and tried to seal as many potential penetrations on the main floor. Trying to locate the source of musty odors and the cause of ghosting. Musty odors coincide with the HVAC running. Only thought is there attic issues since all others were addressed.
As a side note, the attic seemed much hotter after sealing the rim joists and main level penetrations.
Do you have mechanicals (furnace, vents, ducts, etc) in the attic? That would introduce an entirely new set of issues. You usually want to keep mechanicals out of attic spaces. If you have an existing system in the attic, you can either convert the attic to conditioned space (which brings it inside the building envelope, typically by insulating the roofline inside of the attic floor), or seal ALL ductwork and fittings, ideally with mastic. If your HVAC system is in the attic, then that's probably why you're seeing the problems you're seeing.
Ideally you want a slight positive pressure in the attic, so a little more intake (soffit) vent area in comparison to exhaust (usually ridge vent) attic area. It sounds like you have that. It makes sense that your attic is hotter after the air sealing work was completed since you were probably leaking cool air from inside into the attic before.
From your last post, I'm thinking you have your HVAC system in the attic, or at least a fair amount of ductwork, and that system and/or ductwork is leaky, bringing attic air into your home when the system runs.
Bill
Thank you Bill.
We have a home in Texas (from my previous post) with mechanicals in the attic. Looking to seal everything as the previous owner had leaky ducts supply and return) and an open return but there was a distinct mold smell after we moved in, especially with unplugging all the air fresheners throughout the home. We are having some rippling in the ceiling drywall, not sure which method would be best.
The home in WI has mechanicals in the basement. Prior to purchase house was vacant 3 years, no dehumidifier. As time went on we found many penetrations in the house including 4 beams in 4 cathedral ceiling areas. 3 years ago it came to a head where we noticed moisture issues and smells. A lot of reading, including this site to try to find ways to correct this the right way.
Thank you for your replies!
I think you're going to need to open up some of those suspect walls and see what's going on inside. You may well have mold issues in some of the stud cavities if moisture has been running down inside the walls. You should probably consider a remediation contractor for this work since they'll know where to look and how to safely handle things.
Bill
Thank you.