Ice Melt and Leaks in Attic
In our 2-story Hudson Valley 1928 balloon frame stucco house, there is frost and ice that accumulates on three gable ends of the house in the attic during the winter. Climate zone 4A/5A. When the temperature increases the frost/ice melts and drips down the cavities, and leaks into the house at the top of windows on the first floor and most significantly at a bay window on the first floor. Looking down the wall cavities at the gable ends, we can see frost/ice on the interior of the stucco. We can’t see down far enough to determine if it’s down the full 2 stories, or just down a bit from the attic.
The bay window ceiling and the wall above it have been repaired/replaced at least twice before us since the house was built, so it’s not a new problem. The bay window ceiling and part of the wall above it are currently exposed. The attic has new bathroom fan vents which don’t leak.
The exterior of the house is stucco over wire lath, attached to the framing. Interior of the house has 2″ cork (as insulation) attached to the exterior wall studs, then 1.5″ traditional plaster over that. The roof is slate over plank sheathing, is annually maintained and in good condition. There are no eaves. One room of one corner of the house was renovated and blocking and wall insulation installed (code requirement), another room on the second floor has had the same. These have had no effect good or bad on the attic situation, accounting for less than 5% of wall area.
Except for the ice/melt/leak issue there are no problems.
What can we do to address this? Stripping the stucco or interior plaster are not considerations. Looking for a simple, elegant long-term fix (isn’t everyone). I thought about putting a piece of plastic over the studs on the gables in the attic to reduce moisture buildup on the stucco interior there, but it wouldn’t completely stop air flow.
Thanks for your insight. -Tom
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Replies
Your issue is relatively common and unfortunately, complex and difficult to fix. Stucco, especially painted stucco, is relatively vapor-impermeable. So, the water vapor naturally stored in the interior air condenses against the back side of the cold stucco, freezing and eventually melting and running down inside. If there were a simple, elegant fix, everyone would do it, but alas, none exist that I know of. Keeping indoor humidity very low will help but may be uncomfortable and is certainly hard on furniture, flooring, etc.
The best, easiest and cheapest improvements can be had by aggressive air sealing of the entire house. A (big) side benefit will be reduction in energy costs. There are lots of simple places where you can DIY air sealing after some study and experimentation. There are lots more that are difficult and/or expensive to air seal. If you haven't already, take advantage of state-subsidized detailed energy auditing (must include blower door testing). Work with the auditor to select techniques that will improve air sealing over insulation. Stopping air leaks will also significantly reduce moisture transport. Insulation is not bad, it just needs to be done after, or along with air sealing.
FWIW, in my last old-house renovation, one of the few places we used Closed Cell Spray Foam was in the bay window. We did the wall studs, underside of the roof, and up into the second floor stud cavities, making the entire assembly air and vapor tight. Worked like a charm. An area this small can be done with a froth-pack system if you don't want to get a foam contractor out there - most have minimum charges. This is generally not a DIY project unless you are particularly skilled and diligent. It is very messy and can go very wrong.
Tom,
To add to the good advice Peter has given you I'd add this from another discussion:
" Randy Williams | Jan 23, 2022 02:20pm | #5
There is an interview in the current Fine HomeBuilding magazine, February/March, 2022 with William B Rose you should read. He touches on the subject of freeze/thaw cycles in historic buildings. Very interesting."
Thanks, both of you, for your advice, it was very quick and is much appreciated. I'll keep you posted, and come back if I have further questions. -Tom