Why seal the attic of a leaky house? Everything else leaks…. Also, Quadmax?
I’ve got the roof off and I am considering sealing the top plates to the top of the drywall while everything is off. I was considering using Quadmax for the small lines and fireblock foam in a can for the penetrations. The more I think about it, the less it makes sense to me. I understand the benefits in other environments where moisture and cold air are big factors, but I’m struggling to see the benefit in San Diego.
Edit- ALL of my ceiling penetrations (lights, boxes, fixtures, etc) are already sealed. Its the top of the top plate to tops of drywall that I am referring to now.
Its a San Diego home, its always been leaky, its always been dry.
1. Why seal the attic, (or rooms I renovate for that matter) if the rest of the house is leaky. Wont that just pull the same amount of air from another dirty space?
2. Wont that make it harder for the walls of my 1950s house to dry if they were to have an intrusion of water? Can’t it make radon and other indoor impurities build up faster?
3. Aren’t I now just adding chemicals which could dry out or deteriorate and be toxic in themselves in the future? No one likes to breathe polyurethane dust, right?
4. If I do seal, is there anything wrong with quadmax at the small seams and fireblock spray foam at the large stuff?
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Replies
Buildingfun,
Air leakage effects more than just moisture accumulation. If also reduces the efficiency of heating and cooling, and reduces indoor air quality.
1. Air-sealing doesn't just move the air-movement elsewhere, it reduces it, especially at the ceiling where the pressure differential is higher due to the stack effect.
2. a) Relying on random air-leaks as a strategy to keep your walls dry if there is water intrusion simply isn't effective. The chance of the air-leaks aligning with the wet areas is pretty low.
2. b) We know how to effectively provide good AIQ by either mechanical or natural ventilation. Drawing air through random holes in the building enclosure simply doesn't do that.
3. The air-sealing you are proposing is outside the conditioned area of the house. There should be little or no off-gassing from the sealant.
4. Isn't Quadmax an exterior sealant for doors and windows?
Yes, Quadmax is an interior/exterior sealant for doors and windows. Is there a better caulk you would use? Most government and energy efficiency websites i've read just say to use caulking and spray foam.... no mention of caulking type but in my experience, Quadmax is many times more durable than typical caulking.
“Why air seal a leaky house?”
For the same reasons you close your windows and doors. You paid good money to condition the air inside you home and if you allow the conditioned air to escape you will spend more money to condition the air that replaces whatever escapes.
Walta
People frequently act like air leakage in a house is like a evenly perforated building.
It isn't
It is a badly installed window, a gap in a floor, a crack in the ceiling
Result is a cold room where you cannot balance the heating cooling load.
Seal best you can
Be comfortable
Sealing up some of the leaks, but not all (which seems to be what you're implying you can do here), doesn't mean all the remaining leaks will just "leak more". You accomplish a little every time you seal something, and it all adds up. Every time I do a renovation project on my own home (which tends to be room by room), I make a point of doing an air seal and insulation upgrade at the same time. Sometimes this makes an immediately noticeable difference (such as my office, which is an outside corner and used to have pillows literally freeze to the wall of the bay window in the winter -- that no longer happens after the upgrades!), other times I see a change over a season's worth of billing (spray foaming a vaulted ceiling that had a T+G interior saved a lot on heating during the following heating season).
Air sealing and insulating are nearly always worth doing. where you can run into cost/benefit issues is usually on the insulation side -- going for R150 or something like that. Air sealing alone is pretty much ALWAYS worth doing, and it's usually not even all that expensive to do.
Bill