Getting started air sealing a 1920s home in Chicago
mdjnewman
| Posted in General Questions on
Hi folks!
First time poster and absolute novice here. Not in the industry for my day job, but I want to do the right thing by a 1923 bungalow style home in Chicago (zone 5A).
Originally a 1.5 floor home over a full height basement, it’s now almost two full stories after a 2004 renovation. From everything I’ve learned here, some of the renovation work isn’t great from a home performance perspective. It’s poorly insulated and air sealed (even the new construction).
Currently I’m looking into the attic behind the knee walls, at the front of the house, where the original brick and hip roof framing is.
I’m planning to start with air sealing while ensuring that I don’t cause any issues for the old & soft brick we have. The brick is in good condition for the most part, no major water issues that I know of.
Looking down from the attic, there seems to be a cavity between the brick exterior and the lath and plaster. The same cavity can be seen from the basement looking up, but I’m not sure how continuous it is.
When air sealing, how should I handle this? My current plan (that I’d love to hear your thoughts on) is to leave the top open, and seal the bottom, to prevent moist air from the basement getting up into the attic. I understand it is best to allow whatever warm, humid air that finds its way into that space to exhaust at the top, as that’s not in the envelope of the home, and will help the brick dry out. I’ll air seal everything else in the attic.
Please let me know if this makes sense, and I hope this isn’t too basic a question. I have learned so much from this site and the forum!
Cheers,
Matt
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Replies
"Looking down from the attic, there seems to be a cavity between the brick exterior and the lath and plaster. "
No matter how tempted you are never bridge the gap from the brick/ masonry. While we think of brick/ masonry as water proof materials the fact is they are NOT. The back side of the brick will often get wet and at the base of the wall you should find weep holes IE joints without mortar allowing liquid water to escape. The gap lets any water run harmlessly run down the brick and out a weep hole.
If you fill the gap water will cross over and get the wood wet making mold and rot likely.
Walta
Walta and MDJ,
I don't know building science so read the experts here and look at the drawings. What Walta says makes sense to me so the back of the brick can dry by dripping down to the weep holes and evaporating up. But isn't this at odds with the attached drawing from the detail library that shows whatever the exterior is (it doesn't say it's not brick) sort of connected to the interior wall via the top plate then sealed tight to it with sealant??? The drawing is from https://www.greenbuildingadvisor.com/cad/detail/conceptual-air-sealing-strategy-at-roof-eave .
Thanks,
My wild guess is your house is very leaky maybe so leaky that a blower door will not be able to achieve the 50 Pascal pressure we test leakage at. On a windy day 100% of the air in this house maybe escaping 20 time per hour.
You could have a blower door test done but it might scare you to death and cost you $400. The number is not really that important anything that makes the house tighter is a good thing.
Try taping a box fan or 2 into windows blowing out. Then starting at the upstairs ceiling go around with burning incense sticks the smoke will show you when you get near a leak. Stop each leak with caulking. Stop when you get down about 1/3 of the building height and start working on the lowest 1/3. The 1/3 in the middle is almost irrelevant as it has less of a pressure differential to make the air move.
Walta