Deep energy retrofit of a 100-year-old house – need advice
I’m renovating a 2,200 sq. ft., 100-year-old home in southeast Alabama (Climate Zone 3A). The original house has 2×4 heart pine framing, a vented crawl space and attic, R-13 fiberglass in the walls, and deteriorated Masonite siding. A newer addition has 2×6 walls with Visqueen, R-19 fiberglass, exterior foam board, and Masonite siding.
My plan is to remove the old siding and felt, replace all windows, air seal the house, treat the framing with Bora-Care, reinstall the wall insulation without the kraft facing, install ZIP sheathing, continuous exterior rigid insulation, a rainscreen, and new Hardie or vinyl siding.
My questions:
- Should I remove the Visqueen vapor barrier in the addition’s walls, ceiling, and floor?
- Does this retrofit plan follow good building science practices for a hot-humid Climate Zone 3A?
- Is there anything you would change to improve moisture control or energy performance?
I’d appreciate any suggestions before I begin the project.
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Replies
When you say replace the windows, can we assume you will install new construction type windows as opposed to replacement that would reuse the original frames? Note the new construction windows will totally destroy the interior trim and replacement style window will be next to impossible to make air and water tight with your new Zip sheeting.
I like your wall plan but problem is if you do the work yourself and put any value on your time or pay anyone to do the labor for a deep energy retrofit the math simply never works. You will have way more invested in this house than you could sell it for.
The big problem with old houses is the old timers made less than zero effort to make them air tight. They wanted them to breathe. The fact is they did not do all that much to keep out the rain and they counted on the lack of insulation to put enough heat energy in the wall to evaporate the water they knew would find its way in and needed all that air movement to carry away the water vapor.
The exterior walls are not your big problem. Energy wise you really need an air tight ceiling and crawlspace connected to your new walls and only then do you insulate. Undoubtedly all the plumbing, electrical kitchen and baths are inadequate. Don’t forget every interior wall is total covered in lead paint and trying to poison your children with its dust.
Do your self a favor and make a realistic budget for everything not just the windows sheeting and siding top to bottom inside and out. My guess is almost everything gets replaced before your happy.
I am not trying to be mean. I wasted a ton of time and money on a house half as old and it was not worth a dime more that its untouched twin across the street.
Walta
Ellie,
1. In CZ 3A, definitely remove the poly from the walls, and ceiling. We'd need to know more about your floor to say whether it's a problem there too.
2. I'm not an expert on hot/humid climates, but it seems like a good plan to me.
3. See #2.