Siding and insulating a 1920’s house
We’ve been developing a best practices approach to the insulation and residing of our 1928 house. It’s a balloon frame, 1,500 sqf, 2 story, uninsulated kit house. What we have so far is based on this exchange in a prior Q&A and learnings along the way. There is no broad access to the stud cavities. We have a few more questions before we can get started planning the work – looking forward to hearing your thoughts. Thanks to @DanaDorsett and @Akos for their responses to the last post. Here is the schedule and rational to date.
1) Seal everything that has penetrated the plaster and/or the sill in the basement, or the top plate in the attic and into the exterior wall cavities including anchors, electrical boxes, conduit, pipes via the walls, the baseboards. Hit the shoe molding and the picture hanging molding with calk.
2) Since our house has replacement windows we have to check to ensure that the window frame pockets that once held the counterbalances inside the original window frames are also filled and sealed.
3) At some point in their history our plaster walls have had alkyd paint applied, so we already have an interior vapor barrier and will check that off our list.
4) From the outside, cut holes in the tongue and groove sheathing and blow in dense-pack cellulose at 3 – 4lbs per cubic foot; need to determine if our walls can handle this pressure. Loose-fill is not an alternative because our house is balloon framed and any moisture would eventually force the insulation to settle leaving half of each continuous cavity uninsulated.
5) With dense-pack, the moisture will spread more uniformly across the cellulose and not accumulate at the bottom. This allows the system to dry out more quickly than any other insulation alternatives including fiberglass, rock wool, and foam.
6) Fill and seal the holes in the sheathing.
7) Install a new weather-resistant barrier.
8) Install prefab window casings/lintel/sills from Trim Solutions.
9) Install insulated clapboard vinyl siding. Nail only into studs so we don’t have to worry about puncturing the new WRB.
So far, so good, but we still have a questions…
1) What is the best way to ascertain if our walls can handle the 3-4 pounds of pressure from the dense pack?
2) Though we’ll do everything we can to prevent moisture from entering – when it does, how will it escape?
3) We plan on using close cell to insulate the sill plate, will that inhibit evaporation of any moisture that works it’s way down into the base of the walls?
4) We plan on bringing the attic into the conditioned space using closed-cell foam on the roof deck and down to the top plate and blocking the soffit. I assume that the top of a balloon frame house will have a significant hot air build up into the top of the stud cavities. Right now I’m sure that the house dissipates that heat rather freely. Will sealing at the top plate inhibit that hot air from escaping?
5) It seems that the choice of WRB is a very important component of this retrofit. Is there a proven, breathable Gore-Tex type available?
Thanks in advance for your views. – Jim.
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