Retrofit Balloon Frame Envelope
Greetings GBA community,
Our home is a beautiful onion. More layers than I’ve ever seen (no insulation except attic). 1880 balloon frame in Zone 6. Electrical issues have led to many interior areas of our home being opened up. It’s been a great opportunity to really get to know this home. Our budget is tight right now but priorities from the inside are fire blocking and air sealing everything I can get to without removing plaster/lathe. Sill plate is accessible inside basement and second floor ribbon area is reasonable to get to from above. I keep landing back at a necessity to address the envelope problems from the outside because of insulbric or similar product on the exterior. Am I missing a simpler more cost effective approach?
Assembly Details:
Panelling 2/3 layers over top of plaster and lathe walls (some places 3/8″ drywall between). The wall assembly has 1″ thick solid wood horizontal boards both inside and out of the true 2×4 studs 24″ oc. The ribbon board is not let into the studs on the second floor. Main floor joists sit on true 2×4 sill side nailed into studs. There is no capillary break between the stone foundation and the sill. Poured concrete is reinforcing the stone from the slab up to about 4′ which leaves 3′ of stone exposed above. Three layers of exterior siding products 1) insulbric 2) stucco with metal mesh and at least one layer of heavy weight tar paper 3) vinyl siding on 3/4″ vertical furring. Attic has something loose fill. Soffit appears vented but baffles if present seem compromised. Two whirly birds on top of metal roofing (1 maybe 2 layers of shingles under).
Questions:
1) Is an interior air barrier a good investment for us?
2) Can I spray foam the rim band area without creating moisture problems (no capillary break between sill/stone foundation and necessary inward drying because of insulbric)?
3) Would it be necessary to remove insulbric to be able to blow insulation into the balloon frame walls?
4) Would adding an interior wall to gain insulation and an air barrier make sense in this situation? (opening the balloon frame wall from either inside or outside seems wrong because of the solid sheathing in and out)
Any guidance would be so greatly appreciated,
Dani
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Replies
Hi Dani,
I'll give you a bump and attempt to provide input while we wait for expert input.
1. Installing drywall in an airtight fashion -- along with continuing your air sealing program -- is a good idea. On how far to go with mitigating against the risk of moisture condensing inside walls, I don't know. But here is a quote from a relevant article (@ https://www.greenbuildingadvisor.com/article/do-i-need-a-vapor-retarder):
"Most buildings don’t need polyethylene anywhere, except directly under a concrete slab or on a crawl space floor. The main reason to install an interior vapor retarder is to keep a building inspector happy. If a building inspector wants you to install a layer of interior polyethylene on a wall or ceiling, see if you can convince the inspector to accept a layer of vapor-retarder paint or a “smart” retarder (for example, MemBrain or Intello Plus) instead. Although most walls and ceilings don’t need an interior vapor barrier, it’s always a good idea to include an interior air barrier. Air leakage is far more likely to lead to problems than vapor diffusion."
2. If you used closed cell foam (or rigid foam that is properly detailed) and none of the framing is below grade or behind a reservoir cladding, it's generally okay. (For more detail, see https://www.greenbuildingadvisor.com/article/insulating-rim-joists.) Also... If you can jack up the foundation enough to slip in a capillary break, that would be a plus.
3. ? If you are having cellulose blown into the walls, it probably would be best to get opinions from the local contractor on how to deliver the material.
4. How many decades do you plan to be in the house? Kidding a bit, but it may be hard to justify the expense if the existing walls are okay. Even if the plaster is damaged or falling away, you have to be careful about going overboard on remediation steps (at least from my reading of GBA articles and posts). Air sealing and adding insulation to the attic are generally the best steps in terms of comfort and ROI.
Thank you for the input Steve.
2. Would steel shims act as a capillary break or is there something more suitable? I can't wrap my head around how to jack up a balloon frame. Seems to me you'd have to in tandem jack the walls with one set up and the floor system with another or you would be relying on the nails to not shear off.
3. My concern with the idea of adding blown in to the original walls is more so with the vapour barrier located in the insulbric. I wonder if it just isn't a safe solution in this case. Before fire blocking I hope I can understand this better.
4. Haha, ideally someone will remove me when I'm cold but no guarantees in life.
Hi Dani,
2. I saw a detail here for jacking a balloon frame house: https://www.jlconline.com/how-to/framing/q-a-shoring-a-balloon-frame_o. It is probably not something you'd want to attempt here just to create a capillary break. As Walta and plumb-bob have suggested, this may be one of those areas that's best left alone.
With a house of your age you need to be very careful when you make changes.
Your home survived this long because the moisture entering your home and the moisture leaving your home have found a balance point that works for your house.
The truth is the flashing and water management on old housed was poorly done by modern standards but lots of air and heat was moving thru the walls the water that got in the wall was quickly evaporated by the heat and its vapor was carried out of the building on the tons of air flowing in and out of the old walls.
If you seal the air leaks and or add insulation without fixing the flashing you risk trapping the moisture in the walls and they could get moldy and rot.
I know you do not want to open the can of worms the exterior of your house maybe. Try to remember your house is a system if you change one side of the equation you risk throwing the system out of balance. Before you reduce the drying potential you need to understand your wetting potential.
Walta
Thank you for your input Walter. I hear what you are saying about the balance. I've been wondering if the vinyl on furring strips was an attempt to remedy inadequately flashed stucco. It sort of mimics a rain screen but if I've learned anything its not if the walls get wet but when.
If I'm understanding correctly, air sealing on the interior would keep our hot humid life air out of the assembly. Vapour within the wall would still be able to drive back inwards through drywall as an air seal. Moisture inside the wall can't drive outwards because of the insulbric. Does this seem accurate in this scenario or does air sealing reduces the drying potential inward?
Thanks again,
Dani
I also would be hesitant to start messing with a house that has many different existing layers. Is the bottom plate rotten? If it has lasted this long it should keep lasting.
I would say either bite the bullet and gut the house for a complete systematic renovation, or try to make it work. Maybe look into more efficient heating methods, like a heat pump.
I know the aesthetics of vinyl siding are not for everybody, but installed on a rain screen it can make a well ventilated, high performing wall. Probably the perfect option for your house.
Hello,
The plate is rotting only on the north side. I addressed the water problem there and removed batt insulation that was crammed tighter than tight into the rim joist area. The entire north side has had floor joists replaced at some point. My guess is an issue with snow falling off the metal roof and not being removed off the deck on the north side. Bit of a perfect storm over there.
Thanks for your input Plumb_Bob
-Dani