Cold Walls in Addition
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In late 90’s we purchased a 1904 built home in S. Illinois that had a garage with living room behind it added in mid 80’s. The garage and living room are attached on the West side of the main two story house. The living room is 18′ x 30′ with entire North, entire West, and half of East wall (where attached to main house) exposed to exterior. The living room is attached to the garage along the South facing wall so the garage insulates (to a degree) the living room from the exterior and is not much of a problem. However, the living room suffers from extremely cold West, North and East walls in the winter.
Doing some research I found that the framers sheathed the exterior of the 2×4 framed walls with a outward foil faced 1/2″ foam (maybe fiber-board – yellow color) with no plywood sheathing at all. Uninsulated vinyl siding was hung over the foam sheathing. The walls look to have fiberglass batt insulation in the cavities with a plastic sheeting over the interior studs, then 1/2″ drywall, then wood paneling over the drywall. The addition was built on a 2.5′ deep crawl space where they did at least put the same 1/2″ yellow foil faced fiber or foam board on the interior of the poured concrete foundation and they did fill the floor cavities with fiberglass batts. The floor still gets a little cold too in the winter. The old part of the house sits on a two wythe clay brick basement foundation with poured concrete basement floor. The house is heated with hot water boiler with large ornamental iron radiators in old part of house and cheap fin tube perimeter hot water heat in addition. They never worked well together because the fin tubes had to be heated to a very high temp to provide any heat to the room which made the old part of the house extremely hot – regardless of closing each hand valve to almost closed on each iron radiator.
This isn’t about the heating system but wanted to give the context.
Question (finally): We want to remodel the living room addition and wanted to get a better insulation value to stop the cold wall effect in the winter to be more comfortable & save energy. While I realize that perimeter heat’s purpose is to provide a warm curtain on exterior walls, I am concerned that if I remodel and install cast iron baseboards (Burnham Baserays – better matched heater to old part of house) that I will still have what seems like either thermal bridging or just badly insulated walls or both and will still use just as much energy to heat the room in the winter, still be uncomfortable and possibly worse, have condensation trapped in the wall due to more heat loss with better heating system. My thoughts were to rip out the fin-tube baseboards, carpet, paneling, drywall and fiberglass batting. Then, install cut 2″ x 1.5″ stud caps to thicken the wall cavity to 5.5″, install mineral wool batts for 2×6 walls inside the bays, continuous & taped polyiso (not sure of thickness yet) directly on expanded studs, then drywall. Ceiling (attic with 5.5″ fiberglass batting between trusses) will stay as is. However, if you feel that the ceiling is not insulated enough either please let me know. Wife wants solid wood flooring but I want to go back in with carpeting for the additional floor insulating value (my perception).
I have read a lot of back and forth exchanges on thermal bridging and adding polyiso on the interior behind the drywall as well as using mineral wool instead of fiberglass in the cavities. I am worried that the exterior foam will not allow moisture to dry from inside-out after installing polyiso on the interior with drywall over it. I don’t know if the exterior foam was taped or not. Our budget will not afford both exterior and interior remodeling and because we don’t intend to stay in the house for but another 5 years, I want to provide some sort of fix to have more comfort now and not pass along the headache to the next owner but without blowing my nest egg over it. I know there is a problem and I’m the type who cannot just pass along to the next owner.
Also for more context: some fixes I have done to the entire old part of house: had new double insulated Andersen windows and doors installed as well as blown-in insulation put in exterior walls, new 200 amp panel and wiring throughout entire house (except living room), new 80% efficient HW boiler with newer more efficient circulator and added a circulator for the living room zone, new roof, new flooring etc. Old part of house is very comfortable after its remodel but it has one-by sheathing on exterior and interior of the true 2″x4″ and 4″x4″ framing. Old part of house is very well built/framed. New addition was a jack-leg build in my opinion.
Thanks in advance for any suggestions/recommendations.
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