Partial insulation of old house
I live in a c. 1923 house in Toronto. It is unusual for its age because it is constructed somewhat like a modern brick veneer home with a single wythe of relatively soft moulded brick set in lime mortar tied to (1) a 2×4 stud wall 16 O.C. (2) sheathed with 3/4″ boards (3) covered with tar paper, (4) and an airgap of about 3/4″ behind the brick.
There are no weepholes at the base of the brick wall, but there are no signs of rot on the sills. Some re-pointing and brick replacement work was necessary (especially at the base of the wall) a couple of years ago, the brick was in pretty good shape overall for enduring 93 Canadian winters.
There is no insulation in the wall cavities. However, I have blown something like R-50 into the attic and done extensive air-sealing. My heating bills are more than manageable given the age of my house.
I anticipate an upcoming renovation which will include removing the plaster and lathe from the exterior kitchen wall on the northwest corner of the house and replacing it with drywall. I am considering installing rockwool batt insulation in the stud bays and covering it with a vapour barrier. However this modest ‘upgrade’ will be confined to this particular area.
I have two concerns:
1. I will get wetting of the wall owing to air and moisture leakage around the perimeter of the insulated section (bottom, tops and sides)
2. It will result in damage to the brickwork, which will be unable to absorb heat from the interior of the home to assist drying after periods of wet weather.
3. EDIT: after doing some reading on here, it occurs to me that a third concern may be solar vapour drive especially given the western exposure and the permeability (i.e. gaps) in the sheathing boards.
If there’s any significant risk of these things happening, I would
rather just leave well enough alone.
Any input on these points would be appreciated.
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