Attic insulation retrofit
We live in a 30 year old split level house in North-central Alberta. The house faces south and gets a lot of sun in the front (1 story), but a lot of shade in the back (2 story) It has brick, aluminum siding and stucco for exterior surfaces and an asphalt shingle and tar paper roof. There is a full basement that is partially finished/insulated.
Attic #1 has fiberglass batts, with a south facing gable vent and we added a rolled ridge vent when re-shingling (asphalt and tar paper). It also meets with the south wall of the 2nd story.
Attic #2 is over the unheated attached garage with batts. It has a gable vent on the west side and we added a ridge vent. This attic is also attached to an uninsulated porch overhang with vented soffit at the bottom of a valley between attic #1 and attic #2. The garage is not well sealed and has an uninsulated wood garage door, a 2nd crudely insulated and sealed off wood garage door and wood entrance door and a steel door to the house.
Attic #3 is only over the second story and has east and west gable vents, and added roof vents near the peak with batts and blown-in cellulose over it but not to the edges as there were no baffles installed. It also contains the furnace/water heater chimney, 2 bathroom exhaust fans not vented through the rood, a heat lamp, a plumbing stack and 6 electrical boxes from fixtures as well as a wired in smoke detector that is not functional.
The cantilever is a north facing stucco wall and has a plywood bottom that is not sealed around the wood bottom and the floor is very cold in the winter.
We have plans to have an insulation contractor:
Add cellulose to R-40 and baffles to the kitchen attic
Up the cellulose to R-40 in the 2nd story
Add cellulose into the drywalled wall cavity that is within the garage attic against the east side of the 2nd story.
Spray foam the floor of the cantilever and seal the plywood soffit.
My question is – should I be doing anything prior to any of the insulation going in? Sealing around windows, etc. (I plan to replace trim anyway). What kind of vapour barrier do I need? Can the floor just be sealed at cracks and gaps? The upper attic has vapour boxes over the electrical boxes, and a crude unsealed osb box built over an existing heat lamp that we plan to remove but I’m not sure how best to seal the hole if we do remove it. There is also cellulose right up against the furnace/water heater chimney (not code, nor is it recommended by the manufacturer). I am not sure if there is an existing poly vapour barrier under the batts. From what my insulation guy said it is against code to have spray foam (and foam board exposed in an attic here and covering it with drywall is obviously impractical.
The manufacturer website for the cellulose used says “Weathershieldâ„¢’s high density dramatically reduces air leakage, controlling air and moisture infiltration.” but I’m assuming you will disagree.
We replaced the shingles last year so we won’t be adding insulation, etc to the top of the roof.
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