Question on air sealing attic
Home in zone 5A built in late 17th century with major renovation done in the early 90s. Major insulation projects completed at that time…all walls are insulated and have vapor barriers, new portion of attic has batts + 14″ of blown in cellulose, etc. As detailed in other posts I have been very busy air sealing home itself, insulating rim joist, sealing basement windows, sealing recessed light cans, etc.
On to my specific question:
There is a 20 x 15 attic over the original portion of home. All post and beam late 1600s construction. Ceiling of room under the attic is hand hewn timbers with drywall retrofitted between the joists in such a way that about 60% of the timbers are exposed to the room (very nice looking). Drywall joints are caulked to the joists but given the age of the home and the hand finished nature of the beams there are some small air gaps i’m sure. There are no light fixtures, smoke detectors or electrical holes in this ceiling. Above this ceiling is 1.5″ foam board fit between each joist cavity tight to the drywall, followed by tongue and groove pine planks tight to the foam board running perpendicular to the joists. These pine planks run underneath major 12″ x 12″ framing timbers — getting them up appears to require cutting / major work.
When I moved in I air sealed all areas I could access with spray foam — the top of the wall plate and all attic corners and walls. I also air sealed a major 4″ x 36″ air gap around the chimney with aluminum and fire rated caulk. I then rolled out r-30 batts perpendicular to the joists over the pine boards. I also installed 2″ foil faced poly-iso on attic access door and along staircase walls. And air-sealed attic door with rubber gaskets.
I do not imagine they spray-foamed the seams where the foam board meets the floor joists. I am very reluctant to pull the floor to do so, and really don’t want to get into spray foaming those old timbers if possible.
I am now second-guessing whether I should go back in and seal all the cracks in between the pine boards? If so, could I use a tape product? Or is the best option a small bead of great stuff?
Or are we thinking it’s not worth the effort?
Thanks for all your input. I am new-ish to all this and tend to overthink things!
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