Thank you in advance for your feedback, you have all been so helpful.
Zone 5A (coastal Mass) house.
I have an older 3200 sq ft home with a mix of well-pointed fieldstone foundation and poured concrete. The 1000 sq ft attic is currently air-sealed in most places, and has a mix of fiberglass batts and cellulose for about R-30. I have 10 recessed lights in attic, which have the LED airtight retrofits with gaskets, but are not covered in cellulose. The recessed fixtures are IC-rated. The remainder of the home has vented cathedral ceilings (sigh).
I have a System 2000 boiler and am averaging about 450 gallons/year of oil on heat and hot water.
During the past 100 year freeze earlier this month, I had some frost on underside of roof sheathing. I spent hours digging through cellulose and airsealed some wall plates and open wall cavities that the previous homeowner’s airsealing and insulation contractors clearly missed. There is one 30′ exterior wall plate in the eaves I cannot reach to airseal from inside the attic.
Mass Save (a national grid rebate program) came to the house, and pitched me on pulling up the existing attic insulation, double-checking and airsealing anything I missed, adding 2″ polyiso to a 1′ attic kneewall and blowing enough additional insulation all over my IC cans and around the entire attic to get me to R-49 (this amounts to an additional about 7-12″ of cellulose they say, depending on existing levels). With the 75% off rebate, my cost is $500.
Is it worth pulling the exterior soffit/fascia board to seal that 30′ exterior wall plate? I have a hard time quantifying how much air loss that will stop. Mass Save says they wont do that, it would be up to me.
I know quantifying ROI is tough, but will I see substantial benefits going from R30 to R49 and really burying the recessed lights in cellulose? I was estimating about a 5-year payback?
Pertaining to the basement, my rim joist is air sealed with 2″ XPS and spray foam. I have forced hot air ductwork in basement. I wanted to add 2″ foil-faced polyiso to my poured concrete foundation, which amounts for about 70% of the foundation. Mass save rep says I’m wasting my time unless I also deal with the 30% fieldstone.
Question #3: Is insulating 70% of my basement walls with reclaimed polyiso (about $400 cost to me) not going to provide much benefit?
I have no capillary break between fieldstone and sill plate. I see no signs of rot where I foamed the rim joist in the section, and I understand that fieldstone will wick far less moisture than poured concrete.
Question #4: Long-term, Is jacking up house, slipping capillary break under sill, and then running that vapor barrier to floor, and spray foaming that, best option for airsealing and insulation the fieldstone? Any other practical way to aireal and insulate fieldstone?