Insulation and mechanical upgrades
We recently purchased a 1500 square foot colonial outside of Philadelphia. I’d like to triage energy upgrades for this house and establish a long-term, holistic plan. We’re in climate zone 4, close to the border with zone 5. It was built in 1984, has a finished basement with 1 inch eps foam on the walls a floating slab. Radon mitigation is underway and they will be sealing the slab-wall gap with polyurethane foam. 1300 square feet are split between two floors, and the remaining living space is behind the attached garage, on a slab foundation. This 200 square foot room also contains a fireplace that we plan to convert to a gas insert. Above grade walls are 2×4 with fiberglass batts, and 8 ft ceilings. House faces south, and there are 45 sqft of double pane glass on the south wall and 70 sqft on the north wall. The attic for all living space is accessible and the roof is vented soffit to ridge. It’s forced air heat with central air conditioning. The hot water heater and furnace pull combustion air from the living space and the are ~10 years old. Both run on natural gas.
I suspect a low-hanging fruit is air sealing and adding insulation to the existing R-19 attic, but I think I would feel more comfortable doing this with sealed-combustion heating and hot water. Is it worth upgrading both at the same time? I did a preliminary Manual J calculation and came up with heating load of ~25000 Btu/hr and cooling load of 13000 Btu/hr. I’m not sure I filled out the spreadsheet entirely correctly, but those numbers surprised me given the 70,000 Btu furnace that’s there. We usually keep the heat at 66F, but I used 70F in the calculations.
If the heat load is closer to 25,000 Btu/hr, would it be feasible to heat the house with the gas fireplace and a small wall furnace upstairs after air sealing and insulating the attic? I’m not crazy about the ducted system (hard to access ducts to air seal and poorly balanced), and it doesn’t work very well as air conditioning because the second floor vents are on the floor. The cooling load seems within the realm of one or two minisplits. The heating and cooling equipment will need to be replaced in the future, and I wonder if a wall furnance/mini split strategy is a better route. We will be installing engineered floors and have briefly considered radiant, but I suspect that’s even less cost effective.
What should I plan for short and long term? Is it better to just insulated and then upgrade the existing, ducted system even though duct-sealing and performance aren’t ideal?
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