1952 Cape Cod
First-time poster. In the past 2 months, I’ve read a hundred or so GBA articles and comment threads; I’ve been amazed by the expertise and generosity of the community. I’ve also read extensively at buildingscience and finehomebuilding — I’m new to but very interested in building science. Here’s why:
We just purchased our first free-standing home, a large 1952 Cape on a great piece of property in Maryland (CZ 4). There is too much humidity in the house (inside fountain, which we will remove.) The house is need of air sealing and insulation throughout. (Previous owners did not update air sealing or insulation over 20+ years of ownership.) There are two vented, uninsulated basement crawl spaces. Energy audit/blower door found 4400 sqft of conditioned space and leakage of 7330 cfm50.The HVAC is currently 24 yo oil (no natural gas available in neighborhood) with central air (2 zones, one unit 1994 and one 2015). The smooth front roof is slate, has 2×6 boards as roof deck, and has 5-10 years of life left. The rear roof (2 walkout dormers) is mostly slate; this roof deck has been updated to plywood. Both of these roofs are vented with gable vents – no ridge vent. There is also a rear flat roof over an addition, w/EPDM and poor insulation. Other than these issues, the house is a model of green efficiency!
FULL DETAIL BELOW
After reading feedback provided to other posters, I’m including full detail on multiple aspects below.
REQUEST FOR FEEDBACK
I have used the search function and read every available article on the below topics. I would greatly appreciate your input on my personal situation. I am happy to post photos if helpful and will post results as we move ahead. I’m interviewing insulation contractors now, which is quite a learning experience.
Can you please confirm or improve my tentative plan, below? Our objectives are to 1) increase comfort and 2) significantly reduce operating expenses.
Current: There is currently maximum 2” of blown in fiberglass on the floor. Air handler (AC only) is in attic. 20yo ducts are decent shape but likely very leaky and need to be better insulated.
Plan 1: Remove/vacuum blown insulation. Air seal all seams with Great stuff or caulk, especially the top plates and fixtures. Blow in 16-18” of cellulose.
Plan 2: Either majorly seal and bury the ducts in insulation, and/or move these downstairs when HVAC is updated (see below).
Question: What sealant is recommended?
2. Cape kneewalls.
Current: Kneewall space is unconditioned. Floor joists are wide open. Rafters have 6” of available space for insulation. Roof deck looks like original 2×6” boards. Roof is slate and might need replacement within 10 years. (We will likely switch away from slate.) There is 2-3” rockwool insulation in the kneewalls and under floorboards.
Plan 1: Make this conditioned space. Motivation is 1) maximize performance and cost savings and 2) in future likely move HVAC unit into this conditioned space. We do not need this space for storage.
Plan 2: In future, consider new HVAC unit in this space, for an upstairs zone, either sealing/insulating/burying existing ducts in attic, or installing brand new ducts under 2nd floor (so that supply vents would all come from floor).
Question: How specifically – what technologies – to bring this inside the thermal envelope, given the 6” maximum space between rafters and hope to get close to R49?
Question: Any thoughts on the ducts?
Current: Rockwool stuffed in first 6” of slopes.
Plan: Install block and seal at the top of the kneewall. Insulate between that block and the attic floor. Install block and seal at the attic floor prior to blowing cellulose.
Question: How specifically – what technologies – to block, seal, and insulate here? Closed cell foam? Dense pack cellulose? The rafters will hold 6”, and there might be a couple more inches until the drywall.
Current: The basement is finished, but there are two vented, uninsulated crawlspaces on either side. Uninsulated ducts are in these vented spaces, (!) The floor joists are not fully accessible.
Plan: Block and seal the grates/vents to outdoors. Seal what is possible at the floor joists. Air seal and insulate the concrete walls. See HVAC, below.
Question: How specifically – what technologies – to block, seal, and insulate here? Seal then fiberglass batts? Rigid foam board?
Current: Oil furnace heats whole house. 2 AC zones. Zone 2 has separate ducts in attic.
Plan 1: I was leaning toward geothermal, contingent on the 30% tax credit returning, but having read GBA on this topic am now thoroughly confused. The house layout would be great for mini splits – it looks like a rancher with a partial second floor.
Question: What is current thinking on geo vs ductless?
6. Other notes/questions:
a. I’ve read Martin and others state that external foam board is the best way to seal and insulate, eg in kneewalls where retro sealing can be tricky. External foam board might be possible on the front slate roof, but that has another 8 years or more of life in it (so we don’t to replace it now). On the rear roof (slate w dormers), I don’t think external foam board will be possible. For both of these reasons, I’m thinking seal/insulate from the inside.
b. The flat EPDM room will need to be replaced in 10 years. I was thinking of bringing to R49 with external foam board at that time.
c. We’re just updating oil hot water to hybrid heat pump.
d. Is there a specific technology or product to seal recessed lighting?
Thank you again.