300 year old farmhouse – strategy to make energy efficient and healthy
We’re about to purchase a 300 year old farm house in New England – classic 2 story hall & parlor colonial, with an ell for the kitchen, which has an actively antique wood cookstove. It is currently heated with an older oil boiler with baseboards, and two-three woodstoves in total. Foundation is stone, with a partial basement, and about half the house is over inaccessible crawl space. There is limited fiberglass batt laid down between the floor joists in the attic, with no apparent air sealing. The walls are reported to be R7 cavity filled. Any insulation under the 1st level flooring is poorly installed fiberglass. The windows are older double pane, and appear to be in sufficient order. I’d like inputs on my plan – step 1 is remove existing attic floor boards and remove the fiberglass insulation and air seal the entire attic floor – but what is best practice for that air sealing? After air sealing, blown-in insulation for the attic. I’d like ideas for air sealing and insulating under the 1st level floors, particularly over the crawl space – am considering removing the old flooring and doing the work from above – but then with what materials? The house has no ductwork – I’d like an effective whole house air filtration system – the house won’t require an ERV necessarily, but I want clean air, which is not sucked into the house from the basement, walls & leaks I can’t locate. Thoughts? Thanks! Jim
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With these old houses often the concept of a building envelope is very loosely defined. So as a first step I would make a sketch of the house, and then draw the building envelope on every section. The standard advice is that you should always be able to draw the building envelope without lifting your pencil from the paper -- i.e., it's continuous in all dimensions.
Some particular things to look out for: under the roof you have to worry about venting moisture. In the basement and crawlspace you have to worry about excluding moisture, and often determining where the boundary of the building envelope is going to be is tricky. In the walls, in old houses the exterior walls often aren't as weatherproof as modern construction, they relied on heat leaking through the walls to drive the moisture out. That can cause problems when the insulation is improved as the water starts to accumulate.
I'm not a big fan of wood burning, I've taken chimneys out of a bunch of houses. It frees up a lot of interior space.
Check whether you're under historic preservation before doing anything.
Thanks for your reply. The house is not under historic preservation. Defining the building envelope boundary is indeed a challenge. For the 1st floor over the basement and crawl space, does it make sense to add an air barrier of some sort attached to the underside of the joists, then cavity fill? I'd like to heat via in-floor hydronic - so would replace the existing subfloor with warmboard or similar. Would I be adding to any moisture issues?
In order to address old New England crawl spaces We’ve cut the floor system out of an few older buildings in order to install proper bulk water and vapor management, air barrier and insulation. In one case were able to keep the existing framing intact, while in another we put in an all new engineered floor system. We tied the new floor into the existing historic sill via a new LVL ledger that was shimmed to be plumb and somewhat straight.
The demo can be pretty grueling but the results are very satisfying. It also makes the rest of the project easier working from a solid base.
With your work on old crawl spaces, did you come up with an effective technique to air and water seal the crawl space stone walls? I've thought about applying closed cell foam spray - would that work, or create more issues?? Thanks! Jim