Best Practices for Insulating a Cold-Climate Attic
Thanks in advance to all of you who will finish reading this post 🙂 This is my first remodeling in my first house, so I appreciate all help.
We live in Boston metro area (zone 5) and in a 1901-built house. The top floor has cathedral ceilings (probably converted from the attic in the 1960s or so – we are not sure). Right now it serves as our bedroom with master bathroom + exercise zone. It is crazy hot in the summer and surprisingly tolerable in the winter. We finally have some money now to insulate it, and so I started my research.
As I found, there’s about 3-inch fiberglass in the ceiling – all in poor condition, missing in several places + the kneewalls are not insulated and provide nice heat pockets so that the second story of the house right under gets hot and non-livable as well. The rafter space where insulation is placed is not vented – there are soffit vents (installed to pass some brisk inspection maybe?) but they are covered with wood from inside so not functional, and no rigde vent either.
All in all, any project would be an improvement 🙂
Now, our initial plan was to remove the ceilings and install closed-cell foam (a la “unvented attic”), however, the rafters are only 2×6 and hence we cannot pack more than 5.5inches of foam there. That would give us about R35 – but not R45 required by code. We could add extra strips to the rafters to allow more foam but it is not an option in some areas like bathroom – the space is very tight; even 2 inches of ceiling would cost us a toilet :(.
Our contractor says that since the shallow rafters are “grandfathered design” we would be waived the code requirement, but I am worried if he is right. I called the city permit phone line but they were not helpful. So if someone could give me an idea how to approach this potential problem and whether to dismiss it and start the project, please do. Also, my contractor said that if we do add strips to the rafters to fit more foam, that would not be original design anymore, and no waivers would be applicable. Does that make sense to you?
BTW, I also want to add more insulation to the kneewall area that we know gets the most heat – just in case, you know. That shouldn’t hurt.
To sum it up – if I choose this option, I will get R35/R35+ in the roof, about R20+ spray foam in the walls (there’s none now), extra insulation and renovated/optimized closet space (that we would like to re-map, so this is a great excuse).
Alternatively, I was recently advised to not touch the interior at all, but to dismantle the shingles on the roof, add rigid insulation there, and finish it again. I am not sure if that’s the best idea – true, spray foam is expensive, but having >R40 worth of rigid insulation would require us to deal with a huge overhang (that needs to be covered with trim, new fascia, extended molding etc + lots of labor; the price tag for such project would be way more than simple roof replacement. We have a relatively new roof (installed 2009) in good shape, relatively light color, so replacing it now is totally impractical. The benefit is that I don’t have to deal with interior demo/restoration mess (huge!).
I am inclined towards the first option – if the code conflict is resolved one way or another; then wait and watch, and maybe add more rigid insulation to the roof when we replace the shingles next time.
What would the experts say? I would appreciate your help tremendously.
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