Insulating kitchen extension
Hello,
We’ve been batting around a few ideas for an upcoming project. It’s an older house in eastern Canada and the owner is taking in half of the attached garage as a kitchen extension. When the floor is installed we’ll essentially be creating a crawl space underneath the floor of about 24″, with a the original garage concrete floor underneath and concrete foundation up to the new floor joists. The three ideas for insulating it that I’ve come up with so for have been:
Idea 1:
Tyvek on bottom of joists(facing down)
Fiber Insulation between joists
Vapour barrier on top of joists
Plywood
Idea 2:
Rigid insulation around concrete (VB & insulation)
Rigid insulation on concrete floor
Fiber Insulation between joists
Plywood floor
Idea 3:
Closed cell spray foam around concrete foundation.
Rigid insulation on concrete floor
It’s basically down to taking the new crawl space into the living space’s envelope or leaving it with the garage.
Any thoughts?
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Replies
Daniel,
I vote for Option 2.
Regarding your suggestion to install a vapor barrier on top of your joists: remember that your plywood subfloor is already a vapor retarder.
If option #2, insulate the walls of the crawlspace, and not between the joists. In most of eastern Canada you could safely add as much fiber insulation to the interior side of any rigid foam (floor or foundation wall) without vapor barriers over the fiber insulation.
If you insulated the concrete, then added insulation between the joists, the joist edges run colder, and would take on some moisture as adsorb. If you put all of the insulation on the exterior, the wood all runs warm and dry- it's fully inside of conditioned space.
This might need some fine tuning if you're on the cool breezy shores of Hudson Bay or something. "Eastern Canada" is a pretty broad description, covering a wide range of climate. Can you narrow it down a bit?
Thanks Martin and Dana.
The home is in St. John's Newfoundland right on the eastern tip of the country. Big mixture of cold and warm day and big range of humidity.
I'm sort of leaning toward the spray in closed cell just for the r value and that it's a vapour barrier and all. All the underfloor plumbing would be safe from the cold and the floor would be nice and warm, not to mention a nice dry space underneath.
Thanks for suggestions
Daniel