Exterior insulation in zone 4b
RuthT
| Posted in General Questions on
My garden shed is built. I am cladding with 10” half log white pine, horizontally.
I would like to add exterior insulation under the pine.
The windows are already installed.
what products are best? Cement board? Rockwool panel? Foam board?
This is Zone 4b in Canada. We get big west wind here on Lake Superior.
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Replies
Are you going to be conditioning (heating and/or cooling) your shed? If you aren't, then there is probably no real benefit to exterior insulation. If you are, then I'd use polyiso, which is my go-to for this application.
Bill
Thank you.
I will be heating it in Spring and Fall, on occasion.
Polly’s brand names?
Is this foil backed foam?
"Polyiso" is shorthand for "polyisocyanurate", a generic name for certain type of insulating foam -- it's not a brand name. Lots of companies make it, R-Max, Johns Manville, Dow, many others. Use what you can get easily in your area unless you have any special requirements (which you probably don't in your application).
Foil faced is most commonly seen in the residential world, but there is also a fiber faced ("kraft" faced) version that is commonly used in commercial roofing. You can use either here if you have some type of cladding over it. I'd try to see if you can find any reclaimed polyiso in your area to save money, otherwise you can get it from box stores and insulation suppliers.
If you built regular studwalls though, I'd probably just use batts and not spend the extra money on polyiso. The overall savings in such a small structure probably won't really pay off over time. Aside from the cost and installation time/labor though, there is no reason you can't use exterior insulation on your shed to up the energy efficiency a bit. The reason it won't make as much overall sense is that the losses through your doors and windows will dominate in this small structure, since they appear to be a very large relative percentage of the overall area of the perimeter of the structure.
Ruth,
Lake Superior is all climate zone 6 & 7.
https://www.greenbuildingadvisor.com/article/climate-zone-map-including-canada
You are going to lose most of your heat through the doors and windows, so I wouldn't go overboard insulating the walls. 1 1/2" foam is probably the sweet spot. I'd use whatever is cheapest at the Big Box stores.
Thank you.
Much appreciated.
I am in Sault Ste. Marie on the St. Mary’s River as it flows down from Superior. It is garden zone 4b here.
Thank you.
Ruth,
Nice country. I have friends in The Sault.
Note that plant hardiness zones are NOT the same as the "climate zones" we talk about in the construction world. We use the climate zones used in the building code as shown here:
https://basc.pnnl.gov/images/iecc-climate-zone-map
The building code climate numbers get higher as you get up into the colder and more Northern areas, pretty much the opposite of the garden zones.
Bill