Insulation and R-values
user-6846735
| Posted in Green Products and Materials on
I live in Edmonton, Alberta. I am remodeling a home and trying to figure out the R-value I want in the walls and attic. I have seen recommendations in building codes and on several websites.
I am trying to figure out the difference in efficiency and cost/savings of different R-values. Any charts that explain this would be helpful.
Please let me know if you know where these charts can be found.
thanks
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Replies
The actual costs and cost savings all vary with location & energy costs. In Edmonton going with the IRC 2015 code minimums for zone 7 will almost always be cost-effective in new construction, and if it's easy enough to hit to those levels in a remodel it's well worth it. See the bottom row of this table:
https://up.codes/viewer/int_residential_code_2015/chapter/11#N1102.1.2
User-6846735 (real names are better; here's how to change yours: https://www.greenbuildingadvisor.com/blogs/dept/green-building-news/how-gba-site-displays-readers-names), the cost/benefit analysis depends on many factors, so no chart is going to be very useful. If you double the R-value of the insulation, you cut the rate of heat flow through the insulation in half. But much of the wall is framing and windows, R-value varies a bit as the temperature changes, and airtightness has an impact, etc.--so there are many variables. That said, at bare minimum, you should use what your building code recommends. An computer energy model such as BeOpt (a free download) can give you a good idea of the potential savings for your particular situation.
Also, R values are one thing, air tightness is another. In a full-gut rehab it's an opportunity moment to caulk the wall sheathing to the framing inside every stud bay, and tape any horizontal plywood seams with an appropriate tape (which may need to be reinforced with some duct mastic if the sheathing is dirty enough that long term adhesion is iffy.) Use a decent quality polyurethane caulk (or acoustic sealant), and be sure to seal between doubled up framing such as top plates, jack studs, headers, etc., as well as a bead where the bottom plates meet the subfloor.