Thoughts on insulating — renovation
I ‘m trying to decide what insulation value to go with on a house we are renovating in Toronto, ON. It’s a 1 ½ storey that we are making 2 storey with adding addition on the back and attached garage.
The 1st storey walls are to be left, 1950s double brick walls no insulation. The 2nd storey I would like to go with either 2×6 with R24 Roxul or 2×8 R28 or 2×4 x2 with 3xR14=R42 and 3”Roxul Comfort board IS R12 on the outside.
So I get either R36/R40/R54, but on the main floor inside I can only go 2×4 R14 or 2×6 R24 max, plus I’ve been told the brick =R4???? Then the 3” R12 outside for R30/R40 Is it worth it to go R54 upstairs if down is not even close, will I have issues with the uneven top to bottom R-values???
Thanks
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Replies
Dave,
To answer your question, you need to use energy modeling software to calculate the annual energy usage of your home under all of the scenarios you list. You also need to do a cost estimate for all of the options.
If you don't want to do the math, you'll just be guessing.
I'm willing to guess, however, that the cost of building high-R wall assemblies for a retrofit like the one you are anticipating will have a very long payback period. In other words, high-R retrofit walls usually don't make a lot of economic sense.
Of course, it certainly makes sense to build any new walls (the walls of your addition) to a high standard, even if you can't retrofit your older brick walls to the same standard.
For more information on insulating old multi-wythe brick walls, see this article: Insulating Old Brick Buildings.
I figured I'd have to have someone do the energy modeling, I'd just like to have some ideas before I go to them. So you don't see the high R walls being worth it? or just the lower brick ones, would you still try and go with R40-54 in the additions?The plan is to live in the house for 20 years. The interior existing walls needed to be stripped down( lots of cracking) so new studs are going to put up with new drywall, so I figured insulate why I'm at it. I have read that article before and thought if Insulate both inside and out I shouldn't have a problem??? I was hoping to have this home as energy efficient as possible, it's quiet large at 3800sq' with the addition. The next step is figuring on the new heating system.