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Window insulation rating subtleties and question

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  • Jan 9th, 2021 5:02 pm
[OP]
Sr. Member
Mar 1, 2020
643 posts
193 upvotes
GTA West

Window insulation rating subtleties and question

Building/Home enthusiasts:

I always read (And therefore assume, rightly or wrongly) that windows are extremely poor in insulation -- even double paned or triple paned ones. they're always rated to have "low R" rating vs walls/ R-50(?) insulated attics etc...

This article tries to debunk such "myth" - while still acknowledging the weakness of windows still . (which is good for knowledge)...
https://www.constructioncanada.net/wind ... ergy-myth/

As someone who never grew up nor lived for long periods in cold weather climes (only more recently in this century LOL), I've always wondered -- arent double / triple paned windows really as "sealed" as walls with insulation (whether batting/foam) - they certainly look "sealed" LOL ? If they're not energy efficient, then why condo buildings with floor to ceiling windows? Also, wouldn't windows "offset" their low "R" ratings by allowing more sun during sunny days (and your room would stay warmer" longer?

Clearly it's not as simple as that - bottom line - since this is a RFD forum after all, would it be rather a "waste" of $ buying super high end insulating windows (as specified in that article link) and replacing them every 10 yrs or so? wondering the cost/benefit of such? eg replace to triple paned, worth it if one lives in a house for a few years only after replacement? surely, there's a cost benefit to these things -- if one doesn't live in one's house more than 10-20 yrs, seems like it's not diff than replacing shingles with shingles rather than say, metal roofs? (eg replace double pane to triple pane when you're only living in the house for 10 yrs)

Thanks for any thoughts...
3 replies
Deal Fanatic
Jan 25, 2007
9971 posts
5251 upvotes
Paris
Let’s looks at a wall first...My house at the back is siding (r=.01) 3/4 foamboard (3) pink (12) vapour barrier (1) drywall (.5) total= R16.51.
The problem is, every 16 inches its: siding (r=.01) 3/4 foamboard (3) 2x4 (4) vapour barrier (1) drywall (.5) total= R8.51

So walls aren’t anywhere near 50. Most likely, your attic was blown to R30 and has settled into R23ish if you have a newer house, and if its older its probably batt insulation at around R12-16.

As for windows, most builder grade windows sit around R2, while replacement windows start at R4ish and can go as high as R10 (which are massively expensive). There is a nice middle ground between R4 and R10 for cost, and its usually around R4.6-5. You are right, in many circumstances triple isnt great value right now, with the exception of when there are government rebates for triple.

As for replacing every 10 years, you should not need to replace renovation quality windows every 10 years. They are built now to last a lifetime. Builder windows are built to last 2 years in Ontario which is all Tarion warranties them for.
Deal Guru
User avatar
Nov 18, 2005
11329 posts
2784 upvotes
Kingston
Any solar heat gain from Windows in the winter is also experienced in the summer when it is a bad thing.

This article breaks out the savings from the various window features. All of them are pretty ordinary except triple pane and krypton gas which are both expensive and of little benefit (despite the article's title).
[OP]
Sr. Member
Mar 1, 2020
643 posts
193 upvotes
GTA West
So far it seems like it's not "worth" the benefit of triple pane if one is indeed not really staying in a house longer than 10 yrs... I'll stick with what I have and let the future owner deal with this (and in the meantime just pay more for heating/cooling) rather than waste $ on window replacement... Thanks guys...

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