contractor installed R14 fibreglass as exterior wall insulation – Toronto canada cold/mixed climate – can/should I add insulation now
Hi, I am currently renovating an old split level home in Canada cold climate- zone 7 I believe– it had plaster walls which were all removed , frame is 2×4 , my contractor put up R14 insulation based on the walls being 2×4 …I am feeling a little uneasy as I know the standard r value now recommended for my climate zone is higher… is there that big of a difference between the r14 and r20 that should make me concerned ?
The exterior is some kind of particle board , then plywood I believe and vinyl siding … he has already done the insulation and added the poly so it would be a pain in the butt to take it down now , wishing we had had a conversation about this before hand and possibly added the furring strips to make walls 2×6 but that didnt happen and here we are..original quote /scope of work stated min r20 would be put up but he quoted
us before the walls were removed so I guess he didnt know the frame inside was 2×4 and didnt think to talk to me about extending the frame and just added what would fit
side note- my roof will be spray foamed and can only get r30 in the space
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Replies
Too late for exterior rigid insulation?
hi yes it is...only interior options available
Jewell33,
It's not great, but the biggest improvement in both energy consumption and comfort will come from air-sealing you have had done.
If you want to increase the R-values with a minimum of disruption to what has been done, you can add a 1" layer of continuous foam insulation on the inside. It would be comparable to R-20 in the stud cavities, as it reduces thermal bridging. That would necessitate adding extension rings to the electrical boxes.
thanks for your response, what do you recommend for air sealing measures? and if I added the foam it would be tricky to install drywall after wouldnt it?
Jewell33,
No the drywall is fine as long as you stay at 1" or less foam thickness. However it's an open question as to whether it's worth doing at all for the reasons others have offered.
Just remember that insulation, and its associated costs have a return on investment.
You have to ask yourself if the extra cost, time and loss of space, is worth saving a difference of a marginal number like $50-100 per year of extra heating costs. Of course, I can't tell you exactly what your number is, you would have to do an energy model of your house and compare the two wall assemblies. However, I picked that number to express that the extra R6 you're concerned about is not mission critical.
Certainly having higher R value in the walls is good practice, but if I was renovating my personal house, I would much rather save the space and the shenanigans of furring out all the exterior walls, and associated detailing involving the existing electrical, windows and doors and stairs.
I'd say put your focus on air sealing and the details with the vapour barrier. Or any other air sealing efforts on the exterior walls..That'll be much more efficacious for the effort.
Now, the contract issue is another matter, maybe your contractor can throw in a bone for the difference in expectation vs reality.
Just my opinion, I hope it helps.
Jamie
Hi Jamie, thanks for the response, what measures would you recommend for air sealing?
Toronto is around 7000 heating degree days. Say the place is around 2000sqft, it would have about that many sqft of walls.
A 2x4 stud wall with R14 batts is about an R12 assembly.
So over a heating season you would loose
7000HDD*24h*2000/R14=240 therms
Bump up the wall to 2x6 so around R19 assembly, you cut that down to 150 therms.
Gas here is pretty cheap, so you would save around $100/year. Not nothing but not a lot.
More important thing to get right is to air seal properly. With older structures you loose more energy from air leaks than for the lack of insulation. Before the drywall goes in, get a blow door test done along with some blower door directed air sealing. Well worth the investment in terms of energy savings and more importantly comfort. A draft free house is a very comfortable house.
Hello Akos, thanks very much for the in depth response, I feel better now knowing that its not that much of a difference, I have never heard of a blow door test before I will definitely look into that then, are there any other measures I should take to check the air sealing before the drywall goes on with regard to the poly install?