Home & Garden

basement insulation. What R value is needed in Ontario?

  • Last Updated:
  • Oct 16th, 2020 9:56 pm
[OP]
Jr. Member
Nov 22, 2018
164 posts
58 upvotes
Mississauga - ON

basement insulation. What R value is needed in Ontario?

Does anyone know for sure what the R value requirements are for a basement reno?

I think I've made a mistake and am worried I've not put enough XPS insulation up before building my studs.

due to cost (I know) I went for 1" Owens XPS - R-5 (RSI-0.88) thinking the code was R-15. So this plus R14 of the batts would take me well over that

Now I'm hearing the required R value is 20, which means I am below code if I use the standard R-14 batts (Rockwool or Owens fibreglass)
So when the inspector comes round to view my installation, am I going to have to rip down my walls and put the thicker R7.5 XPS boards with R-14 batts - to take me up to 21.5?
16 replies
Member
Jun 23, 2019
365 posts
209 upvotes
I'm not sure what the current code is, but 2018 build house has R20 from the ceiling down to the floor.
Deal Addict
Nov 9, 2008
1635 posts
657 upvotes
Toronto
I believe code for NEW BUILDS is R20.

For retrofits of existing homes that pre-date the new code, I believe it's R12 or R14?
Deal Addict
Nov 18, 2005
4997 posts
1381 upvotes
Kitchener
Depends on where you live and local building codes, but R20 is typically the minimum. Guess if the inspector is picky, you could install 1/2" XPS board over the walls and then drywall, probably have to move electrical boxes out another 1/2"
Last edited by Drthorne on Oct 5th, 2019 9:25 pm, edited 1 time in total.
Sr. Member
User avatar
Feb 25, 2018
567 posts
213 upvotes
You are suppose to insulate on the exterior wall of the basement not the interior. It may cause mold if you insulate other wise. Concrete foundation walls need to dry - inward.
[OP]
Jr. Member
Nov 22, 2018
164 posts
58 upvotes
Mississauga - ON
DaveVentura wrote: You are suppose to insulate on the exterior wall of the basement not the interior. It may cause mold if you insulate other wise. Concrete foundation walls need to dry - inward.
not sure I'm going to rip up my driveway and my yard deck, to dig a 10' trench around the perimeter of my house - in order to rebuild an interior wall in the basement
Deal Addict
Dec 17, 2007
2405 posts
1373 upvotes
Alliston, ON
jacquesstrap wrote: I believe code for NEW BUILDS is R20.

For retrofits of existing homes that pre-date the new code, I believe it's R12 or R14?
Age of the house doesn't matter. What matters is when the building permit was issued. Anything after Dec 31/2016 is following the new R values
Sr. Member
User avatar
Feb 25, 2018
567 posts
213 upvotes
EndeavourX wrote: not sure I'm going to rip up my driveway and my yard deck, to dig a 10' trench around the perimeter of my house - in order to rebuild an interior wall in the basement
You don't insulate a wet basement, it will just turn to mold and you can rip it out every year. You need a water barrier under the slab and exterior walls.
That is why basements are unfinished or only semi finished.
Deal Fanatic
User avatar
Sep 8, 2007
9019 posts
10320 upvotes
Way Out of GTA
EndeavourX wrote: Does anyone know for sure what the R value requirements are for a basement reno?

I think I've made a mistake and am worried I've not put enough XPS insulation up before building my studs.

due to cost (I know) I went for 1" Owens XPS - R-5 (RSI-0.88) thinking the code was R-15. So this plus R14 of the batts would take me well over that

Now I'm hearing the required R value is 20, which means I am below code if I use the standard R-14 batts (Rockwool or Owens fibreglass)
So when the inspector comes round to view my installation, am I going to have to rip down my walls and put the thicker R7.5 XPS boards with R-14 batts - to take me up to 21.5?
You mention a basement “Reno” .....is there already framing and insulation down there or a complete start from scratch situation?. I believe if there’s already framing and insulation along the frost walls that you are not subject to the new code. But if you are framing for the first time along the exterior walls you have to follow the 2017 code revisions. Which entails the requirement for continuous insulation.
[OP]
Jr. Member
Nov 22, 2018
164 posts
58 upvotes
Mississauga - ON
cartfan123 wrote: You mention a basement “Reno” .....is there already framing and insulation down there or a complete start from scratch situation?. I believe if there’s already framing and insulation along the frost walls that you are not subject to the new code. But if you are framing for the first time along the exterior walls you have to follow the 2017 code revisions. Which entails the requirement for continuous insulation.
replacing the existing framing, which suffered water damage due to small flooding.
it was a finished basement when we bought the house a couple of years ago.

there was no insulation on the exterior walls though - just framing and drywall.

house is 1970's
Deal Fanatic
User avatar
Sep 8, 2007
9019 posts
10320 upvotes
Way Out of GTA
EndeavourX wrote: replacing the existing framing, which suffered water damage due to small flooding.
it was a finished basement when we bought the house a couple of years ago.

there was no insulation on the exterior walls though - just framing and drywall.

house is 1970's
I’d check with your building inspector then. If it’s just replacing existing framing (due to damage) you may be free to insulate as you wish. I’d have a paper trail. If so, I’d look at reframing and using R14 rock wool and vapour barrier. R14 rockwool will fit in 2x4 and does a fine job on its own. It will be up to you then if you want to go R20 but you will lose interior space due to the thickness and have to move the framing back.

That other poster is being intentionally obstinate.
Sr. Member
Jul 11, 2017
641 posts
760 upvotes
How exactly are you supposed to achieve R20 current code for basement wall, with only 3.5 inches?
Deal Guru
Feb 9, 2006
12254 posts
6807 upvotes
Brampton
Bella125 wrote: How exactly are you supposed to achieve R20 current code for basement wall, with only 3.5 inches?
Foam or minimal gap and 2x6 on exteriors walls.
Sr. Member
Sep 15, 2017
535 posts
546 upvotes
DaveVentura wrote: You are suppose to insulate on the exterior wall of the basement not the interior. It may cause mold if you insulate other wise. Concrete foundation walls need to dry - inward.
So literally most every finished basement I've seen with insulation on the interior of the basement walls is wrong? Or am I misreading what you are saying here.
Penalty Box
User avatar
Oct 13, 2008
4837 posts
1758 upvotes
16'x11' Living Room 11' Cathedral Ceiling. Hisense 65Q8G. Denon AVR-S740H 7.2 setup. Jamo Classic 10 280W Towers - FR+FL; Polk S35 - Center; Klipsch R51M - RR+RL; Klipsch R14M - Dolby FHR+FHL; Polk HTS10 Subwoofer x2. Unlocked Android Boxes from Taiwan x2
Deal Addict
User avatar
Sep 9, 2007
2030 posts
146 upvotes
Toronto
I think it was R22 for my basement in Etobicoke which was achieved with spray foam.
Deal Addict
Nov 18, 2005
4997 posts
1381 upvotes
Kitchener
Bella125 wrote: How exactly are you supposed to achieve R20 current code for basement wall, with only 3.5 inches?
Good sprayfoam is R6 per inch

Top