What is the proper way to insulate rim joists?

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Posted by: from Calgary
9/14/2014 at 12:27:56 AM

We are having our basement developed by a local contractor. I believe schedules got mixed up and our "poly and insulation repair" check did not occur. Instead the boarders were asked to do a quick poly check / fix.

My question is - are there building codes for Calgary / Alberta / Canada which indicate proper insulation / poly procedures? In particular, I'm wondering if rim joists need to be air sealed using poly and caulking or if the poly can / should simply be tucked / stapled to the rim joists.

If there are not any codes surrounding the topic - what is the proper way of sealing the poly for both the rim joists and framing around the foundation?

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Date/Time9/14/2014 at 11:21:20 AM

Not positive about Alberta, but I'm sure it's similar to Ontario's building codes.

The joist cavity should be fully insulated with a vapour barrier that is sealed with acoustical sealant or tuck tape. Not just stapled in place, which makes the vapour barrier basically useless with all the air gaps. This is one area that I use spray foam closed cell insulation. It saves time and is perfect for these difficult to insulate areas and it is a perfectly sealed vapour barrier when dryed.

You don't need to call in an expensive foam company for such a small job either. The large foam kits from the big box stores work well and are economical for small areas. Also sounds like you didn't get any permits or inspections. This opens the door for bad contractors to cut corners.

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Buddy in Calgary
Date/Time9/14/2014 at 11:27:47 AM

Hi James thanks your your reply.

Our contractor did apply for the building, electrical, plumbing and heating inspections. Some of the inspections found some minor issues but none of the commented on the insulation / rim joists. According to our contractor's schedule, the insulation and poly check was to occur after the permit inspections. Here in Calgary, there is an extensive amount of construction going on and I can unfortunately see where everyone including inspectors are rushed to do jobs.

If anyone else has some experience in Alberta, I'd appreciate from hearing from you as well.

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Date/Time9/14/2014 at 11:38:33 AM

Hi Buddy,

I just got off the phone with a friend who owns a large plumbing outfit in Calgary.

And I confirmed that the method I use and James from Phoenix uses in the cavity meets code out there.

Code only calls for insulation and then the vapour barrier Tuck tapped to the rim joist and floor joists. But the best method is to use spray foam insulation. This gives you the R factor as well as the barrier. It costs a little more but is far superior.

On Monday you can phone the building department yourself, and they will be happy to confirm this information. I am sure they are as helpful as the Toronto, Mississauga, Oakville and Niagara Falls building departments have always been.

Enjoy the basement.

James Fram

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Buddy in Calgary
Date/Time9/14/2014 at 12:27:40 PM

Hi James F,

Thank you for reaching out to your contact in Calgary - much appreciated. I'll be sure to call the building department first thing in the morning. The contractor is coming back on Monday to take down some drywall to show me that it was stapled, which he said was "enough for code" in the rim joist cavity - no tuck tape or sealant required. Hopefully the building department and his statement lines up but from your responses it sounds like tuck tape and sealant might be required.

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Date/Time9/14/2014 at 5:30:21 PM
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Josh from Welch's Drywall in Portland
Date/Time9/17/2014 at 12:29:55 PM

Hi Concerned!

In Ont. the way we do it out in farm country. We stuff the beam pockets full of as much insulation as you can out to where the framed wall is nailed to the under side of the joists.

When framing the exterior of your basement with 2x4's keep the wall at least 2 inches from the concrete wall, this allows 5 1/2 inch from exterior wall so you can put in R20 or R24 if it's available to you. Vapour barrier up to under side of floor joists and tuck tape it or caulk it. Above that put in between the floor joists 1 inch thick pieces of rigid foam board bought in sheets 4x8x1inch and spray foam around them when you get them in place because they won't fit perfect. This is like foaming around windows and doors that leak air, same principle.

If you want to spend more money, then have the guys come in when you have the walls all framed and wiring in place and have them spray form everything with the big machine,rim joists and framed walls. This is the best way to do the job or just have them spray all the rim joists and just do conventional batting of the walls with the above R values I mentioned.

Hopefully this had helped some. Thanks!

Josh & Dale

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Buddy in Calgary
Date/Time9/17/2014 at 1:18:26 PM

Hello All,

Just following up on this question - I called the building compliance office and they confirmed that indeed all that needs to be done to the floor joist cavity is to to insulate, poly and STAPLE (ie. NO acoustic sealant is required).

I think this is a sub par code for Calgary. Unfortunately out in Alberta we don't have as strict standards like R2000 like they do out east.

Thanks again to everyone who responded to this thread!


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