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Band joist insulation in a retrofit.

Hello GBA,

We know the band joist of an older platform framed home is a thermal weakness. Often un-insulated, often leaky.

During the course of an air sealing and insulation retrofit, is it typically cost effective to cut into the perimeter of the first floor ceiling in order to access this weak point? With access, spray foam or dense packed cellulose could be applied in order to seal and insulate this portion of the wall assembly.

Will accessing and addressing this area lead to substantial CFM50 reductions and thermal improvements to the home?

My gut tells me that this portion of the assembly is probably right near the neutral pressure plane, and that real world air infiltration is probably not a huge problem at this location.

Thoughts? Thanks!

Asked by Art Vandelay, AIA/LEED AP+, Zone 5
Posted Sat, 02/05/2011 - 10:52

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13 Answers

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1.
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Art,
Could you please clarify your Platform framing? As I understand, platform framing can be set on wood or concrete foundations creating a crawl space or basement; or on a slab-on-grade. There is also Balloon framing which maybe more in tune with your description. Your thoughts?

Answered by Armando Cobo
Posted Sat, 02/05/2011 - 13:07

2.
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My gut tells me that this portion of the assembly is probably right near the neutral pressure plane, and that real world air infiltration is probably not a huge problem at this location.

Art,
Martin's recent blog,
"Questions and answers about air barriers" and the following commentary contained some discussion about the "neutral pressure plane" and it's relationship to air-sealing. Your gut is right provided the cracks you want to seal are near the "neutral pressure plane".

During the course of an air sealing and insulation retrofit, is it typically cost effective to cut into the perimeter of the first floor ceiling in order to access this weak point?

It's not clear what you are describing...
Are you talking about cutting through a finished ceiling under the floor framing?

With access, spray foam or dense packed cellulose could be applied in order to seal and insulate this portion of the wall assembly.

What climate zone are you in?

Answered by Lucas Durand - 7A
Posted Sat, 02/05/2011 - 14:52

3.
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Thank you Armando and Lucas.

Lets say we are looking at a typical center hall colonial built in the early 1980's. The task I am considering is cutting access into the finished ceiling of the first floor around the perimeter in order to address the band joist framing member that is between the first and second floor. The band joist is part of the floor assembly of the second floor.

I am in North Jersey, climate zone 5.

thanks.

Answered by Art Vandelay, AIA/LEED AP+, Zone 5
Posted Sat, 02/05/2011 - 15:38

4.
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Armondo

I dont think you understand platform. With platform framing as the name implies the first floor consists of a platform built atop the foundation. Then the exterior walls for the 1st floor are erected. The the floor joists and dck for the 2nd floor are installed and the 2nd floor is built then the 3rd if needed.

Since there is no insulation in the cieling of the 1st floor. So his question is how to get insualtion in this area.

Answered by Robert Hronek
Posted Sat, 02/05/2011 - 17:32

5.
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Art,
I would make sure I was working with a HERS rater to do a blower door test. Your leaks maybe coming from the rim joist, but also from interior and exterior wall penetrations, under sealing of sheetrock and framing members and the lack of a WRB and/or exterior air barrier. Now, the best and easiest way to air seal interior rim joists in retrofits is with open cell foam from the inside. Installation can be determined by location and accessibility. You could spray with a long nozzle through small holes in the ceiling but it’s hard to obtain consistent quality. If you have carpet upstairs you could make small holes or slits in the floor, which it’ll make it easier to see and later to cover than a lot of sheetrock holes. If you have balloon framing as I thought you were describing, that would be a different issue.

Robert,
I mayI suggest some good reading I have: Architectural Graphic Standards, Wood - Frame House Construction and Graphic Guide to Frame Construction to better understand framing techniques and history.

Platform framing: (Google – Wikipedia. It was easier to copy/paste…)
“In Canada and the United States, the most common method of light-frame construction for houses and small apartment buildings as well as some small commercial buildings is platform framing. The framed structure sits atop a concrete (most common) or treated wood foundation. A sill plate is anchored, usually with 'J' bolts to the foundation wall. Generally these plates must be pressure treated to keep from rotting. The bottom of the sill plate is raised a minimum 6 inches (150 mm) above the finished grade by the foundation. This again is to prevent the sill-plate from rotting as well as providing a termite barrier… etc. etc. etc.”
There is a lot of information in Google if it makes it easier.

Answered by Armando Cobo
Posted Sat, 02/05/2011 - 18:39

6.
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I am working with a blower door, and I know there is air coming in through the band joist between floors. The question is whether or not it is not HOW to address the area, but if it is cost effective to address......

Answered by Art Vandelay, AIA/LEED AP+, Zone 5
Posted Sat, 02/05/2011 - 18:57

7.
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Will accessing and addressing this area lead to substantial CFM50 reductions and thermal improvements to the home?

Definitely, yes. I am a CEA in BC. When I talk to customers following their retrofits, the comment almost everyone makes goes along the lines of " when the insulation guy came in and sprayed the rim joists we noticed the difference the same day"

Answered by Ray Smith
Posted Sat, 02/05/2011 - 20:41

8.
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Ray: Thanks for the input. I just want to clarify....are you talking rim joists in the basement, or band joist between floors?

thanks.

Answered by Art Vandelay, AIA/LEED AP+, Zone 5
Posted Sat, 02/05/2011 - 20:49

9.
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Hi Art,
Are you the same Art Vandelay who designed the addition to the Gugenheim?

I think your question is interesting.
In the Blog that Lucas referenced ... Martin says"Air leaks in the center of the house — in the vicinity of the neutral pressure plane — are less important."

Looking at this photo suggests to me that insulating AND air sealing at the rim joist can be important at ALL floor levels.

rim joist.JPG
Answered by John Brooks
Posted Sat, 02/05/2011 - 21:07
Edited Sat, 02/05/2011 - 21:08.

10.
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Thanks, John. Yes, the addition to the Gugenheim was one of my more well known projects. Not to get off topic, but I had been working as a freelance importer/exporter when I had a mid-career crisis and got into architecture. The rest is history....

Do you have any more information on the problems in the picture above? I would love to see exactly what happened here.......

thanks.

Answered by Art Vandelay, AIA/LEED AP+, Zone 5
Posted Sat, 02/05/2011 - 21:20

11.
Helpful? 0

Art,
the photo is from this blog
http://www.greenbuildingadvisor.com/blogs/dept/musings/install-stucco-ri...

the rim joist and air sealing was not the subject of the blog... but the photo still seems to telegraph the rim joist.

I always wanted to pretend to be an importer/exporter

Answered by John Brooks
Posted Sat, 02/05/2011 - 21:26
Edited Sat, 02/05/2011 - 21:27.

12.
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Looking at this photo suggests to me that insulating AND air sealing at the rim joist can be important at ALL floor levels.

John, good point.
"less important" is not the same as "not important"

Answered by Lucas Durand - 7A
Posted Sun, 02/06/2011 - 07:36

13.
Helpful? 0

Armando

This picture shows what I was talking about. There is a band/rim joist qt the base of each floor. The OP wants to insulated/seal between the 1st and 2nd floor.

I see 3 ways of doing this. Hole in the cieling from the 1st floor. The 2nd would be to as you suggested if to come from the floor of the 2nd floor. The 3rd would be from outside- I only see doing this if there is vinyl or wood lap siding.

I think you could do it with injection foam. If you had a way to get a plug in you could also use dense pack.

I dont know about the cost aspect. Homeowners may not be to keen on cutting into and repairing cielings in each room. Pulling back carpet to go through floors may be doable, wood or vinyl floors proably not.

platform framing.jpg
Answered by Robert Hronek
Posted Sun, 02/06/2011 - 17:24

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