How to insulate rim joists?
Ine
| Posted in Green Building Techniques on
In a current thread on open cell vs. closed cell spray foam, Robert Riversong commented that spray foam may not be very green and may have problems as it ages. Even the crew doing my dense pack cellulose quoted me on using spray foam around the rim joist. What alternatives are there that would be cost effective and provide a good air seal here?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Donald,
If you are dead-set against closed-cell spray foam, install blocks of rigid foam insulation between the joists, and seal the edges with canned spray foam or foam-compatible caulk.
Rigid foam is no more "green" than spray foam, but at least it's produced in controlled factory settings which have far stricter health and safety regulation as well as environmental controls.
The problem with insulating and air-sealing rim joists is a problem with conventional framing practices. Framing systems, such as certain types of double-wall and Larsen truss, eliminate those thermal bridging and air-sealing defects at the design stage.
We're building in a peak-oil, global warming, species extinction, age of extreme environmental degradation with framing techniques that haven't changed in 100 years.
There are open cell foams that are soy-based... no petroquemicals!!!. For what is worth, you’ll spend more money on labor cutting, fitting and sealing foam boards (and in between trusses if you’re using them) and headaches than you’ll have if you just go for the sprayed foam. Some times people need to realize that green building needs to be easy and not bring the green police to very solution. Been there done that a million times.
Also, your climate zone and wall assembly may dictate if you need to use open or closed cell.
Donald... sorry, I wrote last point... (wrote your name in the wrong spot)
Bio-based?
Soy-based polyurethane foams are just as toxic to apply as petroleum-based products, since the chemical composition is the same.
Replacing depleted petroleum with food products (such as with corn ethanol or bio-diesel) while millions starve is no more "green" than using petrochemicals.
Soy-based products ARE safe. One must have caution with installation procedures as well as most other insulations, including cellulose. Please read the whole document including OSHA comments: http://www.biobased.net/products/SpecSheets/Finished%20Foam%20MSDA/MSDS%20-%20Bisobased%20501w%20%20Foam%20Insulation%20November%2020,%202008.pdf or you can get more product documents at http://www.biobased.net/ just to name one company.
I like cellulose and I have specified it several times, but IT IS NOT a cure for all. To be fair lets look at cellulose as well and some of its issues:
http://ntp.niehs.nih.gov/index.cfm?objectid=58BE4A0E-F1F6-975E-72E7FA7644178104,
http://www.healthyhouseinstitute.com/a_688-Cellulose_Insulation, http://www.buzzle.com/articles/fiberglass-vs-cellulose-insulation.html.
As you can see, pretty much ALL insulations have +s and –s. Even blown fiberglass has its place in many of my jobs. One insulation I won’t use is BATTS, not because is bad material but because it never gets installed correctly. That’s way is so important to know when and where to use a specific insulation.
Armando,
Did you deliberately avoid responding to my point or did you just miss it entirely?
"Safe", if it is to have any meaning, must mean safe at all phases of a material's life cycle, safe for the environment, for the manufacturers, for the applicators, for the users, and for those who dispose of it. And it must also mean that it does not have secondary or tertiary impacts which cause harm, such as global warming or competition with hungry people.
To suggest that fiberglass is not a "bad material", when it is a recognized carcinogen and typically contains formaldehyde, the primary chemical sensitizer for multiple chemical sensitivity, indicates that you have either not done your homework or choose to ignore the facts.
The only truly green materials are those that nature provides. The only truly green methods are those that have sustained us for millennia. The only truly green mindset is one that does not buy into the destructive mythos of modern consumer culture.
My bad… I just responded to your statement.
1. I know you live in New England with small farming to know better, :-)), but “down here” in real farming America, LOL, small towns have thousands of silos overflowing with grains like corn, wheat, beans, etc. because there is no room to store after their harvests so they have these grain mountains on the ground until they have a place to store. Millions of bushels get wasted in this endeavor.
2. Grain prices have stayed pretty much the same for the last 30 years (I know, I worked in farming and custom harvesting in my college years) and just recently farmers have had the opportunity to have some of their crops go to the production of ethanol, and they are all loving it since their grain prices have gone up.
3. There are countless of government programs that pay farmers for DESTROYING their crops because over production. Believe me, even with all the food the US gives and sales around the world, there’s still plenty that goes to waste.
I for one, I’m glad the ethanol producers are there, farmers are getting better prices, the gov. can reduce their crop reduction programs, mountains of grains disappear, the world gets US food, New England continues to enjoy their picturesque small farms and the SOY-BASED companies are creating jobs. Hey, not bad… a win, win, win, win, win, win situation!!!
What about the bio-spray foams made from caster oil?
ICYNENE LD-R-50 uses castor oil in place of a portion of the petroleum-based polyol. Another benefit is that is doesn't take away from food sources.
Seems like a decent product for rim joist applications.
What do you boys/girls think?
You're correct Brett; there are several manufacturers with products or developing products that are bio-based both in open cell and closed cell. But again, you MUST know what works in your climate zone and with your overall wall assembly.
I have done the rigid foam on an existing building as this is less expensive,though more labor intensive, than spray foam. I didn't intend to start a debate on the environmental merits of products. I WAS hoping someone could share details on alternatives to rim joist construction that requires spray foam. I haven't found detail drawings on GBA for this. Is there somewhere else details and drawings for alternate construction would be available? Thanks.
Donald, as Robert mentioned in no. 2 above, there are framing alternatives that do not rely on spray foam at the rim joist. There are many examples to inspire you here:
http://www.builditsolar.com/Projects/SolarHomes/constructionps.htm
Not all double wall designs effectively deal with insulating and air sealing the rim joist area.
A way of using a double stud wall to address the rim joist insulation issue is to end the joists and rim near the inner edge of the sill. The inner wall then rests on the rim/joist area. The outer wall with bottom plate rests on the outer edge of the sill. Filling the cavity insulates the rim from the outside, rather than from inside.
Where there is a second floor, those joists and rim end at the top plate of the inner wall of the first floor. The lower floor outer wall studs and top plate go all the way up to even with the tops of the second floor joists. The subfloor there extends out to cover the top plate of the lower floor out wall. Filling the lowe floor cavity with insulation also insulates the second floor rim from outside instead of inside. Thermal bridging is limited mostly to the short stretch of second floor subfloor that joins the outer wall to the inner walls and floor system.
But a balloon-framed wall cavity (with the double wall as described) would either have to be firestopped at each floor and ceiling with minimum nominal 2x wood or filled with dense-pack cellulose (National Fiber has had their cellulose third-party certified as a firestop).
Soy based or Castor oil based foams only replace a small percentage of the petroleum base, from what I have been able to determine.