Closed-cell spray foam and XPS: green or not?
I’ve posted several times on my pretty badly compromised attic. We live in a 50s ranch outside Chicago with a ceiling that has been butchered by can lights and an AC handler & ductwork. I feel the only reasonable solution is to move the conditioned envelope to the roof. I’ve debated and debated and debated this because the solutions are expensive, a pain to implement, and now it appears environmentally questionable.
Yesterday I was about to place an order for many thousands of dollars of CC spray foam. Then I came across articles describing the GWP of these products. I’m really struggling with how I feel about this.
I have a few questions:
1) The articles I read are ~7 years old. Are these blowing agents still being used? Are there commercially available CC spray options that are more “green”? And do they perform as well?
2) I understand that these blowing agents have >1,000x the greenhhouse effect of CO2 but is the volume of the gases being released significant? I would feel a lot better if someone could tell me that the GW contribution of my sprayfoam solution was equivalent to (for example) the methane produced in a year by 2 1/2 cows. I guess what is the scale of this problem?
BTW, I received bids from several contractors to apply 6″ of Polyiso above the roof deck and re-shingle and gutter. This option was cost prohibitive. I feel very stuck between sprayfoam or leaving the problem be.
Thanks,
Brian
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Replies
Almost all closed cell polyurethane is still blown with HFC245fa. There are a few exceptions. Demilec now has a 2lb foam blown with HFO1234ze (with very low global warming potential) as does LaPolla, and there may be others making the shift soon. One advantage of the HFO blown foam is that it can be installed in lifts of 4"+ without fire hazard or quality problems, unlike HFC blown foam. Most HFO blown 2lb foam is rated ~ R7/inch too.
The lifecycle impact of the HFC blowing agents ARE significant: A 2000' house built with all HFC blown foam in R25-ish (whole wall) SIP walls is the global warming equivalent of lighting 750-800 gallons of gas on fire. But but of course the total impact is a function of the total foam volume you are using. If installing only the minimum required for dew point control in a flash'n'batt situation the impact is going to be substantially less.
Going with 6" of polyiso above the roof deck meets IRC code for the equivalant of R49 between joists/rafters. The same peformance could be had with 3" of polyiso above the roof deck and 6-7" of open cell foam (blown with water) or cellulose on the under side of the roof deck, and would be sufficient dew point control for US climate zone 4.going by IRC chapter 7 prescriptives (or even the warm edge of zone 5 by WUFI simulations, in most houses.)
Location/climate matters- where are you? The IRC prescriptives for dew point control work out to roughly:
Zone 4: ~30% of the total R (MINIMUM!) as closed cell foam under the roof deck or as above-deck insulation
Zone 5: ~40%
Zone 6: ~50%
Zone 7: ~60%
Other factors to consider are the shading factor on the roof (more shade= less solar warming= colder roof = needs more margin) and the color of the roof (light color= less solar warming, etc.)
Brian,
Here is a link to the most recent GBA article about new, more environmentally-friendly blowing agents for closed-cell spray foam: Next Generation Spray Foams Trickle into the Market.
The XPS sold in the U.S. is still bad -- all of it is manufactured with blowing agents that green builders should try to avoid. So when it comes to rigid foam, choose EPS or polyiso.
It's always frustrating when essential home improvements cost more than you can afford. I wish I had a magic wand to help you with the financial side of things, but I don't.
If your roof configuration permits venting, you might consider installing ventilation baffles from soffits to ridge, so that the roof can be insulated with less expensive types of insulation. Of course, that option only works if your roof doesn't have any valleys, hips, dormers, or skylights.
If you do end up having to go the closed-cell spray foam route, here's one more product you can add to the acceptable options list:
In addition to the low global warming potential blowing agents that Demilec and Lapolla are now offering (mentioned by Dana and in the article Martin posted), Icynene also has a waterblown closed-cell foam (Icynene Proseal Eco, MD-R-210). The Icynene water-blown foam does not have as high of an R-value as the newer HFO1234ze stuff, but it performs all the jobs a closed cell foam needs to, so it's a third option for you.
Good to know all your options as your local spray-foam contractor may prefer one brand over another.
We had an Icynene rep in the office recently who told us that the cost premium for Icynene's water-blown closed-cell foam should be only a small increase over their conventional closed-cell foam.
Keep in mind that your spray-foam contractor might not be familiar with the water-blown stuff (or the HFO1234ze stuff) and you will have to be very explicit about which product you would like them to use! Get a submittal on the product and make sure it's the one you asked for!
I wanted to thank everyone for their responses. To close the loop on this and as a general update, I have just contracted with a spray foam contractor who will be applying 6" of the new Demilec CC sprayfoam with HFO1234ze blowing agent to the underside of our roof deck. Although I would have preferred polyiso insulation above our roof, that option was ~2X the cost (although it would have included a new roof). The contractor also informed me that there was no difference in cost to move to the new blowing agent. In fact it saves them labor because the sprayfoam can be applied in a single pass. After ~18 months of debating how to handle our roof, I'm relieved to finally have a solution.
Thanks for the report. It's great to hear that there is no cost premium for HFO.