Wednesday, January 19, 2011

Making Closed Cell Foam Green

If you recall this post, I talked about how the process of insulating our house with closed cell foam would result in the emission of HFC-245fa, a Green House Gas (GHG) with around 1000x the warming potential of carbon dioxide, but which decays from the atmosphere very quickly, in 7 years instead of 400. My solution to reducing the GHG footprint is to track the amount of the B chemical used, which contains the GHG, to calculate the carbon dioxide equivalent released, and then to buy carbon credits of a variety that will take carbon out of the air for up to 80 years, long after the HFC-245fa has decayed.

But carbon credits are always a last resort, when you don't have a choice: flying, whatever part of your gasoline usage you can't get rid of through an electric or hybrid car, and, as in our case, fossil gas and electricity drawn from the grid that can't be offset with renewables or eliminated by efficiency. It would be really great if we could figure out some way to make closed cell foam more green and, in addition, make it more accessible to the average home owner. So here are some thoughts along those lines.

Closed cell foam is a really super insulating material. It's positive properties are:

  • Inexpensive relative to even better insulators, such as aerogel
  • Nontoxic
  • Best insulating value of any affordable material (R-6/inch, approximately)
  • Easy to install
  • Functions as an air and vapor barrier
  • Can be partially made with recycled and plant-based  material
It would be really great if we could figure out some way to reduce its negative properties:
  • Costs 2-3x as much as fiberglass batt, which is a lousy insulator
  • Uses petroleum for the part that is not recycled and plant-based, unlike alternatives such as blown cellulose, which is completely made of recycled material
  • Installation releases HFC-245fa, a powerful GHG
Some folks would include the fact that it burns when exposed to flame as a negative, but I don't necessarily see that. Fiberglass batt doesn't burn, but the paper casing will, and of course so will the studs and other structural materials in a house. As long as there are no additives that produce toxic fumes, the foam itself will simply combust to carbon dioxide and water. Most houses these days have far more stuff in them that will produce toxic fumes when burned.

Let's walk down this list one by one.

First off, cost. I frankly have no idea why closed cell foam is so expensive. Cost for a particular product or  service is generally the sum of the cost of materials, cost of equipment (amortized over some period of time), and the cost of labor.

Is it because the materials that go into closed cell foam are more expensive than fiberglass batt or blown cellulose? I can imagine that they might be somewhat more expensive because they are specialized chemicals, but 2-3x more expensive?

Is the equipment more expensive? Ponzini parked a trailer in front of our house that contained the spray equipment.  Though I didn't see their equipment, I've seen it before when we had open cell foam sprayed into the garage and attic wall. It is obviously more expensive than a staple gun, but I wonder if it is more expensive than the spray device they use to  install blown cellulose? And, in any event, they can amortize it over a lot of jobs.

Is the labor more expensive? It took Ponzini maybe 6 days, 10 AM to 4 PM, to finish our house (well, let's put it this way, they think they are finished, the thermal imaging test will tell if they really are). I can't imagine that it would have been any more or less time than if they had installed blown cellulose or fiberglass batt. Actually, I think it probably would have been more time with either because both require that the installers actually get up to the walls and staple something on: the batt itself for fiberglass batt or netting to keep the cellulose in with cellulose. With foam, they just need to aim the spray gun and fire. It's certainly messier, bits of foam end up everywhere (including in our front driveway where they would pose a menace to aquatic wildlife if they got into the bay) but I'm sure fiberglass batt and blown cellulose installation have their unpleasant aspects too.

Aside from a possible slight difference in cost of materials (and of course absent any hard data),  my conclusion is the exaggerated price difference between lousy insulators such as fiberglass batt and closed cell foam is simply because closed cell foam is a "premium" product and therefore must command a "premium" price. In other words, you get what you pay for. To get the same air and vapor barrier function as closed cell foam with batt or cellulose requires all the cracks in the building's thermal shell to be sealed and the installers to pay close attention to how they are installing the material, all of which would make batt and cellulose more expensive too. Such measures won't increase the R-value of batt or cellulose, of course. In any case, I'd certainly like to find an insulation contractor who wouldn't mind someone taking a look at their cost structure and really getting some hard data on the topic. After all, if the computer industry pricing and cost structure worked the way the building industry seems to work, we would all still be using PCs with 386s and 640K of RAM because the fast Pentiums would be way out of our price range.

Next, use of petroleum. I'm no chemical engineer, but I think that there should be a way to increase the recycled and nonpetroleum content of closed cell foam. Demlec already advertises that it uses soy oils and partially recycled content in its product. If I were an academic with a chemical engineering background, I'd be writing grants to EnergyARPA and the Energy Dept. to do research on the topic. And, let's put it this way, the long term future of petroleum-based products is pretty much known: they will shortly be gone. According to the International Energy Agency, we'll be almost out of oil by 2050.

Finally, GHG emissions. On the face of it, this seems like it might be the most difficult point, but actually, its the easiest. HFC-245fa is used because it's nontoxic, much heavier than air (so the bubbles expand more slowly),  and relatively inexpensive. It's a good choice, except for the greenhouse gas problem. If there were some way we could keep it out of the air...hmm...this brings to mind something that happened when we first bought our house.

The roof had termites. So we had to have it tented. During tenting, the pest control company encases the house in a large, closed tent and fumigates with sulfuryl fluoride, which is extremely toxic to anything that's alive (we had some plants damaged when we had it done) and is itself a green house gas 4800x as powerful as carbon dioxide. There are now more environmentally benign alternatives, we didn't investigate them at the time, since they probably didn't exist. 

Why not enclose a house undergoing closed cell foam insulation in a large tent, sealed as tightly as possible, just like when tenting for termites? While the foaming is going on, a blower can pull air out of the house containing the HFC-245fa and exhaust it through a system that recovers the GHG for reuse. It might also be burned, but the fluorine in the HFC could end up as hydrofluoric acid, which is really nasty stuff. Left behind is the HFC in the foam bubbles, some of which will outgas over time, but the amount that's released during such aging should be much less than during installation. This could then be offset using carbon credits.

Tenting will add something to the cost, but if my suspicions about why closed cell  foam is so  expensive are true, the cost could still be reduced enough that closed cell foam should become  much more competitive with fiberglass batt.

So there's some ideas about how to make closed cell foam cheaper,  less impact on non-renewable resources, and less GHG-polluting.


  1. I like your recovery idea, but it might be easier to vent and recover on a room by room basis than on a whole house basis. This is particularly true on remodels. The blower and recovery requirements for a room-type volume ought to be less than for a house.

    I'm also having trouble envisioning the recovery apparatus. Something simple and small that can handle large gas volumes at high rates seems difficult. Condensation on a liquid nitrogen cold finger is a simple option, but fraught with its own issues.

    Safety might be an issue. I don't think that SCBAs are required now when spraying foam. If a space were tightly enclosed then some sort of alarm might be required at least. Cryogenic safety for the recovery system could be a problem.

    I'm concluding after a few minutes pondering it that switching gasses might be the way to go. Water vapor is denser than air and generally non-toxic. CO2 is as well and has the advantage that it could be recovered from the air in the first place, making it a zero-sum participant in the foaming process.

  2. Hi Brent,

    Thanx for the comment.

    Water vapor and carbon dioxide are used as the expansion gas for open cell foam. The density of water vapor is close enough to air that it expands more quickly, resulting in larger bubbles. HFC is much heavier than air (about a factor of 10) so it expands more slowly, resulting in smaller bubbles. This is why closed cell foam provides a vapor barrier and open cell foam doesn't. But there might be another gas with less GH impact out there that could work, don't know.

    Regarding your points about recovery, individual room tenting is used during removal of asbestos containing drywall, and I guess it could be used in this case too. The cost of drywall removal with asbestos is only slightly more than without, much to my surprise. I think the extra cost is mainly due to waste disposal, since you can't simply take the drywall to the dump. The actual tenting probably isn't such a big deal, and it helps keep the drywall dust down. That would be another advantage with foam, since little bits of foam tend to form everywhere and end up outside the house, where they can get into aquatic ecosystems and cause a problem for aquatic wildlife.

    Combustion might not be such a problem after all, if the products were carefully segregated. The amount of HFC is pretty low, so the acidity of the resulting combustion product might not be such a problem. It could be immediately diluted with water too.

    But I wonder too if there might not be some better technology. One problem with foam in general is that you have to take the drywall off, remove the fiberglass batt, foam the wall, then put the drywall back. This is expensive, messy, and disruptive to the living space. There's pour in foam, but it only works if the wall cavities are empty. A technology/procedure that somehow pulverized the fiberglass batt, allowing it to be vacuumed out, then inject something into the wall that cures into a high R-value insulator would be ideal. Sadly, R&D in the green home space does not seem to be much of a priority in the US.

  3. James,

    there are over a half dozen non-HFC blown closed cell foams. Just google 'water blown' closed cell foam.

    Also foam costs $20 per gallon. your home will probably take 300-500 gallons to insulate. Foam trucks easily cost $60-80,000 and last 3-5 yrs. The upkeep cost for a spray foam truck is 10-15,000 per year. Fiberglass requires no equipment, no skilled labor and the material is very cheap. This is why the costs vary so much