Replies

1. Expert Member
   Michael Maines | Oct 31, 2018 01:11pm | #1

   Hallie, we do discuss regularly on GBA the availability of HFO-blown closed cell foam. Its blowing agents are equivalent to CO2, compared to conventional HFC134a blowing agents which are 1000 times worse than CO2. It has other benefits, including it can be sprayed in much thicker lifts, and retains its R-value better over time. The only installer I know who uses it exclusively charges less for it than he did for conventional foam. Broad adoption is growing slowly, even though the EPA has mandated (through the Federal government) that HFC134a be replaced with HFO blowing agents by 1/1/2020. (Brett Kavenaugh struck down the other part of the order, which related to refrigerants, so I'm not confident that this one will be enforced.) HFO-blown foam still has a significant amount of embodied carbon, so conscientious builders and designers specify other materials when they will do the job.

   I haven't read the BE article yet but I'm sure it relates to their presentation at NESEA's BE18 conference last spring. I was there; they made quite an impact to a standing-room-only crowd of people who are not easily impressed. Since then, the UN released their IPCC report, which paints a dire picture--embodied carbon matters, a lot more than many of us thought it did.

   What are your thoughts on their article, or the topic in general?

2. GBA Editor
   Martin Holladay | Oct 31, 2018 01:33pm | #2

   Hallie,
   In case you missed them, here are links to two relevant GBA articles:

   "Carbon Emissions By the Construction Industry"

   "All About Embodied Energy"

3. 
   hallie17 | Oct 31, 2018 03:22pm | #3

   Thank you both! I am spending more time drawing and less keeping up on GBA articles these days. The ccSF in my own recent renovation project is Gaco OnePass. It is difficult to tell from the manufacturer's information what blowing agents it uses, though a search provides some reassurance that it is probably HFO blown.

   I've got a few thoughts on the topic since I've read the article. First, I would like to know more about the assemblies they used in the "code minimum conventional materials" house, in particular how much foam those conventional materials includes. It would also be interesting to know how our warmer climate (zone 5) here in NE Ohio and our 2009 IECC code minimum requirements would affect the outcomes. Having read it, I am more inclined than before to think about whether an insulation material sequesters carbon or will contribute to GW in the short term. It is also shifting my understanding of the role of insulation and air sealing. As we move towards more renewable energy sources, perhaps the biggest impact of the thermal envelope is how well it allows us to use heat pumps for heating rather than resistance heat or fossil fuels. Of course this also contributes to occupant comfort and resiliency if the energy grid is interrupted.

   Seeing an analysis of a code minimum house using an air source heat pump powered by solar PV makes me put more value on retrofitting existing homes, with the goal of using an air source heat pump without fossil fuel backup. I used to think you needed to do a gut, "deep energy retrofit" for work on an existing house to be really significant from an energy standpoint. Now I am thinking that enough efficiency to ditch the gas is nearly as exciting as a new home following a certification system. That may be more of a stretch in zone 6, but I know of a few houses here in zone five that have done it- my own included.

4. Expert Member
   Dana Dorsett | Oct 31, 2018 05:49pm | #4

   >"The ccSF in my own recent renovation project is Gaco OnePass. It is difficult to tell from the manufacturer's information what blowing agents it uses, though a search provides some reassurance that it is probably HFO blown."

   Only the Gaco OnePass Low GWP is blown with lower-impact blowing agent. The standard Gaco OnePass product is almost surely blown with HFCs:

   https://gaco.com/product-details/gacoonepass/

   https://gaco.com/product-details/gacoonepass-low-gwp/

   Gaco's claim to fame is their proprietary chemistry that is devoid of isocyanates. With polyurethane foams using icsocyanates it's more of health risk to the installers than to the homeowners, (unless the installer screw up the mix & temperatures), but it's a feature Gaco uses in their marketing fluff.

   >"Seeing an analysis of a code minimum house using an air source heat pump powered by solar PV makes me put more value on retrofitting existing homes, with the goal of using an air source heat pump without fossil fuel backup. I used to think you needed to do a gut, "deep energy retrofit" for work on an existing house to be really significant from an energy standpoint. Now I am thinking that enough efficiency to ditch the gas is nearly as exciting as a new home following a certification system. That may be more of a stretch in zone 6, but I know of a few houses here in zone five that have done it- my own included."

   Even old-school ducted heat pumps with resistance heat strip backup have been used as far north as zone 7 in Minnesota and North Dakota where residential electricity rates traditionally been fairly cheap. But using cold climate heat pumps taking advantage of vapor-injection scroll compressors seem to be primarily found in mini-splits. This compressor type extends both capacity and efficiency at lower temperatures, with capacity table temperatures of many systems using them low enough to work for many zone 7 locations without backup, and pretty much all of zone 6. Mitsubishi's "H2i" or "Hyper Heating" systems compatible with their full-sized air handlers are pretty easy spec as retrofits for houses in most of zone 6, since there is a specified output at -25C/-13F. So far no US manufacturers have released a product using similar low-temp compressor technology, but they're clearly aware of it.