January 2012

Volume 21, Number 1

Get the PDF

By downloading this digital content, you agree to BuildingGreen’s terms and conditions of use.

Passive House Group Bans Certain Spray-Foam Insulation

Printer-friendly versionSend to friend

By Paula Melton


This Illinois home, which is targeting Passive House certification, is insulated with 12" of high-density fiberglass in the walls and 24" of cellulose in the attic. According to homebuilder Darcy Bean, the project used small amounts of SPF in areas where air sealing would otherwise be difficult.

Photo: Adam Milton Photography

The Passive House Institute U.S. (PHIUS) will no longer give its blessing to projects incorporating spray polyurethane foam insulation (SPF) that uses blowing agents with high contribution to global warming, according to executive director Katrin Klingenberg.

“It does not make any sense at all to use them if one of the major overarching goals of energy conservation in buildings is to counteract and decrease global warming and climate change,” Klingenberg told EBN. “There really is no point to go through all the trouble of detailed Passive House design calculations if you use high-GWP [global warming potential] spray foam.” In the past, Klingenberg said, projects have been permitted to use small amounts of SPF, but now that the U.S. group has started its own certification program, PHIUS+, even small amounts will no longer be allowed (see “Passive House U.S. Develops Separate North American Certification,” EBN Dec. 2011). For the time being, projects using low-GWP spray foam can still be certified as long as the “balancing requirements” that weigh material performance against carbon emissions are met.

However, PHIUS is planning to issue detailed guidance on the embodied energy of all petroleum-based insulation materials, Klingenberg said, and “in the future I would like to add the embodied energy to those balances because of the significance in super-insulation.” The PHIUS+ certification will recommend (but not require) renewable insulation materials with low embodied energy except for “a specialty application where no other insulation material will perform.” For below-grade applications, Klingenberg prefers cellular glass but says high-density expanded polystyrene (EPS) is acceptable. For projects that were already in the pre-certification process before the new PHIUS+ program was introduced in November 2011, the SPF rules will be optional.

While other green rating systems, like LEED, devote considerable attention to materials selection, indoor air quality, water, and other issues, Passive House has been known for its singular focus on energy performance. While this move is energy-related, proscribing specific materials is a noteworthy departure.

For more information:

Passive House Institute U.S.


Comments (3)

1 Passive House is a Balanced B posted by Scott Hunter on 01/30/2012 at 03:12 am

The Passive House Standard used internationally is a rational and balanced Building standard addressing health, comfort, durability, and energy efficiency as well as sustainability. As such, it permits the use of SPF (closed cell spray polyurethane foam), though it recognizes the concerns motivating PHIUS to ban it. An example points to the need for balance. I am doing the energy modeling for the deep energy retrofit of an old wooden row house in the often damp climate of San Francisco. It is not possible to air seal or even access the walls adjacent to the houses on either side. In order to air seal and control condensation we are looking at using a 2" layer of SPF in each stud bay with cellulose inside that. This is locally called "Flash and Fill". For more information,see the excellent Building Science Corp report RR-0903 on High-R value walls.

Health Concerns Right from the start, Health concerns were a clear and important issue for the clients and the building team. One client wrote, "I am not a fan of using petroleum based insulation. However I am particularly adverse to health and durability risks where you cannot see them. Therefore, I can live with using the ecologically flawed technology we have today to ensure I don’t have to remediate an expensive and resource intensive disaster in the future."

GWP? I did calculate the GWP of using the Flash and fill system. The SPF volume was estimated at 224 cubic ft or 2688 board feet. Using the conversions published in the EBN June 2010 article, the GWP for the SPF is about 24 tonnes CO2. The clients are reducing the operational energy demand from 1530 Therms/yr to about 40 Therms/yr. The equivalent savings in carbon emissions (assuming a 70% gas/30% electricity mix) will be about 468 tonnes CO2 which is 20 times larger than the GWP of the SPF.

I also look forward to the near future when SPF formulations with greatly reduced GWP will be available.

Scott Hunter Ph.D. P.E. Internationally Certified Passive House Consultant Certified California Energy Analyst LEED AP

2 Carbon payback time posted by Paula Melton on 01/30/2012 at 04:29 am

Scott, are you saying that it will take a year or less to pay back the embodied carbon of the spray-foam? I would be interested to hear whether the actual energy savings match the modeled savings after a couple of years.

You make a good point about the Passive House standard; it is based almost entirely on modeled energy performance and has nothing to say about materials. The fault line between PHIUS and the rest of Passive House is widening, and we are watching these developments closely.

3 not carbon payback time but a posted by Scott Hunter on 01/30/2012 at 06:50 am

Paula, I was not calculating the carbon payback time of the SPF foam but comparing the carbon equivalent burden that will be created by using that much foam with the huge amount of carbon saved over the life of the structure by my excellent client's choice to reduce the operational energy used by building better. By the way, the home will not achieve the passive house standard but again, to me, this is secondary to the great benefit of the clients doing the best they could with the house they have.

For the Passive House standard, two of the criteria are based on modeled performance and the third (air tightness) is measured. But this is not the whole story. For certification, there are numerous checks on the plans, specifications and actual construction. And the PHPP (Passive House Planning Package) modeling software has been verified by comparison with actual energy use for a number of built projects (comparing the mean or median value of energy use with modeled results). I believe the best source of comparison is the CEPHEUS documentation. All in all this is a different and more reliable process than the US approach of model it, collect your gold stars, and move on. Here in California you now have the option of using average values for installed insulation or getting the insulation inspected to get full value to for your energy model (thank you Rick Chitwood!). This inspection is done by HERS raters. PHIUS is working with RESNET raters to arrange for third party verification for aspects of their projects which could be a positive development.

Post new comment

Welcome !
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.
  • Glossary terms will be automatically marked with links to their descriptions. If there are certain phrases or sections of text that should be excluded from glossary marking and linking, use the special markup, [no-glossary] ... [/no-glossary]. Additionally, these HTML elements will not be scanned: a, abbr, acronym, code, pre.

More information about formatting options

December 27, 2011