 |
|
|
|
|
|
Polystyrene Molecular Structure
That said, insulation materials are not all created equal. When we consider the health and environmental impacts of products over their life cycle (with life-cycle assessment or LCA), some materials look a lot better than others. That's just as true with insulation as it is with any other product, from flooring to adhesives and paints.
This brings us to the issue of polystyrene insulation. Recent concerns have been raised about the brominated flame retardant HBCD (hexabromocyclododecane for the organic chemists among us)—see our coverage in EBN about this—that is found in all polystyrene insulation, both extruded (XPS) and expanded (EPS). HBCD may not (yet) be a household word like bisphenol-A has become, but it's been raising plenty of concern.
There is now enough evidence that HBCD is hazardous to both human health and the environment that European agencies are moving to restrict its use. Based on this concern—along with better-understood concerns about the primary constituents of polystyrene plastic (benzene and styrene especially)—EBN now recommends that XPS and EPS should be avoided as long as doing so will not compromise energy performance.
This is the subject of two articles in the August issue of EBN: an in-depth feature article, "Polystyrene Insulation: Does It Belong in a Green Building?" (requires a log-in), and an editorial "Rethinking Polystyrene Insulation" (available for free).
What are the options we have for insulating our buildings without using HBCD-containing polystyrene insulation?
For above-grade insulation, there are lots of options. The easiest drop-in replacement is polyisocyanurate (polyiso), another rigid boardstock insulation material. In fact, polyiso outperforms polystyrene insulation with a somewhat higher R-value per inch. But it's also often possible to build highly insulated wall and roof systems that don't depend on rigid insulation. These can include fiber insulation materials in double stud walls separated by extra space, in non-structural "curtain trusses" or "Larsen trusses" that hang on the outside of the structural walls, and in raised scissor trusses for insulated roof systems.
The application where polystyrene insulation, and especially XPS, dominates the market is below grade. The alternatives here are less familiar. For foundation walls, the easiest option is simply to move the insulation to the interior--where moisture resistance is not so critical (as long as we've done a good job with exterior drainage of the foundation). This option also keeps the insulation away from sunlight and insects.
If you want to keep the insulation on the outside of the foundation wall, there are a couple options.
First, it turns out that building codes do not require flame-retardant-treated foam insulation if there's at least an inch of concrete or masonry between the foam and the building interior — so if we could convince manufacturers to offer flame-retardant-free products, XPS would remain reasonable option. Such products would have to be clearly labeled as being for below-grade applications only.
Assuming such a product doesn't emerge, an alternative to XPS is rigid mineral wool, such as Roxul Drainboard. Not only is the product fully fire-safe without flame retardants, but termites and carpenter ants don't like it so it's less likely to be compromised. And it's also highly hydrophobic (water-repellent). Unfortunately, Roxul and other rigid mineral wool products aren't readily available in the U.S.; I'm hoping that will change. I'd also like to see rigid mineral wool producers move away from formaldehyde-based binders.
Rigid fiberglass can also be used in this application, and it's currently used as part of the Tuff-N-Dri/Warm-N-Dri foundation insulation system.
Another option for exterior foundation walls is spray polyurethane foam (SPF) insulation. I hadn't realized that this was an acceptable application for SPF until my recent research, but it's becoming fairly common in Canada and parts of the Upper Midwest in the U.S.
Beneath concrete slabs, XPS holds nearly 100% of the market today, but the use of SPF in this application is growing in Canada. Some insulation contractors use a higher-density SPF formulation in this application (the type used for roofs). Finally, in Europe rigid mineral wool is used under slabs to some extent, and experts I interviewed for the article said they thought that would be a fine product here.
The challenges are greater with structural insulated panels (SIPs) and insulated concrete forms (ICFs). There are a few polyurethane SIPs on the market, but the vast majority of SIPs today are made with EPS. With ICFs, the only non-EPS products are cement-wood-fiber products (Durisol and Faswall), and these don't insulate as well as EPS products.
I think there's opportunity for some new product development—rigid mineral wool ICFs anyone? For that matter, how 'bout SIPs made with a rigid mineral wool core? Apparently there are some specialized fire-safe panels in Europe with mineral wool cores and metal skins.
The bottom line is that there are enough concerns about polystyrene insulation to look for alternatives when we're trying to make buildings as green as possible. Sometimes there won't be any alternatives available locally, and for these applications I recommend sticking with XPS or EPS, but when there's an option that won't compromise energy performance, I believe it's time to leave polystyrene behind.
You can follow my musings about all this on Twitter.
Comments
First, there is often confusion when making product choices. The choice of foam is rarely made JUST because of it insulation qualities, but because of its structural qualities, its airtightness, moisture resistance, vapor control etc. Hence, fibrous insulation cannot simply replace foamed plastics in most designs. Ignorance of this often results in moisture problems in walls.
Second, all foams are not made the same. Expanded polystyrene insulation has low GWP. But polyiso insulation is also mostly blown with pentane today and hence also has very little GWP. The Harvey paper Ms. Klingenberg references makes it very clear that polyiso has very low GWP. Also, although some spray polyurethane have high GWP blowing agents, others have none.
Both of these points are intended to point out that generalizations in insulation choices are very often wrong. If low GWP is the goal, there are numerous options. If high Rvalue per inch, or airtightness matter, there are other options. Do you care about low embodied energy? There are wall designs that allow one to safely use low embodied energy products.
The fact the European do not use a lot of SPF is entirely irrelevant. I have lived and worked in Europe. I continue to keep up on the scientific research and publish peer-reviewed papers in Europe. They are doing many good things. But Americans, Canadians, Japanese, Scandinavians and others also are coming up with good ideas, and delivering good products and systems. The Europeans will likely learn to use more SPF at the same time we learn to use more rockwool. Hopefully these choices on both sides of the Atlantic will be based on an analysis of the design problem, and an awareness of the range of products that are available.
I dont know the science behind HBCD. I do know there are environmental issues with essentially all of the chemicals used to make all foams, and they use fossil fuels (why that matters, I dont know, but some people do). And there is formaldehyde in most fiberglass products (some people care about this). And the fibers in all fibrous insulation are irritants to human respiratory tracts. I think we need more discussion to encourage the development of real data, but there does not seem to be lots of 'slam dunk' data that makes it easy to make any clear decisions one way or the other. And it certainly does appear to me that there are any simple one product insulation solutions.
Construction time can be cut in half if done with professionals, the structure has proven it can survive category #5 Hurricanes sustaining 250 mph. winds.
The energy bills on ICF construction have shown up to 75% savings and have made it feasible to introduce Solar and other alternative forms of energy because the BTU requirements are reduced such that we have been able to reduce HVAC by up to 75% as well.
One of the things that our opponents seem to like to mislead the public on is R Value. It is true that most R Values of ICF products are in the low 20’s, but whether by design or just pure ignorance, they omit the fact that the overall wall performance in an ICF can reduce the BTU heat loss (this is the formula that is used to calculate the size of heating and cooling equipment) by almost three times.
HBCD is a standard fire retardant used in many consumer flammable materials, such as clothing, carpet, furniture fabric ect…. What is different about these products is that they are in constant contact with us and we generally wash and clean them regularly. The problem with this is that in these case’s, traces of HBCD makes its way into the ground water and although I have seen no hard data to measure the impact it has on our environment, it is cause for concern. When HBCD is used in the production of construction materials such as EPS made ICF, it is exposed only during the construction phase and is covered both inside and out. When in contact with the ground it is covered with a water proof membrane that does not contain HBCD.
When we combine ICF and alternative energy together, we not only create a concrete structure’s that has been proven to with stand the elements for century’s, but we create a structure that can eliminate our need for fossil fuel when use for new construction. (ouch)!!
Each time I see these articles it makes me wonder who is behind it, who is writing the script? Before we throw the “baby out with the bath water” we should indeed see hard data to prove the case either way.
Murray Snider
Thanks for your comment. It poses some more questions for me though. If you don't mind me asking, if you use a lot of spray foam in your buildings (I fully recognize the other benefits of it as you mentioned and in some cases those concerns reasonably overrule the "greenness goal"), I assume that as a concerned building scientist knowing about the GWP problem mentioned in Mr. Harvey's paper, you are using the spray foam with the low GWP. Could you recommend that product? What is the current market share of that particular product and what do you intend to do to increase that market share, which would remove the climate concern with spray foams? Also, if you could clarify for us readers the topic of toxicity of polyisocyanurate and spray foam materials. There also seems to be a vacuum of information. I greatly appreciate it.
As you point out, there is not much data available and we need to encourage the generation of that data. It is very concerning to me. That says to me that we are currently guessing and that we are not making responsible decisions based on solid science. From a point of view of science, would you not be curious to find out why the Europeans are not using much spray foam and obtain their data (it would surprise me, knowing the Europeans, that there was no data available)? It seems your opinion is that they still have to learn and just don't know yet how good spray foam is. In my opinion, they went through a thorough vetting process and decided against it. (Last I knew Scandinavia was part of Europe).
I very much respect your work, but am surprised by you declaring that the fact that Europeans don't use spray foam is irrelevant. Should not "Building Science" be the guiding rope in this time of challenge, enable us to make responsible decisions and most importantly back up decisions and judgements as made in this article? I feel we live in a time of crisis, maybe that's just me, and have not much room for gambling...we need to know what we are doing, make responsible decisions and avoid unintended consequences (such as GWP of spray foams). As far as I can tell, the Europeans have done that and are following a solid rope of science. The HBCD discussion only confirms it. They are down to the details.
Indeed, repeated & prolonged over exposure to Benzene vapors can cause immuno- suppression. Likewise, inhaling or ingesting Styrene in large amounts can cause neurological disorders.
Keeping in mind that EPS insulation is ~95% air - precisely why it’s such an effective insulation material - the amount of Benzene and Styrene is a relatively minute component of EPS, a component encapsulated between exterior and interior finishes. I don’t foresee people cutting through their wallboard or stucco to ingest or inhale their insulation. (Glue may be an easier and quicker ‘fix’).
As for the flame retardant, HBCD, it is incorporated into the foam and unavailable for absorption by inhabitants of EPS-insulated structures. Keep in mind that mattresses you sleep on, carpets you walk on, etc. are treated with the very same fire retardants, with far more dire absorption potential. Likewise coffee cups and food containers pose a far higher ingestion/inhalation potential than intra-wall, inaccessible insulation.
FROM BASF: “Animal studies indicate that HBCD may be slightly toxic if ingested orally and that short-term airborne exposure to very high concentrations of the dust may cause liver or other organ effects at high doses. In typical applications the EPS foam is covered or encapsulated by other building materials which farther reduces potential for exposure”.
In view of the fact, that EPS provides among the highest thermal ratings per inch of material, reduces thermal shorts, does not lose its effectiveness over time, resists moisture and associated problems of mould, mildew, rot & termite infestations, it seems that its advantages far outweigh the negligible toxicity potential.
Furthermore, those of us who live in fire-prone areas, such as Southern CA, the miniscule potential hazards of eating/breathing inaccessible fire retardants, does not compare to the ravages of wild fires fueled by ill-protected tinder-box structures.
Fire safety codes that require use of fire retardants, seek to provide above all, building occupants with reasonable odds of survival.
According to the Department of Energy (DOE):
“Beyond the environmental benefits of the installed product, the energy requirements to make polystyrene can be more favorable than some alternative materials. In one study, when compared to fiberglass insulation, the energy required to produce polystyrene insulation is 24 percent less than what is needed to make the amount of fiberglass needed to achieve an equivalent R-value at a representative volume”.
“Regardless of application, EPS plays a key role in a building’s ability to comply with ASHRAE Standard 90.1-2004 Energy Standard, a benchmark requirement for most energy saving green building programs.
Key Environmental Attributes of EPS:
• Since the 1950’s, EPS has been CFC & HCFC-Free.
• EPS provides stable R-values and does not deteriorate with age.
• Recycled content can be specified for certain building applications.
• EPS mold resistance tests favorably in accordance with ASTM C1338.
• With hundreds of plant locations in North America, EPS is manufactured locally.
• EPS does not adversely affect indoor air quality.”- DOE
“Other rigid foam insulation materials require testing to determine their long-term thermal resistance (LTTR), which can add to product development costs and render a calculated ‘guess’ at the insulation’s real performance over time. EPS does not have to conduct such tests because it is not subject to thermal drift, meaning its R-value remains constant throughout the life of the building” - DOE.
“In a one-year study, plastic building and construction materials saved 467.2 trillion BTU's of energy over alternative construction materials. The energy saved by using plastic building and construction materials in one year, is enough to meet the average annual energy needs of 4.6 million U.S. households”. – DOE
In conclusion, insulation materials that don’t compromise energy performance, and as much as possible, protect occupants from ever-increasing disasters, should perhaps include EPS among the list of options.
Evelyn, Kwik Build Panels
|
Get new posts via e-mail:
Recent Comments
LEED AP Credential Maintenance: Cracking the Code Mara Baum says, “I suspect that many people will need to weigh the pros and cons of "opting in" in terms of...” More... Green Building Myth #3: Green Products Don’t Work as Well as Standard Products Bill Swanson says, “CFL's put LESS mercury into the environment then typical incandescent lamps. By a 1:2 ratio per the...” More... Tony Marshallsay says, “CFLs are still an ecological disaster: non-recyclable; contain poisonous mercury; far more embodied ...” More... Green Building Myth #2: It’s All About Materials Rashad says, “For me green building is all about what have been said, it is the orientation; energy; water; materi...” More... Green Building Myth #1: Does Green Building Have to Cost More? Bob Congdon, Builder Bob says, “Very well put, almost common sense in nature. As we all journey along this path of Green Building l...” More... Archives by Category
AIA Convention '08 (12) [RSS]
AIA Convention '09 (1) [RSS] Alex's Cool Product of the Week (9) [RSS] Authors (13) [RSS] Awards (8) [RSS] Behind the Scenes (61) [RSS] Books & Media (77) [RSS] Build Boston '07 (2) [RSS] BuildingEnergy '08 (2) [RSS] BuildingEnergy '09 (1) [RSS] Bulletin (47) [RSS] Case Studies (29) [RSS] Colleges & Universities (1) [RSS] Editorial Radar (1) [RSS] Energy Solutions (3) [RSS] Events (99) [RSS] Google Earth/Sketchup (5) [RSS] Greenbuild '07 (30) [RSS] Greenbuild '08 (31) [RSS] Greenbuild '09 (16) [RSS] LEED (54) [RSS] Living Futures (5) [RSS] Miscellania (40) [RSS] Mister Tristan Talks LEED (2) [RSS] Nature & Nurture (72) [RSS] Op-Ed (52) [RSS] Passive Survivability (6) [RSS] Politics (32) [RSS] Product Talk (112) [RSS] Q&A (9) [RSS] Science & Tech (31) [RSS] The Industry (102) [RSS] Follow BuildingGreen
Editorial Radar
|
|
|
|
|
|
|
|
|
|
I have been all over the web for several hours now to find substantiating evidence on your concerns in regards to polystyrene and HBCD. What seemed at first an exploratory informational journey has turned into a huge question for me: how come that the greenness of polystyrene is questioned and polyurethanes (SPF) and polyisocyanurate are being recommended as "green" replacements of polystyrene. I am not a chemist, but after looking at all the articles and reports out there published by the European Chemical Agency on toxicity of HBCD and the alternatives of other foams and their components, it seems to me that polystyrene is still, even after the HBCD issue (and that I hope can be solved), looking better than most of the other foam options. We also need to look at the toxicity of the chemicals involved in the making of polyurethanes and polyisocyanurates, as they have been on the toxicity list in Europe as well. Just go on a little chemical journey through wikipedia and type in for example toluene diisocyanate (apparently one of the major components for polyurethane) and find the classification table on wikepedia. Under hazards it says very toxic and identifies it as a carcinogenic. I have heard stories about people spraying foam and even though they were wearing protective clothing getting very sick, read papers about people exposed during the manufacturing process of polyurethane gradually loosing lung capacity. I like to know and see the whole picture so that I can make an informed decision. I think most people want to make the right decision here, we need accurate information.
I am by no means an expert on that topic. I am seeking answers. My last quest to inform myself about unintended consequences of SPFs brought me across the issue of the halo-carbon blowing agents used in spray foam that have 1000 times the global warming potential of CO2. A paper published in Elsevier suggested that the global warming effect that is caused during manufacture and installation is payed back only after 30-300 years (30 with conservative assumptions, in any case way too long to get us out of debt with the climate). These are worrisome numbers, we need to get to the bottom of it using the best of our science. Environmental and human health and also the climate are at stake.
I like to be educated otherwise, but based on my reading, I will continue to use polystyrene over spray foam and polyiso board. The first quest for me is always how can we do it without any of them to begin with. There are other alternatives, just like mineral wool, that would be great replacements for insulation in contact with the ground. Foam glass gravel made from recycled glass for example.
I like to share an observation as we are referring to the Europeans to offer guidance: at the last conference and exhibit that I attended in Europe, I did not see a single high R wall section advertising SPF. Why is that? Yet, where a foam application was appropriate, polystyrene was used, usually in its high density form and graphite enhanced for better thermal performance. I like an answer to that question.
Thank you for initiating the discussion, I think it is an important one.
Katrin