Styrene and EPS/XPS rigid foam insulation
MJDesigns
| Posted in Green Products and Materials on
I just saw a report last night on ABC World news where they indicated that scientists have added Styrene, a component of EPS and XPS rigid foam, to a list of possible human carcinogens. Does it make sense to consider it still as a good option for reducing thermal breaks in wall construction or would a better option be to lean towards double wall construction? Same for its use as a foundation perimeter and sub slab insulation … maybe less of a concern? I’m guessing this has been covered before in the Q&A but I’m rather new as a member of the community and in the process of planning a new home design. Your feedback is appreciated.
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The NY Times had an article on the same subject today pointing out that the biggest risk from styrene was to the factory workers. http://www.nytimes.com/2011/06/11/health/11cancer.html?_r=1&ref=todayspaper) There are many reasons to consider alternatives to rigid foam as a thermal break such as endocrine disrupting chemicals used as fire retardants and global warming potential. There are alternative methods such as mineral fiber sheathing or double wall construction that can provide similar benefits without the use of foam products.
Styrene isn't just a "component" of EPS and XPS foam. Those materials are essentially all styrene, although in polymerized form. The polymer chains resulting from reacting the styrene monomer are very different, chemically, and have essentially nil vapor pressure. Any danger that might result from polystyrene or from any other polymerized material comes from tiny amounts of unreacted monomer remaining in the final product. That tiny amount tends to offgas over time, by diffusion through the polymerized mass to its surface and into the air. That's a tiny amount diffusing very slowly and diluted by a huge volume of air, assuming some ventilation around the product.
As the article points out, there would be more danger to anyone exposed regularly to materials containing significant concentrations of the unreacted monomer. I wouldn't think consumer exposure to end products would be a problem at all, especially after some period of degassing.
I suppose one could apply the "nose test." The human nose often can detect concentations of things too low to measure easily. If you can smell it, there may be too much of it for safety. Hydrogen sulfide and formaldehyde are two that come to mind.
Of the two chemicals mentioned, formaldehyde is a much greater concern for homeowners. (Of course, the issue of workers involved in manufacturing styrene products is an entirely different matter.)
Fortunately, the federal government is moving in the right direction on formaldehyde. As an EPA Web site notes, "On July 7, 2010, President Obama signed the Formaldehyde Standards for Composite Wood Products Act into law. This legislation, which adds a Title VI to TSCA, establishes limits for formaldehyde emissions from composite wood products: hardwood plywood, medium-density fiberboard, and particleboard. The national emission standards in the Act mirror standards previously established by the California Air Resources Board for products sold, offered for sale, supplied, used or manufactured for sale in California. Congress directs EPA to promulgate final regulations implementing the Act by January 1, 2013."
Martin,
Since it appears that you got a chance to look fairly deeply into this, we are you able to check if "engineered woods" such as OSB, TJI's, LVL's etc are still exempt from emission standards as they have been in the past?
Albert,
You're right -- the formaldehyde regulations have lots of exemptions, including the ones you mentioned. Here's the text of the bill:
EXEMPTIONS.—The formaldehyde emission standard referred to in subsection (b)(1) shall not apply to—
‘‘(1) hardboard;
‘‘(2) structural plywood, as specified in the standard entitled ‘Voluntary Product Standard—Structural Plywood’ and numbered PS 1–07;
‘‘(3) structural panels, as specified in the standard entitled ‘Voluntary Product Standard—Performance Standard for Wood-Based Structural-Use Panels’ and numbered PS 2–04;
‘‘(4) structural composite lumber, as specified in the standard entitled ‘Standard Specification for Evaluation of Structural Composite Lumber Products’ and numbered ASTM D 5456–06;
‘‘(5) oriented strand board;
‘‘(6) glued laminated lumber, as specified in the standard entitled ‘Structural Glued Laminated Timber’ and numbered ANSI A190.1–2002;
‘‘(7) prefabricated wood I-joists, as specified in the standard entitled ‘Standard Specification for Establishing and Monitoring Structural Capacities of Prefabricated Wood I-Joists’ and numbered
ASTM D 5055–05;
‘‘(8) finger-jointed lumber;
‘‘(9) wood packaging (including pallets, crates, spools, and dunnage);
‘‘(10) composite wood products used inside a new—
‘‘(A) vehicle (other than a recreational vehicle) constructed entirely from new parts that has never been—
‘‘(i) the subject of a retail sale; or
‘‘(ii) registered with the appropriate State agency or authority responsible for motor vehicles or with
any foreign state, province, or country;
‘‘(B) rail car;
‘‘(C) boat;
‘‘(D) aerospace craft;
‘‘(11) windows that contain composite wood products, if the window product contains less than 5 percent by volume of hardwood plywood, particleboard, or medium-density fiberboard, combined, in relation to the total volume of the finished window product; or
‘‘(12) exterior doors and garage doors that contain composite wood products, if—
‘‘(A) the doors are made from composite wood products manufactured with no-added formaldehyde-based resins or ultra low-emitting formaldehyde resins; or
‘‘(B) the doors contain less than 3 percent by volume of hardwood plywood, particleboard, or medium-density fiberboard, combined, in relation to the total volume of the finished exterior door or garage door.
Carl
Do you have a source/vendor for the mineral fiber sheathing that you stated? Is the sheathing like a rigid board or something else? How would that type of material work in a basement insulation install against concrete or blocks? How does the cost compare between XPS and mineral fiber sheathing?
Dennis,
Not to speak for Carl, but I expect he is talking about mineral wool, or rock wool. Great stuff! All the attributes of foam boards w/o the styrene & global warming potential from blowing agents. It's R 4.5/inch, vapor open, and pretty darn indestructible.
It's great for a basement. I say that generally, but not specifically for your project since I know nothing about it.
Find a local source for Roxul (it's the vendor that I know) and check into the product rockboard 80. It's quite impressive. I have no idea why it so undervalued other than it's a pain to work with because of itchy fibres.
btw... No carcinogens and inhalation does not cause a cancer like asbestos.
I have seen roxul before but I have never seen it applied directly to concrete walls. I have seen XPS used first then roxul on top of it but never roxul alone.
roxul wasn't price competitive until oil prices skyrocketed over the last few years
foam board is light and fairly easy to work with, and consumers are familiar with it
the rock wool board like products are fairly new and don't have all the properties that foam board has which means it can't be a direct replacement. being new, distribution is almost nill.
one downside to roxul/mineral wool is the binders are formaldehyde-based, no? in previous offices, this was the only reason we were tempted to pass... mfr's claim it's basically benign once product is shipped, but i've heard the testing to verify isn't exactly the most accurate.
Mike,
I've looked into Roxul quite deeply and I do not recall seeing any formaldehyde in it at all. I may be wrong, but but I understood that the mineral binder was steel slag.
I'm going to "call you out" on this as the regional rep for Roxul will be at next weds Passive House Seattle meeting and so will you.
I will be very disappointed if this turns out to be true. Mineral Wool is one of my favorite "board form" insulation materials due to it's high R vale, Permeability, and longevity. It's nearly indestructible to most forms of degradation such as off gassing, fire, vapor or liquid water, and pests.
I've not found an insulation material that will equal it on all of those points.
albert,
per MSDS, Cured Urea Extended Phenolic Formaldehyde Binder = 1-6%
http://www.roxul.com/files/RX-NA-EN/pdf/Roxul%20Material%20Safety%20Data%20Sheet.pdf
but outside of that, you're right - the characteristics of mineral wool make it really attractive. foamglas might be close - but slightly higher embodied energy and embodied carbon...
Mike,
That's what I like about GBA -- good questions and good answers, backed up by a source document that we can all view online. Thanks for the answer and the link.
For a retrofit of basement becoming a conditioned living space there is question about Roxul applied directly to CMU foundation walls and in the rims joists-- friction fitted at rim joist and between steel studs ( instead of closed cell foam ): Contractor wants to do this as less expensive alternate to closed cell but there doesn't seem to be a way to create air tight application i.e. can't tape joints or seal top and bottom very well,so there is a lot more potential for air movement and therefore moisture transport through penetrations in a gyp bd wall, such as with electrical outlets or lack of proper caulking at top and bottom of gyp bd.... Isn't there more potential for condensation to occur in this assembly below grade (than say rigid xps or closed cell foam)????
Ann,
Q. "Isn't there more potential for condensation to occur in this assembly below grade (than say rigid XPS or closed-cell foam)?"
A. Yes. Roxul is air-permeable, and the could easily lead to condensation and mold in this application. You should stick with rigid foam or closed-cell spray foam.
OK Thank you .. I will pass this information on to the contractor and the homeowner!