Not all insulations are created equal.
http://www.buildinggreen.com/live/i...Insulation I have also posted the text of the article below (just in case the site takes it down). It is from BuildingGreen.com
Avoid Polystyrene Insulation
Posted August 1, 2009 5:15 PM by Alex Wilson
Related Categories: Op-Ed, Product Talk
Polystyrene Molecular Structure
Polystyrene Molecular Structure
Let me start by saying that insulation is an absolutely critical component of buildings. I like insulation and I like a lot of insulation. In northern climates, I recommend a minimum insulation value of R-40 in walls, for example, and I would personally aim for R-50 were I to build a house today.
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.