The classification of building materials as “green” has become far more sophisticated than the early days, in which only strawbale and rocks were considered organic. We now consider the entire life cycle of the product, and look at the content with a microscope. This is certainly a good step, but still not at the final solution in which we factor in the intended use of the product.
Take insulation, for example. There was a lot of hype about insulation made from recycled blue jeans, or from cellulose byproducts, as being most natural and therefore preferable. On the flip side, foams made from petroleum byproducts got a lot of flack – because they come from – petroleum. Gee - but doesn't byproduct mean it would be in the waste stream had this foam application not been invented? Oddly, soy based foam is touted as super green, as if this foam were farmed in the soyfields of Ohio. In truth, soy replaces only about 15% of the petroleum base for the spray foam.
The final step in evaluating an insulation is the ability to … well.. insulate. Energy Star Raters follows a system of rating insulation based on the installation of the product. To attain a rating of "Grade I", wall insulation shall be enclosed on all six sides, and shall be in substantial contact with the sheathing material on at least one side (interior or exterior) of the cavity. Of course, as we learned from our AirForce Blog (5/28), insulation is only effective if there are limited air leaks. So the Grade I enclosed on all six sides means NO AIR LEAKS.
Then there is the question of Long- Term Thermal Resitance (LTTR). Will R-values stay consistent to the values at time of installation, or will it degrade over time, due to settling, oxidization, humidity, or unstable chemical content. It’s not like you can just reach into a wall cavity and exchange it once it has worn out… For example polyurethane is blown with heavy gases such as hydrochlorofluorocarbons (HFCs), which diffuses out of the foam over time and reduces the effective R-value of the product. However, the EPS foam used in ICFs and SIPS products contain no trapped CFCs and HFCs, and twenty year testing has shown no shrinkage or reduction in insulation values. GreenSpec continues to list SIPs and ICF products in their directory, because the system-related energy-performance benefits counteract the negatives associated with the chemical constituents.
Blogs discussions about EPS foam crop up from time to time, one recently moderating by Alex Wilson at www.greenbuildingadvisor.com/. One post notes the irony of using petrochemical materials to save petrochemical materials. However, that is exactly the point. I would much rather use my petrochemicals now to make durable insulation material in order to avoid the future need to consume it as fuel. As to the discussion of the HBCD, the European concern has to do with bio-accumulation, but not about contact. It is mostly as a result of the more easily separated beads of low density foam used in fruit packing, but certainly the ICF industry can address this issue through construction site practice. HBCD is a fire retardant, and is currently accepted as being one of the least harmful and is thus used in many products. Code prevents us from building without fire retardants.
I would urge builders to keep their eye on the key green goal of saving energy, and choose products which can provide the highest insulation value for a durability and long-term performance of 100 years. Now that would be a great, green, legacy.
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4 comments:
It is a complex decision regarding c2c manufacturing and modern insulation. On one hand, the best insulators are the worst offenders (in regards to linear manufacturing) and on the other hand some of the greenest insulation (like dry earth 2 meters down) isn't practical in anything other than an earthen home.
I think this is an great time to use 2 pound closed or open cell (depending on the application) spray foam. It's worth the initial environmental cost because of the high R value and overall life span of the product. This makes spray foam a great transitional product until we can develop a better one because the offset in energy savings during the life of a quality build dwelling totally offsets the petro chemicals needed to manufacture the spray foam.
Adding a little bit of soy to the foam is poppy cock and more of a marketing decision than one of science.
But, the real trick is taking in the big picture: how can we best located the house on the land, where should be put the windows, etc. etc. Can we group together homes with shared walls? It's too much to address in a blog post, but the whole system needs to be considered. If you employ sound building science and figure out where on the earth to build, it's a great start in addressing the insulation variable in shelter.
Hi Vera
Being a distributor of Logix in NH I am already familiar with the benefits of EPS but it was interesting to see your take on several of the insulations. EPS uses petroleum products to create an almost perfect insulator. And if you combine it with a super strong wall system you have created a building that will only be destroyed by the next ice age glacier to come our way. Now wait and watch as the anti concrete brigade comes along with their rants about the 5% of greenhouse gases that are caused by the manufacture of cement paste. That would be an interesting topic for you to tackle.
Hi Kent,
Yes, you have to weigh the c02 and other downsides of concrete manufacturing, but I agree with you that the initial toxic downside of concrete (in any project: ICFs or countertops) is worth it. The trick is to do it right so it can have a long long life. There is no reason that properly placed well designed cement products can't be in service for hundreds of years.
The problem comes when concrete is wasted, either by bad design or improper application, etc.
Two things will replace concrete in the next generation of building: incorporated nano technology and the use of synthetic calcium carbonate. The research being done now on how sea creatures make their shells of the base materials (commonly found BTW) is the super strong, well insulated, lightweight building material of the future!
On a personal note: I love concrete.
I love concrete and ICFs as well - yet urge us to always keep an eye on the goals (which are non-product specific) and keep ourselves open to ideas which might appear on the edge of the industry. Hmm maybe I'll do a blog on the concrete edge... :)
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