What is more Durable than a Home?
July 6, 2009 by Mark
Filed under Green Building, Green News, SIP's
By David Bates
Why build a house out of polyurethane foam when we can make houses out of natural materials like mud, wood and straw? As a general contractor and a HERS energy rater, I became interested in structurally insulated panels (SIPs) because of the high R-value of polyurethane foam and it’s inherent ability to create an ultra-tight envelope: two things that are essential in building a modern home that adheres to the high level of comfort expected from our housing. I also realized that most modern energy efficient homes already utilize some type of rigid foam insulation or petroleum based air barriers. If they don’t utilize the high R-values that come from petroleum products, they will end up burning more fossil fuels to create heat, far exceeding the petroleum in the insulation and air barriers. Somehow you have to make an airtight shell that has a high R-value. What products are being utilized to create this airtight shell that saves energy? OIL. You can make a monstrous hybrid of natural building materials and petroleum products or you could just make a SIP out of polyurethane foam, which will be a lot easier to reclaim in the future than the typical mix of technosphere and biosphere.
Is straw bale or blown cellulose an exception? I guess that depends on how the cellulose is treated for fire and vermin, what seamless natural material you choose as your air barrier and the detail paid by the architect, builder and crew. If cellulose has an R-value of 3 per inch and polyurethane has an R-value of 7 per inch, then a six inch SIP would be R-42 (8”=R-54) and the equivalent in cellulose would be a 14” thick wall (18” for R-54) and it would not have the inherent qualities of low thermal bypass. It also takes valuable square footage from the home and I have never met a free square foot. So the quandary is should we utilize polyurethane foam as a durable resource in our efforts to be “environmental?”
I traveled to the NCFI in North Carolina to find out where ICS-RM gets their polyurethane foam and how it is handled before it becomes a SIP. I was impressed by the level of care taken to keep any volatile organic compounds from entering the biosphere especially the huge carbon scrubber on their smoke stack. Once the foam is “blown” it becomes inert and the MDI( diphenyl-methane-diisocyanate) cannot be released into the atmosphere as it could as in liquid form- even if it is burned. When it is burned it releases gases and poisons just like any organic compound (even a pile of leaves) but not in the same form as when it reaches a boiling point as a liquid diphenyl-methane-diisocyanate (MDI) and this is the real environmental danger, which is why it is highly regulated at the facilities. To find how they make MDI and how it is handled one would have to tour a plant that cracks the barrel of crude oil like Dow or BASF. The hazards, as with any petroleum product, are going to have to be monitored by our industrial watchdogs and consumer interest groups and we have to make absolutely sure we are not polluting our environment, but it seems like utilizing a small amount of petroleum in a durable manner with the intent of saving huge quantities of petroleum from being burned has its merits. Data from the US Energy Information Administration illustrates that buildings are responsible for almost half (48%) of all energy consumption and GHG emissions annually; globally the percentage is even greater. Seventy-six percent (76%) of all power plant-generated electricity is used just to operate buildings.
I have an associate who is an expert in the field of Earth and Environmental Sciences and a NASA Fellow (Vandy Blue Spikes, owner of a consulting company called Earth Science Agency, Ph.D. in Earth Science) and I asked him his opinion on the merits of utilizing SIPs panels as an “environmental” alternative in the construction industry, and here is what he had to say:
“You can’t build a home without using resources and impacting the environment, however, any effort to build a more durable and energy efficient home is going to reduce the net environmental impact. The question of which combination of building materials has the least impact on the environment can be answered if you look at how those materials were produced and the energy usage of the resulting home over its lifetime. With regard to structurally insulated panels (SIPs), there is a stigma pertaining to the use of petroleum to create the insulating foam, which has earned a negative reputation when used in disposable products like cups and food containers where you get the triple impact of a dirty petroleum recovery and refining process, the release of volatile compounds during the foam production process, and the final products end up residing in landfills for most of their extremely long lifetimes. When producing SIPs there is still a nasty petroleum recovery and refining process, but the manufacturing process for the foam has been cleaned up dramatically, and the final product ends up in a home that will be utilized for more than 50 years. So in terms of environmental impact, the production of SIPs compares favorably with other construction options like concrete and wood-framed walls, all of which contribute to a net gain in greenhouse gases. And when you factor in the amount of energy that is saved over the lifetime of a SIP home, there is no question that it will have less of an impact on the environment when compared to any other type of home that has lower R values and is less tightly sealed.”
The use of fossil fuels in our society right now is a foregone conclusion. The best possible use of these valuable resources is to use is them responsibly and with the greatest efficiency. Not only is it imperative on a personal level because of the rising cost of heating and cooling our homes but there is an imperative as a Global Citizen to lower our environmental footprint. Utilizing polyurethane foam in a durable matter lowers our energy bill and our footprint and what is more durable than our homes?
