Are Structurally Insulated Panels the future of environmental-conscious homes?
January 28, 2009 § 4 Comments
In a world that becomes more and more concerned about CO2 emissions, sea-level rising, melting glaciers and so on, constructions are an important contributor to the pollution of the environment. Not only by all of its materials that take huge amounts of energy in the making but also by heat leakage out of insufficient insulated buildings or the poor standards of many of the actual ones. On one hand the companies are to blame for irresponsibility or lack of interest but also authorities because they are not setting compulsory and tight enough standards.
In this medium the SIPs enter the stage carrying a few substantial pluses like great insulation properties, ease to manufacture -which, in fact, can be automated-, easy to deploy, reduced workforce and time. Also SIPS offer versatility and can be used in a wide variety of builds and are believed to be the future in constructions by many industry leaders.
Let’s see what SIPs are: wikipedia describes them as “a sandwich of two layers of structural board with an insulating layer of foam in between. The board is usually oriented strand board (OSB) and the foam either expanded polystyrene foam (EPS), extruded polystyrene foam (XPS) or polyurethane foam.
SIPs share the same structural properties as an I-beam or I-column. The rigid insulation core of the SIP performs as a web, while the OSB sheathing exhibits the same properties as the flanges. SIPs replace several components of conventional building such as studs and joists, insulation, vapor barrier and air barrier. As such they can be used for many different applications such as exterior wall, roof, floor and foundation systems.” (wikipedia)
One issue SIP panels have been widely criticized for was their environmental footprint. Usually the resin adhesive that the OSB strands are bonded together with isn’t exactly environmentally friendly. It usually contains formaldehyde. “Formaldehyde can be toxic, allergenic, and carcinogenic. Because formaldehyde resins are used in many construction materials it is one of the more common indoor air pollutants.“(wikipedia)
The foam inside the panel is usually petroleum based and thus environmentalists condemn it. They are pretty much right and even if some say that very little in the foam is actually some sort of petroleum fraction it still encourages the petroleum industry, which on the long run is not good.
Lately there have submerged some technologies that make SIPs more environemntal friendly.
On the OSB side there are bioresins that are suitable for using in the OSB production. Common examples of biological sources are soybeam, casein, starch, collagen, blood or tannin.
Cambridge Biopolymers’ bioresin is derived from Rapeseed oil and tests demonstrated good water repellency and other characteristics that ensured it the industry standard for OSB/3. (check out this resource or this presentation in MS PowerPoint format).
On the sandwiched insulator side there are quite a few biofoam products on the market, each of them marketing itself as the most environmentally friendly insulation in the industry. Soy is a common source for oils used to produce the foam. Some more eco-friendly biofoams are waterblown, which means they don’t contain CFCs or HCFCs. Despite huge controversy on how much bio material is actually in the composition (read here an enlightening forum discussion), the biofoam advocates say that the greenest part lays in the greater insulation properties compared to fiberglass, old blue jeans or recicled newspaper.
There are a few other natural SIPs like straw-core SIPs. For example, the New York Institute of Technology team of the Solar Decathlon is using a type of SIPs called Agriboard, which are compressed straw and are completely biodegradeable, including the glue, which is a natural product of the straw when heated. However, straw SIPs offer less insulation per inch of thickness, and they are considerably heavier.
Because of all controversy of liquid soy foam insulation and reduced R-value of straw SIPs I would put my polystyrene alternative bet on Greensulate, which I covered already in a previous post:
Proper installation is a must to ensure the SIPs marketed performance. Fire safety is a common concern about using SIP panels but if the interior of the panel is covered with a fire-proof material like drywall the SIP is protected and the foam remains intact.
Insects and rodents (like with any house) can become a problem for SIPs as well. Any foam insulation product can provide a good environment for these pests to dwell.Aside common insecticides and other less desirable methods of prevention, boric acid-treated insulation panels are also available. These panels keep insects away while remaining relatively harmless to humans and pets.
Having these said, I encourage you, readers, comment and add useful information that I have missed, perhaps a profesinal of the SIP industry can comment and point at some important issues not covered here. Or share it on your social network of choice: