| |
SIPs make up the main exterior walls |
Structural insulated panels (SIPs), also known as foam core or stress-skin panels, are a highly energy efficient alternative to stud-frame construction. These wall and roof sections are factory-built under controlled conditions, which increases the quality and precision of the finished product. Door and window openings are precut at Murus using state-of-the-art CNC (Computer Numerical Control) automatic cutting equipment which ensures square and level openings. The SIPs are shipped flat on a truck to the building site where they are assembled, resulting in a highly insulated, tight, finish-ready structure. Because SIPs have the insulation and sheathing already in place, there is less on-site assembly, which translates into a more predictable, higher quality product. In comparison, a site-built, frame structure has many site-related variables such as weather and the skill level of the building crew, to name a few.
R values measure the capacity of a material, such as insulation, to resist heat flow. The higher the number, the better the resistance. Murus's polyurethane SIPs have an impressive aged R-value of 6.76 per inch, higher than any other insulation material. We use 5-1/2", R-33 wall panels and 6-1/2", R-40 roof panels in our homes. When the finish materials are added, the composite R-values are R-37 (walls) and R-42 (roof). Murus's SIPs are Energy Star rated and are listed in the Greenspec Directory; an independent agency that qualifies green and sustainable construction products.
Our SIPs contain much less wood than conventional construction because there are no studs! The only lumber used in the panels is oriented strand board (OSB), a structurally-rated sheathing material made from fast-growing, renewable, self-regenerating forests or plantation-grown trees. Murus's OSB manufacturer is a member of the Sustainable Forestry Initiative.
Polyurethane has been used extensively for over 50 years and is safe to humans and to the environment. It does not contain formaldehyde or CFCs. Once cured, urethane is an inert, thermo-set material that does not support combustion. It has a Class 1 fire rating, the best available. Several of our past clients with chemical sensitivities have tested samples of urethane panels. Not one has ever had a reaction. We like polyurethane because with its high R-value, it does its job better in a smaller amount of space.
Structural insulated panels are made from either polyurethane or polystyrene. Murus makes both. There are significant differences between the two types of foam. Polystyrene (the white "coffee cup" material) has an R value of 3.85 per inch, compared to 6.76 per inch in polyurethane panels. Polystyrene is a thermoplastic. When heated to high temperatures, as in a fire, thermoplastic materials melt. Polystyrene panels are much more common and are manufactured in many locations across the country because the manufacturing is more simple. Sheets of styrene are glued to skins, usually OSB. As a result, polystyrene panels are less expensive than polyurethane panels, and more readily available.
During manufacture, polyurethane (a two-part, epoxy-like foam) is injected between two OSB skins. The OSB skins are held in a press as the foam expands to fill the cavity. As the urethane cures, it forms a mechanical bond with the skins, creating an incredibly strong, monolithic structure. The resulting SIP panel is much like an I-beam except the OSB skins are connected by foam instead of webbing. Structurally, urethane panels are much stronger than frame construction or polystyrene SIPs because of the mechanical bond between the skins and the foam.
The machinery used to manufacture polyurethane panels is more sophisticated and costly than the process used to make polystyrene panels. For that reason there are only a few urethane SIP manufacturers in the US. We are not affiliated with any manufacturing system. This allows us the flexibility to choose whatever system best fits our needs. We could purchase styrene panels more conveniently and for less, but we prefer to use Murus's urethane SIPs because of the quality of their product, their integrity and their customer service, which has impressed us for over 15 years. Having a long-term working relationship with one panel company allows us a higher level of consistency and quality in our end product. |
|
