GreenDwellingSeattle

As part of their ongoing efforts to build homes that consider efficiency and the environment as much as design and livability, Dwell Development has decided to use SIP Walls for the exterior envelope of their new project, Dwell Over the Park.  Let’s take a look at exactly what a SIP (Structural Insulated Panel) is and talk a bit about the many benefits their use offers for structural durability, energy efficiency, and reduced environmental impact.

SIP’s are most commonly made of OSB (Oriented Strand Board) panels that are sandwiched around a foam core made of expanded polystyrene.  These core materials are made of 98% air and the blowing agent used to expand the foam is CFC-free.  Only a small amount of petroleum is required to create the foam insulation and the manufacturing process uses 24% less energy than fiberglass of equivalent R-Value.  The OSB panels are typically made from fast growing species such as aspen or poplar and use nearly all of the wood of the harvested trees with very little waste.  To manufacture the panels layers of wood strands are oriented for structural integrity and then compressed and bonded together with wax and low formaldehyde resins.   

The benefits of SIP’s are many, but most notable would be that they create a strong, durable envelope with high insulation values and minimal air infiltration.  The structural characteristics of a SIP are very similar to a steel I-beam with the OSB skins acting as the flange of the I-beam and the rigid foam core providing the web.  For comparison, a 4-inch SIP wall has an insulation value of R-14 and will outperform a 2×6 stick frame wall with R-19 fiberglass insulation.  When a blower door test is conducted after the home is constructed SIP’s have been known to be 15 times more airtight than their stick framed counterpart with fiberglass insulation.  This is significant when you consider that up to 40% of a homes heat loss is due to air leakage. 

Constructing a home using SIP’s can save as much as 55% over conventional wood framing costs and from an operational standpoint they can reduce heating and cooling costs upwards of 50%.  They are manufactured offsite to custom specifications and as such offer a reduction in initial resource demand and jobsite waste.  While the technology for SIP’s was developed in the 1930’s in the severe Wisconsin climate, they are now widely used in construction projects all over the world. 

Dwell made the decision to use SIP’s for their latest project because of what they had to offer from a structural, efficiency, and environmental benefit perspective.  The future homeowners here will value them for their durability, comfort, and reduced utility costs. 

If this is the first post you have read in our Seattle Green Building series please take a few minutes to look over past posts.  There is a wealth of interesting information there designed to help you understand how homes are built and how homes built with the environment in mind are the logical and necessary future of homebuilding. 

Sources: www.sips.org, www.en.wikipedia.org/wiki/structural_insulated_panel