WHAT ARE SIPS?
Structural Insulated Panels. These panels form a foam sandwich: OSB (oriented strand board) on either side, foam in the middle. The foam drastically reduces thermal bridging that happens where lumber or other heat conducting materials form parts of walls (like in stick framed walls).
They’re stronger, lighter and far better thermally than traditional stick framing. We believe they are more sustainable on multiple levels.
We use SIP’s on the exterior walls and roofs of our buildings, since that’s where it’s most important to keep the cold air either out or in.
The particular panels we use are polyurethane, rather than the industry’s standard EPS,and have a proprietary connection mechanism called the cam-lock, which connects the panels to each other without the typical splines that other companies use, further reducing thermal bridging.
Polyurethane R-value: 6.9 per inch of foam
EPS panels R-value: 3.84 per inch of foam
SIP sample showing the cam-lock system that connects the panels to each other.
R-value vs. U-value
Although r-value is important to consider in the construction of a building, it’s not very comprehensive. For instance, if a traditional framed wall is said to have R-13 insulation, that means that the best part of the wall is R-13, then you have to consider that around 25% of the wall is wood (which has a much lower R-value than the insulation), then that’s also assuming that each cell of the framing has been perfectly insulated without gaps for air to pass through (which they’re very unlikely to be). SIP’s are cut in a factory and assembled in our factory to cut down drastically on gaps as well as the amount of lumber that’s used in each wall so that the amount of energy used to heat and cool our homes can be minimal, especially given their size.
U-value is calculated by finding the percentage of each wall various materials occupy, then using their R-values to come up with an overall rating for the entire wall assembly (far more difficult than assigning an R-value for a single material). The more insulation and less lumber or windows present in the building envelope, the better it will perform. That said, windows can really improve the quality of spaces, so we try to use them only where they add the most benefit (like our great room areas where we’ll be spending the most time).
Our panels come from Murus and we’ve really enjoyed working with them.
Steve with his very first SIP house panels
To learn more about durability, materials, lifespan, sustainability, disaster survivability, or anything else about the SIP’s industry please visit the Structural Insulated Panel Association website