Although we do not manufacture Structural Insulated Panels (SIPs), we have used them in many of our building projects over the years. We’ve compiled the following information to help you understand this type of construction.
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| Comparative R-values
When it comes to the insulative properties of structural panels, the stated R-value is only half the story. The monolithic construction of SIPs dramatically reduces the amount of air leakage in and out of the building. The result is that, although the panels’ R-value may only be 15-20% higher than standard insulation, the actual energy- conserving capabilities of SIPs can be as much as 40% greater than traditional stick-frame construction of walls the same thickness.
SIPs are manufactured with a variety of different foam materials: the denser the foam, the greater the R-value and the higher the price. The table below compares two common types of structural panels with traditional stick-frame construction.
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4.5" wall
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6.5" wall
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8.5" wall
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Traditional construction
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R-13
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R-19
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R-25
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Polystyrene SIPs
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R-16
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R-23
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R-30
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Polyurethane SIPs
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R-26
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R-33
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R-40
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Polystyrene is basically the common styrofoam found in everyday items like disposable cups and plates. This type of panel is very sufficient for most climates.
Polyurethane is a denser, heavier material than polystyrene. This type of panel is used in harsher climates and higher altitudes where sustained winter cold and wind are prevalent.
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Heres an excerpt from an article titled SIPs: Are They Right for Your Next Project published in Fine Homebuilding, June 2007, pg 60.
SIPs Cost Less Over Time
The cost of the SIPs for a 1000-sq. ft. house built in West Virginia in 2005 was $13,500. That’s more than double the cost of framing lumber and insulation for a like-size house built with stud framing. However, the final project cost was $110,000, so adjusting for a less-expensive HVAC system, the homeowners paid only a 6% premium for SIPs. With tax breaks (www.energystar.gov) and reduced heating and cooling loads, the savings averaged $120 per month. After two years and eight months, the homeowners broke even on their investment. If they live in the home for 10 more years, they will have an overall savings of $14,400. If they put the money back into their mortgage, the 30-year term would be reduced to 20.
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