Insulated Panels - SIPs
The US Forest Products Laboratory built the first SIP structure in 1935; however, energy efficiency concerns didn't exist until fuel prices increased. The first increase, in 1974, saw the cost of crude oil rise from $11.45 per barrel to $18.21, a jump of over $6.75 per barrel or 59%. Product performance and affordability were impacted by the introduction of oriented strand board in 1981, which eliminated the use of plywood.
Benefits to the Builder
SIP builders establish a specialty market that separates their business from other builders because they provide the community with a finished product that has superior energy efficiency and structural performance.
SIPs combine structural framing, insulation, and sheathing into one step, therefore providing the opportunity for more projects per year. SIPs are easier to work with during the cold winter months. Sip walls can usually be erected in 1-2 days, with roof erection taking about the same time. After quickly installing the panels, the rest of the time on the project can be spent completing the work on the interior.
SIPs reduce job site waste by reducing the cost of waste disposal. According to statistics, the average builder pays $750 per 2,000 sq. ft. home for waste disposal. Wood products account for 35% of this waste. The typical exterior framing waste of an SIP home can be hauled off in a 55 gallon container.
Almost every builder experiences job site material theft. It's much more difficult for SIP panels to be stolen than it is with standard lumber.
SIPs reduce the margin for framing errors. Each panel is numbered to correspond with a blueprint. Panels are built to exact specifications, taking the guesswork out of design and quality control on-site. Our panels are also scanned with an infra-red system to confirm the even distribution of the foam fill before they leave the plant.
Maintaining a consistent profit margin becomes easier with SIPs, since the builder knows upfront exactly what the exterior framing cost will be.
Stick framing relies on the integrity of a multitude of connection points between 2x's and sheathing. With SIPs, loads are distributed across the entire panel due to the continuous bond between the sheathing and rigid insulation. A SIP panel can be compared to an I-beam, with the sheathing acting as flanges and the insulation as the web. Because of this, a SIP structure is many times stronger than a conventional structure.
Benefits to the Homeowner
The biggest benefit of the SIP system is energy efficiency. The home is wrapped in polyurethane insulation without the thermal breaks experienced in 2x framing at each stud and around the electrical work. Also, polyurethane insulation maintains its integrity over time, whereas batt insulation settles and absorbs dust and moisture.
The US Department Of Energy compared 5 different building systems for clear-wall R-value (Measures the R-value of an uninterrupted insulation cavity section of a wall) vs. whole-wall R-value (Takes into account the areas where most thermal performance is lost, such as corners, studs, wall to roof, window, and door areas). The test concluded that SIPs maintain 88% of their clear-wall performance after whole-wall R-value is measured. This is 58% better than 2x6 stick framing.
SIP Panels provide a quieter and healthier living environment. Polyurethane insulation is an excellent sound barrier, and the naturally tight construction of a SIP shell helps prevent dust and allergens from penetrating the home. The installation of air exchangers is normally recommended to promote healthier air quality and control humidity.
A SIP home provides flexibility and freedom of interior design. There is no need for a stud-finder. The entire inside is sheathed with oriented strand board. Finding a place to support a nail for pictures, curtains, or cabinets isn't a problem. There is significant time and money to be saved when it comes to applying sheet rock! It will be noticeably faster since you don't have to worry about hitting the studs.
SIPS are typically composed of two materials- OSB and expanded polystyrene or OSB and polyurethane, and are environmentally safe. The OSB is derived from short growth, or “Replaceable” tree crops. The polyurethane insulation does not contain any CFCs, (chlorofluorocarbons) or formaldehyde.
SIPs vs. Conventional Framing
The cost of SIPs is always compared to stick-frame construction, but this is not an “Apples-to-apples” comparison, since 2x construction cannot compete with the thermal efficiency or strength of SIPs. To build a house out of conventional materials that would perform with the same thermal efficiency and strength as a SIP house would cost 40-50% higher than a SIP home. Although the material cost of SIPs is higher than 2x construction, you are actually paying for some of your framing labor when you purchase panels. The finished home cost difference is only a few percent more than a stick-framed home. The difference depends on labor and materials costs in your area. The minimum 50% energy savings quickly recoups any additional initial investment over the cost of conventional framing. The savings continue even when you sell your home. A study released by the EPA in 1998 revealed that energy efficiency increases the resale value of homes by $20 for every $1 in annual energy cost savings. This savings has grown increasingly important as energy costs continue to soar!
The results of yet another construction process analysis was written in a 1998 report to the U.S. DOE, Department of Industrial Engineering and Management Systems, University of Central Florida, Orlando, FL. The study focuses on the construction of two similar single-family homes, one SIP and one stick-built, built by Habitat for Humanity during fall 1997. The data indicated that the SIP home saved 65% of the site labor when compared to the stick-built home. Cycle time savings are of similar magnitude. Volunteers were interviewed after framing the SIP house to gauge their perception of SIP construction. The results suggest that both construction professionals and other volunteers believed that SIPs reduced construction effort significantly, averaging about one-half the work of conventional construction.
The EPA has developed a program called Energy Star Homes to help homebuyers offset the up-front cost of building a better home. Some incentives include Energy Efficient Mortgages through lending partners such as Chase Manhattan Bank, Wells Fargo, and others. The perks of Energy Efficient Mortgages include debt-to-income ratio loan variances, closing cost rebates, and lower interest rates. Also, owners may earn a tax credit of 1% of the purchase price with a maximum of $2,000 for newly built homes, which use at least 50% less energy than the Model Energy Code.
Today some builders are still resistant to changing their construction methods, but this is changing because customer demand will dictate acceptance. In the future, most all builders will give customers the option of building with SIP panels. After all, considering serious utility cost increases on the horizon, why would anyone build with anything else?