Energy Costs May Increase SIP Use In Construction

October 22, 2008
| By Pete Daly |
Text Size:

SIPs have been around for a long time, but a lot of people have never heard of them. The skyrocketing cost of energy may soon change that.

SIPs — structural insulated panels — come from a factory to the construction site pre-cut to the exact size, with holes already made for doors and windows. SIPs are a solid sheet of expanded polystyrene sandwiched between two sheets of wood, metal or drywall, but usually OSB (oriented strand board, similar to plywood). The foam insulation can range in thickness from 4 inches to almost a foot, and the largest panels are 8 by 24 feet. The panels themselves provide structure as well as insulation.

They are used in commercial construction as well as home construction — but only about 1 percent to 3 percent of new construction, in general, incorporates SIPs, according to the people who make them.

Yet SIPs are much more energy efficient than stick-built construction, and they have other advantages, as well.

"The panels have been around for a very long time but it seems like nobody really knows about them, and they are afraid of them a little bit," said Randy Vander Hoff, project executive for restaurant construction at Rockford Construction.

But Vander Hoff is very familiar with them. Rockford Construction has built dozens of Wendy's restaurants in West Michigan in the last 10 years, according to Vander Hoff, and all of them are SIP construction.

Vander Hoff said he is "kind of a salesman" for SIPs because they permit very quick construction, which is a critical issue in many commercial projects.

"The energy savings is just kind of a bonus," he said. SIPs are 30 percent more energy efficient than stick-built construction, according to Vander Hoff, although other estimates range even higher.

SIPs construction costs a little more per square foot than conventional construction, but "the time savings is well worth it," added Vander Hoff. According to the U.S. Department of Energy, although SIPs cost more than traditional building materials, they require less labor to install. "Therefore, the total cost is roughly the same," states the DOE Web site,

R-values for SIPs range from about R-4 to R-6 per inch of thickness, depending on the type of foam core used, according to the DOE. Most SIPs use EPS foam, although some manufacturers reportedly use polyurethane and isocyanurate.

SIPs have been around since the 1930s, according to Chris Kreple, SIPs product manager at PorterSIPs, a division of PorterCorp in Holland. The first ones were made in a U.S. government lab in Wisconsin by technicians experimenting with new types of potential forest products. PorterCorp was one of the first manufacturers of SIPs, starting in 1964 when it was founded by CEO Bill Porter as W.H. Porter Inc. During the 1950s and 1960s, Porter was the R&D manager at boat manufacturer Chris Craft Corp. The marine industry had found that an economical way to build boat hulls was with a plastic foam core sandwiched between fiberglass.

W.H. Porter began making pre-fab geodesic dome structures, which were invented by R. Buckminster Fuller in the late 1940s. The Porter domes incorporated insulated foam-core panels — in essence its first SIP. PorterCorp still makes tubular, bolt-together steel frames with concealed bolts, called Space-Frames. The Space-Frames are used in commercial construction, incorporating the company's SIPs brand: PorterSIPs. PorterCorp, which has about 100 employees during the construction season, produces more than 1,000 buildings a year, including the popular frame park shelters it introduced under the brand name Poligon.

SIPs eliminate many of the studs used in construction, and studs are a major conduit for thermal conduction.

PorterCorp SIPs were used in the Wendy's restaurants built by Rockford Construction, and also in the New Holland Brewing Co. Last year PorterCorp SIPs went into 50 to 100 commercial, industrial and institutional buildings, said Kreple, but the firm also makes SIPs for home construction.

"We've seen moderate growth over the last two to three years, where the rest of the (home construction supply) industry has contracted quite a bit," said Kreple.

SIPs construction is more airtight than stick-built and, depending on the thickness of the foam core insulation, can reduce heating and cooling costs in a structure by as much as 50 percent, compared to stick-built construction with conventional insulation between the studs, according to Kreple. For maximum insulation advantage, SIPs are used to form a complete, air-tight envelope, including SIPs on the roof and under the floor.

The thinnest SIP from PorterCorp is 4.5 inches thick and has an R-value of 16. The highest R-value PorterSIPs, slightly over 12 inches in thickness, are being used in One-Watt-Houses built by Conservation Technology International Inc., a Chicago-area company founded by Marko Spiegel, an engineer and entrepreneur born and educated in Germany. One-Watt-Houses are designed to reduce total overall energy demand by 60 to 90 percent, compared to typical Midwestern homes.

Porter, who is 81 and still actively manages the company, holds about 30 patents, of which "three or four are really good," he joked.

Porter said SIP technology advanced dramatically around 1980 when Weyerhaeuser introduced OSB panels measuring 8 feet wide by 24 feet long (standard plywood sheets are 8 by 4). But the acronym SIP hadn't even been invented then. Porter said in the early days they were called "sandwich panels" or "stress skin panels." Around 1990, he and several other manufacturers of the panels got together to form a trade organization, but first they had to come up with a name for their product. They decided on structural insulated panel.

Porter does not reveal annual sales revenues of PorterCorp, but he said the company just invested $1 million in a new CNC machine and will also probably put that much into R&D — even though business in Michigan in general is flat and costs of everything are rising. "It scares me to be investing in R&D and big machinery" with the economy so weak, he said, "but saving so much energy — it's the right way to gamble."

Porter and Kreple figure that SIPs are used in only 1 or 2 percent of all construction, but that if SIPs were used in all construction, the amount of energy used in America could be reduced by more than 6 percent a year.

"It's much cheaper to save energy than generate energy," said Porter.

Another West Michigan plant producing SIPs is Team Industries Inc. in Kentwood, which employs about 45. Wayne Gasser, vice president of manufacturing and operations, said its brand of SIP is called R-Control. There is also a sister plant making SIPs in Virginia.

Gasser said energy cost inflation is definitely generating more interest in SIPs.

"The SIPs industry last year actually went against the trend of general construction. It was up about 7 to 8 percent last year, while overall construction was down somewhere around 30 percent, is what I heard," said Gasser.

He said SIPs production has been split about fifty-fifty between home construction and all other. "At the moment it's running a little bit heavier on the commercial side," he added.

Gasser said the current public and industry interest in "green" construction has something to do with the interest in SIPs.

"Everybody obviously is looking to save money" on energy, but he added that many owners and builders really do want to be better stewards of the earth in general, and manufacturers of SIPs expect to see sales volumes increase this year.

At the same time, Gasser said manufacturers are being challenged by price increases of all kinds. Natural gas costs for Team Industries have already increased this year to 40 percent over last year.

Gasser would agree with Bill Porter that the percentage of construction involving SIPs is "very small." He has heard it is 3 percent or less. When asked why, despite the advantages of SIPs, Gasser said it is "probably because the SIPs industry has not done a good job of promoting its project."

But he said that is changing. "We are getting much more aggressive," he said. CQX

Recent Articles by Pete Daly

Editor's Picks

Comments powered by Disqus