By now, just about everyone in construction knows what makes a structural insulated panel, or SIP: a sheet of foam insulation, usually expanded polystyrene, laminated between two sheets of oriented strand board, or occasionally plywood. Whether you call them sandwich panels, insulated stressed-skin panels, foam-core panels, or SIPs, their advantages are getting pretty well known: they go up fast, they insulate superbly, and they’re only a little more expensive than stick-framed and batt-insulated construction.
And for most builders, that’s the end of the story. Because few have any plans to use them.
SIP panels have been around for quite a while: the first SIP home was built in 1952. In the decades since, they’ve been repeatedly hailed as the next big thing. Some have compared SIPs’ place in the market now to gypsum board four of five decades ago, or to manufactured trusses in the 1960s: a good product on the verge of taking off to near universal acceptance.
The SIPs industry can in fact boast an enviable growth rate, averaging about 15 percent lately and reaching 30 percent in some years. The total square feet of production has more than doubled in the past decade. Total volume reached 30 million sq. ft. in 2000, up some 35 percent from the previous year.
For most industries, such numbers would be spectacular. But SIPs’ overall numbers remain modest, with less than 1 percent of the residential and commercial markets. As a product of near-universal applicability, expectations have run high. A 1991 study by Steven Winters Associates noted that a “fully mature” market would absorb 2.2 billion sq. ft. of SIPs.
So are SIPs finally on a steady upward path to acceptance, ready for take-off? Or will they remain a specialty product?
It certainly isn’t consumer interest holding them back. “When it’s a residential project, it’s usually either because an architect has specified SIPs or an owner has done some research, on the Internet or wherever, and has decided on SIPs as a green building material,” says Al Cobb of Panelwrights, a West Virginia SIP distributor.
Builders, on the other hand, seldom push SIPs, and many actively resist working with the material. “Builders are the biggest obstacle,” says Chris Spaeth of Energy Panel Structures of Graettinger, Iowa. “They want to keep doing what they’re used to.”
“The construction boom of the last five to seven years has allowed builders to duck new things,” says Cobb. “Why try something new, faster, or better when you’re keeping busy? There’s little incentive to change. Now that there’s been a decline, builders need a product that will set them apart.” Cobb thinks the declining skills of construction crews will help drive acceptance, especially with the automated design and pre-cut panels being offered.
Independent of customer satisfaction, there are a lot of things for builders to like about SIPs.
– SIPs go up fast. Sure, stick framing is fast too, but SIPs also replace sheeting, batt insulation, blocking, and vapor barriers.
– SIPs are installed with a minimum of jobsite labor, which is at a premium for the foreseeable future. When they’re factory cut to plans, the panels have no problems with inaccurate layouts.
– SIP panels won’t bow, shrink, or twist like stick framing. Dimensional lumber quality has bounced up and down in recent decades, leading many contractors to use engineered products like I-joists, and SIPs are the logical next step. And they provide continuous nailing surface for drywall and trimwork.
– While SIPs can’t eliminate the causes of mold, their solid-wall construction means no drafty wall cavities or soaked insulation, and less material that can’t dry out.
– SIPs can reduce material wastage and jobsite cleanup.
– SIPs are ideal for creating well-insulated vaulted ceilings. They can be used for just the walls, just the roof, both, or in selected parts of a building.
Not all builders are just stuck in their ruts, of course. Many have looked into SIPs, and some have actual objections, whether justifiable or not. Some of the ones we heard:
– The panels can be difficult to handle. Although 4-ft. by 8-ft. panels weigh about 112 lbs. and can be easily handled by two workers, it’s the larger panels, up to 8-ft. by 24 ft., that truly save installation time and improve airtightness. These require cranes to handle, and that requires planning and access to equipment.
– Electrical subcontractors unfamiliar with the system sometimes balk at taking on SIP jobs. “The only disadvantage to SIPs is the electrical,” says Jim Haselhoff, an Iowa builder who does a lot more metal buildings and conventional structures than SIPs. “The owner needs to know where they want the outlets before you build. If you want to move a box after you’ve ordered the panels, you need to cut the panel, use a hot knife to melt the insulation. But that’s it, really. It’s a good system.”
“There’s still a shortage of experienced tradesmen, but that doesn’t mean there aren’t plenty with open mind,” says Cobb. As a distributor who trains builders, he routinely works to eductate tradesmen, especially electricians. “We show them how best to pull wires, we provide a layout. We address the issues from the very beginning. Sometimes our crews will run wires through panels if that will help.”
– Many builders are uncertain about building houses “too tight,” assuming that a home that doesn’t breathe will grow mold or have ventilation problems.
In fact, building an energy-efficient structure of any kind requires new attention to ventilation and air quality issues. And given growing concerns about mold, asthma, and allergens, most buildings are going to need what SIP builders recommend: some kind of mechanical ventilation, such as an air-to-air heat exchanger. “Tight is the best way to build a house,” says Cobb, “but you need the right HVAC system to allow for it.”
– That Juneau thing. A year ago SIPs got some bad publicity when mushrooms started growing out of some roofs in Alaska. Subsequent studies have pointed to shoddy workmanship as the culprit (see story below).
– Costs are higher. Most SIP builders concede that the panels are pricier than stick framing, but put the additional cost at 1 to 5 percent. Some up-front costs may be reduced by downsizing heating and air conditioning systems, but the real payoffs are elsewhere.
– Some manufacturers have refused to warrant their asphalt shingles when applied to SIPs because they will not stay as cool as over a ventilated attic.
The simple solution, notes Cobb, is to buy a better shingle. “Only a handful have bothered to do the testing,” he says. “An architectural-grade Elk laminated shingle on a SIP is a much better choice than going with a cold roof just to save with the cheaper shingle.”
– Many builders assume that energy savings is for the Northeast. Prime territory for SIPs is indeed the cold Northern regions, but SIPs have been shown to reduce energy costs by 18 percent even in moderate Louisville, Ky. In a cooling environment, the airtightness offered by SIPs can enhance air conditioning more than leaky insulation.
Many builders can cite objections while admitting that a lot of it is a matter of unfamiliarity. “If I ever used them I’d probably change my perspective,” says Dennis Hoyt of Hoyt Construction, Three Rivers, Mich., who’s wary of electrical layout changes with SIPs. As a post-frame builder, Hoyt is also waiting for manufacturers to figure out a way to install SIPs between posts, rather than having to lift them up and slide them down. He’d also look for treated plywood along the base of the panels for use in ground-contact structures.
But for his market, which includes churches and commercial buildings, Hoyt says SIPs aren’t yet cost-effective simply as a way to replace girts, sheathing, and insulation. “Energy concerns just aren’t at the top of people’s agendas. When they are, I’ll be looking in to them.”
In the end, it seems it may take an outside push to get SIPs truly aloft. A spike in dimensional lumber prices would help, certainly. But only a long-term increase in heating and cooling costs will push an energy-efficient system like SIPs into the building mainstream.
But then, why would anyone think that energy prices could go up?