Except for what he needs for interior walls, Don Ferrier doesn't buy framing lumber anymore. For the envelopes of the half-dozen custom homes he builds every year in the Fort Worth, Texas, area, he uses structural insulated panels (SIPs). And he's not the only one.
Conventional wood framing still dominates U.S. home building, commanding a nearly 80 percent share of above-grade walls, according to the NAHB Research Center. But SIPs, insulated concrete forms (ICFs), structural steel framing, and precast concrete panels have helped steadily reduce framing lumber's market share by more than 10 percent in the last decade.
For most alternative structural systems looking to eke out market share in the residential realm, getting builders to try something new is the biggest bugaboo to mainstream acceptance. Other hurdles to widespread market acceptance include building codes that lag behind technology and cutting-edge builders, a lack of skilled labor for these new systems, price premiums for materials and labor, and logistical and supply chain issues that take contractors out of their comfort zone of their local lumberyards.
Still, with the combined pressures of increasing energy costs (and consumer consciousness), ever-faster cycle times, skilled-labor shortages, concern about customer satisfaction rankings, and waning lumber quality, housing insiders predict an upward trend will continue.
Here is a run-through of the features, advantages, and disadvantages of two of these systems, ICFs and SIPs:
Insulated Concrete Forms
ICFs are molded from expanded or extruded polystyrene into lightweight, interlocking foam blocks that serve as permanent forms for poured concrete walls. The resulting walls combine the thermal mass and strength of concrete with the energy-saving benefits of integral insulation panels. Sophisticated systems feature metal inserts that act like rebar within the blocks and as vertical, standard on-center nailing strips on both faces of the insulated wall structure.
Of the alternative structural systems trying to enter the mainstream of housing construction, ICFs have made the most headway. The NAHB has tracked the industry's trajectory from a 0.7% market share of above-grade walls for single-family homes in 1997 to a 6.5% share in 2006—equaling more than 103,000 homes in that year alone.
There are now about 60 manufacturers distributing ICFs across the country; the International Building Code accepts ICFs among poured-in-place concrete systems, enabling their use nationwide.
ICFs' most recent popularity is fueled by current events, primarily the Gulf Coast hurricane seasons of 2004 and 2005, as well as nationwide energy price hikes and the green building trend. "We're talking about a system that resists fire and high winds, creates an energy-efficient home, mitigates noise, and is highly durable," says Jim Niehoff, residential promotion manager for the Portland Cement Association in Skokie, Ill.
ICFs also offer production benefits. "Builders love them because they're easier and faster to use [than removable forms] and there's one less sub (insulation) to hire," says Frank Chambers, regional vice president of The Contractor Yard, a dealer in Nashville, Tenn.
Minnesota custom builder John Vogstrom took to using ICFs eight years ago, specifically to reduce the potential for mold- and moisture-related issues. Since then, he's further leveraged the energy efficiency of the system to get the most out of geothermal heating, among other green building practices; he also enjoys the ability to create larger window openings than he could with lumber.
Still, ICFs' 5 percent to 10 percent materials-only price premium over CMUs and poured concrete, not considering the labor savings of having integral insulation and permanent forms, is a tough nut to crack with price-sensitive builders. ICFs also suffer from regional building cultures that are married to stick framing and slabs and from a shortage of trained installers to meet demand.
To address the latter issue, the ICF industry is working with the NAHB and its Home Builders Institute educational arm, as well as the United Brotherhood of Carpenters union, to "transition them from stick-framing to ICFs and concrete," Niehoff says. Owens Corning, meanwhile, announced a training and certification program for its ICF system last year.
As for distribution, the ICF industry seems typically fragmented for a relatively young industry. While some manufacturers are actively initiating direct sales relationships with builders to help keep prices competitive, others are willing to suffer supply channel markups of up to three times the cost of a block to enable local support for the technology.
Structural insulated panels
Structural insulated panels sandwich a thick foam panel between two layers of OSB to create structural wall and roof sections. The resulting panel is ready to finish on both faces. It also creates a thermally superior and more reliable envelope to a stick-framed house; a
4-inch SIP wall is 36 percent more thermally efficient than an insulated 2x4 wall, according to the Oak Ridge National Laboratory.
According to NAHB research, SIPs were used as the structural wall material for 1.7 percent of all new, single-family homes built in 2005, a full percentage point higher than five years earlier and now representing nearly 30,000 new homes annually.
Because SIPs are a wood-based system, they are more familiar to framers than a concrete alternative. SIPs are easily manipulated on site with common construction tools, are compatible with other wood framing materials and practices, and offer greater design flexibility and mainstream marketability.
As full wall panels, they often assemble even faster than ICFs, and require no pour or cure time. Those savings help balance a 15 percent or more materials-only price difference between SIPs and stick framing, one of several hurdles the industry faces.
SIPs' installed cost savings, and the system's energy-saving benefits, are what drove Ferrier to the technology. "SIPs give me the biggest bang for my energy-efficient buck," he says.
SIPs walls were adopted into the International Residential Code (IRC) last May, though they may still be hindered at the local level. The language in the IRC was based on a prescriptive method for SIP wall construction developed by the Partnership for Advancing Technology in Housing. The standardized method for calculating and using SIPs enables builders to gain code approval without the stamp of a licensed architect or engineer and puts the technology on par, code-wise, with ICFs and steel framing in residential construction.
The question is whether SIPs manufacturers are ready for a larger wave of demand from the housing industry. "We're seeing more demand, but there aren't experienced and qualified contractors in the field to install it," says Al Cobb, director of SIP School, an outreach education and training effort based in Shenandoah Junction, W.Va.
Like ICFs, the SIPs industry also is still grappling with its supply chain model. Bill Wachtler, executive director of the Structural Insulated Panel Association in Gig Harbor, Wash., isn't aware of any lumberyards currently stocking SIPs, though some may be acting as distributors or middlemen. "I could see a customer ordering SIPs as an option when purchasing a house package [from a dealer], but not walking down an aisle and picking out a panel," he says.
"At a lumberyard, you can just swing by and grab a few sticks from the pile when you need them," says Gary Pugh, a SIPs builder in Santa Rosa, Calif. "With SIPs, you have to think about them long before you start building."
Although Wachtler can envision LBM dealers one day supplying SIPs, the most likely scenario is one in which manufacturers sell their systems through existing component manufacturers. Until then, builders are left to look for the best SIPs they can find and afford, often going out of market to get them.
Indeed, whether it's overcoming distribution hurdles or learning new installation techniques, alternative systems such as ICFs and SIPs require builders to shift some of their thinking. But an increasing number are finding that the benefits of these methods outweigh the initial adjustments.
Structural Steel Framing
The primary difference between non-load-bearing steel channels and studs used for interior wall framing and those used for structural steel components and assemblies is the gauge (or thickness) of the material. Load-bearing sections are typically 16- to 20-gauge, while so-called drywall studs and related components are 24- or 26-gauge. Steel framing components are galvanized and considered "light-gauge," and are cold-formed as opposed to hot-rolled steel I-beams and other heavy-gauge components.
During the past 20-plus years, steel framing's market share in single-family residential reached as high as 1.2% in 2000, per NAHB's calculations. As of 2006, however, it stood a half percentage point below that, thanks in large part to lower composite lumber prices and spiking global steel costs. That's a far cry from its estimated 38% share of the commercial construction market, according to the Steel Framing Alliance (SFA) in Washington.
But steel proponents and manufacturers see greater potential for the product in housing, pointing to specific geographic markets, such as Hawaii and the desert Southwest, and multifamily construction, where acceptance and use is significantly higher among home builders. "Steel framing is a relatively new entrant in the residential segment, but one in which there is an opportunity to generate three times the demand [compared to commercial]," says SFA president Larry Williams, referring to the greater number of homes of all types versus non-residential buildings constructed each year.
Steel's advantages over wood include a higher strength-to-weight ratio that enables longer spans at smaller dimensions, the net effect of which is more-open floor plans and greater resistance to high wind and seismic loads. Steel also is inorganic and of consistent quality end-to-end, meaning it won't warp, twist, rot, or otherwise react to climate changes in application. Steel is non-combustible, and it's resistant to termites and other wood-boring pests.
Once you get a steel frame erected, in fact, it looks like a shiny wood frame, with the telltale wall studs, roof trusses, and bracing you'd likely see with lumber. It sheathes and finishes with the same materials, requiring little, if any, changes in those specs. And, unlike other alternatives, steel has a long track record of code acceptance and a contractor-training infrastructure through the SFA and other trade associations and unions, albeit primarily serving commercial framers and drywallers to date. Material prices historically were stable until 2004, when global demand doubled the material's price in a few short months, from which the industry is still recovering.
So why hasn't steel taken off among home builders? Simply, the system requires framers to carry an entirely different set of tools. Hammers become screwguns, while utility knives and chalk lines are replaced in a framer's toolbelt with snips, vise grips, and felt markers. Usually, instead of a wood framer switching to steel (or being skilled enough to do both), builders switch to steel framers-if they can find them.
That fact, in turn, severely limits a builder's ability to use the material as a structural system in all but a few markets. "I've built all-steel houses, and both then and now there's no one doing it [as a specialty trade]," says Orlando custom builder Williams. For the small-scale, second-floor shell he built out of steel in 2006, Williams had to import a crew from another market and supplement it with a local commercial drywall crew to finish the job.
"The lack of lead framers who know steel framing is our biggest hindrance in single-family," admits SFA's Williams. Price is another, specifically as it relates to the installed cost of a steel frame by inexperienced crews or those in short supply able to leverage premium wages. "Worst case, steel is about 81 cents per square foot more than a wood-framed house," he says.
To combat those issues, the industry is evolving into panelization from the precut or uncut "sticks" that suppliers traditionally provide to a jobsite. An example: recently unveiled insulated steel-framed panels from Accelerated Building Technologies, a joint venture of Dietrich Metal Framing and NOVA Chemicals.
Precast Concrete Panels
Precast concrete is a panelized system for poured concrete in which wall and floor sections are molded and cured in a factory setting, shipped to the jobsite, and craned into place to create the structural shell and bearing walls. Increasingly, precast panels incorporate an integral layer of rigid foam insulation to increase the thermal mass properties of the system.
Panelization in general is already an accepted and increasingly common method of home building, especially to combat shortages in skilled labor via faster on-site assembly. Precast concrete panels have hung onto the coattails of the trend toward component wood framing and, to a lesser extent, SIPs. As of last year, precast reached an estimated 2.7% share of above-grade walls in single-family construction, equaling about 41,000 new homes, up from a zero share just a decade earlier by NAHB's count. Its use as a below-grade foundation system, meanwhile, is estimated to be about 8% of the residential market, with some geographic markets (those near manufacturing facilities) measuring significantly higher.
Like steel framing, precast cut its teeth in commercial, quickly becoming a faster way to build repetitive building sections in multi-story, multi-unit projects. The system translates across the International Building Code, enabling its use as a foundation and above-grade wall system in a residential setting.
Akin to their faster on-site assembly (by some industry estimates, they can save up to three weeks compared to wood framing), precast panels are an all-weather system. They provide an efficient thermal mass, increasingly supplemented by integral insulation, that significantly reduces—if not eliminates—the transfer of air and moisture through the structure.That benefit not only reduces energy use and costs for homeowners, but often enables smaller and more efficient (and less expensive) HVAC equipment specifications as well. The system also delivers superior sound abatement and resistance to a variety of natural forces, such as high winds and fire.
All those benefits, however, have yet to produce a sweet spot in single-family housing, a segment that precast may never crack on a large scale. Custom builders like the system's performance aspects, but can't afford the one-time cost premiums for engineering, shipping, and crane-assisted assembly. Large-volume production builders, meanwhile, are generally too price-sensitive to consider anything out of their comfort zone of wood-based systems; on a per-foot materials basis only, precast might cost at least 20% more.
Another hurdle to acceptance for any builder is the system's requirement for exceptionally detailed planning for all openings and mechanical runs; simply, once the panels are cast, those placements are set, literally, in stone. "There's no room for error. You have to be dead-on," says Mike Williams, a custom home builder in Orlando, Fla.
Low- and mid-rise multifamily housing, attached townhomes, and small-scale subdivisions of similarly styled single-family homes are likely to be where precast finds its niche. "If you are building 10 homes on the same block, it makes more sense," says Brian Bock, vice president of sales and marketing for Dukane Precast in Naperville, Ill., a scenario that amortizes the cost of the panels and crane rental across multiple units while significantly shortening cycle time. "There's an economy of scale that can be achieved."
Distribution is arguably the biggest impediment to precast's achieving widespread popularity. More so than any other alternative system discussed here, the system's proliferation is tied to the proximity of the jobsite to a manufacturing plant, typically within a 300-mile radius.
"We franchise our system to local manufacturers with exclusive distribution to control the brand against other building products," says Aaron Schoenberger, director of marketing for Superior Walls, a precast panel manufacturer that targets only foundation applications.
The company's current network of 21 franchised plants supplies builders east of a line extending from Minneapolis to Orlando, a geographic region in which basements are common. A new plant is an investment of up to $3 million, says Schoenberger.
Like SIPs, a direct relationship between a builder and the system's manufacturer is almost requisite given the planning that needs to take place before the panels are cast, a process that can take months instead of the minutes a framer might spend grabbing a few 2x4s on the way to the jobsite. -- BUILDING PRODUCTS
This article originally appeared in ProSales magazine. Maggy Baccinelli and Katy Tomasulo contributed to this report.
| WinterPanel. The company offers SIPs in three panel types: StructureWall, CurtainWall, and PineClad. StructureWall panels, which replace studs and rafters, are twice as strong as a 2x4 wall, according to the manufacturer. CurtainWall panels, ideal for timber-frame or metal-frame buildings, include an interior skin of gypsum for finishing. PineClad panels offer the benefits of StructureWall but with an interior finish of tongue-and-groove pine. Foam cores are available in expanded polystyrene or polyisocyanurate. 802-254-3435. www.winterpanel.com. |  |
 | Arxx Building Products. Lightweight and pre-assembled, Arxx ICFs save builders time and money by providing formwork, framing, insulation, a vapor barrier, and strapping all in one step. The completed walls have a thermal resistance of R-22, the maker says. The product provides an STC rating of up to 50 or higher, is wind resistant up to 150 mph, and has a two- to four-hour UL/ULC fire resistance rating. An exposed X-web allows for a solid-to-solid attachment of finishing material and reduces the likelihood of screw pops, according to the company. 800-293-3210. www.arxxwalls.com. |
| Nudura Corp.Nudura ICFs combine six wall elements—forms, wall structure, insulation, air barrier, vapor barrier, and anchorage—into one system. The company's 8-foot-by-18-foot ICFs are the largest standard form on the market, the maker says, and the completed walls can withstand winds up to 250 mph and provide STC ratings suitable for homes, schools, and apartment buildings. The ICFs feature a hinged folding web for easy handling and efficient storage and a sturdy four-way reversible interlock that allows for interconnectivity for better utilization of cut-off segments. 866-468-6299. www.nudura.com. |  |
 | Reward Wall Systems. The T-form ICF works with the manufacturer's iForm system to make it easier to construct interior demising walls. Eleven inches in overall width, the T-form provides a 6-inch concrete core for both intersecting and longitudinal walls, the company says, and can be used for below- and above-grade applications. It is universal and reversible. 800-468-6344. www.rewardwalls.com. |
| R-Control Building Systems. R-Control FrameGuard Coated SIPs are treated with FrameGuard Coating—comprised of organic fungicides and a borate aprevents mold, mildew, and termite damage to its wood components, says the firm. In addition, the expanded polystyrene core is treated with Perform Guard termite protection. 800-255-0176. www.r-control.com. |  |
 | ECO-Block.ECO-Block ICF expanded polystyrene panels snap together quickly and easily to create walls from 4 inches thick and up in 2-inch increments, the company says. The panels cut into any shape for unique window openings and arches; pre-formed corners also are available. The completed walls can have up to a four-hour Fire Resistive Rating, have an STC rating of 51 for a 6-inch concrete core, and provide an energy savings of up to 50 percent, says the firm. 800-595-0820. www.eco-block.com. |
| Owens Corning.Fold-Form ICFs can be used to build insulated foundations and buildings with concrete walls from 4 inches to 16 inches thick. The finished walls achieve up to an R-23 insulating value, protect against flying debris from winds of up to 250 mph, and have an STC rating of 44 to 47, compared to 36 for traditional framed structures. Fold-Form can be used with the company's WeatherProtectR self-adhesive membrane to create a complete foundation seal, the maker says. 800-438-7465. www.owenscorning.com. |  |
 | Fischer SIPS. The company's SIPs products are manufactured with recyclable materials and utilize 15-year-old trees that are young and renewable. According to the firm, the SIP walls install 30 percent faster than traditional stick framing and lead to homes that are two to three times stronger. Research by the company indicates the product can save homeowners more than 50 percent on energy costs. 800-792-7477. www.fischersips.com. |
| Premier Building Systems.Premier SIPs provide a 55 percent higher whole-wall efficiency versus traditional 2x6, R-19 construction, says the maker, and can help lower the home's energy costs by up to 60 percent. The OSB portion is manufactured with fast-growing species, and FSC-certified OSB is available by request. The OSB and the polystyrene are made with recycled content and are recyclable, according to the manufacturer. 800-275-7086. www.pbssips.com. |  |
 | Insulspan. Consisting of solid one-piece pre-cut SIP units, the Insulspan Structural Insulated Panel System comes ready to assemble as wall, floor, or roof components, reducing construction time and improving efficiency, the company says. According to the firm, the system's roof and wall assemblies offer a 40 percent to 60 percent reduction in heat loss, and significantly reduce air leakage. 800-726-3510. www.insulspan.com. |