Florida’s weather can be a double-edged sword. Many are drawn to the state’s warm, tropical climate, yet the Sunshine State also can be very hot and muggy and often is barraged by hurricanes. Homes must be built to deal with the challenges this kind of weather can bring.
For the Mattos House in Fort Myers, steel allowed the design and construction team to create a residence that can protect its occupants from dangerous flying debris and insulate them from the sweltering hot, humid temperatures.
When Dan Mattos and his wife found out their home needed a great deal of renovation work, they decided to tear it down and build a new, longer-lasting, energy-efficient home in its place. The 2,500-square-foot (232-m2) new house places the majority of the living spaces on the elevated level with the garage and a few utility spaces on the lower level. The home has simple, elegant lines on the exterior and is full of sunlight provided by windows surrounding the home and the roof’s cupola.
The walls, floor and roof structure of the home are made out of steel structural insulated panels, or SIPs. The 9,032 square feet (839 m2) of SIPs used on the home consist of polystyrene insulation sandwiched between a layer of steel sheet metal on each side. When installed, the panels can withstand a Category 5 hurricane and save up to 50 percent on heating and cooling costs when compared to a similar-sized house built to code. Also engineered to withstand severe hurricanes, the home’s metal roof is attached directly to the SIPs.
A Smart Material
The SIPs used for the Mattos House feature 26-gauge Galvalume steel sheets on both sides of the panels. Galvalume, rather than galvanized steel, was chosen because it is highly resistant to corrosion, has low heat reflectivity and allows the fabricator to provide a 20-year warranty.
SIPs typically are constructed of rigid-foam insulation sandwiched by structural skins of oriented strand board. Other structural skins are integrated to address unique building conditions. The steel structural skin on the panels used for the Mattos House protect the home against flying debris during hurricane weather. The panels pass the structural and water-resistance No. 2 missile-impact criteria test in Florida’s state code.
The polystyrene insulation between the panels of SIPs can be 4-, 6- or 8-inches (102-, 152- or 203-mm) wide with approximate R-values of R-17, R-25 and R-34, respectively. In the case of the Mattos House, the wall and roof panels are 6-inches (152-mm) wide and the floor is 8-inches (203-mm) wide. According to the Gig Harbor, Wash.-based Structural Insulated Panel Association, polystyrene insulation is composed of 98 percent air and a non-chlorofluorocarbon blowing agent that takes only a small amount of petroleum to manufacture.
A SIP is similar in structure to a steel I-beam. The skin material acts like the flange of the I-beam and the rigid-foam core acts like the web. A SIP can therefore handle in-plane compression loads, which is why the panels are ideal for floor and roof applications. Because they save on structural materials and are pre-manufactured offsite, SIPs bring efficiency to a project. As little as 1 percent of steel is wasted at the factory when manufacturing the steel SIPs. Although there are varying amounts of recycled content in all steel products, most Galvalume products contain approximately 60 percent recycled content. The panels are manufactured based on finalized contract document drawings and then are shipped to the site along with detailed installation instructions and shop drawings.
During installation, the SIPs’ seams are welded with a special mastic adhesive, then caulked and re-insulated with non-expanding foam insulation. Before the final finishes are applied, each textured Galvalume sheet is coated with a white polyester paint to further protect the steel.
Because the steel SIPs are utility panels, finish materials are required for each surface. Typically, a 3/4-inch (19-mm) plywood substrate is attached to the floor system before the final finish materials are applied. Hat channels are attached to the interior surface of the wall panels at 16-inch (406-mm) intervals to give a nailing surface for drywall and provide an electrical chase for the exterior walls. Plumbing is diverted to interior walls exclusively. The exterior wall panels of the Mattos House are covered with cement lab-board siding on the top part of the home with masonry stucco on the lower level.
Rollformed Roof
Fort Myers-based Crowther Roofing & Sheet Metal of Florida Inc., installed a standing-seam, snap-lock Galvalume roof onto the Mattos House. The 24-gauge panels are 17-inches (432-mm) wide and have 1-inch- (25-mm-) tall seams. The panels were rollformed on the job site. “Having a rollformer on-site allows us to fabricate each panel to fit from the ridge to the eave, eliminating lap joints,” says Ruben Ponce, project manager with Crowther Roofing & Sheet Metal of Florida.
“Rollformers are more commonly found on roofing project sites now because the machinery technology has improved,” Ponce continues. “Having a rollformer on-site is helpful if we need to replace a panel immediately.” On-site rollforming also reduces labor and scrap material waste. Waste is reduced because panels are run to the exact length needed to fit the dimension from eave to ridge. Labor also is reduced because loading and unloading of truck materials is diverted and lap joints are limited to hips, valleys and gable ends.
If the panels are pre-manufactured and delivered to the site, the maximum panel length is 60 feet (18 m). “Having a rollformer on-site allows you to run extremely large panels,” Ponce explains. “We’ve run panels up to 120-feet [37-m] long by placing the rollformer directly on the roof. This eliminates the use of cranes to fly the panels to the roof.”
The metal roof panels were attached directly to the SIP roof deck. First, an asphalt primer was applied to the SIP deck to protect against water leakage. A peel-and-stick underlayment was rolled over the primer. Galvanized clips were screwed into the insulated deck and the metal panels were attached directly onto the clips. “We engineered the clip fastening pattern to handle a 130-mph [58-m/s] wind load. The closer the spacing between the clips, the higher the uplift loads the metal roof can handle,” Ponce says.
The Mattos House represents safety and efficiency in construction. The home’s steel SIPs protect it from hurricane weather, exorbitant utility bills and unhealthy indoor air quality based on reduced air infiltration. The SIPs and metal roof were constructed efficiently in a condensed construction schedule with reduced waste on-site. Lastly, the Mattos House is a simple, smart home built with reduced construction costs appropriate for the challenges posed by the troubled economy and Florida’s challenging tropical climate.
Stephanie Aurora Lewis writes about architecture and metal construction from Columbus, Ohio.