Q: What is a SIP?
SIP stands for Structural Insulated Panel. SIPs are high-performance building panels for floors, walls and roofs for residential buildings. Each panel is typically made using expanded polystyrene (EPS) rigid foam insulation sandwiched between two structural skins of metal or aluminum. The result is a building system that is very strong, predictable, energy efficient, and cost effective. When installed in a home, the SIP provides both structure and insulation. While most commonly used in walls, SIPs can also serve as load-bearing floor, ceiling and even foundation components. SIPS are designed to carry the entire range of structural loads in a building.
Q: What gives a SIP its strength?
The resulting sandwich panel product acts like an engineered I-beam, resisting both compressive forces from above and buckling forces from the side. Engineering tests show that, depending on the type of structural test being administered, SIPs range between two and seven times stronger than traditional framing. In some SIPs, integral studs used as splines for joining panels together also help carry the structural load. SIP manufacturers make their panels to meet code requirements and are listed with the National Evaluation Service, Inc. (NES) or the International Conference of Building Officials (ICBO). These reports have load design charts showing allowable loads for given sizes of structural insulated panels.
Q: Will SIP/Steel construction hold up to nature's forces?
YES! SIP/Steel framing is stronger than conventional construction. Our homes are designed to meet the newest hurricane requirements and can meet as high as 140 MPH wind loads if necessary.
Q: Are the high efficiency claims valid?
Four key factors make the average SIP home very energy efficient. First, foam provides higher insulating value per inch than traditional fiberglass insulation. Second, there is much less wood framing within the typical panel, which again increases total R-value. Third, the foam is continuous and is not susceptible to the commonplace flaws found in average batt installations. Fourth, foam doesn't allow air infiltration around it; with reasonable attention to detail, panel joints can be sealed to provide house tightness that averages between 20% and 40% (for house with wall and ceiling panels). You can slash energy costs by up to 58%. Because SIPs create a tighter building envelope than conventional insulation, you can actually reduce the size of heating and cooling equipment. That reduces costs immediately. Better yet, SIPs keep your costs down from season to season, year after year, for as long as you own your home.
Q: Does the foam lose R-value over time?
The R-value of a SIP varies depending on the thickness and type of foam core used. According to a study by Oak Ridge National Laboratory, the "whole-wall" R-value of a wall with a 3-1/2" EPS core is 28 compared to 9.8 for a 2"x 4" wood framed wall insulated with R-11 fiberglass insulation. When the performance of the whole wall system is considered, SIPs perform better than traditional systems because they are manufactured in a controlled environment characterized by uniform fabrication of components without gaps or air pockets. They are also designed for efficient field installation that reduces air infiltration, and there are few thermal breaks or penetrations in the panels that are typical of wood frame construction. T he R-value of a fully cured urethane panel is about twice that of a fiberglass wall. Expanded polystyrene insulation (EPS) used in most panels offers R-value of about R-8 per inch and maintains its R-value once the panel arrives at the job site.
Q: How do you wire SIP houses?
Wiring a SIP house takes a little extra planning prior to construction. Nearly all panels come with some type of pre-cored chases in the foam. You simply fish the wire through those chases to where the wire is needed.
Q: What about Lightning?
A steel framed home is actually safer than a wood home. The steel is a ground to lightning and in the event of a strike, it is non-combustible, reducing the risk for fire.
Q: What about SIPs in fires?
To the surprise of some building researchers, data from extensive laboratory fire testing as well as reports from house fires indicates that SIP structures tend to be more resistant to house fires than standard wood-frame structures. Fire requires three components: fuel, ignition, and oxygen. SIPs have no "air" within their solid cores of insulation. The fire cannot "run up the wall" cavity. The SIP panel Truly Hybrid Homes uses are certified fire proof.
Q: Bottom line, are SIP houses better?
Assuming the SIPS are properly designed, manufactured and installed, a SIP house will be stronger, more energy-efficient, and more comfortable.