Structural Insulated Panels (SIPs) – An Explanation
If they have ever heard of structural insulated panels (SIPs), most people consider them to be one of the most advanced recent developments in home construction. It comes as a surprise, then, to learn that they were actually developed in the 1930s. Originally conceived by the U.S. Forestry Service, the concept was taken up by the University of Wisconsin which built the first SIP house in 1937. The dedication of this small home was actually done by the First Lady at the time, Eleanor Roosevelt! To those who object to the use of SIPs on their home with a comment like “let’s wait and see how they perform in the real world over time,” we can confidently ask if 80 years is sufficient.
Today, there are hundreds of manufacturing facilities producing SIPs in the U.S. and Canada alone. In terms of the basics, they all make a similar product – a foam core fastened between two skins. There are 3 materials commonly used in the core: expanded polystyrene (EPS) which is the most common, extruded polystyrene (XPS) and polyurethane (PU) which is sometimes actually a chemical cousin named polyisocyanurate. And like the SIP cores, there are also multiple skin materials with Oriented Strand Board (OSB) being the most common (various metals and cementatious products can also be available).
SIPs may be purchased in various sizes and thicknesses as well. Four feet by eight feet is the most common but many manufacturers offer a standard 4 foot width with lengths up to 24 feet to reduce seams in a structure. Additionally, some manufacturers offer a pre-cutting service where all dimensions, angles, and window and door openings are factory cut to minimize construction time in the field. Likewise, multiple thicknesses are offered both for energy efficiency (R-value) and strength considerations. Common thicknesses offered are: 4 ½”, 6 ½”, 8 ¼”, 10 ¼”, and 12 ¼” with R-values ranging from R-16 to R-57.
The use of SIPs as a building technology has increased steadily over the last few decades because, although the material cost may be higher, the benefits of their use are many. Two of the most significant benefits involve reduced labor costs and reduced energy usage:
- Construction efficiency – one BASF study conducted by the RS Means unit of Reed Construction Data shows that residential builders can reduce their framing labor needs by as much as 55 percent by using structural insulated panels (SIPs) instead of conventional “stick-building” methods.
- A SIP structure is demonstrably tighter than a conventional “stick-built” structure – one test at the Oakridge National Laboratories found that a SIP structure is actually 15 times tighter than a conventionally built structure resulting in 50-70% less energy requirements for heating and cooling.
- SIP homes qualify for ENERGY STAR certification without having to undergo a blower door test to measure the air infiltration because SIP homes have a proven track record of exceptional blower door test results.
In addition, there are many “softer” benefits to the builder:
Straighter walls and roof lines making finishing material installation much easier, faster, and resulting in a higher-quality end-product.
- Reduced callbacks for nail-popping and cracks normally caused by lumber shrinkage.
- Less or no temporary heat required when building in colder climates.
Woodhouse uses only Murus™ brand SIPs. Murus was started in 1987 by the founder of Woodhouse, Steve Keller. By that time, Woodhouse had been using SIPs to enclose their timber frame structures for seven years and Steve was unhappy with the overall quality he was receiving from third-party vendors. His vision for Murus was the creation of a state-of-the-art manufacturing facility producing the highest quality SIP available on the market. We believe that Murus fulfills this vision. Their superiority is multifaceted:
Murus produces the only true polyurethane SIP on the market today. Other manufacturers of “polyurethane” SIPs are actually producing a core made from a chemical cousin called polyisocyanurate. The difference between the two is important as the cellular structure of polyurethane is imminently stronger resulting in a more stable and consistent insulating medium.
- Murus produces the only SIP available on the market today with their patented cam-lock installation system which results in a 30% installation labor savings compared to all other SIPs.
- Murus produces their polyurethane SIPs utilizing a proprietary manufacturing process called “Uniform Dispersement Molding” or UDM. This manufacturing technology produces a demonstrably more consistent insulating core than other molded or laminated SIP manufacturing processes.
- When assembling EPS or XPS panels, Murus employs a highly rigid manufacturing system in conjunction with state-of-the-art polyurethane adhesives to ensure that the core adequately adheres to the skins and they stand behind the result with a lifetime warranty for delamination.
- Murus has the largest and one of the very few CNC pre-cutting machines in the SIP industry allowing for very accurate precut packages resulting in far fewer field adjustments.
- Our findings indicate that Murus is the most cost-competitive SIP manufacturer in the market.
Woodhouse encloses every one of our timber frame homes and commercial structures in a Murus SIP enclosure system because we believe that a SIP enclosure system is the highest value system we can provide to our customers. A precut SIP enclosure system reduces package erection labor and results in the highest energy efficient structure available in current building technology. We specify Murus because, again, we believe that their SIP product delivers the highest value to our customers due to its design and product quality superiority combined with a high degree of cost competitiveness.
Should you have any further questions about Woodhouse use of Murus brand structural insulated panels above, please call us at 800-227-4311.