I love new technology, especially when it means that I get new stuff in my materials library. The last couple of years, one of the hottest new technologies for modular construction has been SIP panels. So, this prompted a little investigation to find out what are the benefits and ideal uses for this wondrous material. Here goes:
First, what is a SIP?
typical SIP wall
Well, Wikipedia tells us that a SIP (Structural Insulated Panel) is “a composite building material. They consist of an insulating layer of rigid polymer foam sandwiched between two layers of structural board. The board can be sheet metal, plywood, cement or oriented strand board (OSB) and the foam either expanded polystyrene foam (EPS), extruded polystyrene foam (XPS) or polyurethane foam.
SIPs share the same structural properties as an I-beam or I-column. The rigid insulation core of the SIP acts as a web, while the OSB sheathing exhibits the same properties as the flanges. SIPs combine several components of conventional building, such as studs and joists, insulation, vapor barrier and air barrier. They can be used for many different applications, such as exterior wall, roof, floor and foundation systems.” – thank you Wikipedia.
Further investigation into SIP technology will tell you that this is not really a “new” material. Investigation into these types of stress-skinned panels for construction began back in the 1930’s but didn’t gain much attention until the 1970’s. What I find interesting about that is, according to wikipedia, research into stress skinned panel construction began by Forest Products Laboratory as a way to conserve forest resources way back in the early1930s and yet here we are some 90 years later still relying mostly on stick frame construction for our homes and even light commercial buildings.
The modern structural insulated panel got it’s start in the 1940’s after it was determined that the stress skinned panels could be designed to take on all of the structural load rather than just a portion. Various types were developed, some with plywood or hardboard, and even treated paperboard but this was not suitable to outdoor exposure. In the 1960s polystyrene cores were used and have remained in use even today.
SIP wall and roof intersection
Why you should care.
As the process of manufacturing SIP technology continues to improve, I begin to wonder more and more why this modular material is not used more often? Obviously cost is the gut reaction item that comes to mind. But not when you compare a typical stick frame wall of R-19 with a SIP wall of the same value. A SIP wall, being what it is, has almost no thermal bridging, whereas a stick framed wall has thermal bridging every 16″ o.c. This significantly effects the total performance of the wall and even effects your HVAC system design, thus costing more money. But even still, why would any homeowner trade such an increase in performance and time (construction time that is) for what is arguably a minimal savings in overall construction cost?
The answer almost always comes down to ignorance – clients/homeowners simply are not aware of the real benefits and savings of various “high tech” materials over conventional stick framing. BUT, there is a second and more important answer here. And it’s a problem that I’ve talked about quite a bit – Architects do not advocate as they should for increased building performance when faced with budget issues. Compounding this problem is the contractor trying to save a buck wherever possible to increase project profit.
Architects, being constantly at a disadvantage when it comes to advocacy and education, are nonetheless the last line of defense for our clients to ensure that the building they get will not just respect an arbitrary construction budget, but will also perform to a higher quality standard. Products like SIPs, ICF, Insulated Metal Panels, AAC walls, and others are available to help architects and contractors create more efficient and, hopefully, more beautiful buildings that perform to a higher standard saving precious energy and money. Architecture is about more than initial cost. A building must perform as efficiently as it was built.