Structural insulated panels SIPs
The principal of sustainable building based on efficiency. The concepts of efficiency are paramount to the understanding the practice of building and the application of choosing framing types based on the most desirable outcomes. Regardless of the external environment the practice of building revolves around the acceptability of the interior environment of the building to the occupants and objects therein contained. The pursuit of constructing energy efficient buildings requires the builder, owner or designer to weigh the options available to them to create a structure that is comfortable, energy efficient, economical to build and acceptable for the environment in which the structure is placed. Energy usage for the heating and cooling the building is the greatest energy cost for a single family home. The fabrication of exterior walls provides an opportunity for lowering energy cost. According to Dan Chiras, “Heating and cooling the interior of our homes consumes the largest portion of residential energy--about 44 percent” (Chiras, 2008). The framing of a wall is most often the simplest type where the minimum insulation allowed by present building codes is utilized. This type of wall structure is of 2 X 6” wood construction with R-22 batt type insulation. Where a building is intended to be of greater operating efficiency there are several methods of fabricating the walls where the R-value of the wall far surpasses the code minimum. Building to a higher insulation level creates savings on heating and cooling cost over the life of the building can offset greater cost of fabrication when compared to the minimum code method. These types of homes are termed Super-insulated homes. Advanced frameing methods for super-insulated homes are growing in number, resulting from new methods being developed and technology aiding in lowering cost. One method which has been under development is The SIPs (structural insulated panel) system. The development of Structural Insulated Panels (SIPs) began over 70 years ago at the United States Forest Products Laboratory in Wisconsin (B Ledford 2010). SIPs is a method where wall panels made with a foam insulation core are fabricated in a regional factory. OSB (oriented strand board) or other material is applied on both faces creating a sandwich. Oriented Strand Board adhered to the foam becomes a structural unit as the sandwich creates a type of I-beam which is stronger than traditional wood framing, as shown in a UK study, than standard framing practice “Walls constructed of SIPs provide superior racking resistance to a comparable traditional stud wall designed to BS 5268 or EC5” (Kermani, Hairstans, 2006. p.1811). It has been a long standing conjecture that this method should save labour costs on site as the time required to erect the system should be less than a traditional 2” X 6” framed wall. “Compared to stick framing, SIPs are faster to erect in the field and also provide more strength to resist most loads; they are better with axial and transverse loads.” (B. Ledford, 2010. p 2). In contrast, anecdotally one author/ architect has noted that in his experience SIPs cost 5-10% more than traditional framing “In my experience, using SIPs usually costs slightly more than stick framing, adding about 5 to 15 percent to the total cost of the home” (D. Wright. p 57). The panels are delivered pre-sized in large sections and erected as a complete section of wall without the need for additional steps for sheathing, insulation and vapor barrier. There is however little direct comparisons which have been made in ease and speed of construction. It is rare that two similar enough structures have been studied side by each. The most notable of direct comparison is an informal study by Habitat for Humanity accomplished through building two structures similar to each other. One of these structures was traditionally framed and the other was framed with SIPs. “Volunteers...
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