Date ant Time: July 30, 2011 8:00am
Tour Guide: Stan Dimmick, President
Korwall Industries, Inc.
Korwall Industries, Inc. is a small business engaged in the manufacture of structural insulated sandwich panels. The company was started in 1962 by Stan Dimmick. Stan mentioned the problems they initially had with inspectors accepting his panel system since they were accustomed to wood stud construction and these panels had no interior structural wood studs. All codes now accept these panels as an alternate building system.
The panels are constructed of One (1) pound density expanded polystyrene sandwiched between two layers of wafer board (oriented strand board) skins. The expanded polystyrene has an R-Factor of 4 per inch giving these panels excellent insulating properties.
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| typical panels |
Homes manufactured with this system can have various roof configurations including hip, gable, gambrel and mansard. This construction system makes for a very tight building having been tested to a negative air pressure of only ½ air change per hour. This compares with conventional home construction at 4 air changes per hour. This results in added energy efficiency. Stan recommends using a good quality insulated window in the building envelope.
The panels are manufactured in dimensions of 8 ft x 24 ft. The thicknesses are nominal dimensions as per conventional construction such that a 4 inch panel is really 3.5 inches. Stan estimates that the panels are 4x stronger than conventional wall studs. In the construction of a building, each panel has its own drawing also showing location of electrical outlets and any necessary penetrations. The joining of the panels are done with one panel having a male wood spline and the adjoining panel having an indentation.
Following are photos showing the procedure for making the panels. You have 45 minutes from the time you lay the catalyst to putting the panels in the press under pressure in order to adhere the skins to the expanded polystyrene.
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| rolles for applying adhesive to the panels |
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| skins are bonded to the polystyrene under pressure |
The structural and insulating properties of these panels make them suited for exterior walls and roof construction. An 8 inch panel used for roof construction can clear span 16 feet with a 27 lb per square foot loading. They are not used for second story floor construction as there is no necessary for an insulating panel inside a conditioned space. Also, ground floor construction is more cost effective using a concrete slab on grade. If panels are used for floor construction they need to be overlaid to prevent puncture. 6 inch panels have been used in the Gulf Coast and are able to withstand 120 mph wind loads. The panels come with a lifetime guarantee. (not including damage from floods or abuse)
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| typical construction using sandwich panels |
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| connection of roof to wall system |
At the present time the wafer boards can be recycled but the expanded polystyrene is used for filler material for packing.
Following is the web page for Korwall Industries:
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