Alan Hoffman - Alan Hoffman Company - UCD-Dallas, TX

 Alan Hoffman, owner of Alan Hoffman Company presented to us on July 2, 2011.
Over his 17 years as a "green" home builder in the Dallas area, Alan has developed a composite system of building homes that makes them highly efficient.  His ancestors are from Europe and when visiting there he made note of the massive 3 feet thick perimeter walls of his relative's home.  The thick walls acted as a thermal mass that allowed the interior temperature to be moderated by the average 60 degree ground temperature.  There was a kiva-style fireplace built into a wall that helped warm the house in the winter but no A/C was necessary even though the house was 400 years old.

Alan's design incorporates insulated concrete forms (ICF) exterior shell walls with a conventional wood framed roof that is insulated with open cell foam insulation.  The houses are tornado-resistant, termite-proof with fire-proof wallls.  The thermal mass of the walls in conjuction with the insulating form allows more temperature benefit from the ground on standard slab-on-grade foundations.  Also because the exterior walls are a monolithic structure air infiltration is very low.

He built the first and second LEED homes in Dallas, both of which are LEED-Platinum.
His latest house is 2,656 s.f. requiring only a 2.5 ton HVAC unit.  He incorporates locally quarried stone features into his homes as well.

Alan uses ICF products manufactured by ARXX ICF which has a manufacturing facility near the Dallas area.

His next venture is a 22-home urban infill deveopment in the Lakewood area of Dallas, TX.  The development will include community greenspace that all the homes will face as well as a rainwater harvesting system that will provide irrigation water for the neighborhood xerascapes.



To find out more about Alan Hoffman Company and ICF check out: http://www.concretehomestore.com/

Korwall Industries - Arlington, TX

KORWALL INDUSTRIES

Korwall Industries' manufacturing facility in Arlington, TX

 On July 30th we toured Korwall Industries in Arlington, TX and met one of the founders and owner Mr. Stan Demmick.  Korwall Industries produces Structural Insulated Panel Systems (SIPS) which are an engineered "sandwich" of expanded polystyrene foam between two sheets of oriented strand board (OSB).  The properties of this pressure-bonded panel create a structure known as a monocoque.  Mr. Demmick told us that he got this design idea from the manufacture of airplanes which are built using similar design processes.

Korwall began as a manufacturer of mobile home with paper honeycomb core floor panels and styrofoam core walls.  Even though their product was of much higher quality than the competition they were 30% higher in cost which made it difficult to sell their product.  In 1962 they moved to their current location and began marketing their panels as an alternative to stick-built homes.  Mr. Demmick said, "the lack of studs was mind-boggling to building inspectors" and they frequently had to educate officials about the integrity of their product.

Mr. Stan Demmick explains the history of Korwall Industries



The beauty of SIPS built homes is their air-tightness.  Mr. Demmick explained how a "door blower" air leakage test is done to simulate 15mph winds striking a house from all four sides at the same time.  Standard stick-built construction normally tests at 4 air changes per hour where SIPS construction tests out at 0.5 air changes per hour or a factor of 8 times less.  Because there is less air leakage there is less outside air that has to be conditioned to meet the thermostat setting inside the house.  This allows air handling units to be sized much smaller on SIPS buildings, frequently by half.  Even though SIPS cost about 5% more than conventional stick-built construction, erection time and labor is cut dramatically not to mention the savings in a much smaller HVAC unit for the same size house.  Korwall is also not limited by rainy weather the way conventional home building is because the panels are constructed in a factory not on a jobsite.  Erection of a 2000 s.f. home can be accomplished in about 2 days as opposed to weeks for stick built construction.

Mr. Demmick's grandson adds framing members to a panel

Their panels are currently constructed of a 1# density polystyrene foam core pressure bonded with a catelyzed glue to 7/16" think oriented strand board on both sides. Panels are 8' wide by 24' long in nominal thicknesses of 4", 6" and 8" standard. They will make thicker custom panels up to 10" or 12" for walk-in refrigerators with short spans.  Eight inch thick panels will clear span 16 feet without deflection under a 27 pound per square foot load.



8' x 24' x 8" thick blank panels waiting to be used

The polystyrene foam can be purchased with a 1.5" square groove at 18 inches from one side to correspond with the standard height of electrical outlets.  The groove becomes a wire race once the panels are assembled.  Korwall will install non-standard height outlet boxes and provide raceways in panels as needed.  All electrical outlets and wireways are integrated into the panels at the factor so all the electricians have to do on the jobsite is pull wires and connect terminal devices.

Glue applying machine

Korwall has tried using treated lumber in lieu of standard lumber but the panel strength was reduced by 23%.  SIPS panels are typically used just for the shell of the building (walls and roof) with the interior walls being standard construction and concrete slab on grade floors.  They can be used for floors in pier and beam construction but must be overlayed with a hard surface flooring to avoid puncturing the OSB skin.

Korwall panels carry a limited lifetime warranty.

You can find out more about Korwall here:  http://www.korwall.com/SIPs/PanelHomes/Default.htm