Whirlwind Solar, a Division of Whirlwind Steel Buildings, Inc., in conjunction with Corey Saft, an Architecture Professor at University of Louisiana at Lafayette, has completed the first application of Solar Laminates on a certified ‘Passive House’ home.
“He’s blazing a trail,” said Keihly Moore, with the Illinois-based Passive House Institute US. According to Moore, the house is the first of its kind in the South.
The use of solar photovoltaics, in conjunction with Passive House design criteria calling for a 90% reduction in energy usage over traditional homes built to current codes, makes the project a viable zero-energy prototype for the extreme conditions in the hot and humid South, and just about anywhere else.
Following the general Passive House strategy, the home is super-insulated and extremely well sealed, making the construction act like a thermos to preserve the conditioned air inside, whether cooled or heated. Combining the super-insulating and superior sealing with the efficiency of Whirlwind's solar laminate panels turned the dwelling into a zero energy consumer in its first month of operation.
The systems in the house are all standard and readily available. It is their integration into a whole house design strategy that makes the final product so efficient and unique. The primary HVAC system is based on a 1-ton mini-split air-conditioning system and the Ultimate Air RecoupAerator Energy Recovery Ventilator (ERV). With 95% energy recovery, MERV 12 filtration and dehumidification, the ERV is the black box of the system. Saft’s design also uses an air-to-water heat pump to supplement cooling and dehumidification, and to provide hot water.
The home’s walls are much thicker than normal and play a different role in reducing the energy bill. The walls feature wood studs assembled on 24”centers and laid out using advanced framing techniques. Half of the house’s studs are 2 x 6 but the double-height space utilizes heftier 2 x 8s. Inside the home, the added mass of the concrete counters, tile and extra thick drywall is used to store the cool in the summer and the warm in the winter. The spaces between the studs are filled with open-cell spray foam for an extra air seal and the whole house is then wrapped with 1” of polyisocyanurate insulation to eliminate thermal breaks. There is then a radiant barrier and an air space that is used to back-ventilate the final exterior skin of fiber-cement siding. This rain-screen system also acts as a whole house sun-shading device, ridding the building of much of the heat even before it gets to the insulated walls.
In addition to its energy efficient qualities, the home is designed for comfort. It incorporates a modern, open floor plan that boasts a 16’ double-height space. The kitchen, the mezzanine and the stairs hanging off of it create a dynamic spatial experience. Feeding the large open volume is a 12’ bank of north-facing clerestory windows that fill almost the whole home with artist-quality natural light. When artificial light is required in the evening, there is a mixture of LED and CFL lights to keep the energy draw to a minimum and allow the small solar array to balance all its needs.
The house was an experiment on many fronts. As well as being the first home anywhere in the South to meet the stringent energy requirements of the Passive House standard, it is also designed to be a cost effective urban prototype. With a footprint of less than 800 sq ft and a total livable square footage of 1200 sq ft, it is a 3 bedroom 2 bath designed for great density. Its long, thin and tall form allows it to be easily converted to a row house or flats above a commercial base on any downtown street. The rich spatial and experiential qualities could easily be maintained in any dense urban situation while the energy requirements would be reduced because of the shared party-walls and reduced number of exterior walls. With these efficiencies and a larger roof area to strategically group the solar array, the project could easily be used to create a net-energy-producing urban block.
The project’s construction was a collaborative effort between Saft and Jaron Young, one of his former students. Young's company, H.J. Construction, oversaw the building process and also understood it as a unique experiment. Beyond Passive House certification, the home is in the final stages of attaining the first LEED platinum rating in Acadiana from the U.S. Green Building Council.
One of the main difficulties in building homes like Saft’s is financing. The appraisal that the underwriting of a traditional construction loan requires rarely takes into account any of the innovative construction. Without them factored in, homes of this nature wind up being substantially undervalued. This, notes Saft, is probably the most significant impediment to a large-scale transformation of the nation’s building stock.
The solar array, which is laminated to the Whirlwind Weather Snap metal system, is sized at 3.264 kW. The solar laminate system enabled some of Corey Saft's students to more fully understand photovoltaic's and at the same time be involved with some cutting edge technology.
The “Made in USA” BIPV system is manufactured by United Solar Ovonic LLC, based Rochester Hills, MI, and is sold through their authorized distributor, Whirlwind Solar, a division of Whirlwind Steel Buildings, Inc., headquartered in Houston, TX.
The Solar laminate system is comprised of approximately 24 photovoltaic laminates each 16” wide and 18’ - 0" long, and approximately ¼” thick. Each panel fits between the ridges of the building’s standing seam metal roofing system and face south for maximum efficiency. The solar laminate technology is lightweight (less than one pound per square foot). The combined weight of the panels is approximately 576 lbs. and covers an area of approximately 576 SF. The solar laminate technology is better at capturing off-angle light than traditional crystalline solar panels. Therefore, the photovoltaic laminate array does not need to be at the perfect Tilt Angle (Slope) or Azimuth Angle (perfectly oriented South) to create a great deal of electricity. The solar laminate utilizes unique triple-junction amorphous silicon solar cells, where the blue, green and red light of the sun is absorbed in different layers of the cell. This technology results in better performance in low and diffuse light conditions. Solar Laminates demonstrate superior energy production in high temperatures, low light levels, cloudy conditions, and shading.
The use of a thin-film system translated into cost savings for Saft, as the heavier crystalline panels wouldn't added 3 to 6 lbs. Per square foot to the structure when framing is factored in. And depending on installation methods, mounting the panels requires penetrations through the roof which compromise the integrity of the roof system.