Solar Panels /Tiles
Innovation and Structural Considerations
With the increasing implementation of green-building practices, concepts from the past have been resurrected and are being presented as advancements within the residential construction industry.
ADVANCE FRAMING/ OPTIMUM VALUE ENGINEERING
In our recent column, we discussed "Advanced Framing/Optimum Value Engineering," and presented an overview of advanced framing, which was developed in the 1970s by NAHB and HUD and referred to a variety of techniques designed to reduce the amount of lumber used (reducing structural redundancies) and waste generated in the construction of wood-framed houses. In addition, it also improved energy efficiency and acoustical performance.
SOLAR PANELS
In addition to the above efficiencies achieved through advanced framing for residential construction, the evolution of solar panels has progressed immensely since the 1970s with the implementation of a combination of revolutionary materials to drive efficiencies from below 10% to the high teens. For example, an individual 32"x62" SunPower 215 solar panel produces 215 watts at 17.3% efficiency. SunPower gains greater efficiencies from their panels partially because the electrical contacts are placed on the back of the solar cells, which also results in a better-looking panel compared to the conventional silvery-blue solar panels with which most of us are familiar.
Current solar panel systems have been refined to "stand off" current roofing material with sufficient attachment to withstand wind uplift loads, as well as to provide adequate ventilation below the panel for maintenance purposes.
Since solar panels are typically installed postconstruction, the additional 2.4 lbs./ square foot beyond the existing roofing material weight may warrant evaluation of the current roof structure (stick framed or trusses) for its ability to vertically support the added assembly. Also, the added panel weight may increase the seismic lateral loads at the roof level sufficiently enough to exceed the existing shearwall panel capacities and/or wind loads (solar panels will act as hydrofoils upon pitch roofs), creating uplift connection and framing concerns. Thus, within high wind or seismic regions, having a structural review and implementing recommendations by an engineer may be prudent.
SOLAR TILES
Recent advancements in technology over the past decade have brought about the introduction/improvement of solar roof tiles, which have been integrated into new residential home construction utilizing flat or S-Tile concrete roofing material.
Solar tiles have been recently accepted by home buyers without reservations and have even provided bragging rights for homeowners to their friends and colleagues. But who wouldn't be bragging about being ecologically friendly as their SunTile roof converts up to 22% of available sunlight into electricity!
Since the solar tile material (5 lbs./ square foot) is installed during new construction, the originally prescribed concrete tile roofing material (7.5 to 9 lbs./square foot) is substituted with the solar tile (SunPower SunTile) without any structural ramifications.
COMMERCIAL APPLICATIONS
Solar panels are rapidly appearing within new retail construction as well as existing retail buildings, which are being structurally evaluated/rehabilitated to accept rooftop-mounted solar panel arrays and associated equipment, such as control panels/converters.
The electricity produced utilizing the rooftop-mounted solar arrays are easily powering the interior store lights for thousands of Big Box stores (like Macys, Lowe's, Target, Wal-Mart). Can you imagine the number of solar panels you can get on a 50,000-square-foot box store?
SUMMARY
Solar energy is present every day (OK, unless you are in Alaska … which experiences variances of almost 24-hour daylight to 24-hour night).
We have millions (more like hundreds of millions) of square feet of retail rooftops and billions of square feet of residential rooftops in the U.S., which all see the light of the sun. Our task is to effectively capture this energy resource consistently with solar tiles and rooftop-mounted solar panels while folding it into current designs (architectural and structural) that enables the installation of "optional (solar) equipment."
June 2008 Builder Architect Edition Issue
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