Renewable energy from the sun can provide building heat and power needs through solar electric and solar thermal technology using the sun to directly generate electricity with rooftop-mounted photovoltaic cells or by using the sun to heat domestic hot water — all with standing seam metal roofing. This meets the requirements of LEED Energy and Atmosphere Credit 2 (Renewable Energy), which incrementally awards up to three points for generating 5 percent, 10 percent, or 20 percent of the building’s energy use with renewable power.
These building-integrated photovoltaics provide increased value by simultaneously serving two purposes: power generation and architectural function.
Using solar energy to heat domestic hot water is more commonly implemented on residential buildings but because of rising conventional fuel costs and because of its relatively short payback, solar water heating is increasingly seen as a means of offsetting the cost and difficulty of generating grid-based energy.
However, because the efficiency gains created by solar thermal technology do not in fact generate power, they are not considered part of the Credit 2 renewable category, but are instead captured by LEED Energy Credit 1.
Most architects recognize the value of solar technologies but have been leery of the aesthetics of highly visible collectors mounted on roofs. While solar power historically has been synonymous with environmental consciousness, traditional types of solar systems have been avoided because of their unattractive design.
Either the technology was cumbersome and expensive to install or there simply was not very much interest among builders and homeowners to use solar despite a myriad of local, state, and federal development and tax incentives around the country.
That picture may be changing. New photovoltaic and solar thermal technologies are emerging that are much simpler to install and have been designed to work specifically with standing seam metal roofing. Recent breakthroughs in PV design and thermal technology have produced materials that are attractive, effective, and virtually invisible to the naked eye.
Even some of the older crystalline PV technologies that required the installation of box-like crystalline arrays are changing. A chief concern was how the photovoltaic modules could be attached to metal roof systems without jeopardizing material and weathertightness warranties. One answer is a novel clamping technology, called S-5! for standing seam metal roofing. The attachment clamp and its attendant round-point setscrews enable the entire installation without a single penetration through the surface of the metal roof, even with thousands of individual attachment points.
But the newest photovoltaic material is an extremely lightweight and unbreakable self-adhesive laminate material less than a quarter-inch thick that is attached to standing seam panels with a hand roller. They are made exceptionally durable by encapsulation in UV stabilized polymers. The polymer encapsulation is partially constructed of durable ETFE. The material is bonded to conventional standing seam roofing panels for use on any south facing roof with good solar access or to structural standing seam panels for shops, barns, and sheds. The laminates can be attached before or after the standing seam panel has been installed and in many cases, provides all the electricity a building needs.
The newest solar thermal collection system is comprised of a 1-inch thick conductor that employs glycol protected fluids to collect and transfer solar energy to building systems using closed loop heat exchange technology. The system is concealed under the standing seam metal roof laminated with the amorphous silicon PV system. Upon completion, the solar thermal system becomes an integral part of a hardened building envelope that provides storm resistance, energy security, and lower operating costs by replacing fossil fuels and electricity with solar energy.
Because they are fully integrated, they reduce cooling loads on buildings and can directly contribute to process and space cooling by dissipating excess heat through radiational cooling.
Building owners can realize immediate benefits from the reliability and operational simplicity of these modern integrated mechanical systems.
Another reason why the integration is occurring rests with the individuals who are installing it. Architects who espouse rooftop photovoltaics for environmental reasons and to gain lucrative tax and building incentives are finding roofing and electrical contractors who will install the rooftop installations quickly and efficiently. They are realizing the need for both to work together not only for installation reasons but to be able to offer commercial and residential building customers metal roofing and solar warranties at the same time. Architects interested in solar would do well to find the major electrical and roofing contractors doing solar installations in their markets. They are generally the first installers you would talk to once a building has been specified with photovoltaics on a metal roof. In some cases the manufacturer will also provide installation.
Many architects and builders active in the U.S. Green Building Council program already know that buildings with standing seam “cool” roof material can generate seven LEED credits for heat transfer, reuse, and recyclability — a major step in accumulating enough points to earn government and public utility financial incentives for a project.
But metal roofing can also be a major stepping-stone to several other LEED credits, in the category that PV and thermal energy roofing materials apply to — Energy and Atmosphere-Credit 2 — Renewable Energy. There are up to three points awarded for this category, based on the amount of renewable energy the building produces. The requirements are to supply at least 5 percent (one point), 10 percent (two points), or 20 percent (three points) of the building’s total energy use through on-site renewable energy systems. Another possible credit category is Energy and Atmosphere-Credit 1 — Optimize Energy Efficiency. There are up to 10 points awarded in this category, based on percentages of energy cost reductions. For example, a 60 percent reduction will earn the maximum 10 points and is likely attainable with use of a metal roofing system with an integrated photovoltaic system. The project team gains a credit for successfully demonstrating energy cost savings of 10.5 percent and one point for each additional 3.5 percent of savings.
Sophisticated computer modeling tools utilizing computational fluid dynamics (CFD) calculations help designers reduce uncertainty and unpredictability in using these strategies to complement or replace forced air ventilation, qualify for LEED credits, and for tax incentives and rebates.
In effect, before a building project can be considered for LEED certification, the project team first must show the building and its systems meet the energy standard’s compulsory conditions for compliance. The team also must prove compliance with whichever criteria is most rigorous; cost savings are determined by comparing the performance of the proposed building design with that of the baseline design, which meets specific prescriptive requirements
The amount of electricity produced by a PV system is based primarily on the size of the system, but the output of the array will depend on climate and geographic orientation, amount of sunlight available at the location, the slope of the roof, its orientation with respect to due south, and other considerations not affecting the system itself include local utility rates, tax credits, and maintenance.
Typically, the energy payback time for PV systems is five to 10 years. For this reason, integration with a metal roof becomes a critical factor. Given that a well-designed and maintained PV system will operate for more than 20 years, it is almost natural they would be combined with standing seam metal roofing systems that offer the same kinds of longevity, often backed by warranties. Unlike other forms of roofing material that must be replaced in 20 years or less, metal and PV will often operate for close to 30 years, producing far more energy over their lives than was ever used in their manufacture. Unlike sheet-membrane roofs that may require replacement before the usable life of the PV expires, the standing seam metal roof has a life expectancy consistent with that of the crystalline modules, laminates, and the solar thermal system. Homeowners won’t be forced to dissemble the entire system when a shingled or flat roof begins to deteriorate several years after installation. PV system reliability and durability are outstanding — typical PV systems may last 30 years with minimal maintenance.
And there are also many grants and tax credits that come with the installation of PV and standing seam systems.
For example, net-metering states require utilities to buy back any surplus power generated on-site. In New York, the Green Building Tax Credit for business and personal income taxpayers provides a 100 percent photovoltaic for the incremental cost of building-integrated photovoltaic systems or 25 percent of the incremental cost of non-BIPV units and California offers a 7.5 percent credit against the cost of an installed solar energy system. Many more states, and the federal government, offer incentives and grants as well.
More than 20 states provide tax incentives in support of renewable technologies. Eighteen states have public benefits programs that have active energy efficiency and renewable energy programs.
The opportunity for architects to introduce new rooftop energy saving technologies and expand their business is unquestionably there. And while it may not represent the bread and butter of their business, it is an area of growth worth investigating.
Kevin Corcoran, vice president of business development at Englert, is a 27-year veteran of the metal roofing industry and has been responsible for introducing scores of metal roofing products and programs to builders and architects during his career.
Gene Johnson is a chemist and manager of quality, safety, and environment at Englert. He has more than 30 years of experience in developing and analyzing metal roofing materials and their coatings for residential and commercial building applications.