War of the Worlds – The Exploding Sun – Part 2

In my previous post we discussed the most common type of solar module utilized today, crystalline silicon panels, which are encapsulated in glass. Another type of rooftop power generation that produces electric energy is Concentrated Solar Power, or CSP. CSP uses lenses or mirrors to concentrate solar thermal energy onto a small area such as a tower. Typically, the mirrors are positioned on the roof to reflect sunlight to the tower mounted on the ground at one end of the building. The tower houses an engine (usually steam), to drive an electric generator.

CSP requires very clear skies to work most effectively, and steam generation requires a fair amount of water which can be an issue in hot, dry climates. Compared to PV, more maintenance may be necessary due to the moving parts in trackers and generators. But focusing the sun in this way also has several advantages.

First, less space is required for the collection units; so less land or rooftop space is required. The cost per watt for CSP is currently par with PV, but has the potential to be half that of PV. CSP steam generators produce AC power so they can integrate directly into existing infrastructure without power inverters. With natural gas back-up or molten salt heat storage systems, CSP has the potential to operate continuously in the event of extended periods of cloudiness or shading of part of the array. CSP is projected to have a larger share of solar power generation within 10 to 15 years due to its efficiencies and potential reduction in cost (and by extension – the ability to generate power more cost effectively) due to technological advancements.

War of the Worlds – The Exploding Sun – Part 1


The invasion Orson Wells described so vividly on the radio October 30, 1938, was only sensational because of its time and place in history. What did Wells know about future events that we don’t know? Maybe he foresaw last year’s supernova or exploding star (it was best seen between the big and little dippers September 7-9, 2011), or the growth of solar power generation (photovoltaics = PV) or the implosion of Solyndra. Maybe he foresaw the green movement (little “green” men).

Now that I’ve got your attention, what does this have to do with today’s topic? Other than to introduce a discussion on the power of the sun, not much. Over the next two posts I will discuss photovoltaics (PV), a.k.a. solar power, its history, and the types available.

The most common type of solar module utilized today, crystalline silicon panels, are encapsulated in glass. They make up about 95% of all PV systems installed. Monocrystalline cells invented by Bell Labs in 1954 were cut as wafers from specially grown cylindrical silicon crystals. They are still among the most efficient PV systems, but they have poor tolerance for low light, are fragile and, very expensive, and require very heavy frames for rooftop mounting.

Polycrystalline cells are made from multiple sources and are not as dependent on perfect crystal growth. They are less expensive than monocrystallines, extremely fragile, and less efficient at converting sunlight to electricity.

While some crystalline manufacturers claim higher levels, typical silicone-based PVs have power production between 12 and 18 watts per square foot and operate with 14-20% efficiency. High temperature and shade reduce their output.

Thin-film PV systems don’t use crystalline silicon, but very thin layers of materials such as amorphous silicon, a mixture of copper-indium-gallium-diselenide (CIGS), or cadmium telluride. They can be flexible or rigid and can be adhered to a roof covering or rigid material.

First generation thin-films are mounted on a glass substrate and are relatively inexpensive to produce, but they are about 50% less efficient than monocrystallines. A heavy support frame is required and there have been issues with longevity and durability.

Second generation thin-films are mounted on a flexible substrate. They also do not require crystalline silicon and are easier to manufacture than first generation thin-films at the same cost. There is no requirement for special framing or support structures because they are much lighter than other PV systems. These thin-films are rugged and can often be integrated with modern roofing membranes after they are installed.

Because thin-films are typically surface-mounted, heat gain is an issue and these systems can compromise the benefits of reflective roof systems. Thin-film systems have power production of 5 to 10 watts per square foot and operate with 6-12% efficiency. Compared to crystalline silicon systems, thin-films are more effective in low light situations and are less affected by high temperatures.

In the concluding post I will introduce another type of rooftop power generation that produces electricity from the sun: Concentrated Solar Power, or CSP.

Why Photovoltaic? Why Now?

Photovoltaic (PV) systems have been around for a while now, but the growth of rooftop PV installations has increased dramatically over the past few years. What is causing this surge?

There are many reasons PV systems make sense now and for the future. Energy costs will continue to escalate, and supply will continue to be chased by demand. Expanding the use of renewable energy sources such as PV can help meet some of the demand and relieve some of the cost pressures on electricity.

Rooftops are a good place to locate PV systems because they are typically little used and are free from obstructions that can hamper PV performance. Utilizing rooftops can also reduce land use, making it available for other purposes, or simply as green space.

PV is a clean, unobtrusive energy source, meaning that it does not pollute while it produces energy; eliminating the environmental issues associated with many other forms of electricity generation. The question arises as to whether the net benefits from PV electrical generation outweigh the monetary and environmental costs associated with production, installation, and disposal of a PV system. That analysis has not been done, but it could prove interesting.

Incentives from federal, state, and local governments and from utility companies can ease the financial burden of an investment in PV, plus encourage its introduction and the development of more cost competitive PV technologies. A good source of information on incentives is the Database of State Incentives for Renewables and Efficiency at www.dsireusa.org.

Increased use of PV can help reduce some dependence on foreign sources of fuel, leading to less potential for hardship due to supply disruptions.


While improving energy efficiency in buildings is essential (by way of reflective coatings, better insulation, high efficiency windows, day lighting, etc.), it cannot be the only component in pursuing Zero Net Energy Building design. Sources of renewable energy are necessary to supplement conventional sources.

Finally, as the cost of conventional energy sources goes up and availability goes down, the cost of solar electrical production is approaching parity with most conventional sources.

PV systems can be expected to last 20 years or more, so they should be paired with a roof system that doesn’t require much routine maintenance and has a similar lifetime.

Solar on Life Support? Not So Fast…

“The reports of my death are greatly exaggerated.” So said Mark Twain more than a century ago. Despite the recent and well-publicized demise of Solyndra, the photovoltaic industry might echo Twain’s remark, given the rousing attendance at this year’s Solar Power International (SPI) show in Dallas. More than 1100 exhibitors displayed their wares to an estimated 20,000 attendees at the Dallas Convention Center, October 17-19.

The Duro-Last booth was busy, as we demonstrated to visitors how the Duro-Last roofing system is “solar-ready,” with prefabricated flashings that easily provide a watertight fit around PV mounting racks and other rooftop penetrations.

We were joined in the booth by Duro-Last independent sales reps Daniel and Leah Lakstins (West Texas) and Buddy Wilson (East Texas). Also dropping by on my watch were representatives from Duro-Last authorized contractors Jaco Roofing & Construction (Clute, Texas) and LaFerney, Inc. (Kingsport, Tennessee).

Kevin Kelley and Drew Ballensky warming up pre-show to greet the throngs of visitors to the Duro-Last booth at SPI!

Are You Ready for Solar? Integrating Single-Ply Roofing With Photovoltaic Arrays

The growth of rooftop photovoltaics (PV) has exploded over the past few years, aided by incentive programs, technological improvements, and the need for alternative sources of energy. Rooftops can be an excellent place to install PV because they are usually unused and unobstructed spaces. But utilizing a rooftop to locate PV is not without its risks – one of which is the potential to compromise the integrity of a critical component of the building envelope: the waterproof barrier that is the roofing system.

PV and roofing systems that have been effectively integrated will work in harmony to provide clean energy, savings in energy costs, and protect the building and its contents for many years. It is important for a building owner to be aware of all the elements to consider when selecting a roofing system to go under a rooftop PV system. Examples of some issues include foot traffic, roof access for repairs, access for fire fighters, access for HVAC service, excess heat impacts on the roof, weight, snow and seismic loads, fire ratings, wind, hail resistance, drainage, and building codes.

A poorly designed and improperly matched roof system is a candidate for failure, and can lead to damage to a building and its contents and possible premature removal of a PV system for repair and/or replacement of the roof.

The best single-ply roofing systems are those that are able to integrate with virtually any type of PV system and mounting method, and provide years of leak-free performance while the PV system is generating power. You can learn more about what it takes for a roofing system to be “solar-ready” by downloading our “solar-ready” roofing system flyer.

Duro-Last Exhibits at Solar Power International Expo

Duro-Last exhibited at the Solar Power International Expo held October 12-14 at the Los Angeles Convention Center. We participated in this show because rooftop photovoltaic (PV) installations are growing exponentially, and these systems require a roofing membrane that is “Solar-Ready™.” Although the rooftop solar market is still in its infancy, Duro-Last’s custom-prefabricated roof system has been able to accommodate the roof penetrations typical to PV installation for more than 30 years.

The Duro-Last message was well received by the many solar integrators and installers who attended the Expo and who recognize that the watertight integrity of the roof system beneath the PV equipment plays a vital role in the success of solar installations. Duro-Last was represented by President Tom Hollingsworth, Western VP Tim Hart, California Regional Manager Curt Jaffe, and yours truly, along with California independent sales representatives Scott Franklin, Matt Stephens, and Chris Hemphill. In addition to working the booth, we were able to walk the show and interact with many of the 1,100 plus vendors and the estimated 27,000 attendees.

This show enabled us to get familiar with the rooftop mounting systems that PV systems use. It’s the largest B2B Expo for the solar power industry, and provided a wonderful opportunity to interact with manufacturers of these systems. In general there are two types of mounting systems: those that attach to the roof’s structural supports and those that sit atop the roof system and utilize ballast blocks to stay put when the wind blows. Both types of systems have pluses and minuses which will be the topic of future posts on this blog. One thing is certain: the demand is so great that many rack and roll-formed steel manufacturers are jumping on the solar bandwagon and introducing mounting systems in a wide variety of shapes and sizes.

Many roofing contractors around the county are also getting involved by forming solar divisions within their companies. One such Duro-Last contractor is Competitive Commercial Roofing, of Hood River, Oregon, owned and operated by Steve Leslie. Steve’s solar company Competitive Solar provides solar-related services in addition to a roofing product that is ideally suited for use with solar. Steve, April Chen, and Chase Drum of Competitive Solar attended the Expo and provided valuable insights regarding the integration of the Duro-Last roof systems and PV to visitors of the booth. Many thanks to Competitive Solar for the valuable assistance!

Duro-Last staffers Scott Franklin, Tim Hart, Matt Stephens, and Curt Jaffe chatting it up with a couple of booth visitors.
A rack system that will mount to a roof's structural supports.
A rack system that will sit on a rooftop and be held down with ballast blocks.

Solar-Ready…and Moving Forward

This photovoltaic (PV) segment of the roofing industry continues to grow while most others decline. This trend is mainly due to rising energy costs and federal stimulus goals of making our country greener. Combine these factors with state and/or local incentives in many areas of the country and the return on a new roof and PV system investment can be less than ten years in some cases. The Database of State Incentives for Renewables & Efficiency (DSIRE) (www.dsireusa.org) provides a “comprehensive source of information on state, local, utility, and federal incentives and policies that promote renewable energy and energy efficiency.”

As with any major building investment, there are number of considerations that must be addressed with a rooftop PV installation: how will the system be mounted on the roof – with penetrations, ballast, or adhesive? Can the building structure support the additional load? What about local codes and permits? How will the watertight integrity of the roof be ensured during and after installation?

When building owners are interested in solar, the roof system must be addressed. The PV system should be installed in an environment that will not require extensive roof maintenance or replacement for 20 to 30 years because the cost to remove and reinstall PV systems in order to (for example) find a leak source can be expensive. Another consideration: the incremental cost of a new roof will be minimal compared to the cost of the complete new PV system – a smart building owner will take care of both at the same time.

Although PV is an electrical application, roofing is the trade that owns the rooftop, and the majority of solar PV decisions/installations are controlled by roofing contractors. In California (where the use of PV is common) many roofing contractors have created in-house PV departments or have working relationship with solar integrators – the experts that design the systems for each specific building.

Solar technology will continue to show gains, both in efficiency and usage. Currently, it is widely accepted in only a few states because of the financial incentives available in those areas. Incentives will continue to expand to other parts of the country, and if the demand for rooftop PV has not hit your area yet, it will within a few years.


What We Mean When We Say Green

The term “green roof” has become narrowly defined in recent years to refer to “vegetative roof.” But “green roof” can also mean “sustainable roof” – one that provides long-term environmental benefits that building owners want roofing systems to deliver for their high-performance facilities: high reflectivity; recyclability; able to accommodate photovoltaic systems; able to help facilities obtain LEED credits; etc. This brief video discusses these benefits and more. For additional information about green roofing, visit www.whiteequalsgreen.com.


Project of the Month: Merrick, Inc., Vadnais Heights, Minnesota

The Duro-Last roofing system has been installed on the Merrick, Inc. building in Vadnais Heights, Minnesota. The project was completed at the end of August 2008 and is the largest solar electric application in the state, with 525 solar panels installed that are expected to produce 130,000 kilowatts of electricity a year. Beneath the solar electric system, the building is protected by over 50,000 square feet of Duro-Last’s single-ply PVC roofing system.

Merrick’s prefabricated roofing system was manufactured at Duro-Last’s Sigourney, Iowa, facility and installed by authorized contractor Four Seasons Energy Efficient Roofing, Inc. of Marine on St. Croix, Minnesota. “Duro-Last’s white membrane was the ideal system for this installation because it is solar-ready. It’s easy to install, and because it’s prefabricated, I can be confident that Merrick won’t have to worry about leaks underneath the solar system,” said Darrell Schaapveld, owner of Four Seasons.

The Duro-Last roofing system is an excellent sustainability choice. The white membrane’s high reflectivity benefits the building in rooftop areas where sunlight is not being collected by the solar panels. Because every Duro-Last roof is factory-prefabricated, less on-site waste is produced during installation.

The Duro-Last-plus-solar roofing assembly complements the buildings many other sustainable building features. Among them: a geothermal energy system under the parking lot, powered by the rooftop solar panels, will provide both heating and cooling; every room will have occupancy sensors to control electrical usage; the building will have energy-efficient insulation and windows throughout, maximizing natural light.

According to Duro-Last Vice President of Sales and Marketing, Steve Ruth, “This installation reinforces our leadership in the sustainable roofing market. The Duro-Last roofing system is increasingly being installed throughout the United States as the waterproofing membrane of choice for solar, vegetative, and other ‘green’ building applications.”

Project of the Month: Bardessono Inn & Spa, Yountville, California

The Duro-Last roofing system has been installed on the Bardessono Inn & Spa in Yountville, California. The spa is scheduled to open in February 2009, and will be submitted to the U.S. Green Building Council for LEED Platinum certification. The spa consists of five separate buildings that are protected by almost 80,000 square feet of Duro-Last’s single-ply PVC roofing system.

The spa’s prefabricated roofing system was manufactured at Duro-Last’s Grants Pass, Oregon, facility and installed by authorized contractor Fidelity Roof Company of Oakland, California. Fidelity is also an approved installer for SunPower, the manufacturer of the PowerGuard solar electrical system that will provide electricity to the spa.

The Duro-Last roofing system is a key component of this sustainable construction project. The white membrane has reflectivity and emittance characteristics that exceed California’s Title 24 building requirements. Because it’s prefabricated, less on-site waste is produced during installation. As a company, Duro-Last recycles manufacturing scrap back into roofing membrane or other construction products. And unlike other roofing materials, the Duro-Last system is also recyclable at the end of its useful life.

The Duro-Last-plus-solar roofing assembly complements the spas many other sustainable building features. Among them: a ground source heat pump will provide both heating and cooling; every room will have occupancy sensors to control electrical usage; the spa makes extensive use of wood salvaged from native California trees; concrete and steel materials include a high percentage of recycled content; low-VOC paints and adhesives are used throughout the complex.

Steve Ruth, Duro-Last Vice President of Sales, said, “This project makes a strong environmental statement, and we’re proud to be an important part of it. The fact that the Duro-Last system has been installed on the Bardessono facility reinforces our leadership in the sustainable roofing arena.”