Dynamic Duo: Optimizing the performance of spray polyurethane foam and photovoltaic systems

Rodney Strong Vineyards

Spray Polyurethane Foam (SPF) and PV systems are increasingly paired together as a joint solution for energy savings. With the continued push toward sustainability and growing movements such as zero net energy (ZNE) construction, SPF and PV systems combine to provide a logical solution to generate renewable energy while conserving the energy used in heating and cooling.

Regardless of whether ZNE is the end goal, SPF and PV combined on the roof can be highly beneficial, but proper installation is key. Here are some technical considerations to ensure optimization of these energy solutions.

Rooftop PV Installation types for use with SPF

Rooftop PV systems may be installed on racks or adhered directly to the roof surface through typical means with either ballast or penetrating supports. Each option offers advantages and disadvantages. For example, ballasted racks may block water flow and affect drainage, while penetrations require proper flashings. But, uniquely, SPF easily self-flashes around penetrating supports.

SPF and coating selection

Higher density SPF systems are often preferred with PV because their compressive strength increases as density increases. SPF systems will be stressed during PV installation, however coatings and granules protect them during installation and maintenance. A roof surface below PV panels may dry slower than non-covered portions. Select coatings that withstand standing water and biological growth.Installation and regular maintenance of PV systems can increase foot traffic. Protect trafficked areas with additional coating and granules or walk pads.

Electrical safety

Electricity is produced when a single panel is exposed to light. Workers may inadvertently complete the circuit by connecting the two wires from the backside of a PV panel. Working around PV panels requires some degree of caution.

When maintaining a PV system, disconnection or removal of individual panels from a string or array may eventually be required. Follow proper shutdown procedures provided by the inverter manufacturer as part of a lock-out/tag-out program. SPF contractors should never disconnect or decommission a PV panel or system unless trained for it.

Heat buildup and SPF lifespan

Photovoltaic panels convert approximately 15 to 20 percent of light to electricity and release unconverted energy as heat. The majority of rooftop installations thus encourage airflow under panels to reduce their temperature, improving conversion efficiency and releasing heat effectively. Panels installed 4 to 5 in. above the roof will adequately cool the PV panels, providing surface shade and drying, potentially extending the SPF system lifespan.

Structural load

PV panels add load to a rooftop. A structural engineer should analyze existing structures to determine if their weight and additional wind load is acceptable. Rack-mounted arrays with penetrating attachments are fairly lightweight at 2 to 3 lbs per sq ft, and ballasted arrays add 4 to 6 lbs per sq ft. With the latter, more ballast is utilized at perimeters and corners of a PV array. Thus, localized loading from ballast may reach 12 to 17 lbs per sq ft. Most SPF roofing systems have a compressive strength of 40 to 60 psi.

Additionally, roofs are required by building codes to provide live load capacity that include people, snow and temporary weight-bearing scenarios. Although the weight of PV systems is not significant, live load capacity will decrease by the addition of the PV system.

Other design considerations include increased wind loading and the potential to catch drifting snow, which may add loading to the roof structure.

Equivalent service life

Expected service life of the roof and PV systems must be considered. The labor cost to remove and reinstall a PV system is costly. When installing PV, residual service life and replacement cost of the existing roof should be evaluated. For older roofs, it may be worth replacing the roof system just prior to PV installation. In other cases, when new or replacement roof systems are installed, provisions for future PV systems may be considered (e.g. pre-installation of penetrating supports).


PV arrays often have many contact points with a roof which may block or slow drainage. Position PV racking to minimize ponding water and/or include notched pads under contact points of ballasted systems to allow water to move toward drains and scuppers, especially for ballasted systems.

PV system access for maintenance and removal

Roof mounted PV systems should be inspected and maintained at least twice a year. Inspect wiring, attachment points and flashings. Cleaning the top surface of PV panels may be required. Workers need access to both the roof and PV systems. PV systems should not block access to drains, penetrations, flashings, mechanical units or rooftop equipment. PV should be installed so workers can access wiring, inspect panel-to-racking connections and clean top surfaces without stepping on panels.

Power Spray

Rodney Strong Vineyards combines spray foam roofing with solar power

Rodney Strong Vineyards

A major force in wine, Rodney Strong Vineyards’ Healdsburg, Calif., facility includes a barrel storage facility housing 28,000 oak wine barrels for their two-year aging process. The barrels must be stored at a consistent temperature and humidity. These factors, married with the large size of the facility, made it a prime contender for the combination of energy efficient spray foam on the roof (which acts as a thermal, moisture and vapor barrier) and solar power.

“In 2003, when we first installed solar, Rodney Strong Wine Estates became one of the greenest wineries in the world,” says Larry Solomon, facilities manager of Rodney Strong. “In 2018, we replaced and increased our rooftop photovoltaic system and recognized this was an ideal opportunity to insulate our barrel storage warehouses with sprayed polyurethane foam roofing. We expect that the insulated roof will provide substantial energy savings, providing a more consistent temperature for barrel storage while eliminating leaks and essentially providing a new roof that will last for the lifetime of the solar array.”

Central Coating Company installed the new 2-in. spray foam roofing system over the existing metal roof to provide R-13 of continuous insulation. The solar contractor, SolarCraft, installed 5,005 solar standoff penetrations for the 1.5-MW photovoltaic system. In February, Central Coating Company won an Industry Excellence Award for the project. Presented by the Spray Polyurethane Foam Alliance, the award recognizes the Rodney Strong Vineyards combined roof solution as one of the year’s best-in-class applications of spray polyurethane foam.

Rick Duncan is the technical director of the Spray Polyurethane Foam Alliance (SPFA), the industry’s leading organization representing contractors, material and equipment manufacturers, distributors and industry consultants.

— Solar Builder magazine

West Valley-Mission Community College District adds solar + storage system via SunPower

sunpower logo

West Valley-Mission Community College District (WVMCCD) recently selected SunPower to deploy a fully integrated solar and storage project across its West Valley and Mission College campuses in the heart of California’s Silicon Valley. SunPower Helix Carport systems installed will total 5.4 megawatts, allowing the District to offset approximately 75 percent of grid electricity use with solar energy. A Helix Storage system will be installed at each campus, totaling a combined 2 megawatts (3,800 kilowatt hours) and delivering significant demand charge savings to WVMCCD.

This SunPower solar initiative will be the second for WVMCCD. Since 2011, 2.2 megawatts of highly-customized SunPower solar carports operating at both West Valley and Mission Colleges have generated an estimated $860,000 in electricity savings each year to the District. In addition to renewable energy, the colleges are home to a total of five U.S. Green Building Council LEED certified buildings, and feature drought tolerant landscaping and bioswales across campuses.

“Our district has a long-standing commitment to creating environmentally responsible and highly sustainable campuses for students, faculty and staff,” said Ed Maduli, Vice Chancellor of Administrative Services, West Valley-Mission Community College District. “Renewable energy from SunPower has proven to be a valuable investment and a critical component to reaching our goals, and we look forward to building on our efforts with storage which will allow us to avoid expensive utility demand charges for years to come.”

Solar-and-storage system construction is planned to commence this fall, with completion expected in 2020. The project is funded through local Measure W which authorizes the District to issue bonds to finance facility and technology updates. The District will own its solar power system, with SunPower providing operations and maintenance, as well as a performance guarantee for 25 years.

— Solar Builder magazine

NASA partners with Ameresco on solar project at Goddard Space Flight Center

nasa ameresco solar project

Ameresco broke ground last week on a solar project at NASA’s Goddard Space Flight Center’s Wallops Flight Facility in Wallops Island, Virginia. The savings-funded solar renewable energy project will help NASA WFF to meet its ambitious energy-savings and sustainability goals.

Designed to be completed in two phases, the project will meet at least 80% of the site’s electrical consumption once complete. Given its size and scope, the solar installation is expected to reduce the facility’s carbon output by more than 4,310 metric tons per year. The project will include ground-mounted solar panels installed near NASA WFF’s airfield as well as carport-canopy panels.

Deal structure

The project includes $14 million in renewable energy and infrastructure improvements. It will provide more than $537,000 in first-year energy cost savings; in future years, solar output combined with energy conservation measures are expected to allow for $3.1 million in energy cost savings. Because the partnership between NASA WFF and Ameresco is an energy savings performance contract (ESPC), NASA WFF will accrue no upfront costs. Instead, through the ESPC, NASA WFF will fund the project through energy cost savings derived from the solar installation.

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“This is a significant project for Wallops because it will create a renewable source of energy for our facility in the near-term, while also laying the foundation for the energy generated onsite to contribute to our region’s existing energy grid in the future,” said Dave Pierce, Wallops Flight Facility Director. “The installation of a solar field in such close proximity to a critical airspace is a rarity, and our project serves as a model to other similar facilities that it is possible to install a meaningful solar farm that will greatly reduce carbon output, even with limited real estate.”

— Solar Builder magazine

Green Street Power Partners enters Minnesota solar market, closes financing on 17.5 MW portfolio

solar commercial loan financing

Green Street Power Partners, LLC (GSPP) closed on tax equity investment and long-term debt financing for a 17.5 megawatt community solar portfolio in Minnesota. The portfolio will consist of commercial and industrial customers and represents GSPP’s initial foray into the Minnesota market. GSPP will own and operate the solar assets long-term. The portfolio, consisting of 4 different sites, is expected to be fully operational between now and Q3 of 2019.

GSPP secured tax equity financing for the project from Rockwood Group, through its partnership with The Guardian Life Insurance Company of America and ~$25M in long-term debt with Celtic Bank, a top-ten nationwide SBA lender headquartered in Salt Lake City, Utah.

“Guardian Life Insurance and Rockwood Group have proven to be ideal partners in this transaction. Their focus on long-term, sustainable investments aligns well with the funding opportunities we have to offer at GSPP,” stated Scott Kerner, CEO of GSPP. “We are excited about securing this investment from such reputable firms and we look forward to continued growth within this new partnership.”

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“Celtic Bank is excited that it will expand its lending portfolio with this group of community solar projects in Minnesota” stated Jasna Filipović, VP of Renewable Energy & Specialty Finance at Celtic Bank. “These solar farms will both significantly increase solar production in the state and reduce energy costs to households. We are grateful to GSPP and our partnership in these great projects.”

The clean energy generated by the four projects in this portfolio will offset over 15,000 tons of carbon dioxide annually.

GSPP continues to experience rapid growth as they expand into the Midwest commercial solar market. With this most recent addition to its portfolio, GSPP now has over 70 MW under management and will generate power in 10 states.

— Solar Builder magazine

California’s electrical infrastructure receives D- grade, more businesses should add solar + storage says Revel Energy

D minus examination result grade red latter mark.

The 2019 Report Card for California Infrastructure showed that the Energy sector received the lowest rank of all sectors, scoring a D- from the American Society of Civil Engineers (ASCE). Investor Owned Utilities (IOU’s), like Southern California Edison, Pacific Gas & Electric, and San Diego Gas & Electric are tasked with updating their severely under-maintained infrastructure.

Many upgrade projects are currently in effect. “The public utilities are modernizing their grids to accommodate the changing energy market. For example, from 2018-2020, SCE is replacing over 2,000 miles of cable, upgrading lower voltage wires so they can better accommodate…” explains the ASCE.

What does this mean exactly? California’s Revel Energy shared its thoughts with us. Dedicated to renewable energy solutions since 2009, Revel Energy was formed to provide Commercial, Industrial and Agricultural businesses with alternative energy beyond solar.

What does this mean for California businesses and commercial property owners? 

Continued rate hikes will be the normal going forward. To pay for these major upgrade projects, IOU’s will need to increase rates, manipulate Time of Use and raise demand charges. California businesses can expect to see growth of their electric bill to outpace inflation significantly.

How do businesses protect themselves against these rising costs?

California business owners who spend $1,500 or more each month on electricity will need to look at alternative energies like commercial solar and energy storage systems.

“Our customers approach us to help lower their energy consumption from public utilities,” explains Ken Fournier of Revel Energy. “As rates go up, cutting energy usage and investing in renewable energies looks more and more of a necessity for business owners.”

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Gaining energy independence through commercial solar and other renewable energies is a fast-growing concept. Southern California business are the fastest growing adopters, due to its solar saturated climate.

What kind of savings can businesses expect?

A lot of factors play into saving. Available square footage for the technology is a major pacing item. Other factors include, climate, building codes, and time of operation. Many businesses can see anywhere from 30% energy cost savings to well past 100% (in this case they would receive credits for future use). Here is one example of a San Diego mushroom grower who saves over 60% a month of electricity costs.

The average payback time via saved electricity costs is around 3-5 years. Many factors can expedite or slow repayment period, consult an energy consultant today for your business.

What upfront costs can businesses expect?

This depends heavily on the size of the system and how many layers of sustainable technology the business owner wants to use. For example, one manufacturer was running night shifts and was unable to capitalize with just solar. They installed an energy storage system to feed their electricity need when the sun went down.

Effective, commercial grade technology is not cheap like some consumer brands available. Incentives and Federal Tax credits can cut the cost of a comprehensive system significantly, sometime more than half. For businesses that don’t want to invest upfront, flexible financing options and lending programs like PACE are a good option.

What kind of businesses are good candidates to counter these rising costs?

California businesses that spend $1,500 or more each month in electricity are urged to contact an energy saving professional (Contact Here). Commercial energy contractors like Revel Energy will conduct a simple energy audit to point out opportunities for your business to save substantially on energy costs and start to put money back in your pocket.

— Solar Builder magazine