Spray polyurethane foam is combined with photovoltaic system to provide a more energy-saving joint solution

- Jun 25, 2019-

Spray polyurethane foams (SPF) and photovoltaic systems are increasingly becoming joint energy saving solutions.Driven by the growth of sustainable development and zero-net energy (ZNE) construction, the combination of SPF and pv systems provides a rational solution to generate and conserve renewable energy for heating and cooling.

Whether or not ZNE is the ultimate goal of *, the combination of SPF and pv systems on rooftops can be very beneficial, but proper installation is the key.Here are some technical considerations to ensure that these energy solutions are optimized.

Type of pv system installation for SPF roof

Roof PV systems can be mounted on racks or adhered directly to roof surfaces by devices with ballast or penetration supports.Each option has advantages and disadvantages.For example, ballast shelving may block water flow and affect drainage, whereas permeable shelving requires proper waterproofing.Unique, however, is the SPF's ease of being waterproof and supportive.

SPF and coating options

For photovoltaic systems, higher density SPFS are usually preferred because their compressive strength increases with density.The SPF system is stressed during the installation of the photovoltaic system, and the coating and particles protect the SPF system during the installation and maintenance.The surface of the roof below the photovoltaic panel may dry more slowly than the uncovered part, so choose a coating that can withstand standing water and biological growth.The installation and regular maintenance of the photovoltaic system increases the frequency of people walking on the roof, so additional coatings and particles or walking MATS can be used to protect SPF where people are walking.

Electrical safety

Electricity is generated when individual panels are exposed to light.Workers may inadvertently electrify the panels by connecting two wires on the back.So working around photovoltaic panels requires a certain amount of caution.

When maintaining photovoltaic systems, * may eventually need to interrupt or remove individual panels from series or parallel.Follow the correct shutdown procedure provided by the inverter manufacturer as part of the locking/listing procedure.Unless trained, SPF contractors should not disconnect or disable photovoltaic panels or systems.

Caloric accumulation and SPF life

Photovoltaic panels convert about 15 to 20 percent of light into electricity and release the unconverted energy as heat.As a result, most roof installations encourage air circulation under the panels to lower their temperature, improve conversion efficiency and effectively release heat.Panels 4 to 5 inches above the roof will cool the PV panels sufficiently to provide surface shading and dryness, potentially extending the life of the SPF system.

Structural load

Photovoltaic panels add to the load on the roof.Structural engineers should analyze existing structures to determine whether their weight and additional wind loads can be sustained.Rack arrays with penetrating attachments are fairly lightweight, at 2 to 3 pounds per square foot, and ballasted arrays weigh 4 to 6 pounds per square foot.The latter USES more ballasts around the edges and corners of the photovoltaic array.Thus, local loads of ballast can reach 12 to 17 pounds per square foot.Most SPF roofing systems have a compressive strength of 40 to 60 pounds per square inch.

In addition, the building code requires the roof to provide living load, including walking, snow and temporary load bearing scenarios.Although the weight of the photovoltaic system is not important, the live load capacity can be reduced by adding photovoltaic systems.

Other design considerations include increased wind load and the possibility of capturing drifting snow, which may increase the load on the roof structure.

Equivalent life

Consideration of the expected service life of the roof and photovoltaic system is necessary.The labor costs of removing and reinstalling photovoltaic systems are high.When installing a photovoltaic system, workers should evaluate the remaining service life and replacement cost of the existing roof.For older roofs, it may be worthwhile to replace the roof system before photovoltaic installation.In other cases, when installing new or replacement roof systems, consideration may be given to future pv systems that may be installed in the future (for example, pre-installed penetration supports).


Photovoltaic arrays typically have many points of contact with the roof, which can block or slow drainage.Position the pv bracket to minimize accumulation of water and/or include a notched pad below the contact point of the ballast system to allow water to move toward the drain pipes and drainage holes, especially for ballast systems.

Maintenance and removal of pv system

Roof-mounted photovoltaic systems should be inspected and maintained at least twice a year.Check wiring, connections and waterproof plates.It may be necessary to clean the top surface of the photovoltaic panel.Workers need access to rooftops and photovoltaic systems.Photovoltaic systems should not block drains, floor drains, mechanical devices or roofing equipment.For workers who can touch wiring, check panel to shelf connections and clean top surfaces without stepping on panels, the roof should be installed with a photovoltaic system.

RodneyStrongVineyards combines spray-painted foam roofs with solar energy

RodneyStrongVineyards, a major wine producer, has a barnyard storage facility in healdsburg, California, capable of holding 28,000 oak barrels for two years of aging.Drums must be stored at a consistent temperature and humidity.These factors, combined with the large facility, make it an ideal user for a combination of energy efficient spray foam on the roof (which ACTS as a heat, moisture and steam barrier) and solar energy.

RodneyStrongWineEstates became one of the environmentally friendly wineries in the world when we installed solar energy in 2003.We replaced and added a rooftop pv system in 2018 and recognized this as an ideal opportunity to insulate our bucket storage warehouse with sprayed polyurethane foam roofs."We want to save a lot of energy by insulating the roof, providing more stable temperatures for barrel storage, eliminating leaks, and providing a new roof that will basically last the life of the solar array."

Central coatings has installed a new 2-inch spray foam roofing system on the existing metal roof to provide continuous insulation for the r-13.Solar contractor SolarCraft installed 5,005 solar stent penetrators for 1.5 megawatt photovoltaic systems.In February, Central coatings won the industry excellence award for this project.The award was awarded by the spray polyurethane foam consortium, which voted RodneyStrongVineyards portfolio roof solutions one of the best spray-on polyurethane foam applications of the year.