In the following Q&A, Scott Bader’s solar PV expert, Andrew Harvey, discusses how structural adhesives improve solar installation, and how they should be utilized for optimal installation.
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Can structural adhesives be used to install flexible and traditional solar panels?
Yes. Flexible solar PV panels can be attached directly to roofs, and conventional glass-faced solar panels may be installed by bonding the aluminum rails that hold them directly to the roof.
What are the advantages of structural adhesives compared to mechanical fasteners for installing purposes?
Bonding flexible solar PV panels or aluminum rails for the installation of conventional glass-faced solar PV means holes do not need to be drilled into the roof, which increases the risk of rainwater leaks. It also means that the roofing manufacturer’s warranty on the roof's watertightness does not get invalidated.
In coastal regions, problems can also arise from galvanic corrosion, where the roof and mechanical fastener begin to rust, impacting the installation’s long-term durability.
What is Scott Bader’s product offering in the solar PV market?
Scott Bader’s Crestabond M7 range are methyl methacrylate adhesives formulated for bonding flexible solar PV panels and aluminum rails for installing conventional solar PV to rooftops. Another key point to bear in mind is that it is primerless, making installation both quick and easy.
What types of roofs can the adhesives bond to?
Crestabond M7 may be utilized to bond aluminum rails to all kinds of metal roofs, such as standing seam, trapezoidal metal roof panels, polyester spray or powder coated and PVC plastisol coated roofs. For flexible solar PV panels, which are usually 80 % lighter than conventional glass-faced solar PV, Crestabond M7 may be utilized to bond the panels directly to metal or metal-coated roofs and PVC single-ply membranes, which are frequently used on the flat roofs of commercial buildings and residential apartments.
How strong is the attachment, and how does it measure up against mechanical fasteners?
On thin gauge steel trapezoidal roofing of 0.5 mm, Crestabond M7’s bond strength is up to three times higher than that of a mechanical fastener.
This happens because, when using a battery-powered screwdriver and Tek screws, the thread fabricated in the steel is contained and cannot be easily threaded if the screwdriver torque is too high.
For thicker gauge steel roofs of 0.7 mm, the strength of a bonded rail and mechanically fastened rail, when installed as per the manufacturer’s recommendations, will be similar and will carry the imposed load by more than three times the wind speeds usually generated by a typhoon.
Bonding solar panels with structural adhesives
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What warranty is available to ensure the adhesive will last the 25-year service life of the solar PV panels?
Both static and after-climate-cycling testing have been carried out to ensure that the adhesively-bonded rail or flexible solar panel will survive the 25-year service life of the solar PV panel.
That said, variables exist beyond Scott Bader’s control. These include roof preparation, proper storage, and usage of the Crestabond M7 cartridges, which can impact the bond’s strength. If required, the main installation contractor can conduct simple tests on-site to verify the roof coating’s quality.
For large commercial installations, Scott Bader can carry out testing and release a report to check the bond strength and durability of a sample of the roof panel and rail. This will give confidence that the bonded flexible solar PV panels or aluminum rails will meet the project’s needs.
What is the process and how long is needed to bond flexible solar panels or aluminum rails to roofs?
Scott Bader’s comprehensive step-by-step installation guides discuss all aspects of installation, from roof preparation to installation of flexible solar PV panels or aluminum rails. The process is extremely easy and will be more time-efficient than using mechanical fasteners.
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How can one prepare the roof for bonding?
The roof needs to be cleaned with soapy water or, if heavily soiled, via a jet wash and then left to dry prior to bonding the flexible solar PV panels or aluminum rails.
What needs to be done if the roof’s coating is flaking or seems to be bad quality?
If the roof’s coating is flaking or cracking, a preparation disc needs to be used to get rid of the coating in the area where the solar PV panels or aluminum rails will be bonded.
A simple coating adhesion tester can examine the roof coating’s quality; details of the addition tester are available in the solar PV installation guides on Scott Bader’s website.
Can the flexible solar panels or the aluminum rails be removed if required to replace a damaged panel or for routine maintenance of the roof?
There are a couple of options for flexible solar panels. To begin with, if the panel is damaged and bonded to the roof, the junction box atop the panel may be removed, and a new panel can be bonded directly atop the existing panel.
Next, if bigheads or bonding plates have been utilized to affix the flexible solar panel to the roof, the panel may be taken away by simply unscrewing the attachments.
For aluminum rails, a paint stripping gun that is either battery or mains-powered may be utilized to heat the rail to around 150 °C, at which point the roof coating or adhesive will soften and allow the rail to be separated. A local repair of the roof coating can be undertaken with paint of the same color.
How easy is it to use and apply Crestabond structural adhesives?
The Crestabond M7 adhesive is supplied in a cartridge format alongside a mix head. It can be dispensed with a manual, pneumatic, or battery-powered dispense gun.
How long does it take for the adhesive to cure before the glass-faced solar PV panels can be installed?
When utilizing Crestabond M7-05 at an ambient temperature of 23 °C, the working time is around 5 minutes. In just 15 to 20 minutes, it will have accrued enough strength to begin installing the conventional solar PV panels. How much time this takes varies according to the ambient temperature. As such, reference should be made to the relevant technical data sheet to know specifics.
Does the weather affect when flexible solar panels and aluminum rails may be installed with Crestabond?
Bonding the flexible solar PV panels and aluminum rails at any ambient temperature between 0 °C and 30 °C is possible. However, installation should not be undertaken while raining or where there is excessive moisture on the roof’s surface. The roof needs to be somewhat clean and dry.
How can one check if the roof coating is sufficient to bond flexible solar panels or aluminum rails?
A coating adhesion tester may be utilized to check the coating’s quality and bond strength. The solar PV installation guides, which can be downloaded from the Scott Bader website, discuss this in further detail.
This information has been sourced, reviewed and adapted from materials provided by Scott Bader Company Ltd.
For more information on this source, please visit Scott Bader Company Ltd.