A Solar Installer Explains the Many Ways Roofing Contractors Can Be Involved in Solar Installations

The solar-power industry has changed dramatically in the past five years. Products and manufacturers have come and gone; tax incentives have become less attractive; and requirements for utilities to maintain a certain percentage of their energy portfolio from renewable sources are not enough to help the market in most places. Despite these negatives, unique financing mechanisms and the remarkable decrease in the cost of solar panels keep the industry booming. These ups and downs demonstrate why Matthew Bennett, vice president for design and engineering and founder of Dovetail Solar & Wind, Athens, Ohio, refers to the industry as the “solar coaster”.

Bennett’s business, which was established in 1995, installs solar on residential and commercial buildings. As such, he has worked with a number of roofing contractors over the years and sees synergies between the trades. Roofing asked Bennett how roofing contractors and solar installers can improve their relationship and achieve successful solar installations upon watertight roofs.

Roofing: When must you coordinate with roofing contractors?

Bennett: On almost every commercial roof where roof penetrations are required we’ll have a roofer come in and flash the penetrations and sometimes install a sleeve to get our conduit off the roof and into the building.commercial solar array

The other common reason for coordinating with a roofer is because the roof may be under warranty. Sometimes the warranty is held by the roof manufacturer, so we receive a list of roofers who can do the inspection. Usually there’s an inspection that needs to happen before and after the solar installation. We’re sometimes paying $1,000 to get inspections.

A lot of times we’re not fastening solar panels to flat commercial roofs; we’re installing what’s called a ballasted system where we may need to use an approved pad or put down an additional membrane to protect the roof from the pan that is holding ballast and keeping the array on the roof. Sometimes different roofing manufacturers are picky about what they allow on the roof and different kinds of roofs require different treatment, so it’s important to have a good roofing contractor available.

Roofing: When you hire contractors, what are you looking for?

Bennett: We’re looking for a roofing contractor that does quality work at a fair price because, I’ll be honest, we’ve been overcharged by roofers more than any other subcontractor. We take notes when we work with a roofing contractor: how easy they are to work with, how responsive they are to emails and phone calls, the quality of work and the price. We know roughly what to expect after being in business all these years. If we get a fair quote from a recommended contractor, we’ll often go with them without looking at other bids. We prefer to use a roofer who is familiar with the roof. A good relationship with the customer also is an important consideration.

Roofing: Are there situations in which you defer entirely to the roofing contractor?

Bennett: It’s a little unusual. We just put a system on a slate roof on a million-dollar home. The roof was very steep and we didn’t even want to get on the slate, so we hired the roofer to install the rails and solar panels. We did all the electrical work and procurement. We provided one of our crew leaders to be there the entire time to train the roofing crew and help them because they had no experience with solar. They knew how to get around on a slate roof and mount the solar flashing and they actually installed the whole array. They did it in not much more time than we would’ve done it. We were very impressed with them.

Pages: 1 2

Rooftop Equipment Mounting and Penetrations for Low-slope Standing-seam Metal Roofs

Standing-seam metal roofing offers a durable, sustainable alternative to other roof types and can provide maintenance-free service for five to 10 decades. Sadly, this exceptional lifespan often is sabotaged with the mounting of essential rooftop equipment and ancillary mechanicals.

Metal roofing can make use of special seam-clamping hardware that grips the standing seam without puncturing the membrane. Seam clamps have made metal roofing a preferred roof type for mounting photovoltaic solar arrays. PHOTO: Metal Roof Advisory Group Ltd.

Metal roofing can make use of special seam-clamping hardware that grips the standing seam without puncturing the membrane. Seam clamps have made metal roofing a preferred roof type for mounting photovoltaic solar arrays.

Regardless of the roof type involved, consultants generally agree that the best way to prevent roof-related problems is to clear the rooftop of everything possible and just let it function as a roof—not a mechanical equipment platform. However, such a perfect roof continues to elude us, as it becomes necessary or convenient to mount HVAC equipment, screens to hide it, piping to fuel it, scuttles to access it and walkways to service it. The list of rooftop mountings also may include plumbing vents, satellite dishes, lightning protection, snow retention systems, solar collectors, advertising signage and fall-protection systems to maintain all the foregoing. To help achieve relatively trouble-free roofs, this segment provides some basic understanding of the dos and don’ts in situations where rooftop equipment mounting is requisite.

Penetration-free Attachment

A good “first rule” about any rooftop mounting is to avoid penetrating the membrane whenever possible. While this may seem obvious, the tenet is often violated with standing-seam metal. The norm for attaching things seems to involve anchoring the item to the structure through the roof. When this happens, it not only threatens weather integrity, but can also violate the membrane’s thermal-cycling behavior by inadvertently pinning the panel to the structure. Such a point of attachment will fatigue and fail from forces of thermal expansion within a short time. Fortunately, scores of items and equipment can be securely mounted to metal rooftops without any penetration whatsoever, actually making metal roofing more user-friendly than other roof types.

In terms of mounting ancillaries, metal roofing can use special seam-clamping hardware that grips the standing seam without puncturing the membrane. Unlike many other types of roofing, metal is a rigid, high-tensile material. The seam area creates a beam-like structure that can provide convenient anchorage for walkways, solar arrays, condensing units and gas piping without harming the roof’s weathering characteristics. Mechanicals can be safely and cost-effectively secured to these seam clamps, leaving the roof membrane penetration free. Seam clamps can provide holding strength of up to several thousand pounds on some profiles and gauges, last the life of the roof and preserve thermal-cycling characteristics. Using seam clamps when possible for ancillary mounting will eliminate unwanted holes and other potential problems.

Seam clamps allow even cumbersome ancillary items to be attached to metal roofs without penetrating the rooftop. PHOTO: Metal Roof Advisory Group Ltd.

Seam clamps allow even cumbersome ancillary items to be attached to metal roofs without penetrating the rooftop.

Clamps should be made only of noncorrosive metals—typically, aluminum with stainless-steel mounting hardware. These metals are compatible with virtually anything found on a metal roof, except copper (with which there are dissimilar metallurgy issues). Dissimilar metals in electrolytic contact will induce galvanic corrosion of the less noble metal. In cases involving copper roofing, brass clamps should be used with stainless-steel hardware.

Seam clamps generally integrate with the profile and seam folding, and in some way “pinch” the seam material to anchor them in place. Preferred methods of doing this involve setscrews tightened against the seam causing a detent in the seam material that in turn creates a mechanical interlock of the setscrew, seam and clamp, providing the greatest holding strength and durability. Setscrews should have round, polished points to prevent galling metallic coatings, which can lead to corrosion. In like fashion, and regardless of the method of engagement, any clamp device should avoid any sharp points or nodes that could potentially pierce or gall metallic coatings of steel or cause fatigue and fracture points of other metals.

It also is important to remember that any loads introduced into the clamp will be transferred to the panels and their anchorage to the structure. Consequently, anchorage must be capable of withstanding the added load. The best practice is to utilize clamps that have been appropriately tested for material and seam-specific holding strength; be sure in-service load does not exceed that of the published holding strength, including factors of safety. The roof manufacturer should also be consulted with respect to approval of devices used.

Pages: 1 2 3 4