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Mind the Gap – How NOT to Install Solar Animal Guard

This is the second post in our series explaining common mistakes and animal guard failure modes.

When it comes to installing solar animal guard, the old saying applies: Do it right or do it twice. There is nothing worse than spending the time and money to install critter guard, only to have an animal sneak in and build a nest anyway. This can happen if the installer leaves too large of a gap between the fencing and the roof/array, creating an incomplete seal.

Maximum Gap Size

To prevent this from happening, solar contractors should maintain a clear, company-wide standard of 1/2″ maximum gap between wire mesh and other objects (such as the roof, PV modules and protruding rails or conduit). 1/2″ matches the wire spacing of industry standard wire mesh, which has proven effective at blocking small critters.

Allow no more than a 1/2″ gap to ensure animals can’t sneak through.

You may be wondering if animals can get under the PV array through the gaps between the solar panels themselves. These gaps are determined by the racking system used to attach the panels to the roof, and can be as large as 1″ (for UniRac SolarMount). Though many rodents can squeeze through a 1″ gap, we have yet to hear a report of this happening. Please share in the Comments if you have observed otherwise!

Now let’s take a look at some violations of the 1/2″ rule and see how they could be avoided.

Rail & Conduit Penetrations

90% of rooftop solar systems have some sort of object(s) sticking out from the array around the edges, such as rail ends, conduit, roof vents and junction boxes. These interrupt the uniform gap between roof and array, and must be worked around when installing animal guard.

In the photo above, the wire mesh is cut and attached to each side of a rail. Obviously, this leaves a huge gap under the rail. The mesh is also poorly supported and could be peeled back by a rodent. Below is another shoddy approach to rail ends that failed and led to pest incursion.

Solution

Cut small “windows” around penetrations and leave the mesh as intact as possible, as shown below in a still from the Rail Mount Method instruction video.

Sometimes you need to cut a slit in the mesh to fit around a piece of conduit. After installing the mesh, Be sure to “stitch” the slit back together with hog rings or metal (never plastic) zip ties.

Flat & Floppy Wire Mesh

When wire mesh is installed as a flat piece of material with no bends in it, it is floppy and unstable. This presents three problems:

  1. The mesh tends to be “wavy” after being installed, creating unacceptable gaps.
  2. The waviness looks unprofessional.
  3. When flat, the mesh has no rigidity and can be peeled back or pushed in easily by snow and critters.

This video clip illustrates the third point:

Solution

Crease the wire mesh into an L- or C-channel before fastening it in place. This gives it 3-dimensional stability and eliminates waviness.

A wire mesh C-channel has a professional appearance and no waves or gaps.

Railless racking systems

“Railless” racking systems are intended to speed PV system installation and use less materials to reduce costs. Unfortunately, they make it particularly difficult to keep pests out from under the solar array.

Roof Tech’s E Mount AIR and Apex products require short, hollow aluminum channels to be installed around the array perimeter. Unfortunately these act as “rat tunnels” and are difficult to seal as shown below.

Zep (now owned by Tesla) and IronRidge FX are two other railless racking systems that pose a similar problem due to their irregularly-shaped roof attachments protruding from under the array.

Solution

The best solution we’ve heard of for sealing these systems is to build an external “cage” around any hardware protruding from under the array.

While this method works, it is not as secure or discreet as a C-channel tucked under the array. The wire mesh is out in the open and may be vulnerable to damage by wind-blown branches and snow loads.

Tile Roofs

Tile roofs require extra time and attention to adequately seal with wire mesh. The gap shown here is unacceptable, as small rodents and birds can easily squeeze through.

Tile roofs are the bane of every animal guard installer’s existence! Whether they are flat concrete tiles, S-tiles or trapezoidal, tiles create an uneven surface that is difficult to seal. Unfortunately, the only way to seal an array over a tile roof is to cut slits in the wire mesh and bend it to match each step in the tiles. It’s a slow but necessary task; small birds and rodents can and will enter through gaps around tiles.

Solution

There is one trick that will speed up the process of conforming wire mesh to a tile roof and ensure the best possible seal. Rather than attempting to cut the wire mesh perfectly to match the roof, bend a 1-2 inch “flange” into the wire mesh where it meets the roof. Then cut slits into the flange, and bend the flange down to meet the roof. Bending the flange gives you more room for error in your cuts, as the flange can take up as much or as little space as needed. The flange also lends some rigidity to an edge that would otherwise be floppy and unstable where it meets the roof.

Metal Roofs

How not to install animal guard over a standing seam metal roof. (1) leave “bays” between standing seams open to pest intrusion, (2) leave large gaps or flimsy patches around rail protrusions, (3) use plastic zip ties.

PV systems over metal roofs are the most difficult type to seal. As shown in the photo above, standing seams create an uneven surface just like a tile roof– but unlike tile roofs, we cannot allow the wire mesh to touch and scratch the painted roof surface. We don’t know any installers who are 100% confident of their method for metal roofs, and many are refusing to install animal guard over metal. Several companies (including Slick Tools) are working to develop products that address this need; sign up for our email list to be the first to hear about them!

That said, protecting metal-roof PV systems from animal damage is possible. We’re going to devote our next article to this topic, including a breakdown of our recommended method, little-known facts about metal roof warranties, and an installer horror story!

Thanks for reading, and good luck out there!

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Solar Info

Cutting Corners – How NOT to Install Solar Animal Guard

This is the first in a series explaining common mistakes and animal guard failure modes.

In the photo below, wire mesh wraps around the outside corner of a solar array. At the corner, the mesh has been partially cut through, leaving a large gap for animals to pass through. Unfortunately, this is a common mistake. How did it happen?

The wire mesh was cut at this corner and left without a patch – providing easy access to pests.

The answer has to do with the J-hooks that attach the wire mesh to the solar panels. For J-hooks to hold wire mesh in place, the mesh MUST splay out from the array and be supported by the roof, as illustrated below.

This outward splay is necessary because unlike SnapNrack or CritterBlok, J-hooks do not fully support the mesh. If the wire mesh were suspended above the roof, there would be nothing to stop it from getting pushed under the array by animals, snow or wind.

Because of this splay, a slit must be cut into the mesh when wrapping it around a corner.

Most J-hook manufacturers recommend patching each corner using an extra piece of wire mesh and zip ties. Unfortunately, these patches are ugly, unreliable and time consuming to install. Unscrupulous installers will not bother with the patch, as we saw above. Even if a patch is applied, it will only last as long as the fasteners holding it in place (about 2-5 years for plastic zip ties in our experience).

This outside corner was patched with a piece of wire mesh, but the patch was secured with plastic zip ties. The zip ties broke after a couple years in the sun, allowing an animal to enter and build a nest.

Here are several ways to avoid all of these problems:

Solution 1: Don’t use J-hooks

Whenever possible, we recommend the Rail Mount Method or a full-support clip like CritterBlok instead of J-hooks. Those methods allow wire mesh to wrap cleanly and continuously around corners with no splay.

Wire mesh C-channels make for crisp, continuous corners – no patching or zip ties required.

Solution 2: Use wire mesh C-channels with J-hooks

Sometimes you are stuck with J-hooks – for example, when installing animal guard to a railless PV system. In these situations, use wire mesh C-channels instead of the traditional L channel. In addition to getting clean, patch-free corners, your entire pest barrier will be more durable.

Just like the Rail Mount Method, the wire mesh is bent into C-channels on the ground and tucked into place between the roof and the PV array. However, attachment is done with J-hooks instead of self-tapping screws. At each J-hook location, cut a small tab in the upper flange of the C-channel, so that the tab presses against the outside edge of the PV module. This keeps the wire mesh from being pushed under the array. Below are some examples of the finished product.

Solution 3: Secure patches with metal hardware

If you absolutely need to patch a corner, do not use plastic zip ties. Instead, use hog rings which are faster to install and will last for decades. Check out our AG Sourcing Guide for more info on hog rings and stainless zip ties, which are another good option.

We hope this info saves you and your team time and money! Share with your coworkers using the links below, and join our email list to get notified as we continue this series.

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Solar Info

New Instruction Video: Installing Solar Animal Guard with the Rail Mount Method

When I started designing and manufacturing tools for the solar industry, it quickly became clear that making great tools would only be a small part of the job. The real work would be to educate installers and operations managers around best practices to drive demand for these tools. It’s a roundabout form of marketing that requires a big up-front investment from Slick Tools, but I hope that educational materials like the video below will boost installer pride, profitability and willingness to invest in best-in-class equipment. And hey– if no one buys our tools, at least we’ll have made a few installers’ lives easier and accelerated the growth of clean energy!

On that note, I am thrilled to share the fruit of what has been a months-long effort to build a high quality, technically detailed instruction video on installing solar PV animal guard. The video demonstrates what I call the Rail Mount Method, which I learned at Namaste Solar Electric during my time as an installer there. I was surprised to find that very few other installers around the country are using technique. After studying every animal guard product and installation method on the market and speaking with a number of industry veterans, I feel this is simply the best method to install long-lasting animal guard for most situations.

A wide range of neighbors, friends, family and former coworkers helped make this video possible – from lending a leaf blower to clear unexpected snow off the array on shoot day, to providing dozens of hours of editing time at a “buddy” rate. In particular, thanks to Mark who allowed us to film on his roof; David and Tage from My Storyline, who filmed the video; and Joe Sherman who edited the footage!

Watch the video below and learn more about the Rail Mount Method at its dedicated web page.

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Solar Info

Announcing the Solar Animal Guard Sourcing Guide

Today we’re excited to share a section of our website that has been in the works for months! The Solar Animal Guard Sourcing Guide contains a breakdown of the most popular animal guard materials and tools on the market. Its main target audience is procurement folks at solar installation companies, but we expect this info to be super helpful for DIY-minded solar homeowners as well.

The Guide contains a section on each major component – the wire mesh, the fasteners, etc. For each section, we explain what to look for in that component – such as material, attachment style and other features. Then we provide our recommended product based on input from our installer network across the US. Finally, we list all the other options and their pricing. We’ve identified the lowest-cost retailer/distributor we could find for each product (Slick Tools does not distribute any of these products ourselves, other than the AG Bender).

We will continue to update this guide as new products come on the market and prices change. If you’re a manufacturer or distributor who would like to recommend an update or addition to the Guide, reach out and we would be happy to include you. There are no fees or strings attached, and we’ll make our best effort to objectively highlight the benefits and drawbacks of every product.

Finding the right tools and materials is just one piece of the animal guard puzzle. Stay tuned as we continue to publish resources like this for the solar community, including an upcoming step-by-step instructional video on AG installation!

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Solar Info

How Pests Damage Solar PV Systems

Thanks to prolific service technician Michael Payton for many of these fantastic images!

Nesting

Animals build nests under solar arrays because the arrays provide shelter from predators and the elements. Nesting is a precursor to every form of damage described below. Squirrels, birds, rats and raccoons are the main offenders.

Primary Damage

Chewed wires

Squirrels, rats and other rodents must regularly gnaw on material of a particular hardness in order to sharpen their teeth. The vast majority of modern PV systems have exposed wires underneath the array which cannot be enclosed in conduit. These wires have a thick coat of insulation which is, unfortunately, irresistible to rodents. Note – you may have heard of the phenomenon of rodents being drawn to soy-based wire insulation. Whether or not those stories are true, soy is not an ingredient in the tightly regulated wiring used in modern PV systems.

Once an energized wire’s insulation has been chewed through, there is a risk of fire, electrocution and lost production.

Roof rot

Most roof surfaces are will slowly degrade if moisture is continually present. When an animal builds a nest under the solar array – or sticks and leaves simply blow in and accumulate – the organic material retains moisture and prevents normal drying. Nesting animals also have a tendency to scratch away the roofing material at the nest site (both squirrels and raccoons have been known to burrow clear through the roof and into the attic). This leads to water damage.

Hot spots

Every solar PV array performs best when it’s kept at a low, uniform temperature. When a nest reduces airflow at one location under the array, a few individual PV cells heat up and become restrictive to the flow of electrons through the system. This causes them to heat up even more, creating a “hot spot” with an outsize impact on system performance. The presence of a hot spot may also increase fire risk, with under-array temperatures routinely reaching 150°F even for normally-functioning systems.

Secondary Damage

Water damage

When the waterproofing membrane of a roof is compromised due to roof rot or animal burrowing, water can enter the home and cause direct damage to drywall and paint as well as long-term mold issues.

Fire

While PV-related fires are extremely rare, they have occurred. Nearly all documented cases we’ve found were the result of wires or connectors being damaged or improperly installed, such that current flowing through them was restricted but not cut off completely. Such a restriction converts electrical energy to heat, and can ignite nearby materials. Unfortunately, a restriction in normally-current-carrying conductors (as opposed to an outright severance or ground fault) will not trigger any safety mechanism – allowing the problem to continue unnoticed. Roofing materials and PV components are designed to be fire-resistant, but the organic materials of a nest can ignite easily.

Electrocution hazards

When the insulation around an energized conductor is compromised, that conductor presents an electrocution risk to anyone who comes in contact with it. This risk is amplified when the conductor comes into electrical contact (e.g. when it rains or snows) with other metal components of the PV system, such as the racking or module frames. Modern, code-compliant PV systems include a safety mechanism that will shut down the system if such a ground fault is detected, making this more of a lost production hazard than a safety hazard. However, ground-fault protection systems do not always function as intended, and older inverters may lack protection and require replacement if there is a ground fault. Any PV system with suspected insulation damage should be deenergized immediately.

Lost production

In a 2020 report based on observations of 100,000 PV systems over 5+ years, the National Renewable Energy Laboratory found that “damage caused by animals may not occur often, but… can have substantial impact on annual production.” The report tracked lost production specifically attributable to pests, and found an average 28% production loss during the year in which the animal-related event occurred. For reference, this would represent a loss of about $350 for the average US residential PV system.

When a PV system stops operating entirely due to a ground fault, broken conductor, or during repairs, it of course stops generating income and reduces the system’s return on investment. Such disruptions often take longer than expected to fix due to high demand and low supply of solar service technicians.

A bigger problem, though, is when system output is reduced due to animal activity but not stopped entirely. This is likely to go undetected by the system owner because solar PV production is so variable to begin with (due to weather, temperature and other effects). Production losses can then persist for years.

What to do about it

Phew… now for some good news!

All of the hazards described above can be virtually eliminated through the careful installation of a good quality solar animal guard. This is best done by an experienced professional, but homeowners on a budget can do it themselves.

Stay tuned as we publish more info to help homeowners, installers and investors decide whether animal guard is worth the investment, and how to perform a top-quality install.

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