Solar Mounting System Guide: Racking Matters
You have already selected your home solar panel system and now you are trying to figure out where to place it, on your roof, in a field, on a pole. Even though most systems are designed for your roof, you do have other options. The racking system that you choose will be a critical component for the durability and safety of your system. So don't forget to look at the options and this learning article will provide you with a guide to the various racking systems available.
When houses were first designed and built, their roofs were never intended to hold large amounts of weight. Snow, rain and debris buildup is one thing, but anything more and the roof runs the risk of being damaged. In this day and age of technological advancements like renewable energy, many homeowners are installing home solar panels on their roofs. This is fantastic, but you can't simply lay your solar panels on your roof and hope for the best. They must be installed correctly and protected from high winds and various weather conditions. 
On top of that, each solar panel weighs between 25 and 40 pounds. Multiply that by 15 to 20 panels, which would be an average array, and you are looking at quite a load for your roof to endure. This is where racks/mounts come in. In this learning article, we will be discussing the different types of panel mounts, floating versus non-floating mounts, different types of penetrations, array edge screens and more.
Roof mounts, ground mounts and pole mounts
For the purposes of this article, we will mainly be covering roof mounts. However, we will touch on all the different types to give you a general knowledge of all of them. Roof mounts are generally used for mounting solar panels on the roofs of buildings. Roof mounts come in various forms, which we will get into a bit later.
Ground mounts, as you might guess, are primarily used for mounting solar panels on the ground anywhere on your property. If your roof lacks the space for a roof mount or is heavily shaded by trees or location in the sun's path, this is a viable alternative. These are usually adjustable to allow them to tilt up or down for maximum solar absorption at various times throughout the day.
Finally, pole mounts are used for anchoring solar panels to, you guessed it, poles. There are two major kinds of pole mounts, "top-of-pole" and "side-of-pole". The former allows the solar panel to sit on top of a pole, elevated several feet off the ground. The latter anchors solar panels to the side of poles.
Related Article: Solar Mounting for Your Home Solar Panel System: Pole Mounts
Different types of roof mounts
Flush mounts are the first type of roof mount that we will cover. They are an inexpensive and a simple option suitable for most roof-mounted solar panel installations. They are generally not adjustable, and as the name suggests, they are designed to lay flush with the roof surface on which they are mounted. The solar panels are generally secured using metal clips that hold the panel in place, leaving about 2-4 inches of space between the roof and bottom of the panel. This allows for plenty of airflow along the underside of the panel, which keeps the panel cool and operating at maximum efficiency. If a panel overheats, its efficiency drops and so does its life.
These mounts are great for homeowners, less so for business owners. Roof mounts in general aim to protect your roof as well as the solar panel itself. The flush mount reduces wind load on the solar panels. Flush mounts are ideal for reducing the dead load on your roof, they work for any type of system, are suitable for high wind areas, there is room for flexibility in the panel slope and orientation and they provide minimal interference with roof drains.
They are not without faults though. Depending on the type of roof you have, installing a flush mount could require a roof penetration (penetrations are not required normally), which will increase the risk of roof leakage.
Ballasted mounts are similar to flush mounts, but use weights to hold the solar panels in place on your roof. This design can save labor time and costs, but presents an additional challenge of getting the weights onto the roof, which can be quite substantial when dealing with larger systems. Ballasted mounts do not require roof penetrations, are faster and cheaper to install and allow for a panel tilt of up to 20 degrees for optimal solar exposure. However, this mount increases the load on your roof, has lower power density, and is less suitable for high-wind areas. They are limited by certain site conditions like roof slope and building height.
There are also hybrid mounts, which you can probably guess are a combination of flush mounts and ballasted mounts. They use some structural elements of both mounts to accommodate some roofs that can't support either. Hybrid mounts require minimal roof penetration, can be fast to install (depending on the model) and allows for custom design optimization based on factors like load bearing and wind. These mounts are typically more expensive and can take up more space on your roof, leaving less room for your system.
Roof-ground mounts are similar in design to normal ground mounts, but are able to "sit" on your roof. Depending on the type of roof you have, this may be better than a flush mount. Roof-ground mounts have the ability to come adjustable or fixed for maximum solar exposure throughout the year.
Roof mounts are optimal when your home or building has sufficient space for all of the solar panels that you require. They also have the option of being fixed or adjustable and can also be installed with a solar tracker. Solar trackers are an automated system that allows your panels to track the sun's path throughout the day for optimal solar exposure and collection. However, while solar trackers do increase efficiency and reduce manual upkeep of your panels, they are not commonly used due to the hefty increase in total cost and the addition of another moving part that potentially break down and cause problems for your array.
Related article: Beginners' Guide to Solar Trackers: How to Increase Output for Your Home Solar Panel System
Mounting your solar panels
As stated before, for the purposes of this article we will be focusing on roof mounts. Whether you have chosen a flush or "roof-ground" mount, the racks(the rails on which the solar panels sit) need to be mounted to your roof. These are generally mounted in rows across the length of your roof.
There are a few things you must know before installing your panels:
- Type of roof surface (Spanish tiles, flat gravel, concrete tiles, asphalt shingles, etc.)
- Length and width of the array space
- Number of rows needed
- Thickness of the roofing material between the mount itself and the rafters of the roof
- Distance between the beams of the roof
Overall, the potential problems that come with racking and mounting your solar panels have nothing to do with the weight of the system and what that does to your roof structurally. With the proper racks, mounts and installation, your roof will have no trouble handling the load. The main concern is the solar panels catching strong winds and flying off of your roof, taking a chunk of the roof with it. As long as the racks and mounts are installed properly though, this isn't a problem. Most, if not all, mounts are rated to withstand wind speeds up to 150 mph.
Leaking roofs are another large area of concern many people have when installing solar panels, but again, if the install is done correctly, leaking roofs should never be a problem. There are some cases of rain water seeping into the penetrated area of the rafters, but flashing the penetrated area, which simply involves covering the area with a metal plate to make it water-tight, can prevent this. On top of that, a sealant is also placed around the penetrated area for additional protection against the elements. These sealants generally last longer then the solar systems themselves, up to 50 years for high-grade sealants.
Related Article: Solar Racking Made Simple: What You Need to Know About Designing Your Solar Energy System
The actual "mount" itself is a clamp that is attached to the rail and "clamps" the solar panel down against the rail, securing it in place. There are a few different types of clamps, and the best fit depends on the type of roof (flat or pitched) and the type of shingles.
Standard roof mounts and attachments
The standoff penetration is a standard attachment that is best used on flat roofs that are pitched, comp shingle or tile. Roofs with tile or thick roofing material will likely require a standoff. The 4-hole base is meant to be used with TGI rafters and can accommodate up to a 10 inch standoff. HD standoffs are used on flat roofs where there is a lot of built-up foam installation and a taller standoff is required. The L-foot with base and flashing (displayed in the image at right) is recommended for simple, flush mounts to a roof with composition shingles only. Finally, there are standoff tilt kits that allow for 10 - 45 degree tilts of your solar panels. Depending on the roof type, it may require a combination of these components to achieve the optimum conditions.
Metal roof mounts and attachments
For metal, non-standard roof styles, there are a few options to consider. The metal roof seam clamp attaches an L-foot or PV module directly to a commercial grade standing seam metal roof without penetrating the metal. The corrugated roof block allows attachment (displayed in the image at left) of the L-foot directly to a structural member covered with a corrugated metal roof without collapsing or crushing the ridge in the metal roof material. The new metal roof base provides a robust self-sealing mounting base for common corrugated metal roof profiles. The base seals to the roof with an integral EPDM Rubber Washer and a sealing top cap. This new base assembly kit has been tested to withstand over 4,000 lbs. of uplift force(from strong winds, for example). Finally, the hanger bolt clamp allows a versatile installation on roof surfaces that won't allow L-feet or stand-offs.
Array edge screen and accessories
The array edge screen(or critter guard) is designed to keep birds, squirrels and other small animals from making their homes under your solar panels. These screens are attached to the sides of fixed solar panels secured by a flush mount and are made from vinyl-coated steel mesh screening that can be adjusted to fit many different height variations. The mesh screen is rugged enough to keep even the most persistent creatures out.
Some accessories for your solar panels include splice kits, which allow you to attach two lengths of rail together to create a strong single support. Rail end caps cover the ends of the rails to create a seamless line to the end of the array. Rail covers provide a complete wire management solution and a clean look to an installation. Channel nuts snap into the rail and provide a mounting location for a standard bolt. Finally, the microinverter attachment kit includes all of the hardware needed to attach microinverters to a system.
Related Article: Solar Panels for RVs: Racking Solutions
Floating solar systems
Floating mounts, or floating your solar system, while not extremely practical for residential systems, has seen growth recently. Land is a hot commodity and, unfortunately, finding enough land to build solar systems on can be a challenge. That is where floating mounts come in. Have a pond on your property that you aren't doing anything with? Float a solar system on it! The obvious benefit to this would be that you don't need to worry about taking up any precious land for your solar system. The downsides, however, include being more expensive and difficult to install. In addition, the environmental implications could be heavy depending on what organisms live in the body of water that you are floating your system on.
Conclusion
Always remember to take into consideration climate, common weather patterns/conditions and how much roof space you have available versus how much you need for your system. These factors play a large role in deciding whether or not a roof mount or ground mount is right for you. No matter what type of roof you have, or what kind of mounting system you need for your solar system, SolarTown has everything you need to make mounting your system easy and stress-free.