It’s ironic that the best place for solar panels (rooftops, yo) is also the most difficult place to mount them. Solar panels need a place that’s sturdy, unshaded, and pointed towards the sun, and roofs fit that bill nicely.
But getting up there can be a pain, and attaching panels to the roof means drilling huge bolts into the rafters by commercial roofing companies. Also, because of the huge variation in roofing materials and construction techniques, the solar industry has had to invent many different methods to attach mounting hardware.
Well, invent them it did, so whether your roof is covered in slate tiles, asphalt composite shingles, or cedar shake, you can find an installer who will use the right mounts for your roof and make sure to avoid any of this:
General Information about solar roof mounting
Solar panels are designed to be easily and durably mounted to racks that attach to roof mounts. The mounts themselves have to be drilled into your roof’s rafters, but not because the panels themselves are heavy. Instead, building codes call for protection from “upforce.”
Basically there is way more danger to the panels catching air like a sail and ripping off your roof than there is to them weighing too much and pushing through your roof. If they are bolted to the rafters then they are attached to the infrastructure of your house, and there are no worries.
They drill into roofs, don’t they?
The fear about roof penetration from solar installations is definitely one of the top concerns of people that are serious about installing solar panels, so let’s just clear the air. Yes, just about every solar installation will involve giant screws being attached your rafters, like this Fastjack:
Unless you have a standing-seam metal roof, the mounting system will use bolts similar to this. To prevent water damage, the bolt fixture will be surrounded by flashing, which is a special metal or plastic shield that slips under the surrounding roofing tiles to prevent water from getting in. The flashing will be sealed with tar or underlayment, and the bolt hole will be filled with long-life sealant, as well.
Like we said above, installation practices vary by roof material. Here’s an idea of the unique challenges for each:
- Clay or stone tile roofs sometimes require additional labor to remove tiles, install the mounts and flashing, and make cuts or grooves in the tiles so they don’t contact the mounting hardware
- Wood shake roofs are easier to cut/drill into, but require flashing that extends far underneath the tiles higher on the roof
- Asphalt composite shingles are easy to work with, as long as the installer can find the rafters
- Standing-seam metal roofs are the easiest, requiring no penetration of the roof, because solar mounting clamps can be attached to the seams
What about when I need to replace my roof?
This is another big concern people have, and not without reason. Replacing a roof is expensive, and having to remove solar panels before you do it (and reinstall after) is a big deal, right? Well, kinda, so make sure to contact a roofing specialist before you start.
It costs about $1,000 (could be less or more based on installation size) to pop off existing panels to let a roofer do their thing, and then put them back on. And while it might be advisable to wait to install solar if you plan to replace your roof in the next few years, it might be more advisable to replace your roof sooner, and go solar before the federal solar tax credit expires.
Regardless, if you need remove panels to replace or repair your roof, call a NABCEP-certified solar installer to have the job done right. If you have a PPA or lease contract with an installer, look in your contract to see if they have any rules about who can do the work, or whether they’ll do it for you. The panels are their property after all.
Here’s a little more about mounting solar panels on each type of roof:
Solar mounts for tile roofs
Mounting solar panels on most tile roofs works the same way: remove a tile or three, attach the tile hook and flashing, carve tiles out of the way, and replace the tiles where they were (you can see a tile hook covered by flashing in the image above). That holds true for concrete, clay and slate. The tools used vary by type, but not much.
Spanish tile roofs are the most expensive type to install solar panels on. The reason is installers have no choice but to walk on them, and inevitably break some of the tiles. The owner must have extra tiles lying around, or installers must be able to find a match ahead of time to be able to replace. There is also some added time spent both drilling through them and treading carefully upon them.
These days, though, solar installers have gotten pretty good at working with tile roofs. Just make sure you get something in writing before they begin the work, to make sure their insurance or warranty covers any damage to your roof.
Installing tile hooks for solar
Though the image above shows a tile hook installed under S-shaped tiles, but the method of installation is very similar for other types of tile roofs. Here’s a great video from our friends at Quick Mount PV that shows how tile hooks are installed:
One way to avoid the need to cut or grind the tile is to use tile replacement mounts, which take the place of the tile under which the mount is attached to the roof.
Solar mounts for wood shake roofs
Wood shake shingles are a fun way to cover a roof, and they work pretty well, too… until you start putting holes in them.
Solar installers need to be particularly careful when working with shake roofs, because the shake pieces can be brittle, but the actual installation of the mounts isn’t that complicated.
Nearly all shake roofs are made in the same way, with layers of underlayment between the rows of shakes. That means an installer just needs to get flashing up under the previous layer of underlayment and ensure a good seal. The picture above shows how a properly-seated flashing looks as it extends underneath the rows of shakes.
Solar mounts for asphalt composite roofs
Asphalt composite roofs are popular. Heck, you’ve probably got one over your head right now. They’re relatively inexpensive, simply constructed, and generally very durable. That makes them a great surface on which to install solar panels. As long as the installation is done right.
Mounting solar panels on asphalt shingles is similar to mounting under cedar shake, in that the installer will insert flashing under the previous layers of shingles to maintain water-tightness, then seal the hole into which they’re screwing those giant bolts. When done right, it looks like the image above.
When done wrong, it looks like this:
That sealant might hold for 25 or 30 years up there, or at least as long as it needs to before the roof is re-shingled in a decade, but it’s ugly, and it probably voids the roofers’ warranty. You don’t want your home’s watertight integrity to be beholden to that crappy craftsmanship (crapsmanship?), do ya?
Solar mounts for standing-seam metal roofs
Standing-seam metal roofs are awesome. They look good, they’re watertight, and they last for 50 years without much trouble. Oh, and those seams are the perfect place to clamp solar mounts, without drilling into the roof.
The longevity and ease-of use makes standing-seam metal roofs the perfect roof for solar panels. Once your panels are up there, aside from the occasional cleaning, you probably won’t need to worry about them much for the next few decades. And of something does need to be done to the roof, the panels are easier to remove and replace than on any other type of roof.
On top of all that, the spaces between the seams act as channels for air circulation, which makes your panels more effective by cooling them off during the day.
Isn’t it purdy?
The future: Boltless? Roofless?
Now it’s time to look ahead. Tesla’s got that pretty looking solar roof, which means your solar panels become your roof. They’re made of glass that’s designed to look like clay, cement, or slate tiles:
But the solar roof tiles are better for new construction. Even if you’re going to replace your existing roof, the substrate might not be ideal for Tesla’s tiles, and retrofitting would likely add thousands to the cost.
Another up-and-coming invention is a unique kind of ballasted solar rack that sticks to sloped roofs like a lizard’s feet stick to a window. The installation uses heavy frames with a special kind of polymer that grips the roof surface tighter as pressure (from the panels or wind) increases.
So the future of mounting solar on roofs might be bolt-less. Or it might be solar roofs. Or it might not be either. It’s too early to tell, and it’s almost always better to start saving money on energy today.