Brian Sadler of Solaris Renewables discusses how to assess if a home is suitable for solar panels. Factors include roof orientation, shading, and space.
John Maher: Hi, I am John Maher and I’m here today with Brian Sadler, Vice President at Solaris Renewables, a solar company in Massachusetts, providing premium solar and storage technologies with exceptional customer service; and designing, installing and servicing solar systems in Massachusetts, Southern New Hampshire and Maine. Today we’re talking about “is my home suitable for solar panels?”. Welcome, Brian.
Brian Sadler: Hi, John. Good to be with you.
Key Factors in Assessing a Homeowner’s Roof for Solar Panels
John: Yeah, you too. So Brian, can you walk me through the process of how you assess whether a homeowner’s roof is suitable for solar panel installation? What are some of the key factors that you consider?
Brian: Absolutely. This piece has matured quite a bit over the years. First, we kind of stuck our thumb up in the air and said, “Oh, it looks like it’s about 80% solar access.” And we had a tool that we…it was a lot of eyeballing, right? And then there was a couple different tools that would’ve been checked maybe with the site visit, the project manager. Pathfinder was one, SunEye was another one. And these were tools you could get the pitch and some of the solar access by putting the device on the roof and taking some really basic measurements. Some of it did more calculations like the SunEye than the Pathfinder did when you did the calculations yourself. And now a lot of this is really done remotely through really advanced software tools that use a variety of different measurements through satellite imagery.
Some of it has planes flying over that are taking imagery as they fly and we get more updated images through that. You have LIDAR, which is measuring the height and relationships of height between buildings and trees and topography. So there’s really massive strides and advancements in the tools that we have, to get really accurate measurements, for actual physical measurements between of roof sizes, pitch and obstructions on the roof or on the property. And then, taking into consideration the latitude/longitude where the house is, the topography, and getting really accurate data on the potential for each roof or the site in general.
So it’s really been a massive advancement there. And when we boil it down though, there’s really three factors that we’re looking for. And if we talk about these in general terms as opposed to what the industry terms are we’re looking at, the first thing is orientation of southern exposure. In this measurement is, in the solar world, is called azimuth. That’s basically on the compass. So due south being 180 degrees is ‘perfect’ and the opportunity to get the most sunlight throughout the day in the Northern Hemisphere. And then the second piece is really shading or lack thereof. So in terms of the solar, it’s solar access or sun hours, how many sun hours are hitting that surface that we’re targeting to put solar panels on? And then the last piece is roof space or how many panels can we fit compared to what your needs or what your goals are. And that comes down to kilowatt system size, how many panels and what is the wattage and what’s that fit going to be.
So those are the three factors that really are going to dictate how Solar is going to work on any surface and any site. I should mention that pitch comes into play, as well, on the roof’s surface, and what is that? The tilt of the panels themselves as well. And that does play a role. And all those factors come together to what’s called the TSRF or Total Solar Rating Factor. And that basically gives a score between zero and a hundred percent and depending on the equipment and the setup the TSRF will basically dictate how productive, how many kilowatt-hours that system and that surface will be able to generate.
Shade Tolerance of Solar Panels
John: Okay. So obviously like you said, sunlight exposure is crucial for solar panel efficiency, and one of the things that you mentioned was sun hours. Does the amount of shade that your roof might get play into that number of sun hours? And how much shade tolerance do solar panels have? And when you come to the house, do you assess things like nearby trees or structures that might impact shade on my roof?
Brian: Absolutely. Yeah, shade is a huge indicator. It’s really that second piece, right? Aside from which way your roof is facing now, how much sun is that getting and shade is going to be usually the key components of blocking that sunlight from getting that. Now, like you said, it could be trees or the building itself, like an adjacent roof surface or dormer or obstruction on the roof surface or nearby obstructions as well. But, generally speaking, it’s trees, and fortunately we have a lot of trees here in New England, which makes our area beautiful, but it also, for some sites, can be a challenge to getting the right mix of design and panels in order to make it effective for the homeowner. Fortunately, we have plenty of wide open spaces and the panels, like you’re just asking, the panels have come a long ways and are more shade and snow resistant as well.
And it’s kind of one and the same because when there’s snow on the panels or if there’s shade on the panels, it makes them essentially less productive, and some of how they wire the panels now and kind of set them up into either two different halves or different quadrants depending on the manufacturer that can give some key resilience to shade. So sometimes you can have some panels, older panels, you might have a little bit of shade on the panel and it will shut down the whole panel. Now we can have shade on half the panel and the other half the panel’s working, or shade on a portion of the panel and the rest of the panel is working. So that really comes down to working with your solar provider and professionals to understand the equipment and the science behind the site to find a solution that’s going to work best for you.
Roof Age and Condition
John: So then in terms of the roof itself, is there a certain age or condition that my roof has to be in in order for it to be suitable for solar panels?
Brian: Yeah, good question. Sometimes this gets a little bit overlooked, so we want to make sure that we are going to install the system and have it be there for the long haul and we want to make it a situation where it can be a set it and forget it type of scenario for the home and they don’t need to worry about removing it, and roof repair,s and so on and so forth. So, we’d like to see a minimum of 10 years roof life left in the system, excuse me, in the roof. But a lot of times that’s longer than that, or if the condition of the roof is substandard, we’ll recommend re-roofing before going solar and then you don’t have to worry about that for the long haul.
So that is definitely a key factor. Another piece is the structural integrity of the roof. In every single project we have an independent structural engineer do the calculations of the system that we’re proposing on the roof substrate and the structure of that to make sure that it’s protecting the homeowner and their property and that the solar system can be supported by their existing roof structure.
Roof Pitch
John: Then you mentioned pitch earlier, let’s talk a little bit more about that. Here in New England we have everything from maybe a flat roof or close to flat roofs to A-frame houses maybe up in New Hampshire that have an extremely steep pitch to them. How does that factor into how efficient the solar panels can be and is there anything that you can do within that to work around that?
Brian: Yeah, absolutely. So we’re on the 42nd parallel on the earth. And so logic would think that okay, so you want to be 42 degrees and then square yourself up to the sun, but the sun moves throughout the year. It’s lower in the winter and higher in the summer. So roof pitch does play a role in the productivity of that roof surface. I would say any pitch is good because now you’re lifting to get more year round sun involved. And an extreme pitch might be better in the winter, but it might be a little bit less productive in the summer because you’re bringing that pitch up to meet the lower sun angle. If it’s extreme, like you’re saying like a 60 degree on an A-frame or something like that, it’s really extreme, but also now you’re likely bringing more potential shading that’s close by into the picture as well.
Every roof surface really has potential, and between a flat pitch where we can lay them flat in certain situations, because maybe space confinements and we want to get as much power on there. If it’s a big wide open flat roof, we have tilt kits and a variety of different options to be able to tilt the panels up. Usually we go to 10 degrees and that allows to bring more sunlight in throughout the year. But you’re really going to be cooking more in the summer months when the sun is overhead more and you’re getting longer days and just be more productive throughout the year. I would say that certainly roof pitch plays a role, but there are applications really for any type of pitch and to make it effective.
Suitable Types of Roofs for Solar
John: What about the type of roof that you have? Most houses here have asphalt shingle roofs, but there’s other things, some people have metal roofs. Are things like metal roofs appropriate for solar panels and are there any other types of roofs that you’ve seen?
Brian: Absolutely. We have old housing stock here in New England and so we get every type of roof. We have wood shingle roofs, slate roofs, asphalt like you mentioned, rubber and a variety of membrane roofs and even metal, you brought up metal. There are a few different options there. So we see for metal roofs alone, we see corrugated metal roofs, which kind of have a profile to them and wavy and we see them in home applications as well as barn and outbuilding applications. Then we see standing seam, which is a little bit more of a finished and robust metal roof surface. And then we see now there’s metal shingled style roofs that kind of have tiles that clip together from the side. All of them have a long lifespan, which is why they’re attractive to homeowners, as well as shed precipitation really well. But we have applications for all of those types of metal roofs.
So there’s certain installation methods for standing seam, for corrugated metal and for shingled metal roofs as well. And then the same thing with rubber or membrane or rolled asphalt or shingled asphalt, we do have applications for all those roof surfaces. Wood and slate I would say are particularly challenging and require a really significant amount of labor and are also a little more challenging to work on. And even I would say could be dangerous, the slate in itself is slippery. A lot of times they’re on very steep roofs. And wooden shingled roofs, if they’re old and you’re not aware that they’re rotting out, they can give way, as well as they can get build-up of slime and moss and be a little slippery. So there are some challenges with those as well. So we pretty much have decided to do everything aside from slate and wooden shingled roofs.
John: But everything else, like you said, it might change a little bit of the structure of how you’re affixing the solar panels to the roof, but you have ways to work around any of those different things?
Brian: There’s different mounting techniques and equipment to meet the needs of the roof surface.
Ground Mounted Solar Panels
John: Okay. So what if my roof is not really suitable for putting solar panels off? Maybe I have a wood shingle roof or something like that and I just can’t put them on my roof. Are ground mount solar panels an option? What are some of the advantages and disadvantages of ground mounted systems versus roof mounted ones?
Brian: Absolutely. Yeah. So we do, and have long done, different ground mounted solutions, and there’s a fixed ground mounted solution which is basically an infrastructure supporting rows of panels. So we see them on the side of the highway a lot of times with a lot of the solar fields and such. And then we also do a dual access tracker, which is more of a pole mounted installation. It stands up a little taller, and then that tracker, it follows the path of the sun and the angle of the sun throughout the year. So it actually moves and it tilts based on the time of year and the height of the sun and then it moves side to side to follow the sun throughout the day. So the trackers are an opportunity to have a smaller footprint and less panels to have more production. They’re generally about 40% more productive than a fixed panel.
And then the fixed ground mount solutions are also great if you have wide open space. So they come out to be essentially similar in cost. So it kind of depends on your landscape and what your prerogative is. Some people just love the idea of a tracker. It is a really cool technology and device. It’s actually just amazing to watch it operate. So really at the end of the day it comes down to your land. And you need for both of these, any ground mounted solution, you want wide open space. So you want to have significant wide open space because you want these to be shade free and now that they’re lower as opposed to a roof on the top of a house, they would be bringing in more shade. So it really needs to be a wide open area.
But we have a lot of space here in New England, so there’s a lot of opportunity for ground mounts to be a great solution for homeowners, but it’s not necessarily meant for your side yard in Revere and whatnot. But it’s definitely more of a wide open space solution. But we’ve had some unique applications across the state as well and we’ve had a lot of homeowners that have been willing to change up their landscape by removing trees or we’ve even put one in a boulder and a tracker in a huge piece of ledge. And so I think there’s definitely opportunities, it depends on how flexible the homeowners are and what kind of landscape do you have?
John: Is there a minimum amount of land that you need to make something like that work? Do you need a few acres or something like that?
Brian: So you don’t necessarily need a few acres. And again, it depends on how big, because we can do a ground mounted solution that’s as small as, I don’t know, 16 panels for instance, or the tracker is 24 panels or 20 panels. So it really comes down to having some wide open space and no tree cover.
John: Right, it’s more about the way that your land is laid out. Like you said, if it’s just open field and there’s no trees right nearby, then you don’t need as much land as you would if you had tall trees around the border of your property or something like that.
Brian: Yeah, we want to position it facing due south as much as possible. Sometimes we’ve tilted it a little bit off the due south, but you want to get that facing due south to give the most opportunity to collect sun. And kind of a generic rule of thumb that you might use is if a tree in question would fall and it would hit the ground mount or your roof as well, if you’re thinking of it that way, that tree is likely to create shade. So if you’re thinking of how positioning a ground mount or is my roof good for solar as well, but you’re worried about this tree or that tree, think of it as if that tree were to fall towards where we’re targeting to put the solar array, would that tree likely hit it or not, I think is an indication. And if it’s falling and going to really smother the array, well it’s probably going to create more significant shade. Like I said, those ground mount units are lower to the ground and they will bring in more shade. So you really do want to target more open spaces.
John: All right, well that’s really great information, Brian. Thanks again for speaking with me today.
Brian: Thank you ,John.
John: And for more information you can visit the website, it’s solarisrenewables.com or call (781) 270-6555.