Rooftop Solar And Exclusion Zones: Where Solar Panels Dare Not Go

solar panel exclusion zones

How close to the edge of the roof should your solar panels go?

In the past I’ve written about solar panel clamping zones which determine where, on a solar panel’s edge, you can place the clamps that attach the modules to their mounting rails.  What I didn’t do was go into just where on a roof solar panels can and can’t be installed.

Depending on the roof mounting system used to attach the panels, there may be ‘exclusion zones’ where no solar panels are allowed.  These zones exist because winds are strongest around the edges of roofs. Installing away from the roof edge reduces wind loading on the panels and makes them less likely to be damaged or even torn off in a storm.

I looked at five different manufacturers of solar roof mounting systems and was able to find Australian installation guidelines for four of them.  Only two of these guidelines were available on manufacturer websites and so should be the most up to date versions available.  Of the four systems for which I had installation manuals, two do not require exclusion zones, one has a small exclusion zone of 20 centimeters from roof edges, while another has a massive exclusion zone that can be over 80% of available roof space — but I assume this information is out of date.

Installers are required to follow manufacturer recommendations in order to comply with Australian standards.  If they want to do anything that isn’t recommended, first a certificate has to be obtained from a structural engineer that states the specific changes being made won’t reduce the strength or safety of the installation.  Even when manufacturer guidelines don’t require it, installers still need to leave enough space at the bottom edge of a roof so water flowing down solar panels doesn’t overshoot the gutter.  It is also good practice to leave at least 20cm between panels and roof edges.

While I said some manufacturers don’t require exclusion zones, I will mention that air is automatically an exclusion zone and if any part of a solar panel extends beyond the edge of a roof, that is not a good thing, unless it is part of a special construction that a structural engineer has signed off on — but they never are.

overhanging panels

Overhanging the edge is not allowed – unless you have a certificate from a structural engineer.

Roof Mounting System Basics

Australia is divided into four main wind zones ranked from A to D in order of increasing maximum expected wind speed.  D is Australia’s most dangerous cyclone zone in Western Australia.  While not an official description, you may find the following makes them easy to remember:

  • A for All Right
  • B for Beware
  • C for Cyclones
  • And D for you are going to Die

The more dangerous a wind zone is, the more roof attachment points are required to securely hold a solar power system in place on a roof.  Some roof mounting systems may not be suitable for some wind zones, but all four systems for which I was able to find installation manuals are.

Installers are also need to pay attention to the surrounding terrain as maximum wind speeds will be higher if a building is surrounded by open ground and lower if it’s surrounded by structures and/or trees.  Other factors that can affect the number of attachment points required are building height and roof slope.

With Roof Mounting Systems You Get What You Pay For

Tragically, it’s not always true that you get what you pay for.  There are plenty of rip-off merchants in the world just waiting for their chance to overcharge you so they can make another payment on their diamond powered Lamborghinis. But for solar panel mounting, equipment price is a good indicator of quality.  This is because it is bought and installed by hands on professionals who are obligated to return and fix any problems it may cause.  This means if the components of a roof mounting system aren’t top quality then their price has to be low enough to to compensate for the possibility an installer will have to return to fix problems.

All roof mounting systems have to be certified, so no matter what is used your solar power system isn’t likely to blow off your roof in a storm.  But there’s a big difference between getting top marks and just scraping by with a passing grade.  If you pay more for quality your roof will be less likely to suffer minor damage or leak, which can lead to major damage.  If you do have problems, the solar installer is required to fix them, but it’s a lot better to not have problems in the first place.  To be clear, I am not saying you will have problems if you choose a cheap option, it will depend on what kind of roof you have and how carefully the installation is done, but the risk will be greater.

Australian Made Is Best

If you were to ask me which country makes the best roof mounting material I would say Australia.  Two Australian manufacturers, Radiant and Sunlock, make some of the best gear around.  These people know what Australian conditions and cyclones are like.  So while I normally approve of destroying Australian industry1, just this once I will make an exception and recommend these Australian products to people interested in high quality.

10 Year Warranties Are Standard

Roof mounting systems generally come with a warranty of 10 years.  Clearly this is a problem if you are expecting your system to last as long as the 25 year performance warranty most solar panels have.  This is one more reason to select a high quality system as they are likely to last longer.  All the mounting systems I discuss below have 10 year warranties with the possible exception of Radiant.  While only 10 year warranties are currently mentioned on their website, in the past they have offered 15 year warranties2.

Popular Mounting Material Manufacturers

In Australia most roof mounting systems are supplied by the following manufacturers:

  • Clenergy
  • Grace
  • Radiant
  • Schletter
  • Sunlock
  • Titan

Clenergy

Clenergy is a Chinese company that produces lower cost mounting materials.  Their PV-ezRack SolarRoof system can be used to mount solar panels on metal and tile roofs with slopes from 0 to 60 degrees.

The interesting thing about Clenergy’s exclusion zones is it doesn’t seem to have any.  There’s no mention of them in its installation guide or this brochure.  In this picture from the brochure you can see the panels get quite close to the edge of the roof:

Clenergy Picture

Here’s another picture from the Clenergy brochure that shows the system is really edgy:

Gutter Jump

That system is close to all the roof edges.  It’s so close to the bottom edge I hope during a downpour water flowing over those panels won’t fly over the gutter and miss it completely.

Grace

Grace Solar, also known by the rather insulting name Grasol3, is a Chinese producer of low cost solar panel mounting gear.  On their website I couldn’t find any installation instructions or information on exclusion zones.  Looking online I was able to find a PDF of their installation manual, but because it didn’t come off their site I can’t be certain it’s up to date4.  It contained the following diagram on exclusion zones:

Grace Exclusion Zones

Their formula makes for very large exclusion zones.  If a house has an average height (H) of 4m, a depth (D) of 10m, and a breadth (B) of 15m and the exclusion zone around the edge of the roof is equal to “Minimum of 0.2B, 0.2D or H All Round” as the diagram says, then the smallest figure would be 0.2D for an exclusion zone of 2m.  If the roof has a 15 degree slope and consists of two identical rectangles then each would be 5.27m by 15m.  With a 2m exclusion zone the area for panels on each half of the roof would be only 1.27m by 11m, which isn’t much and is less than 18% of the total roof area.  That might have been fine back in the days when the typical solar power system was only 1.5 kilowatts, but it’s certainly not sufficient in these days of larger solar panel systems.  While I approve of having some kind of exclusion zone, I think this is definitely taking things too far.

But what I find really interesting about their apparently huge exclusion zone is Grace uses this illustration on their website:

Grace Illustration

And also this one:

Another Grace Illustration

So as you can see, Grace has clearly changed their rules for exclusion zones since that diagram was published.  Either that or they just don’t give much of a damn about them.

I have emailed Grace and asked them to clarify the issue5.

Radiant

Radiant is an Australian company that produces high quality roof mounting equipment6  It’s located in Capalaba which is just across Tingalpa Creek from Brisbane.

Unfortunately, I couldn’t find any information on exclusion zones in their brochure or website.  But I did find this installation manual online.  Note that because it’s not off the company site I don’t know if it’s up to date.

In the manual I found an interesting diagram with the words “Edge Exclusion Zone” written on it which I will reproduce below:

Radiant Diagram

This diagram is interesting because it is exactly the same one as from the Grace manual.  But while the Grace manual states nothing should be installed within the edge exclusion zone, for Radiant it’s not an exclusion zone at all.  Solar panels can still be installed in what they call the edge zone, provided the rails that panels are clamped to have around twice as many attachment points to the roof as the rails in the internal zone.  So provided rails are fastened as the installation manual recommends, panels can be installed up to the edges of roofs.

At the moment Radiant only mentions a 10 year warranty on its site, but as they used to have a 15 year warranty I am crossing my fingers they’ll soon go back to that.

Schletter

Schletter is a German company that produces high quality roof mounting systems in Bavaria and freely admits to using “lasers” in the process.

Unfortunately, I was unable to find any information specific to installing them in Australia.  I searched their website for information on exclusion zones but only found the following information in a brochure on mounting systems for flat roofs:

Schletter Letter

Please don’t hesitate to look into it yourself if you want to understand Schletter better.

SunLock

Sunlock is an Australian company that produces high quality roof mounting components.  Well, I say they’re an Australian company, but while they manufacture in Australia, SunLock is actually owned by Flex which is an enormous US company with headquarters in Singapore.  But that’s fine by me.  After all, if you can’t trust a globe spanning, multi-national corporation, who can you trust?

SunLock roof mounting systems do have an exclusion zone.  It is displayed in this diagram from their installation manual which was very easy to find on their website:

SunLock Diagram

Sunlock has a central zone where the rails that solar panels are connected to require fewer attachments to the roof than those in the end zones.  These zones are surrounded by an exclusion zone where no panel can go, but rather than being potentially enormous, SunLock’s is only 20cm from the edge.  That’s roughly the length of my manly hand or considerably less than the length of my first wife’s manly hand.  Wind strength is greatest at the edges of roofs and so 20cm is enough to take some of the bite out of it without wasting too much roof space.  As a result, this is recommended for all systems regardless of what installation manuals may say.  It’s also a good idea to leave however much space is necessary at the bottom edge of a roof so rain running down solar panels doesn’t fly over the gutter.

I would like to thank SunLock for making all the information I was looking for very easy to find on their website.  I’ll even go as far as taking my hat off to them.  I’m not going to eat my hat, but I will nibble it a little.

Exclusion Zones And You

If an installer uses SunLock, Radiant or other high quality roof mounting systems you can be very confident they are motivated to do good quality installations.  Someone using SunLock isn’t suddenly likely to get lazy and forget about its exclusion zone and someone using Radiant is likely to leave at least 20cm between panels and roof edges anyway as that is good practice.  A possible exception to this is if a less conscientious installer is only using a high quality mounting system because the customer requested it.

If you are concerned about exclusion zones then it is best to bring it up with your installer before they put a system on your roof.  You can check if an exclusion zone is required and if not, how much space from roof edges they are going to leave anyway.  Note that if you push for as much solar panel capacity on your roof as possible, you may end up with panels that are closer to roof edges than is ideal.  The customer isn’t always right, but they often get what they ask for anyway.

If solar panels have already been installed on your roof then it gets a bit more complex.  If your installer violated manufacturer’s instructions by placing panels in exclusion zones than you can request they remedy the situation.  Note that you are protected by Australian Consumer Guarantees regardless of what your written warranties may say or if they have expired.  Also note you may end up with a smaller system if not all the panels can be made to fit.  I lack the strength to go into detail on this at the moment, so for now I’ll just leave you with a link to the Clean Energy Council’s page on warranties, complaints, and disputes.

Footnotes

  1. Politicians are always going on about saving Australian industry, but have any of them ever tried destroying it instead?  This could be what we’ve been doing wrong all this time!
  2. I’ve left Radiant a message on their answering machine.  Hopefully they’ll call me back and fill me in on their warranties.
  3. I can’t tell if companies in China don’t consult native English speakers before coming up with these names or if they do but the native English speakers are constantly taking the piss out of them.
  4. I also can’t really be certain it’s not some kind of cunning forgery, but that seems a lot of effort to go to.
  5. I’m not expecting a reply.
  6. Here’s one positive review.
About Ronald Brakels

Many years ago now, Ronald Brakels was born in Toowoomba. He first rose to international prominence when his township took up a collection to send him to Japan, which was the furthest they could manage with the money they raised. He became passionately interested in environmental matters upon his return to Australia when the local Mayor met him at the airport and explained it was far too dangerous for him to return to Toowoomba on account of climate change and mutant attack goats. Ronald then moved to a property in the Adelaide Hills where he now lives with his horse, Tonto 23.

Comments

  1. Water run off needs to be taken into account too. Too close to the gutter and the gutter won’t catch the water.

  2. Sorry, Ron. I must profusely apologise as I only counted three times and I wished to reiterate as I have seen this issue on multiple occasions via multiple media conveyances and I have seen for myself at various sites. But thanks for trying to belittle my comment, as I had subscribed to your blog and have enjoyed your insight on multiple occasions.

  3. No probs Ron, so was I.

  4. where can i find a diagram of Australia`s wind zones

  5. Davyd Lewis says

    The most important exclusion zone is to exclude Modern Solar from your installation. I had these guys install a 3 kW system on my roof and, had it not been for another contractor going onto the roof and warning me, I would have had what amounted to a suicide machine built onto the top of my house. They left a variety of materials on the roof including aluminium battens and they didn’t secure the panels properly. The electrical connections where left bare so that I would have had a 900 volt zincalum roof.

  6. Ezza Terrick says

    For maximising use of available roof space it may be time to consider solar tiles.

  7. Has mention been made anywhere, which warns against installing panels too close together?

    Enough allowance (say a 1 to 2 centimetre gap) needs to be made between the edges of each panel as a buffer to allow for heat expansion, otherwise, if butted together, the glass component of the panels may crack under pressure as the metal in the panels, expands.

  8. Erik Christiansen says

    Many thanks for the timely article, Ron. I’ve had plans in with the council for nearly three months now, so hope for planning approval soon, so I can proceed to the building approval holdups with a building surveyor. On the basis of some googling last year, and a generous dollop of caution, I’d allowed 1m at the ridge, 0.5m at the spouting, and 0.6m at the gable ends. That’s on single storey in an A1 wind area, with Sunlock SLRC700 clamps gripping onto Klip Lok 700HS from Lysaght. (There are then no roof penetrations.)

    The 28 panels that allows on the 30 degree northern skillion will probably do.
    If I put up more, then I’ll have to spend yet another fortune on batteries, or take up bitcoin mining, as it’s off-grid. (I’m seriously thinking of a Redflow ZnBr flow battery which can safely be hammered into the ground in an overcast period, plus a 10 kWh LiFePO4 bank for a DC coupled battery inverter which can then be fed 4 kW or so for high-load periods. (The Redflow is not allowed to be charged at more than 2.4 kW or so, so can not easily be thrown into a high capacity DC coupled system, I figure.)

    If I can lay my hands on some 1 or 2 kW DC motors and controllers, it would be tempting to put the LiFePO4 battery bank in an on-farm electric vehicle for mowing, firewood carting, and boring the occasional posthole on the 7 km boundary fence, (Third motor with high gearing for the postholes.)

    • Why do more panels require more batteries? In general the opposite is true. Also i’m interested in your on-farm EV. Got a link?

      • Erik Christiansen says

        When off-grid, power is either consumed, stored, or lost. I’ll have trouble enough consuming 7 kW most times, so adding more generation needs more loads or more batteries to be of any use. ( Otherwise I could as well use colourbond for the shade they provide.) As mentioned, the Redflow will only take about 2.4 kW, and LiFePO4 will take about 0.2C, i.e. 20A per 100 AH capacity. Once that limit is reached, excess generation is lost, even in the short term. By the end of a sunny day, generation will find no use as it is.

        OK, in deep winter, generation will only be about 1/3 of nominal, so I’ve already overdimensioned the array. But enough? I’ll take another look now that there’s more room.

        Sadly, I too am looking for a link for an on-farm EV. The reason for scouting for 1 or 2 kW DC motors and controllers is that I figure I’ll have to build one.
        OK, I can design and build a 48v (brushed) DC motor controller (BLDC is harder), but in between battling planning/building approval bottlenecks, I’m already designing some DC electronics for the new build, with a couple of PCB layouts done, and some firmware just started. (At least I’ll let a builder do this house. I’ve left it too late for another full OB build.

        What I need is 25/8 uptime.

  9. Two storey – don’t forget access for gutter cleaning

  10. Hi lots of worry re close to ridge how does that compare to tilt frames 40 deg on flater roofs

    • Ronald Brakels says

      Hi Richard

      As with panels mounted flush on a roof it will all depend on the manufacturer’s guidelines. Some roof mounted tilt frames have no specified exclusion zones while others don’t. If you follow the link in the article to the SunLock installation manual, or follow it here:

      http://sunlock.com.au/pdf/SunLock%20Installation%20Manual_v4.5.pdf

      You can see in the diagrams at the end that while they have a 20cm exclusion zone around all roof edges for panels mounted flat on a roof, for panels with tilted frames they have no exclusion zone but divide the roof up into a large internal zone, an intermediate zone, and an edge zone. Panels can be mounted anywhere in these zones, but more attachments are required in the intermediate zone and a lot more are needed in the edge zone, so it’s easier to avoid installing in those zones when possible.

  11. Hi Guys, is it correct that all panels should face same direction ? Reason I ask is I’m about to have 21klw installed on my shop but it means one side will be one pitch and other side will be absolutely different

    • Ronald Brakels says

      Hi Mick

      Most solar inverters can two Multiple Power Point Trackers or MPPTs. This means they can accept two independent arrays of panels and so it’s no problem for your shop to have two sets of panels facing different directions.

  12. I was having some issues with how my panels were installed in relation to water runoff missing my gutters. Whilst I couldn’t see anything in the standards that specifically relate to water, The Clean Energy Council put me onto the following information from AS1170.2 regarding wind design.

    The following are excerpts from the AS1170.2

    AS AS1170.2 APPENDIX D – SECTION D6 – SUBSECTION C
    Minimum gap between 50-300mm underside of the panel and the roof

    AS1170.2 APPENDIX D – SECTION D6 – SUBSECTION D
    Panels with a minimum distance between the panel and roof edge of 2S where ‘S’ is the gap between the underside of the panel and the roof surface.

    So if you have a 50mm high gap between panel and roof = 100mm minimum distance panel from the roof edge. 60mm gap = 120mm from roof edge, 70mm gap = 140 mm from roof edge etc)

    I am sure that in high rain events that water will still miss my gutter, but this is a start

    Hope this helps.

  13. Just came across this article.

    Interesting reading about the exclusion zones and mourning systems.

    My question includes optimal gaps between panels on the same track.
    As well as merit in installing horizontally as opposed to vertically, or even a combination of the 2 for max panel fitment.

    My north facing 22.5° pitch Hip roof, a basic quote shows I could fit 18x panels but I’m trying to work out if there is another config horizontal or combo that will allow me to squeeze in more.

    Any tips on how to calculate this?

    • Ronald Brakels says

      Hi GLO

      Panels only need a couple of centimeters between them. If you want a really low tech solution you can get the area of the roof you intend to use (the full area of the roof which is greater than the ground area it covers) and draw it to scale on a piece of paper with to scale paper rectangles to represent solar panels. Or if you are any good at image manipulation you could take a photo of your roof from google maps and use that.

      Note you only lose around 14% of output by facing panels east or west and even south facing ones may only lose 25% — depending on location. So perhaps you could have say 4 kilowatts of panels facing north and 2.5 facing east or west. (This is assuming you have single phase power. If you have three phase power or otherwise can install more than 6.6 kilowatts of panels feel free to install as much as you can.)

  14. Olaf Meyer says

    Please Help. Can anyone suggest an engineering company that will provide a legal variation to AS AS1170.2 APPENDIX D – SECTION D6 – SUBSECTION C.

    The installers have mounted up to the ridge line and they have not left the specified gap. The article says above “… certificate has to be obtained from a structural engineer that states the specific changes being made won’t reduce the strength or safety of the installation.”

    Who will do that for us?

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