Rooftop Solar Energy

Solar panels on metal roof

The “Sustainability begets resilience” blog ended with a nod to rooftop energy production. So, how will you respond when, not if, a building owner asks you about rooftop solar energy? An appropriate and accurate answer is, “The combination of a metal roof and solar energy is a recipe for a long-term, high-performance roof system,” or something like that. The fact is a metal panel roof is an ideal substrate for a solar energy system.

Installation Methods

Solar energy is the broad term for two sub-categories: photovoltaic (PV) systems (electricity) and solar thermal (hot water) systems. Besides the obvious differences, the rooftop attachment concepts for both systems are quite similar. PV panels and solar thermal panels are commonly rigid with metal frames. Attachment to metal roofing panels can be direct or include rails. Both methods use a customized clip that attaches to the metal roofing panel seam; then, metal-framed PV panels or rails are attached. The need for rails (think “purlins”) depends on the seam spacing and layout of the roof panels relative to the size and layout of the PV or solar thermal panels. Overall roof slope matters, too. Directly attached solar energy systems match the slope of the roof, which is not necessarily the optimum slope for energy production.

Structural & Performance Requirements

Other considerations include the structural load, fire resistance, wind resistance and the use of code-approved materials and components. A solar energy system adds weight to the roof. Does the structure need updating to carry the gravity load as well as any increased wind uplift loads? Adding panels to the roof will increase the sliding load (i.e., drag load) on the clips holding the roof panels to the substructure. And let’s not forget about the potential for snow retention or increased snowdrifts that will add weight.

Fire and wind resistance should be discussed with the manufacturer or designer of the PV or solar thermal system. Fire and wind design are incredibly important, and there are very specific code requirements to meet.

Layout Considerations

Rooftop layout of solar systems, especially PV, should not block drainage or impede roof maintenance. Also, clearance at roof perimeters and access to critical roof areas (e.g., drains, rooftop units) is necessary. Last but certainly not least, check with the metal panel roof system manufacturer about warranty issues regarding a rooftop solar energy installation.

While there are many things to consider when installing solar energy systems on roofs, the long service life of metal panels and the ease of installation certainly make metal roofs and solar energy a great combination!

Metal Roofs & Walls a Big Plus When It Comes to Net Zero Energy

Kickapoo Tribe Government & Community Building
Kickapoo Tribe Government & Community Building features MBCI’s CF Architectural Insulated Metal Panel

Are you familiar with “Net Zero Energy?” No, it’s not that sense of power you got from using that early dial-up Internet browser of the 1990’s (The company, by the way, is still in existence, and comes up in searches for the term Net Zero. Who knew?). The Net Zero Energy I’m speaking of is the enviable, sustainable state achieved when the creation and use of energy within the same building system are equal.

Though achievable, the cost and capacity for producing energy within a building system is greater than that of creating energy efficiency in one. The good news is that metal roofing and ,a href=””>wall panels are extremely useful on both sides of the equation.

On the energy efficiency side, insulated metal panels (IMPs) provide roof and wall systems with the thermal and radiative performance needed for sustainable design. Insulated wall and roof panels provide continuous insulation and eliminate thermal bridges. As building and energy codes become increasingly more stringent, insulated metal panels are an ideal choice for thermally efficient building envelopes.

Baker Hughes features MBCI’s CF Mesa Insulated Metal Panels

On the other side of the equation, a common method of generating energy is through the use of photovoltaics (PVs), and metal roofs provide the best possible surface to host a photovoltaic (PV) array. Solar photovoltaic systems and solar water heating systems can be installed on a metal roof, penetration-free, resulting in high performance with minimal risk. Both the use of IMPs and the installation of PVs on metal roofs can be used with proper designs to maximize building energy efficiency.

Of course, metal roofing, known to last 40 years or longer, is the only type of roof that can be expected to outlive the PV system mounted on it, which results in virtually zero maintenance and a very low in-place cost for the roof and PV system together.  A sustainability win, a durability win, and, of course, an aesthetic win.  The result is anything but a zero sum game.

Find out more about MBCI’s Insulated Metal Panels

Solar Roofing: Overcoming Misconceptions

As an engineer who works for a metal roofing company that also sells roof-mounted photovoltaic (PV) equipment, I have the incredible opportunity to help people turn their metal roofs into money making machines. That’s more literal than you think, especially if you have good incentive programs available to you or your electricity costs are high or varying over the course of the day. I’ll leave the environmental green reasons for another blog.  I’m talking cold, hard cash here, folks. I’ll be very honest: A PV system is a sizable investment.  But they can also have rates of return associated with them that make day-traders salivate.

However, I do find that the vast majority of my time is spent educating potential owners of PV systems on how these systems operate and how that translates into cash flow. Along the way, I have discovered many misconceptions that very smart people have about PV. I have listed them below and this is my attempt to put some of those things to rest. Are you ready? Let’s power on.

1) I have to put holes in my roof to support a PV system

Call me old school if you want, but from where I come, putting a hole in your roof is a bad thing. Fortunately, if you are blessed with a metal standing seam roof, there is a very good chance you can mount a PV system on it with ZERO roof penetrations. Zero, zip, nada, or as the soccer folks say, nil. There are some very good mechanical mounting systems out there and many of them do not require expensive aluminum railing because they attach directly to the roof seam. That’s a huge cost savings but in my opinion, the risk it mitigates is even more important.  I may sound like Captain Obvious when I say this, but every time you penetrate a roof, you increase its chances of leaking in the future. This just in: Roof leaks are bad.

2) I need a battery system to work with my PV system

I run into this misconception every day. Unless your building is in a place where your electricity service is questionable or non-existent, batteries are not required or even advisable. Why? They are expensive, maintenance intensive and a power drain. Case-in-point: Your cell phone battery. Granted, they are typically different technologies than PV system batteries but the situation is very similar. If you’ve ever priced them, you know they are expensive. If you’ve ever had one that wouldn’t charge all the way because you haven’t been draining it all the way, you know they are maintenance intensive. And if you ever felt one get very hot as it charged that last 10% or while you were using your GPS, you know they waste power. (That heat energy has to come from somewhere, right?) They also only have about half the life expectancy as a PV system. By contrast, the electrical grid is like the world’s most perfect battery. It costs you nothing (I mean the grid itself, you obviously pay for it indirectly when you buy the electricity), it basically lasts forever and someone else is responsible for maintaining it and fixing it when it does break.  But most importantly, when you put power into the grid, you get 100% price credit for that electricity, provided your utility supports net-metering.  It’s really a no-brainer.

3) PV Systems only make electricity during the day

OK, this is not a misconception; it’s true. But so what? You don’t use electricity during the day? Your building probably uses more electricity during the day than any other time. And even if that’s not true, if you are a net-producer of electricity and your utility supports net metering, your meter simply runs backwards during this time, offsetting the cost incurred when you are using electricity. All of this with no battery involved. It’s why there are more grid-tied systems being installed now than battery systems and that trend is not likely to change.  Furthermore, if you live in California or other places where your electricity rate is higher during the day than it is off-peak, PV systems can really have a huge impact on your bottom line because they are producing the most when demand is the highest.

4) My roof doesn’t face south, so it’s not worthwhile to put PV on it

Au contraire, roof azimuth has less effect than you might think and it is certainly secondary to what your incentive and electricity cost situations are. I won’t go into a deep technical explanation here, but I’ve learned one thing after years of running payback calculations on PV systems:  If the money is right, the building is right. You may not have the absolute lowest payback or highest ROI theoretically possible, but the cash flow will still be very favorable. Also, don’t fall into the same thought process because you’ve heard that that the PV modules have to slope the same angle as your latitude. Oh look, that’s our next misconception!

5) My roof doesn’t slope enough to hold a PV system

While it is true that PV systems theoretically produce more electricity when they are pitched at an angle equal to your latitude, much like azimuth, this effect is far less than you think. Obviously, it’s not advisable to mount a PV system on the northern slope of a 12:12 (45 degree) roof. But like most things in life, PV electricity production operates on a sliding scale and the end result is a function of many factors working together. If you focus too much on any single factor, you’re missing the point. (To refresh, the point is to put money in your pocket.) And, THIS IS IMPORTANT, there are other more serious issues with racking and tilting systems that you have to contend with. Keep reading, this is getting serious.

6) I need to have a rack system on my roof to support the PV

Not true. PV systems work very well on flat or near flat surfaces. Besides, if you live in certain parts of the country where heavy snow or high winds are a concern, I’d highly advise you to stay away from rack systems. Think about this: What does a rack system look like to you?  Spanish Armada-era sailboats sitting in a harbor, perhaps? Do you REALLY want an air foil on your roof if you live within reach of a hurricane? I’m guessing not. Perhaps even more dangerous is the potential snow accumulation that can happen under a rack-mounted PV system in snow country. This is a situation we engineers call aerodynamic shade and it is a serious concern from a structural standpoint. After alternating heavy snows and freeze-thaw cycles, hundreds of pounds per square foot of snow can gather under and around a roof obstruction and I doubt your building was designed for that. I highly encourage you to call your structural engineer and have this discussion with him or her before you put a rack-mounted PV on your roof. I’m being very serious here; the consequences are severe or even life-threatening.

So, there you have it. There are many more aspects of PV than I can cover in this forum but hopefully, this charges your brain and sheds some light on a subject that is just starting to heat up. Since I’ve obviously blown my pun quota, I’ll have to cut it here. But if you want more information, please visit

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