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Everything you need to know about going solar with a flat roof

Avatar for Dan Hahn
Published on 03/15/2020 in
Updated 03/15/2020
flat roof solar install

Even if you have a flat roof, you can still go solar. Having a flat roof is actually an advantage, because your system pitch and orientation can be fully customized to generate as much electricity as possible.

Because there are extra components needed to orient your panels and tilt them toward the sun from a flat roof, some installers have decided to not install on flat roofs to streamline their operations and costs.

This can be especially true if you live in an area without many flat roofs. Therefore, you may need to connect with multiple installers to get bids for your home energy upgrade.

The main thing your installer will have to ensure is that your panels are tilted at the best angle toward the sun based on where you live and that the panels face true south. The closer you live to the equator, the less tilt you’ll need to generate the most power.

How are solar panels attached to flat roofs

There are three main ways to attach panels to your flat roof. Your installer can directly drill the solar panel racking and tilting system into your roof’s framing, they can use ballasts to weigh the system down in place, or a combination of both approaches can be used. The strategy used for your flat roof should be determined by your installer’s experience and guided by a thorough engineering review.

1. Direct attachment or fixed racking

direct attachment flat roof solar

Attached system mounts allow for a wide range of tilt angles but need a lot of screws, bolts and fasteners which penetrate into your roof’s surface. Any time you have holes going into a roof, you should be concerned about leakage. This is why many installers work with a roofer simultaneously or have roofing backgrounds. For leak protection, rack footings are protected with specialized tape and caulking.

2. Ballasted systems

ballast solar flat roof

If you’re concerned about new holes in your roof, non-penetrating ballast system technology has improved to provide needed stability and strength flat roof applications. Ballasts make simple use of concrete blocks and gravity to keep your panels where they should be. It’s usually not an issue for a newer roof to support the extra weight.

However, if your roof is older or less robustly constructed, having heavy concrete blocks up there for decades is a significant amount of unplanned force which could lead to some sagging down the road. We recommend you get a structural engineering review if your installer suggests a ballasted system is the best way to go.

3. Hybrid systems

If you have a newer flat roof, your roof isn’t actually flat. It’s slightly tilted toward your gutters for drainage. Regardless with a flat-ish roof, you still may be at heightened risk for water pooling in areas where your solar panel racking may need to be attached to your roof.

If you do have water pooling issues, you may need to work with a contractor to install a drain before proceeding.

In special cases like these, your installer may choose to use a combination of ballasts and attached racking systems to make sure your roof is as well protected as possible and has optimal longevity.

If you live in a high wind region that typically sees hurricanes, local structural codes may dictate that you may only use penetrating attachments to go solar.

Solar panel spacing on flat roofs

solar panel with shadow

As we’ve been mentioning, for optimal energy harvest your panels will need to be tilted toward the sun. Each degree angle of tilt will cast an added length of shadow around your panels. The shadow will get more severe in the winter, and the last thing you’d want is for your panels to be shaded under full sun.

Therefore, your installer will need to ensure appropriate spacing of your solar panel rows on a flat roof, especially if you have a limited amount of roof area to work with.

Under some conditions like in the featured image at the top of this post, the extra panels which can be installed in a flat orientation on a space limited roof may be financially advantageous. However, extra cost will be required to clean those panels once a year, as dust and grime much more easily build up on solar panels which do not have a tilt.

Is installing solar on a flat roof more expensive?

While mentioned above that not all installers work on flat roofs due to the costs associated with carrying specialized equipment, that doesn’t mean your costs will be higher to go solar when working with an installer that does work on flat roofs.

It can be challenging to work on pitched roofs, as fall protection is required and care needs to be paid to each step taken. This isn’t the case on your flat roof.

While more careful planning and angled panel mounts are required to provide optimal solar panel tilt and orientation to the sun, your installation cost will still be just about the same as an installation on a more typical pitched roof, as your installer can move about freely and more efficiently get their work done.

Click here to connect with our network of solar installers we trust to help you upgrade your flat roof home with solar.

Last modified: March 15, 2020

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