What are the major roof types for installing solar?

There are many roof applications for solar installations, how do you know which racking solution applies to which roof type?

As long as there is enough space and enough access to the sun, solar panels can be installed on just about any roof.  The way the panels are attached to the roof depends on the type of roof.  And, therefore, the cost to install the panels will vary as well.  Solar panels will actually reduce some of the weather-related wear on the parts of roof they cover.  But they are not a substitute for a roof replacement (unless one is using solar shingles).   So if a roof has existing problems or is approaching the end of its warranty, it should be replaced before installing solar panels.

When installing solar panels, it is important to consider both the angle of the roof that the panels will be installed on and the direction that the roof faces.   To capture adequate amounts of sunlight, panels should face south to the greatest extent possible and should be mounted at an angle as close to the latitude of the site as possible.   These two requirements generally do not prevent buildings from installing solar panels; however, they do determine what kinds of installations are possible on specific roofs and determine the performance of the resultant installation.

Common roof types on homes include gable roofs, cross-gabled roofs, hipped roofs, and cross hipped roofs.  All of these have moderate pitches and can be ideal for solar installations, provided that they have sufficiently large south-facing surfaces. These roof types are amenable to installations where photovoltaic shingles are desired rather than separate panels.

 Flat roofs - which are commonplace on commercial buildings – and even more exotic roofs such as Mansard-style roofs can actually provide a great starting point for highly effective solar installations. On a flat roof, the solar panels are typically installed on free-standing frames that can optimize array performance by providing the ideal tilt and directional orientation.  The same is true for Mansard roofs that include relatively large flat spaces.   The only obstacles that cannot really be overcome are roofs that don’t have south-facing surfaces (such as some shed-style roofs) and sites with unacceptable amounts of shading from nearby trees or structures.

 The cost and complexity of installing panels varies with the design and the composition of the roof.   Most roofs use composition shingles and solar panels are attached to rails that are affixed to the roof through bolting mounts into the roof rafters.   Flat roofs are typically covered with either tar and gravel or polyurethane foam.   The racks that hold the panels generally don’t require drilling into the roof structure at all; often some kind of ballast such as concrete blocks is used to keep the racking stable.  Roofs with wooden shake shingles or ceramic tiles are the most expensive roofs to install PV modules on.  This is because the shingles are fragile and difficult to walk on and drilling into them for mounting the racking is delicate work and time-consuming.

There are, of course, more exotic roofs around with complex curved surfaces and other unusual features.  Such roofs present unique challenges to PV installers but, provided that there is enough space, enough sunshine and enough determination, solar panels can be installed on nearly any roof.

 

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Comments

When thinking about types of rack another way to think about it is ballasted or non-ballasted.   In a ballasted system, which is used for flat roofs, you use a weight or ballast to secure the panels on the roof.  Typically you use paving blocks to offset wind forces and you don't need any penetrations.   These systems need to engineered to the specific application so that the ballast weight is designed properly. (see past tech article Wind Load Calculations for Solar PV arrays) In a non-ballasted racking system, you need to penetrate the roof to secure the racking.  There are many ways and techniques to affix the racking to the roof and it all depends on the type of roof structure as outlined in this article and the roof material.   (see past tech article Flashing Solutions for Solar PV Roof Mount)


After several jobs are completed and the costs entered, compare the profit per square on each job and make sure that your costs are not creeping up on you and cutting into your profit. Another thing to watch for, as crazy as it might sound, is for profit creep. If your profits steadily rise, you may want to consider lowering your per square price once you start losing jobs to lower priced competition. Thanks for sharing information.

Regards,

single ply roofing Southampton


Adding solar panels to roofs for energy or for hot water is truly one of the best ways to obtain energy and help our environment. Now if we could only get the prices down so that everyone can afford them.

The problem with flat roof applications here in Connecticut is that the ballasted racking systems typically are only tilted to 10 or 15 degrees, which I'm afraid will get buried in snow and lose a month or more of production.  We had 6 feet of snow fall last winter, and freezing temps kept it from melting off anything not steep.  I would love to see production data from flat roof ballasted systems in CT last winter, and I'm interested in the annual production figures for such 10 and 15 degree tilted arrays.  Until I see good production figures for such systems in our locale, I can't in good conscience try to sell them to the million potential flat roof commercial customers all around us.

Willwilkin,
Snow is an understated problem for any solar install, not just flat roofs - 6 feet of snow can cover almost anything, and snow is a great insulator...

Here's a great article on the ASES website that has some interesting comments: ASES Article

There are a number of ways to manage and mitigate snow losses - one of the most interesting is the use of solar trackers. A tracker can be "docked" at a 60 degree angle for snow events and it will shed snow as well as an A-framed cabin - one type of tracker can even stow upside down to stay completely clean until the snow, rain or sand event has passed.