Understanding the exact measurements of your roof is key in planning your project. You will need to get up on the roof with a tape measure, pencil and paper and map out the exact dimensions of the roof as well as the locations of any and all obstructions like exhaust vents, etc.
Using a software tool like Visio or SketchUp, lay out the measurements as a drawing so you can see the available space for your solar panels. Remember, it’s most cost effective to have the largest system you can, so measure and map carefully!
Once you know your available space, you can start plugging in the dimensions of the solar panels you are considering. Links to the solar panel specifications are usually available on the vendor and/or manufacturers website.
Example: The cheapest panel at time of publication ($0.78 /watt) has dimensions of 65.0 x 39.1 as shown on the vendor’s website:
Roof Support Beams
It is also necessary to know the location of your roof’s support beams to safely secure the mounting hardware to your roof. Our 2010 installation was timed along with a roof re-shingling so that we could easily identify the support beams that the mounting standoffs needed to be drilled into. Our 2012 project was a garage rooftop installation and therefore, the support beams were already visible from inside the garage.
Securing Mounting Hardware
The Iron Ridge Design tool helped us determine how many standoffs were required to hold up the rails and provide adequate support for our specific solar panels as well as the maximum distance (or span) between them and the length of rails needed. The picture above shows the standoffs (and flashing) before the rails were added. Here’s a picture later with the rails installed: