Can My Roof Support Solar Panels?
There are a lot of logistics that go into determining if your home is a good fit for solar panels. If you want to do some research on your own, you’ve come to the right spot. In this article, we will be covering the basics of supporting roof-mounted solar, some basic technical terms, and potential hazards when it comes to installing solar on your roof.
Will My Roof Support the Weight of Solar Panels?
An understanding of solar loads will give you the tools to determine if your home is ready for solar panels, or if it needs to undergo a reroofing process to make rooftop solar a possibility. If you have an older home or one which may have sustained structural damage in the past, it may be worth it to have your roof inspected beforehand. This is to avoid any potential damage to the home during the installation process or afterward. It also helps to avoid potential costs for the homeowner, as repairing a roof post-installation will be much pricier than pre-installation. Even if you don’t get an inspection beforehand, the city will have to inspect your installation afterward.
Dead Load and Rooftop Solar Considerations
A roof is built to take on quite a bit of pressure without collapsing or losing shingles. Heavy winds or snow are common in many parts of the country, which underscores the need for sturdy roofs. The ability of a roof to shoulder weight is determined by its dead load and live load.
What Is Dead Load?
A dead load is the weight of the roof itself, plus any permanent structures installed on it (e.g. solar panels). The maximum dead load depends on the roofing material and could range from 15 lbs per square foot (PSF) for asphalt, to more than twice as much for clay or concrete style tiles. When actuaries calculate home insurance rates, they figure in dead and live loads.
Why Does Dead Load Matter for Solar?
A roof with too much dead load on it can present an obstacle for going solar. If your roof can’t support much of a dead load, or it already has quite a bit of dead load already present, it could limit the size of your system. If the dead load is particularly high, it could prevent you from going solar entirely until you renovate your roof — a potentially costly endeavor.
Live Load and Solar for Home Considerations
Roofs also have a live load to provide extra support for temporary weight on the roof, known as a live load. Live loads could involve someone on the roof or heavy objects such as snowfall. In areas with cold winters, a roof might be designed to shoulder a dead load of 20 PSF, plus a live load of 20 PSF. A sharp slope on a roof, however, could decrease the maximum live load to 15 PSF. A typical home can hold four feet of snow, which is equivalent to 20 PSF, without collapsing. Your solar engineers will factor this into their assessments.
Additionally, the slope of your roof matters for live load. The steeper your roof, the more weight is concentrated onto a smaller point. More shallow roofs can spread that weight over a larger area, but the gravity of a steeper roof means that you need to be more careful. A roof that’s too steep may not be fit for solar, as it wouldn’t be able to handle the extra weight.
Uplift Load and Your Roof
A subset of the live load is known as uplift load, which accounts for the wind. When the wind blows at a wall, it will be directed upwards and downwards, with the upward flowing wind pressing upon the roof from below. A dead load of most roofs will easily defeat uplift, but an area with severe windstorms might pose a problem. Some roof construction types may be more susceptible to damage from the uplift.
Average Size and Weight of Solar Panels
Relatively speaking, solar panels are quite lightweight. They are designed to sit on a roof for decades without causing damage or collapse. The average solar panel measures about 65 inches by 39 inches and weighs around 35-45 lbs. If installed correctly each panel will minimize the dead load at any single point in the roof.
When taken together, the average solar installation will come out to around 3-4 PSF. This number includes the weight of your racking system and your inverter wiring. If you’re in an area with heavy snowfall, you may want to get your roof inspected beforehand to ensure that the extra weight of the panels won’t cause any issues down the road. This can also inform you of any potential structural damage or wear and tear on your roof.
Other Roofing Factors To Consider When Thinking About Rooftop Solar
Of course, there are other factors that interested buyers should keep in mind before they arrange to have solar panels installed. A roof’s dead load and live load are determined by its construction and material, but also its condition.
A roof that has sustained water damage in the rafters, or has a roofing material that needs replacing, may require repair to be able to support any additional weight placed on it.
Buyers who are thinking about replacing their roof sometime in the next couple of years may want to complete this task first, as roofing repair or upgrades are more complicated after solar panels have been installed. However, a roof that is well-built and maintained should be able to handle the weight of solar panels with proper installation and care.
What If My Roof Can’t Support Solar Panels?
That’s okay! A common misconception about solar is that the only type is roof-mounted. In fact, there are many types of solar installations that can be installed if your current roof can’t support panels. Let’s go over a couple of the options to give you a better idea of the variety of options available.
Ground-mounted solar is when the panels are installed in a special foundation built into the earth. This usually happens in the backyard for most homeowners, though it could also be in different areas if need be. A strong foundation is laid, usually of concrete, then the panels are installed on a special, extra strong racking system to ensure maximum stability. The wiring is particularly tough, as it won’t be protected by the roof.
Ground-mounted solar is the perfect compromise for those who may have a roof that can’t handle solar, whether from damage or structural problems.
Solar Shingles: When You Need to Reroof
For those who are planning on renovating their roof completely, or building a new home, then solar shingles could provide a solution. Solar shingles are not as efficient as regular monocrystalline solar panels and, as such, you need more of them to provide the same amount of energy. They are also much more expensive than regular solar panels. However, if money is no object and you want to integrate solar seamlessly into your roof, then solar shingles can provide a sleek alternative.