Are you building a house with solar? Here are the details you need to pay attention to when building a solar home.
1. Direction of Your Roof (Azimuth)
First, because we live so far north on the planet, the sun arcs across our sky significantly to the south. So solar arrays need significant southern exposure. Let’s start with the roof. An ideal roof has a large, uninterrupted surface facing south, or slightly southeast or southwest. By uninterrupted, we mean keep your chimneys, vent pipes, dormers, and skylights away from that nice big southern expanse! Designing a system to avoid the chimney’s shadow and skirt around the skylights is less than ideal. A well-producing solar home should have a southern facing orientation or “azimuth”. The closer the solar azimuth is to 180 degrees true south the better the system will produce. Roof angles are also something to consider.
When you’re deciding where you want to put your home on your land it is best to avoid any trees on the Southern side. Planting a gorgeous maple to the south will mean shadowed solar panels in a few years. Go ahead and tuck the northern side of your home into the trees, but any tree that casts a shadow on your south roof for any significant portion of the day is no good for solar.
3. Roof Pitch
At SunCommon, we install on pitched roofs, not flat ones. At our latitude here in the Northeast, a 35-degree pitch is just about ideal at capturing both the low winter and the high summer sunlight though any roof over a 10-degree pitch can work (A 35-degree slope falls between a 8/12 and a 9/12 pitch.) If you’re building a house with solar, you want a roof pitch between 10 degrees and 45 degrees.
4. Roof Material
Roof composition really matters when building a house with solar. Asphalt shingles or metal roofs are great, slate and cedar shingles are a no go.
With Asphalt, it is important to choose a shingle that will last as long as your solar system. A 30-year rated shingle would be best. Also, minimum 3/8” sheathing on the roof is recommended.
If you decide on Corrugated Metal, we recommend that your contractor install the roof with the screws on the flat sections of the metal, and not on the ridge of the rib. This type of fastening is stronger for the roof and better for our installers to walk around on during the installation process. If possible, we also recommend installing the corrugated roof onto plywood sheathing and not onto purlins. This cuts down on the costs of your PV system by reducing hardware. If you, or your contractor is going to install purlins between the corrugated metal roof and the roof surface, please provide the purlin spacing to our Solar Home Advisor so that we can plan accordingly in the design of your system.
If you are installing a Standing Seam roof, SunCommon needs the seams to be “double lock” seams. This ensures the mounting clamps for our PV system have a strong surface to grab onto when we install our system.
Once you’ve sited your home and designed a solar-ready southern roof, there’s one last step for building a house with solar. The solar panels on your roof will need to be connected to your electrical service panel (the box with the circuit breakers) in your basement or garage. It is easier (and hence cheaper) to run conduit between the panel and where the panels will be before the walls, floors, and ceilings go in.
On existing structures we run this wire on the outside of the house along a route that blends it into the house. With a new construction project, you have a second option for running the electrical wire. If possible, you can build an electrical chase into your house. An electrical chase is usually an opening that houses a 1” EMT conduit that runs from the attic, all the way down to the basement. The advantage of this chase is the electrical conduit can be run in the interior of the house and it will not be seen on your exterior building. This can be aesthetically more pleasing to you, and easier for the installer to run, potentially saving costs on the overall system price. So, ask your electrician to run a conduit up to your attic while wiring your home. Then, as soon as you have a roof, we’ll be happy to come out, install your solar system and celebrate with you as your meter runs backwards.
5. House Electrical
One thing to consider with the electrical work on your new project is where your main panel will be located. We recommend installing your main service panel in an open area or large service closet. This way we can install our electrical equipment for our PV system near your main panel. In general, we will use about 4ft by 8ft of wall space for our equipment. If your new construction project already has a main panel, and is located in a different section of your house, don’t worry! We design your system to accommodate for the many different electrical setups in your house.
6. PV Systems Add Weight
A standard PV system adds less than 3lbs per square foot on the roof. Making sure your roof can support this weight across the house is important and your contractor should be able to factor this added weight into the design.
7. What We Need From You
In order to facilitate a Design and a cost estimate for your PV system, we will need some information about your project. Some of the things we will need are:
- Contractor Phone Numbers (if any)
- Design/ Architectural Drawings
- Structural Information
- Electrical Information
- Building Timeline
To summarize, when building a house with solar, you want a south-facing roof, that is unshaded and free of obstructions such as dormers, chimneys, or skylights; pitched at or close to a 30° angle; made of solar-friendly materials such as metal or asphalt shingle; and structurally supported by accounting for the weight of the panels and leaving room for the necessary electrical work to connect the panels to your circuitry.
We hope this information will be useful while you work on your home. Remember these are strictly recommendations and you should build your home to how you prefer it. If you (or your contractor) have any questions about how to better integrate your new home project into the solar system, our engineering team will be happy to assist you!
Have any specific questions, we’re happy to answer them here or via email.