Ask the experts: How to build a solar-ready home

By Brandon Walton on October 22, 2015

Solar installers are good at designing systems to fit homes. But what about designing a home to fit solar? If you are looking to build your home and are thinking about going solar, building with solar in mind will optimize your system’s output while simplifying installation. We spoke with solar installers Watt Bradshaw of Blue Ridge Energy Company, Joe Moore of Altenergy, Randall Peltola of Genesis Home and Energy, and Ryan Healy of Convert Solar for their recommendations on how to build your home to be solar ready.

What is the best roofing material and design for solar in new construction?

Watt Bradshaw: The most economical roof is with shingles. I have replaced some solar systems on 20+ year old roofs and the shingles looked like the day they were installed. The “best” roof might be a standing seam metal roof. There are mounting systems that can attach to the standing seams without any penetrations.

Joe Moore: The roofing material we like best is a standing seam metal roof since they are easy to attach, require no penetrations to mount the panels and have a long life. We come across many different roof styles and there are mounting options for each.

Ryan Healy: I prefer asphalt shingle roofs due to the ability to flash penetrations. They should use a 30-year shingle to last the life of the PV system. A two story ranch style house facing South with around a 6/12 or 7/12 pitch would be ideal void of trees blocking the roofs solar access.

Is it possible to pre-wire and make a home solar ready or any special electrical or wiring guidelines I should follow?

Joe Moore: The two main points here are to run a 1″ EMT conduit from the attic to the utility room and to make sure you leave an open breaker space for a double pole breaker. If this is done, we can take care of the rest and you have just saved yourself some money.

Randall Peltola: Pre-wiring on a new home can be done. Micro-inverter systems use the appropriate Romex type of house wiring, as they are a standard 120/240VAC before entering the house. Electricians should follow the NEC Code section 690 for all wiring of a solar array. If electricians are not familiar with it, work with a solar installer on establishing a plan and path of the wiring, because every home and array is a little different.

Ryan Healy: This is a good idea although different systems will require different wire combinations. With string Inverter with dual string inputs, you will have two sets of the following: two #10 AWG wires and #6 AWG for your ground. With micro Inverters with two strings, you will have two sets of the following: three #10 AWG wires and #6 AWG for ground. Remember, DC wires inside a building must be in a metal raceway (usually MC Cable or Metallic Liquid Tight).

If you don’t want panels on your roof, how can you best design your property and space for ground- mounted panels?

Joe Moore: We are doing more and more ground arrays as prices come down because they typically allow for larger arrays. You want to make sure that the proposed area is not going to present an eye sore if you are looking at a massive solar array. To use the term loosely, it needs to have good Feng Shui.

Randall Peltola: As with roof panels, the best direction is south with an angle of about 33° with no shading from 8am till 4pm all times of the year. If the ground is not easy to penetrate for up to six feet, additional engineering may be required. Check with your local Building Department and Utility Company for restrictions and for permit requirements.

How soon after my home is built can I have solar installed?

Randall Peltola: If you plan to install solar, work with a solar contractor before and during the building process; you may end up with a better installation at about the same cost. Utility companies don’t usually allow the solar system to operate until after the home’s final electrical inspection has passed and the net meter is installed.

Ryan Healy: The solar can be installed at any time after the home is built although most systems work using the grids frequency. Therefore, the system may not be operational until the home is hooked to the utility grid.

What’s the best way to make sure my home contractor is familiar with solar and will help me design and build the most favorable site for solar?

Watt Bradshaw: The best way to make sure is to have your contractor contact/work with a solar company from the start. This will help to make sure all of the design elements are compatible with solar, saving time, money, and energy.

Ryan Healy: Bring someone into the mix that has experience with solar design. A solar expert can consult and make recommendations as well as walk through the wiring details with the electrician. It would help to decide beforehand with the homeowner what components will be used to specify the necessary wiring and make sure the electrician is on the same page with what needs to be done.

What are the biggest barriers to effective solar design that you’ve seen in new construction? How can they be avoided?

Watt Bradshaw: The biggest mistakes are improper orientation and poor south roof design – think unshaded southern orientation! Having the south roof not all cut up with dormers, skylights, vents, etc, will provide a safer economical place for the solar panels using the roof system as the support structure.

Randall Peltola: Make sure that there is ample room for solar panels on a south facing roof with a 33° or 8/12 pitched roof. Many people don’t realize how many solar panels are required to achieve net zero. Consider how much energy your home will need and have a solar system designed that will target the offset you would like.

Any additional considerations or advice?

Watt Bradshaw: The most economical house designs incorporate passive solar strategies which help the house itself become a collector and storage system of solar heat. Additionally, climate responsive house designs can be more energy efficient. It is almost always more cost effective to save energy than to produce it.

Joe Moore: Take your appliances into account when considering solar. If you are designing your house to have a large roof dedicated to solar, you should consider having an electric hot water heater and possibly heat pumps for HVAC. If you go with natural gas or propane, you won’t need as much roof space. If you’re all electric, you will need a lot. Just be aware that the two are closely linked.