From a fact sheet published by Focus on Energy:

Rising energy costs and concern for energy security and the environment are driving forces in a growing trend to incorporate renewable energy technology into residential housing. Focus on Energy and the Wisconsin ENERGY STAR® Homes Program recognize this as an opportunity for builders. The following checklist of building details is a first step to promote and market the construction of new homes that are built “ready” for future renewable energy installations.

To maximize the potential benefit of any future solar renewable energy system, the following should be considered when planning and building a home.

1. Reduce loads
Reduce or minimize energy loads where possible through the home’s heating, cooling, water heating and electrical systems. At a minimum the home should satisfy the Wisconsin ENERGY STAR Homes Program building performance standards and, where possible, incorporate ENERGY STAR qualified lighting, appliances and HVAC systems.

2. Maximize solar access
To maximize solar access, face the roof surface and pitch within 30 degrees of due south. The roof should be unobstructed from both the winter and summer sun and have a slope of between 30 degrees and 60 degrees. For more information on solar access, see the Passive Solar Design fact sheet or contact the Focus on Energy Renewable Energy Program at 800.762.7077 for solar site assessment information.

3. Follow zoning laws and applicable codes
Wisconsin State law does not allow zoning or covenants that restrict the use of a solar energy system except for reasons of health and safety. Also investigate applicable Uniform Dwelling Code and the National Electric Code as they pertain to any pre-installation requirements.