Before installing a solar hot water system, you should investigate local building codes, zoning ordinances, and subdivision covenants, and any special regulations pertaining to the site. In most cases, a building permit is required in order to install a solar energy system onto an existing building. Often times your contractor can assist you with this, as he would most likely be knowledgeable regarding your local permit requirements. If you live in a subdivision or belong to a homeowners' association, it's generally a good idea to check with them as well.