Solar in the District of Columbia starts on a roof that may be flat behind a parapet, pitched under trees, or broken up by a rear ell. Party walls and taller neighbors cut the day on many rows. Wooded slopes lose hours to canopy even when the lot is larger. The covering underneath has to be sound before any array is a serious idea. Say the shape of the roof and the kind of house.
Shade is architectural on the rows and biological on the green edges. The next house, a tree in the court, a parapet, and a dormer can each erase the clear area. A south slope on a wide street is a different site from a north slope into a shaded alley. Describe what you see from the sidewalk and the rear window. Leaves on a pitched roof into autumn belong in that account. A flat roof may have fewer leaves and more ponding.
Do not plan panels over a membrane that ponds or shingles that already stain a ceiling. Attachments and penetrations have to survive humid, wind-driven rain and the occasional ice. If you do not know the age, say what the surface looks like and whether anyone has coated it. An aerial view misses a soft spot and a blocked scupper. The hatch, if you can look safely, tells more than the sky view.
Electrical gear in older District houses is often in the basement and already full. The path from the roof to that panel may cross a finished stair. Interconnection still has to be accepted before the system runs. Mention a service that already struggles with ordinary use only as a condition of the house. Keep the call on roof, shade, and the panel, not on a brand.
Bring the roof shape, the direction of the open sky, and the shade from the next row or the trees. Solar in the District of Columbia is a tight-city site question between two rivers, with flat roofs, ells, and a few truly open slopes. Call the number on this page.