Covering the roof with solar panels would help reduce power costs. Even "vertical" farms usually occupy quite a lot of horizontal space for sunlight to hit. At

Covering the roof with solar panels would help reduce power costs. Even "vertical" farms usually occupy quite a lot of horizontal space for sunlight to hit. At first I thought "Why not replace the roof with glass to let sunlight through?" but then I realized that it would get too hot in the Japanese summer. Solar panels are probably better for climate control throughout the year, and they even help reduce cooling costs by blocking sunlight from hitting the roof.