Home Depot gets a lot of requests to adapt plans to suit local demands, but none so strange as this: A town in Vermont wanted a vegetation-covered roof where cows could graze. Why? Community leaders thought the design would be environmentally friendly; for one thing, it would reduce the amount of heat given off by the building, they said. Home Depot thought better. “A lot of requests are not only impractical, but are illegal,” says a chain spokesman.