Building materials giant Johns Manville, a Berkshire Hathaway company once best known for its asbestos shingles, has just announced that it is entering the solar roof market in a big way. The company will buy thin film solar laminates made by Michigan-based United Solar Ovonic, a subsidiary of Energy Conversion Devices. United Solar has already started bringing green jobs into Michigan, and the Johns Manville connection could mean that more expansion is in store.