Grow houses, such as this residence raided in January on Inuvik Crescent in Kanata, are often dangerous firetraps because the growers bypass hydro meters to obtain the massive amounts of electricity to power the heat lamps and other paraphernalia to surreptitiously grow the plants. Homegrown marijuana has blossomed into a huge industry that collects billions of dollars annually, officials say. Police say there are at least 50,000 houses in Canada that are now used exclusively to grow marijuana, ranging from new homes worth as much as $600,000 in downtown Vancouver to more modest residences sprinkled through the suburban streets of...