this will be my last reply as this conversation doesn't seem to be going anywhere, the link you just put up talks about thermal imaging? yes?, we know they can see hot spots, this isn't new technology, the police need more than just a hot spot on your roof to obtain a search warrent. I have been a roofer for the best part of a decade and have seen roofs with no insulation more times than i can count and i'm confident in the thought that all the propertys that haven't got insulation are going to have their doors kicked in, like i said in my post above there is many reasons your property could be running hot, many old people will have there heating on through out the entire year and there windows and roofs may appear hotter than there neighbours who have gone to work and left windows open or simply left a cold house, If there was technology capable of looking through walls etc then the police would need a warrent to use it as it would be a massive invasion of privacy. In the bbc documentary you keep refering to they clearly state the flir camera or thermal imaging camera is borrowed or rented from the electrical company and is usually used to spot hot power lines. I don't understand the confusion i grow in my attic and live in place that has a problem with commercial grows and don't worry about it, there is many ways to stop your roof from glowing and insulating properly will stop it, there is a reason they pay attention to the windows it's because they warm easily if not they would simply look at the walls for heat signatures and they don't because walls don't heat up as easily as windows. they cannot see through walls end of discussion and until i see a vid or some type of documentation that states otherwise i'll call bullshit on all the youngsters and paranoid people that can't grasp the basics of how a flir camera works