How many lights and what wattage? It is supposed to be illegal in the US to use thermal imaging for grow detection but I do exactly the same as you, I use the heat from the lamps at night for the room. I run two 400wt. systems and my grow is in a totally seperate room from my house. The only prob. I have encountered is the steam emitting from my exhaust fans. Anyway I think if your room is insulated real well you shouldnt have problems, depending on how many and what watt your lights are. Research the laws in your state on use of TI by law enforcement.Good Luck!!:thumbsup: