From what I've hear you really don't need to worry about that. They only use it to check out large scale commercial grows after they have a warrant, they don't just go around searching for houses with attics that are unusually warm.
But also, I think they mostly just see the hot air venting out of the building more than seeing anything actually inside.
Seriously though man, unless you have like 10 1000w lights, they wouldn't even see anything.