I don't believe in these IR blockers. Sure they probably block some IR but you have to understand how these FLIR cameras work. You're in luck becaue I was a firefighter for 15 years and was one of my departments FLIR gurus. First off,
FLIR cannot see through walls! If you only have a couple of HID's you're probably fine. Don't vent to the outside if you can avoid it. Make sure your house is well insulated. If possible, insulate your growroom. Don't grow in your attic if you can avoid it. I say don't waste your money on expensive IR blockers because they won't do you any good. They won't stop all of your heat which is what the cameras see. Best of luck.