I'll end this conversation by answering your first question.
"Have you ever used an IR gun? Do you use them as part of your job? Do you know what Infra Red radiation is?"
YES, and YES, and YES. And I speak Latin, so "below red" isn't hard to figure out. We use IR sensing instruments at my work. Infra red is thermal, not visual.
To the OP, your in England you say. If I was you, what I would do is try to run a length of duct through your attic to another room in the house, maybe even one right next door to the room your in, however the farther the better. Once the duct is out of the grow room, give it a few feet and start poking holes in it. What you want to do is dissipate the heat gradually into other areas. What they look for as mentioned was heat escaping the home as well as "hot spots" within the home. These "hotspots" are a certain temperature or above. So if you cover your heat signature and disipate any excess heat into the home to make it appear natural, you'll be ok. The concentration of heat is what flir detects. A poorly ventilated grow room is what gets you caught.
Now, to the other guy. I used hand held FLIR cams as a home inspector. I also used them as a custom electronics cabinet builder. And thats the reason I know the difference between the styles of cams and what they do. All FLIR are NOT equal, lol. As a home inspector we used them to estimate loss for HVAC equipped structures. They allow you to give the home owner a realistic estimate of their power consumption based on heat or air conditioned air escaping the house/building as well as offer the state code officer the ability to make a proper assessment for retail value. In this case they were specifically used to detect heat signatures and used a 256 color spectral analysis to display the patterns so our eyes can comprehend it. Part of the inspection of the attic is for "IR blocking materials placed in a manor to compromise inspection results of the exterior aspiration" Feel me? You have to look to make sure the home owner doesn't have a bunch of shit up there either "blocking aspiration of heat temporarily", or designed to "effect the operation of the FLIR camera".
About IR Block,
"The two outer layers of Block-IR material reduce thermal imaging heat signatures by 97%. Each layer if Block-IR material is bonded to a durable layer of polyurethane for strength. An inner layer of insulation prevents conductive heat flow. An additional layer of polyurethane gives Block-IR high reliability and strength. Completely line any space with Block-IR for a 97% reduction in thermal imaging reduction."
Now as you pointed out, where does that heat go? Well it does go somewhere, the point of doing an entire cabinet in one is to reduce the amount of light that is transferred into heat to begin with. Doing a whole grow room, probably NOT feasible. As you stated a large room would be better suited with insulation. Pre-fabbed walls are actually the best for this btw. Thinner and more compact, better sealed, easy to maneuver and build with. So, for using things to block heat signatures form close range (outside your house on 'public property') I would use something designed to contain the light itself as well as insulate. Hence IR block has a layer designed to prevent conductive heat flow as well as a layer designed to be 97% reflective, so perfect for growing in small areas. Why use insulation and mylar when you can have them both in one application. If you are NOT looking to use a reflective material in your grow room and are concerned with the heat from the lights the most practical solution is this,
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=180501953497&rvr_id=&crlp=1_263602_263622&UA=WXF?&GUID=9debb7941280a0aad5b77477ffbf0eaa&itemid=180501953497&ff4=263602_263622
So, now that we agree on one thing, the best way to not sweat it is to dissipate the heat through out a large area, ie. the entire home and since it gets cold their this sounds smart to me. We both agree that heat escaping the house (depending on where you live) can easily get you caught. Easiest way is to make the whole house appear the same temp. If you have to vent it outside right from the room your going to need a reason to make it look like its there. Say in a garage, vent it at the ground and cover up the light, now it "looks" like an air compressor or a welder in use.
the reason things don't show up on IR is because they "appear cold" keep that in mind. Using regular Mylar will not make something appear cold on its own. The reason this product has a bad rap is because of other products that have claimed to do the same thing. Also because here in the US a FLIR image or video is NOT enough to enter your home, they need a warrant. Well, until the Patriot Act that is.
I wasn't trying to jack this thread OR start an argument, I just want people making educated decisions. If you want to know about FLIR, talk it over with a cop.
[video=youtube;sudf5xDIhmM]http://www.youtube.com/watch?v=sudf5xDIhmM[/video]
[video=youtube;jXPXE0qsmjg]http://www.youtube.com/watch?v=jXPXE0qsmjg&NR=1[/video]
