Get a camera above 300.
If you’re going to do roof scans on an ongoing basis, there are going to be times when the temperature difference between the moisture and the roof could be very marginal and the higher the resolution and sensitivity you can acquire the less time you will spend trying to get the correct weather conditions.
You cannot manipulate Delta T conditions on the roof inspection like you can in doors.
You can get 320 x 240 cameras for $6,000-$7,000 without all the bells and whistles that are convenient in cameras like the B-400.
If you didn’t know, detecting moisture in a built-up roof is dependent upon temperature in transition. Generally the roof is cooling off from solar exposure during the day. Moisture changes temperatures slower than dry roofing materials and a temperature difference occurs. In some weather conditions this window of opportunity could be quite small and if you have a big roof you may run out of time. To make matters worse, there is always a breeze around reducing your Delta T.
Yes, you can do roof scans with a $2000 camera, but not very efficiently.
When you move from the residential inspection realm into commercial, there is absolutely no reason to go at it from the low end. Low performance and poor documentation will run you right out of town. There is money in commercial/industrial thermal imaging work versus residential. You should be armed with the best tools possible to complete the mission.
I highly recommend that you take a roofing course as well as Level II.
You’ll also need to take on an assistant to help in documentation and to keep you from walking off the roof! Thermal cameras take away your night vision and rooftops are a very dangerous place to be.