I had my herp room completely insulated with r-13 fiberglass insulation to start. The A/C still ran more often than I would like and the temps would get up to 85*. Once again, higher than I would like. I decided to give reflectix a try. I saw on the label it said that it blocked 97% of heat so figured it was worth a shot since I was sure the heat was coming from the roof. Not only was this stuff ridiculously easy to work with (my studs are 22" apart. the fiberglass rolls had to be cut up to fit in nicely), but it did the job amazingly! I was able to get the 24" wide material into the studs nicely and my temps have not seen above 83 and I don't even have the whole roof done yet. There are still a few studs with no insulation at all and my A/C runs very little.

All in all, I would definitely recommend reflectix to someone who is doing a small building without a normal ceiling. It costs about twice the price of r-13 fiberglass but I think the energy costs will more than make up for the money I spent on the new insulation.