The following images were taken with a thermal imaging camera on a cold (15 degree F )January day near Chicago. All images were taken within hours of each other. The first is a Walmart store built with standard block, the second is the Marquardt School, built with NRG block.
Things to look for on the Walmart store are vertical grout and rebar throughout the wall area (slightly different color) which are cold spots, something you will never see in NRG buildings. Also, the Walmart store wall is warmer overall, which means that there is heat being transferred from the interior.