Black & Decker TLD100 Thermal Leak Detector for $29.99 shipped. Here is a screenshot for your reference. Alternatively, it is available at Amazon for $32.14 shipped. This thermal leak detector uses infrared sensors to measure surface temperatures to track down power-draining drafts and includes a 5-step guide to fixing basic energy leaks. The idea is that by locking down thermal leaks, this device will more than pay for itself with savings of the summer air condition bill. Most places have it for about $40.