Black & Decker TLD100 Thermal Leak Detector for $28.99 shipped. Here is a screenshot for your reference. 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 the winter heating bill saved. Most places have it for over $45.