A blower door test is a diagnostic tool used to measure the air leakage in a building. It involves installing a powerful fan in an exterior door frame, which creates a pressure difference between the inside and outside. This helps identify how much air is escaping and where leaks may be located. The results of the test can help homeowners and builders improve energy efficiency by sealing gaps and cracks. By reducing air leaks, the building can maintain a more consistent temperature, leading to lower energy bills and increased comfort for occupants.