The blower door is a key instrument in conducting an energy audit. It measures the air tightness level of a building envelope and indicates the level of sealing and weatherization that needs to be done in order to make a building thermally efficient. It provides the single most important number that a building owner can have to effectively start improving overall thermal performance. Energy Egghead provides this service at a minimum and incorporates it into the energy audit model.
Multiple blower doors are used to create a condition of negative pressure throughout a building in order to locate areas of air leakage and thermal weakness.