Strategies to increase building energy efficiency typically focus on increased efficiency of the HVAC system and increased thermal resistance of the envelope and fenestration. An oft- overlooked, but vital, path to efficiency is reduction of air-leakage.

Heat transfer in buildings occurs in three forms: conduction, convection and radiation. Of these, conduction and convection transfer most of the heat. Conduction occurs when one body transfers its heat to another with which it is in contact–in this case, the transfer between interior and exterior air. Convection occurs when a heated body physically transports itself to another location. In this case air physically moving through leaks in the wall. Thermal insulation prevents conduction but does little to prevent convective heat losses.

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