Abstract:Based on externality theories and buildings’ energy efficiency theories,the externality of energy efficiency reconstruction was classified into different types from four aspects.Then,a set of formula was proposed for computing the externality of buildings’ enclosure structure reconstruction,heating networks and heating production plant reconstruction,and comprehensive reconstruction.The formulas were used to compute the environmental externality of Kouan residential energy efficiency reconstruction project in Baotou city.Results show that there is significant externality for energy efficiency reconstruction of the existing buildings.The findings are useful for governments at all levels to make economic incentive policies about energy efficiency reconstruction of existing buildings.