This thesis takes rounding to the index of heat loss of building envelope

limit value of heat transfer coefficient and the door and window heat loss of the air permeates as main points.The analysis is carried out on residential buildings implement energy efficiency 65% in the extremely cold region.The thesis puts forward the limit value of overall heat transfer coefficient of each part of building envelope.It aims at how to carry out energy efficiency 65%

which discusses the structure and the technique of building envelope.The author elaborates that lowering the heat loss of air permeates of the door and window is the key to the next stage of energy efficiency.