Research On The Effects Of Existing Building Envelope And Fresh Air Ways On Energy Consumption Of HVAC System

With the improvement of the people's energy saving consciousness,more and more people pay attention to the problems of building energy consumption.Thus the building envelope energy consumption and fresh air energy consumption as the main sources of HVAC energy consumption have been widely studied by building energy conservation workers.In this paper,the diagnosis and evaluation method for thermal performance of existing building envelope has been researched,and the building fresh air ventilation method.A new diagnosis and evaluation method proposed can assess the thermal performance of existing building envelope conveniently and rapidly.The energy differences between the different fresh air supply ways also have been analyzed.The thermal performance of building envelope affects the HVAC energy consumption.Equivalent heat transfer coefficient has proposed to diagnose and evaluate the thermal performance of existing building envelopes,based on index evaluation and the equivalent energy consumption model.This method will integrate many of evaluation indexes into an equivalent index.The thermal performance and energy-saving potentiality of building envelope can be evaluated by calculating and comparing the heat transfer coefficient of the two equivalent energy consumption models.It is shown that we only need to measure indoor and outdoor temperature,do not need to measure every parameter of the envelope structure one by one,which can overcome the difficulties in testing of existing building that have complex structures.The method proposed can assess the total thermal performance of building envelope rapidly and evaluate the necessity of retrofitting before energy-saving renovation.It improves the implementation of the energy-saving renovation of building envelope of existing building.In order to research the energy consumption difference between different fresh air supply ways,energy consumption with different fresh air supply ways have been calculated and compared including with opening window(wind blowing or not in outdoor)and mechanical fresh air systems(with and without heat recovery).It is shown that fresh air systems with heat recovery,especially fresh air systems with sensible heat recovery,need lowest energy than the other ways and the ways of opening window need the most energy to meet the demand of fresh air.In addition,according calculated results,different window forms have big difference of energy consumption if fresh air is supplied by opening window.Energy consumption of sliding sash are lowest than that of casement window and that of suspension window.Therefore fresh air systems with heat recovery,especially fresh air systems with sensible heat recovery,should be used to supply fresh air,not by means of opening window and sliding sash should be preferentially considered without the condition of setting fresh air systems.