Research On Design And Operation Performance Of Passive Retrofit Of Existing Residential Buildings In Cold Zones

The passive house advocated by Germany can reduce the heat loss of the building to the greatest extent through high-level insulation,low air leakage,avoided-thermal-bridge design and efficient heat recovery ventilation system.In addition,the passive house actively uses solar radiation to increase the internal heat gains to achieve the target of low energy consumption and high indoor thermal comfort.Nowadays,China is actively promoting the construction of passive ultra-low energy buildings.For existing buildings with huge energy-saving potential,can passive retrofit be carried out?How about the operation performance?And what are the applicable schemes?These are the issues we should care about.First of all,this paper took an existing residential building in Tianjin as the research object,determined the retrofit scheme according to the EnerPHit standard,and simulated the retrofit scheme by PHPP.Simulation results showed that the cooling demand of the retrofitted case study according to the component standard in the design stage in summer meets the certification requirements,while the heating demand in winter exceeds the standard requirement of 25kWh/(m~2·a).Secondly,in the heating season after the retrofit,the operation performance is tested from three aspects:energy consumption,building performance and equipment performance.In terms of energy consumption,the unit power consumption of air-conditioning unit is 38.19kWh/m~2,which is equivalent to 112.28kWh/m~2 of primary energy consumption.Only the heating energy consumption accounts for 83.17%of the total energy consumption limit stipulated in the standard;in terms of building performance,the differences of U-value,insulation of household compartment wall and air tightness between the test results and design values result in additional heating demand for 20kWh/(m~2·a)?24kWh/(m~2·a)?4kWh/(m~2·a)respectively;in terms of equipment performance,tested average COP of the air-conditioning unit is 2.79 under average outdoor temperature in Tianjin,which is lower than the rated heating seasonal performance factor(HSPF)of 3.00.The defrosting power consumption accounts for9.85%of the total power consumption of the air-conditioning unit.The tested heat recovery efficiency of the ventilation unit is 86.1%which is higher than the rated value of 78%.Next,a feasible passive retrofit optimization scheme is proposed for the case study based on the retrofit scheme and actual operation performance.In terms of reducing heat loss from the thermal bridge,the influence of thermal bridge between the floor and exterior wall can be eliminated through combinatorial optimization.In terms of reducing heat loss from the slab,the simulation results showed that under the circumstances of no heating in the basement,the heat loss of the slab is reduced by 20.83%and 54.17%respectively,when the exterior wall thermal insulation is extended to the ground and the foundation,compared with the original retrofit scheme.Finally,exploratory optimization and the generic characteristics of the existing buildings suitable for passive retrofit are analyzed based on the case study.Accroding to the result of simulation,in the selection of applicable target buildings for passive retrofit,we should choose buildings with sufficient sunshine and heat in the layout of the building which are less affected by the surrounding buildings,with small shape coefficient,and with large South and East windows and small North windows.