Research On The Energy-saving Reconstruction Of An Existing Office Building Envelope In Lanzhou By Using "Balance Of Judgment"

With the economic development and the rapid increase of urbanization rate,people's requirements for the comfort of indoor environment have increased.China's building energy consumption has increased year by year.Among them,the energy consumption ratio of public buildings accounts for up to 38.53%,and the energy consumption per unit area of public buildings reaches 30.11.kgce / ?,which are 2.5 times(12.17 kgce / ?)of urban residential buildings and 3.4 times(8.86 kgce / ?)of rural residential buildings.In order to effectively reduce the energy consumption of public buildings,improve the building energy efficiency level and energy saving potential,the energy-saving reconstruction of existing public buildings' envelope structures has become one of the important research directions in building energy conservation.This article takes an existing office building in Lanzhou as the research object,adopts the theoretical analysis and numerical simulation research methods,and according to the "Public Building Energy-Saving Design Standard" PGB50189-2015,the limit requirements for the heat transfer coefficient of the outer envelope of the transformable part,After extensive investigations,the insulation materials and calculated thicknesses of exterior walls and roofs,and the types of exterior window inlay materials were selected;numerical simulation calculations were performed using DeST-C software,and the set parameters were ensured by comparison and verification of measured data before series calculations.The rationality of the calculation and the reliability of the calculation results;in the determination of the transformation plan,the "evaluation of trade-offs" method and economic evaluation were used to comprehensively evaluate the effect of energy-saving transformation of the outer envelope structure,and the following conclusions were obtained:(1)Under a single factor,energy-saving reconstruction of the existing office building exterior wall in Lanzhou area.Simulation results show that 50 mm extruded board(XPS)should be used for exterior wall insulation materials.Its cooling and heating load energy saving rates are 9.02%,41.04%;(2)Under a single factor,energy-saving renovation of existing office building roofs in Lanzhou area.Simulation results show that 65 mm extruded board is suitable for roof insulation materials,and its cooling and heating load energy saving rates are 0.17% and 3.97%,respectively;(3)Under a single factor,the exterior windows of existing office buildings in Lanzhou area were retrofitted with energy saving.The simulation results show that when all the glass facing the exterior window is replaced,the material of the exterior window glass should be double-insulated hollow glass.The heat load energy saving rate is 7.36% and 13.82% respectively.When the south window glass is replaced independently,the outer window glass material should be vacuum coated composite insulating glass,and its cold and heat load energy saving rates are 1.78% and 6.08% respectively;(4)Under the specified indicators,when combined simulation calculations are performed on the external wall,roof and external windows,the existing office building envelope structure energy-saving transformation plan is: 90 mm extruded plastic for the external wall insulation material and the roof insulation material 80 mm extruded board,all directions of the exterior windows are replaced with vacuum-coated composite insulating glass;the total power consumption under this scheme(48.03 kWh / ?)is compared with the total power consumption of the design building(53.63 kWh / ?),The difference is 5.6kWh / ?.(5)When "simulating trade-offs" is used for combined simulation analysis of the envelope structure,the heat transfer coefficients of the external windows and roofs are required to meet the requirements of "Public Building Energy-Saving Design Standards" PGB50189-2015.),The heat transfer coefficient K = 2.9W /(? · k),which does not meet the requirements specified in the standard;the existing office building envelope structure energy-saving transformation plan is: 60 mm extruded plastic for external wall insulation materials,70 mm extruded roof Plastic panels and external windows retain the original ordinary hollow glass(12mm);the total power consumption under this scheme(54.88 kWh / ?)is different from the total power consumption of the design building(53.63 kWh / ?).It is-1.25 kWh / ?.(6)Under the prescriptive indicators,although the energy-saving reformation scheme of the envelope structure has good energy-saving effects,the economic cost is huge;the scheme determined under the method of "balance judgment" can basically meet the energy-saving requirements.Therefore,the energy-saving reconstruction plan for an existing office building envelope structure in Lanzhou area was finally determined as follows: 60 mm extruded board was used for the external wall insulation material,70 mm extruded board was used for the roof,and the original ordinary hollow glass(12mm)was used for the exterior windows.The research results of this paper can provide references for the energy-saving reconstruction of a large number of public building envelopes in China.