Multi-Objective Optimization Of Thermal Insulation Layer Thickness Of Passive Ultra-Low Energy Building Envelope

With the improvement of people’s living standards,the energy consumption of buildings has been increasing year by year,among them,the energy consumption of building heating and cooling accounts for the majority,which has become an important challenge for building energy saving and carbon emission reduction in the building sector.In order to cope with global climate change,promote green buildings and building energy conservation in my country,and achieve carbon peaking and carbon neutrality,passive ultra-low energy buildings are promoted in China as the focus of building energy conservation.In my country,the evaluation indicators and key parameters optimization of passive ultra-low energy consumption buildings are still relatively lacking,such as energy saving effect,indoor heat and humidity environment parameters,economic and environmental protection benefits,etc,and it is difficult to achieve theoretical guidance and application promotion.Therefore,in order to quantitatively analyze the operating parameters of passive ultra-low energy buildings,it is necessary to focus on the research on the thickness of the thermal insulation layer of the outer envelope of passive ultra-low energy buildings,optimize the value of the thickness of the thermal insulation material.First,in order to obtain the optimal solution of the thickness of the thermal insulation layer of the outer wall of the passive house,through the heat transfer mechanism of building envelope,the theory of the whole life cycle of the building,and the single-objective and multi-objective optimization methods,the mathematical model of the three objective functions of the energy consumption of the whole life cycle of the building,the carbon emission of the whole life cycle and the total cost of the whole life cycle was established;A hierarchical optimization method combining non-dominated sorting genetic algorithm(NSGA-Ⅱ)and the above multiple objectives is proposed to quantify the influence of the thickness of the insulation layer on the objective results.The energy consumption simulation method combined with the proposed optimization method is used for analysis and calculation,and the reliability of the simulation software is verified by the comparison between experiments and simulations.Then,using the above method,taking a passive ultra-low energy consumption building in a hot summer and cold winter area as the research background,the simulation calculation of building operation energy consumption was carried out,and the optimal insulation layer thickness of the building under a single objective was obtained.In the decision-making of a practical problem,there may be multiple objectives to be considered.Most of the existing researches on the thickness of the thermal insulation layer are single-objective optimization,and some multi-objective optimizations only give a value range,and often cannot get a unique solution.Therefore,for the two objective of life cycle energy consumption and life cycle carbon emissions,the Pareto front-end is optimized by using the NSGA-Ⅱ algorithm.In this set of non-inferior solutions(Pareto solutions),the total cost of the whole life cycle is optimized,and the unique solutions for the optimal insulation thickness of EPS,XPS,PUR and Rockwool under multi-objective optimization are 121 mm,85mm,67 mm,145mm,the optimization results are basically in the vicinity of multiple single-objective optimization results,and the multi-objective optimization results are to seek balance and compromise in each single objective.In addition,the analysis and calculation of cities in five climate regions were carried out,and it was found that for regions with hot summer and cold winter,regions with hot summer and warm winter,and mild regions,it is not that the greater the thickness of the thermal insulation layer,the lower the energy consumption of building operation.However,as the latitude decreases,the thickness of the thermal insulation required for passive ultra-low energy buildings decreases accordingly.Buildings in hot summer and warm winter and mild areas are not suitable for thick insulation.Even if insulation is adopted,only a small thickness of insulation material is required for insulation.Finally,through orthogonal test and parameter sensitivity analysis,the influence of thermal parameters of some building envelope structures on the optimization results of thermal insulation layer thickness of passive ultra-low energy consumption buildings is studied.The research results show that the greater the influence of each factor on the building energy consumption,the greater the influence on the selection of the thickness of the thermal insulation layer.In this paper,the multi-objective optimal solution for the thickness of the thermal insulation layer of the outer envelope of the passive ultra-low energy consumption building is obtained through research,which provides an analysis method and reference for the selection of the optimal thickness of the thermal insulation layer of the outer wall of the passive ultra-low energy consumption building.To achieve the best effect of building energy saving,emission reduction and cost reduction.