Thermal insulation and energy saving analysis method for residential building outer wall system

Abstract

The invention discloses a thermal insulation and energy conservation analysis method for an outer wall system of a residential building, and belongs to the field of thermal insulation and energy conservation analys.The method comprises the steps that climate characteristics of the residential building are obtained, an outer wall enclosure structure of the residential building is processed based on the climate characteristics, and a plurality of outer wall structures are designed; constructing an energy consumption model of the residential building, and based on the energy consumption model, carrying out annual load analysis on the plurality of outer wall structures to obtain an optimal outer wall structure; based on the energy consumption model, outer wall heat transfer coefficient analysis is conducted on the multiple heat preservation materials of the optimal outer wall structure, and an optimal heat preservation material is obtained; and constructing a life cycle model of the residential building, performing economic thickness analysis on the optimal thermal insulation material based on the life cycle model to obtain an optimal thermal insulation material thickness, and realizing thermal insulation and energy saving of the residential building outer wall system based on the optimal thermal insulation material thickness. According to the method, the optimal thermal insulation layer thickness of the outer wall structure can be calculated, the economical efficiency is best, and the energy-saving rate is highest.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal insulation and energy-saving analysis, and in particular relates to a thermal insulation and energy-saving analysis method for an exterior wall system of a residential building. Background Art

[0002] According to relevant statistics, building energy consumption accounts for more than 40% of the total national energy consumption. The heat loss caused by heat transfer in the building envelope accounts for more than 70% of the building's full life cycle energy consumption.

[0003] At present, many scholars have studied the methods of reducing building energy consumption in building technology, mainly increasing air layers, adding phase change materials, changing the types of doors and windows, adding reflective materials on the exterior walls, changing the position of the insulation layer on the wall, etc. In building energy conservation, the energy consumption of the building envelope accounts for the main part, and the heat transfer energy consumption of the exterior wall in the exterior envelope accounts for about 30% of the total heat transfer energy consumption of the building. Therefore, insulation treatment of the exterior wall is one of the main technologies to reduce building energy consumption. By selecting appropriate energy-saving measures to improve the thermal characteristics of the building envelope, reducing building energy consumption has become a major research direction.

[0004] DeST is a commonly used software for building energy consumption simulation. It is independently developed in China. The meteorological data are used for the correction of actual measured values, which is close to the actual domestic meteorological conditions. It is used by many researchers in the early design and optimization stages of various buildings. Tian Shuai, Zhou Xin and others used the ASHRAE-140 standard to compare and verify the calculation performance of the DeST software air conditioning and heating equipment system. The simulation results were compared with the simulation results of DOE-2, EnergyPlus, TRNSYS, HOT3000, CODYRUN, and ESP-r. The results showed that the calculation results of DeST software had a deviation of less than 1%, and it had good calculation performance in the calculation of air conditioning and heating equipment system performance. Wang Yiqian used DeST-H software to simulate the annual operation energy consumption of a rural residence in Chengdu, simulated the external envelope structure composed of three different walls, windows and roofs, compared the energy saving rates of the three schemes, and finally obtained two suitable renovation schemes. Duan Liying et al. studied residential buildings in Guangzhou and Harbin, where the climates are quite different, and used DeST to simulate the impact of ventilation times on loads. The results showed that ventilation times have a greater impact on cooling loads and a smaller impact on heating loads. Qu Lei et al. used a newly built apartment in Jinan as an example, used DeST software to build a building model and set parameters, simulated the internal thermal environment and energy consumption data of the building under ideal conditions, and proposed an optimization plan. They then simulated and analyzed the optimized building, and finally achieved the design goal of low energy consumption and high comfort.

[0005] However, with the rapid development of the economy, the total number of buildings has increased year by year, and people's demand for comfort inside buildings has continued to increase, resulting in a sharp increase in building energy consumption. Due to the different climate zones in China, the cooling and heating methods in each region are also different. In southern my country, there are more hot days in summer and relatively fewer cold days. The temperature in winter rarely drops below zero. Both summer cooling and winter heating are mainly air-conditioned, and the insulation and energy-saving efficiency of many buildings are low.

[0006] The existing technology should use different methods of insulation and energy saving for the exterior wall system of residential buildings according to the climate of different regions. Especially in the assembled sandwich insulation exterior wall, at present, there are only range standards for the materials and thickness of the insulation layer, and it is impossible to accurately analyze the optimal exterior wall insulation layer materials and thickness under the climatic conditions of different regions. Summary of the invention

[0007] The present invention proposes a thermal insulation and energy-saving analysis method for the exterior wall system of a residential building. The exterior wall system of the enclosure structure is designed through field investigation and literature research. The DeST energy consumption simulation software is used to analyze the influence of different types of exterior wall systems on building energy consumption, and a better exterior wall system structure is selected. Then, a thermal insulation performance optimization study is conducted on the exterior wall system to solve the technical problems existing in the above-mentioned prior art.

[0008] To achieve the above object, the present invention provides a thermal insulation and energy-saving analysis method for a residential building exterior wall system, comprising:

[0009] Acquire the climate characteristics of the residential building, process the exterior wall enclosure structure of the residential building based on the climate characteristics, and design several exterior wall structures;

[0010] Constructing an energy consumption model of a residential building, and based on the energy consumption model, performing a year-round load analysis on the several exterior wall structures to obtain an optimal exterior wall structure;

[0011] Based on the energy consumption model, analyzing the exterior wall heat transfer coefficient of several insulation materials of the optimal exterior wall structure to obtain the optimal insulation material;

[0012] A life cycle model of a residential building is constructed, and an economic thickness analysis of the optimal thermal insulation material is performed based on the life cycle model to obtain the optimal thermal insulation material thickness. Based on the optimal thermal insulation material thickness, thermal insulation and energy saving of the exterior wall system of the residential building are achieved.

[0013] Preferably, the process of treating the exterior wall enclosure structure of a residential building includes:

[0014] If the climate characteristics are high temperature and high radiation, reflective heat insulation treatment is applied to the exterior wall enclosure structure;

[0015] If the climate is characterized by humidity and high rainfall, the exterior wall enclosure structure shall be subjected to hydrophobic thermal insulation treatment.

[0016] Preferably, the several types of exterior wall structures include: internal insulation exterior wall, frame self-insulation exterior wall and sandwich insulation exterior wall.

[0017] Preferably, the process of constructing an energy consumption model for a residential building is:

[0018] Based on the floor plan of the residential building, a three-dimensional building model was constructed using DeST software;

[0019] The model parameters of the three-dimensional building model are obtained, and an energy consumption model of the residential building is constructed based on the model parameters.

[0020] Preferably, the process of performing annual load analysis on the several exterior wall structures includes:

[0021] A reference exterior wall structure is obtained, and based on the energy consumption model, a cooling and heating load analysis is performed on the reference exterior wall structure and several exterior wall structures respectively, so as to obtain analysis results of energy consumption reduction of the several exterior wall structures.

[0022] Preferably, the optimal exterior wall structure is a sandwich insulation exterior wall.

[0023] Preferably, the several types of thermal insulation materials include: polystyrene material, extruded polystyrene material and polyurethane material.

[0024] Preferably, the process of analyzing the exterior wall heat transfer coefficient of several insulation materials of the optimal exterior wall structure includes:

[0025] Based on the calculation formula of the exterior wall heat transfer coefficient and the calculation formula of thermal inertia, the wall thermal characteristics corresponding to different thicknesses of several insulation materials are calculated, and based on the wall thermal characteristics, the optimal insulation material is obtained, and the optimal insulation material is polyurethane.

[0026] Preferably, the process of obtaining the optimal insulation material thickness includes:

[0027] Based on the climate air conditioning electricity consumption calculation formula in the life cycle model, the air conditioning operation cost is obtained;

[0028] Based on the operating cost of air conditioning, the optimal insulation material thickness when the total operating cost of residential buildings is lowest is calculated through the full life cycle cost calculation formula.

[0029] Preferably, the calculation formula of the air conditioner operating cost is:

[0030]

[0031]

[0032] Where W A , W Bare the air conditioning electricity consumption per unit area in summer and winter, CDD26 and HDD18 are cooling and heating degree days, COP and EER are the energy efficiency ratios of the air conditioning system in winter and summer respectively;

[0033] The formula for calculating the total life cycle cost is:

[0034] C=C in +C h ,

[0035] C in =C i δ,

[0036] C h =PWF×C e ,

[0037] C e =0.73×(W A +W B ),

[0038]

[0039] Among them, C is the total operating cost per unit area, C in is the investment cost per unit volume of thermal insulation materials, C h is the total electricity cost per unit area of ​​air conditioning, C i is the unit area cost of the insulation material, δ is the thickness of the insulation material, C e is the electricity consumption cost per unit area of ​​air conditioning, 0.73 represents the average unit electricity price in Changsha, and PWF is the present value factor in the whole life cycle, which represents the future value of funds converted into present value.

[0040] Compared with the prior art, the present invention has the following advantages and technical effects:

[0041] The present invention uses energy consumption simulation software to perform annual load analysis on three different exterior wall systems, effectively reducing the heat load of the building; secondly, the sandwich insulation exterior wall has the lowest heat and cold load index, the lowest total energy consumption throughout the year, is easy to construct, adapts to humid environments, and prevents the insulation layer from getting damp. Comprehensive analysis shows that the sandwich insulation exterior wall is the optimal exterior wall system structure.

[0042] Through energy consumption simulation, three different thermal insulation materials were studied, and it was found that with the increase of insulation thickness, the annual cumulative cold and heat loads of the building showed a downward trend, and had a greater impact on the heat load and a smaller impact on the cold load; the full life cycle model was used to calculate the relationship between the thickness of the three insulation materials and the energy consumption cost, material cost, and total cost. The present invention can calculate the optimal thickness of the exterior wall insulation layer, with the best economy and the highest energy saving rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0044] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0045] Figure 2 Schematic diagram of hourly temperature and solar radiation in Changsha in 2020 according to an embodiment of the present invention, wherein (a) annual hourly temperature; (b) annual hourly solar radiation;

[0046] Figure 3 Schematic diagram of the average rainfall and annual hourly humidity content in Changsha in 2020 according to an embodiment of the present invention, wherein (a) the average annual rainfall; (b) the annual hourly humidity content;

[0047] Figure 4 A schematic diagram of the working principle of a reflective heat-insulating and waterproof building coating according to an embodiment of the present invention;

[0048] Figure 5 It is a flow chart of the DeST software simulation steps of an embodiment of the present invention;

[0049] Figure 6 Schematic diagram of a two-dimensional and three-dimensional building model according to an embodiment of the present invention;

[0050] Figure 7 Schematic diagram of the annual heating and cooling loads under different exterior wall types according to an embodiment of the present invention, wherein (a) the annual hourly heating load; (b) the annual hourly cooling load;

[0051] Figure 8 Schematic diagram of the annual cumulative energy consumption load under different exterior wall types according to an embodiment of the present invention, wherein (a) the annual cumulative energy consumption; (b) the annual cumulative load index;

[0052] Fig. 9 Schematic diagram of thermal characteristics of walls under different insulation materials and thicknesses according to an embodiment of the present invention, wherein (a) wall heat transfer coefficient; (b) wall thermal inertia index;

[0053] Fig.10 Schematic diagram of the annual cumulative cooling and heating loads under different insulation materials and thicknesses according to an embodiment of the present invention, wherein (a) the annual cumulative heating load; (b) the annual cumulative cooling load;

[0054] Fig.11 Schematic diagram of analysis and determination of economic thickness of different thermal insulation materials according to an embodiment of the present invention, including (a) relationship between thermal insulation thickness of EPS material and various costs; (b) relationship between thermal insulation thickness of XPS material and various costs; (c) relationship between thermal insulation thickness of PU material and various costs; and (d) determination of economic thickness of different thermal insulation materials. DETAILED DESCRIPTION

[0055] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0056] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0057] Embodiment 1

[0058] This embodiment provides a thermal insulation and energy-saving analysis method for the exterior wall system of a residential building. Based on the climate characteristics of Hunan Province, the exterior wall system of the enclosure structure is designed through field research and literature research. The DeST energy consumption simulation software is used to analyze the impact of different types of exterior wall systems on building energy consumption, and a better exterior wall system structure is selected. Then, the thermal insulation performance optimization study is conducted on it. This can provide a certain reference value for the renovation of existing buildings and the construction of green buildings in Hunan Province. Figure 1 As shown, specifically including:

[0059] S1. Research and Analysis

[0060] S11. Climate characteristics of Hunan

[0061] According to the thermal design zoning of "Civil Building Thermal Design Code" GB50176-2016, Hunan belongs to the hot summer and cold winter area, with hot summers, cold winters, high sunshine intensity and strong solar radiation in summer and autumn. Figure 2 The hourly temperature and solar radiation in Changsha in 2020 show that from June to September, the temperature is relatively high, with the maximum temperature reaching around 39°C. There are many days with solar radiation greater than 800W / m2, and the maximum solar radiation can reach around 1300W / m2. From December to February of the following year, the lowest temperature is basically above 0°C, and cold weather below 0°C rarely occurs. Changsha's summer is longer than its winter, and the summer has high temperatures and high radiation, so it is particularly important to reduce solar radiation and indoor cooling needs.

[0062] Hunan has a subtropical monsoon climate with more rainy days. Figure 3The average rainfall and annual hourly humidity in Changsha in 2020 show that Changsha has a large rainfall, with more than 100 mm in 6 months, and the maximum rainfall in May reaching 323.900 mm. The relative humidity outside is relatively high throughout the year, which leads to more hot and humid weather in Hunan, greatly affecting human comfort. In addition, high outdoor humidity will also affect the service life of the building and have an adverse effect on the decorative layer and insulation layer on the exterior surface of the building.

[0063] S12. Existing buildings and existing problems in Hunan

[0064] In terms of age, most buildings in Hunan before 2000 were made of clay bricks and tiles, and no insulation measures were taken for such buildings. High-rise buildings that appeared after 2000 also had certain insulation measures, and according to structural classification, they mainly had external insulation of exterior walls and internal insulation. After 2010, new types of assembled insulation exterior walls such as frame self-insulation and sandwich insulation exterior walls appeared.

[0065] Because Hunan has more hot and high-temperature weather and greater solar radiation, we should not only emphasize exterior wall insulation, but also pay attention to building shading and natural ventilation to increase the comfort of indoor personnel and reduce building energy consumption. For building shading, in addition to using window glass types that can reflect solar radiation, building reflective heat insulation and waterproof coatings can also be used to insulate the exterior walls. Its advantages are high reflectivity and low thermal conductivity, which can reflect more than 80% of solar radiation, reduce the surface temperature of the building, and have excellent corrosion resistance, waterproofness, and crack resistance.

[0066] Due to the humid and rainy climate in Hunan, there were many problems with early buildings. The outer wall insulation layer and the finishing layer fell off, most of the outer wall insulation and ground insulation materials were removed by residents during renovation, the insulation layer cracked and hollowed, and the inner surface of the wall was prone to condensation, moisture, and even mold. It was difficult to deal with complaints later, which caused great trouble to the developer and serious waste of resources. These problems will not only greatly reduce the insulation and energy-saving effects, but also bring a lot of inconvenience and losses to residents and society. Therefore, when using thermal insulation materials in Hunan, try to use hydrophobic thermal insulation materials, and do a good job of waterproofing during the construction stage.

[0067] S2. Design of enclosure structure

[0068] S21. External wall design of enclosure structure

[0069] According to the above investigation and analysis of the climate characteristics of Hunan and the problems of early buildings, it is not recommended to use external wall insulation in Hunan. The reason is that the high temperature and hot weather in Hunan has great fire hazards in the external insulation layer, and expensive Class A flame retardant materials must be used. In addition, the overall detachment of the external wall insulation layer often occurs, and it is difficult to repair, which has a negative impact on society and the people. Therefore, this paper takes interior insulation exterior walls (I-IEW: Interior insulation exterior walls), frame self-insulating exterior walls (F-IEW: Frame self-insulating exterior walls), and sandwich insulation exterior walls (S-IEW: Sandwich insulated exterior walls) as the research objects, according to the energy-saving requirements of "Energy-saving Design Standard for Residential Buildings in Hot Summer and Cold Winter Regions" JGJ134-2010

[17] , taking the standard insulated exterior wall (R-IEW: Refer to insulated exterior walls) as the reference object. R-IEW was the most commonly used exterior wall structure in residential areas in Hunan around 2000, and its energy-saving design just met the standard. It was used as a reference object to better observe the energy-saving effects of other exterior wall types. Three exterior wall types, I-IEW, F-IEW and S-IEW, suitable for Hunan, were designed. The recommended practices and thermal performance of different types of exterior wall structures are shown in Table 1.

[0070] Table 1

[0071]

[0072] The thermal inertia index and heat transfer coefficient of the exterior wall in Table 1 are in line with the design requirements of the "Energy-saving Design Standard for Residential Buildings in Hot Summer and Cold Winter Areas" JGJ134-2010. The exterior wall surfaces of the three designs are all coated with reflective heat insulation and waterproof coatings. Figure 4This is the working principle of reflective thermal insulation and waterproof coatings for buildings. When the building is exposed to direct sunlight, the high reflectivity of the material itself is used to reflect most of the solar radiation, reduce the heat gain of the building, and thus achieve the purpose of energy saving during the day. At the same time, since the building is not exposed to direct sunlight at night, the high reflectivity of the reflective thermal insulation and waterproof coating does not take effect at night, but it has a low heat transfer coefficient, which can effectively block the conduction of heat energy and greatly reduce the surface temperature of the coated object. It can not only reduce the temperature difference shrinkage deformation caused by structural thermal stress, improve the structure's crack resistance, impermeability, waterproofness and durability, but also significantly reduce the heat entering through the roof and exterior walls, improve the thermal comfort of the indoor environment, and save energy. According to the requirements of the "Technical Standard for the Application of Reflective Thermal Insulation / Thermal Insulation Coatings for Buildings" DBJ 43 / T 371-2021, the energy-saving calculation of thermal insulation putty is cancelled. In I-IEW, modified polystyrene particle concrete is used to replace ordinary polystyrene insulation materials, which has improved strength and can effectively prevent users from damaging the insulation layer during the decoration process. The use of anti-cracking mortar embedded with alkali-resistant glass fiber mesh can effectively prevent cracking of the roof and wall; F-IEW mainly carries out waterproof layer treatment to prevent moisture from affecting the performance of self-insulating bricks; the insulation layer of S-IEW uses the most commonly used EPS board with a thickness of 50mm, which can optimize the insulation material and thickness. In summary, the three different exterior wall insulation structures designed above are all suitable for the high temperature, high heat, humidity and rainy climate characteristics in Hunan.

[0073] S22. Other enclosure structure design

[0074] This embodiment mainly studies the characteristics of the exterior wall enclosure structure, so other enclosure structures are kept unchanged and only the type of enclosure structure is changed. Considering the diversity and complexity of influencing factors, the use of energy consumption simulation software is more convenient and faster than experimental testing, and can accurately explore the characteristics of different exterior wall structures. The recommended practices and performance indicators of other enclosure structures are shown in Table 2. The enclosure structure design meets the design requirements of the "Energy-saving Design Standard for Residential Buildings in Hot Summer and Cold Winter Areas" JGJ134-2010.

[0075] Table 2

[0076]

[0077] S3.Energy consumption simulation and analysis

[0078] S31.DeST Software Introduction

[0079] DeST (Designer's Simulation Toolkit) is an effective building energy simulation tool developed by Tsinghua University in Beijing, China in 1989. So far, a large number of case studies and theoretical verifications have been conducted, and DeST has become a widely used platform for dynamic simulation of building thermal processes and building energy distribution. In terms of the calculation method of building thermal characteristics and cooling and heating loads, DeST adopts a state space method based on building thermal balance.

[20] To simulate the dynamics of building thermal processes. This method comprehensively considers the heat storage and heat release of building envelopes and objects. It is a dynamic simulation calculation method with continuous time and discrete space, including long-wave radiation heat transfer between the inner surfaces of the envelope and air convection heat transfer. Formula (1) describes the calculation process of indoor air temperature.

[0080] t a,k (τ) = t bz,k (τ)+∑ j φ j,0,k (τ)+φ hvac,k q hvac,k (τ)+φ hvac,kcp ρG out,k (τ)[t out (τ)-t a,k (τ)]+∑ j φ hvac,k c p ρG j,k (τ)[t a,j (τ)-t a,k (τ)] (1)

[0081] Where, t a,k (τ),t a,j (τ) is the room temperature of the kth room at the current moment; t bz,k (τ) is the room temperature of room k at the current moment when air conditioning, natural ventilation, and heat exchange between adjacent rooms are not affected; φ j,0,k is the influence coefficient of room J on the room temperature of room k at the current moment; φ hcac,k is the influence coefficient of the air conditioning heat in room k on the room temperature at the previous moment; q hvac,k (τ) is the air conditioning heat or cooling capacity that needs to be input to room k at this time; G out,k (τ) is the outdoor ventilation volume at the current moment; t out (τ) is the outdoor temperature at the current moment; G j,k (τ) is the ventilation volume from the jth adjacent room to the kth room.

[0082] S32. Building model establishment

[0083] The basic workflow of DeST energy consumption simulation is as follows Figure 5 As shown:

[0084] This embodiment takes a classic six-story residential building in Hunan as the research object, with a total construction area of ​​268.2m2, a floor height of 3.6m, a shape coefficient of 0.363, a south-facing window-to-wall ratio of 0.35, and a comprehensive window-to-wall ratio of 0.18. Figure 6 For architectural floor plans and model drawings.

[0085] In the room function zoning, the master bedroom, second bedroom and living room are air-conditioned rooms, and the bathroom and stairwell are non-air-conditioned rooms. In the room function, the upper limit of temperature is 26℃, the lower limit is 18℃, the maximum tolerance upper limit is 28℃, the lower limit is 16℃, ventilation with the outside is 1.0 times / h, the heat disturbance of people and lights is fixed, and in the air-conditioned room category, there are 2 people in the bedroom, 3 people in the living room, 1 person in other rooms, and 0 people in non-air-conditioned rooms.

[0086] The air conditioner is turned on when people are indoors and the current room temperature is lower than or higher than the maximum tolerable temperature. According to the work and rest habits of residents in Hunan, in summer, cooling is provided from 18:00 to 7:00 on weekdays and all day on non-working days; in winter, heating is provided from 18:00 to 7:00 on weekdays and stopped at other times, and heating is provided from 7:00 to 23:00 on non-working days and stopped at other times.

[0087] S32. Energy consumption results analysis

[0088] Keeping other envelope structures and building benchmark parameters unchanged, the DEST software was used to simulate the hourly cooling and heating loads of buildings in Changsha City under four different exterior wall insulation structures: R-IEW, I-IEW, F-IEW, and S-IEW. The results are as follows Figure 7 shown.

[0089] Figure 7 The hourly heat and cold load of the building throughout the year shows that in Hunan, air conditioning heating is mainly from November to March, and air conditioning cooling is mainly from June to September. Figure 7 (a) is the hourly heat load throughout the year. It can be seen that the building with S-IEW slightly shortens the air conditioning heating time, and the maximum heat load and heat load density are significantly smaller than those of the other three exterior walls. The density shows that the annual heat load of S-IEW is the smallest. Figure 7 (b) is the hourly cooling load of the building throughout the year. It can be seen that the cooling load under different exterior wall types is not much different. The air conditioning cooling cycle of the building using S-IEW is slightly longer than that of the other three exterior walls, but the maximum cooling load and cooling load density are both smaller than those of other exterior walls.

[0090] In order to intuitively study the energy saving of the three different types of thermal insulation exterior walls, a full-year energy consumption simulation analysis was conducted on R-IEW, I-IEW, F-IEW, and S-IEW. The calculation results are shown in the figure. Figure 8shown. Figure 8 (a) in the figure is the annual cumulative energy consumption results of the four exterior wall structures. Compared with R-IEW, the annual energy consumption of the three exterior wall insulation structures designed in this paper is reduced. In terms of annual cumulative heat load, I-IEW, F-IEW, and S-IEW are reduced by 2.13%, 15.97%, and 28.42%, respectively. The energy consumption of I-IEW is reduced less because its wall structure and heat transfer coefficient are similar to those of R-IEW, but its moisture, mildew and crack resistance are improved. F-IEW and S-IEW are new insulation exterior wall structures with small wall heat transfer coefficients, which effectively prevent indoor heat from being transferred to the outdoors, significantly reducing the annual building heat load. In terms of cooling load, I-IEW, F-IEW, and S-IEW were reduced by 11.17%, 13.35%, and 22.66% respectively compared with R-IEW, with a significant reduction. This is because the three exterior walls were coated with building reflective thermal insulation coatings, which reflect up to 80% of solar radiation, effectively reducing the temperature of the wall surface in summer, reducing the heat transfer from the outdoors to the indoors, and effectively reducing the cooling load of the building. The total building load was reduced by 6.00%, 14.85%, and 25.95% respectively, and S-IEW had the lowest annual energy consumption. Figure 8 It can also be seen from the trend of the change of the cold and hot load indicators in (b) that S-IEW has significantly lower heat load and cold load indicators than R-IEW, proving that it has the best insulation effect and the lowest building energy consumption. In terms of construction, the construction and tooling of S-IEW are simpler and more convenient, and can be completed in the factory, greatly reducing the construction time and cost. In addition, the insulation layer is in the middle of the wall, which can effectively prevent the reduction of insulation effect caused by moisture. Based on the above analysis, S-IEW is selected as the optimal exterior wall insulation structure, and the material and thickness of its insulation layer are optimized to reduce building energy consumption and material costs.

[0091] S4. Optimization analysis of S-IEW insulation layer

[0092] S41. Effect of different insulation materials and thickness on heat transfer coefficient of exterior wall

[0093] In order to achieve building energy conservation and reduce building energy consumption, changing the thermal characteristics of the exterior wall is the most commonly used technical means. The lower the heat transfer coefficient of the exterior wall, the better the thermal insulation capacity, the higher the thermal inertia of the exterior wall, the stronger the heat storage capacity, thereby saving building energy consumption. For S-IEW, changing the insulation layer material and thickness can change its wall thermal characteristics. Table 3 shows the basic performance and unit price of the three most commonly used insulation materials for S-IEW on the market: polystyrene (EPS), extruded polystyrene (XPS) and polyurethane (PU) (price source: a thermal insulation building materials factory on Alibaba). Formula 2 is the calculation formula for the heat transfer coefficient of the exterior wall, and Formula 3 is the calculation formula for the thermal inertia index of the exterior wall. The thermal characteristics of the wall under different insulation materials are calculated according to Formulas 2 and 3.

[0094]

[0095]

[0096] In the formula, R i -Thermal resistance of each layer of wall material; σ i -Thickness of each layer of wall material; i -Thermal conductivity of each layer material; S i -Heat storage coefficient of each layer of material; c i -Specific heat capacity of each layer of material; ρ i -Material density of each layer; T-harmonic period, 24h.

[0097] Table 3

[0098]

[0099] The calculation results of wall thermal characteristics are as follows: Fig. 9 As shown, Fig. 9 (a) is the wall heat transfer coefficient, which characterizes the thermal performance of the wall insulation system. Studies have shown that reducing the heat transfer coefficient of the exterior wall will significantly reduce building energy consumption.

[21] . As the thickness of the insulation material increases, the heat transfer coefficient of the wall decreases, but the decrease gradually weakens; Fig. 9 (b) is the wall thermal inertia index, which is a dimensionless index that characterizes the degree to which the periodic temperature wave decays inside the enclosure structure. The greater the thermal inertia index of the enclosure structure, the less the internal surface temperature of the building is affected by the external surface temperature fluctuation. The thermal inertia index is positively linearly related to the thickness of the insulation material. The greater the thickness, the higher the thermal inertia index.

[0100] S42. Effects of different insulation materials and thicknesses on building loads

[0101] Keeping other parameters unchanged and only changing the exterior wall insulation material and thickness, the DeST software is used to simulate and calculate the building's cooling and heating loads throughout the year. The simulation results are as follows: Fig.10 As shown, (a) is the annual cumulative heating load result, and (b) is the annual cumulative cooling load result.

[0102] From the overall trend, there is a certain negative linear relationship between the thickness of the insulation material and the annual cumulative cold and hot loads, that is, as the thickness increases, the annual cumulative cold and hot loads decrease linearly, but the decline gradually decreases with the increase of thickness, which shows that excessive insulation thickness cannot always improve insulation performance and reduce energy consumption. And the change of insulation material thickness has a much greater impact on heat load than cold load.

[0103] From the perspective of insulation materials, different insulation materials with the same insulation thickness have different energy-saving effects on the annual cumulative cooling and heating loads. Taking 40mm as an example, the annual cumulative heat loads of the exterior walls of the three insulation materials are 88561.86kW·h, 77416.26kW·h, and 70222.58kW·h, respectively. The PU insulation layer has the best energy-saving effect, saving about 26% and 10% energy compared to the EPS and XPS insulation layers, respectively. The annual cumulative cooling loads are 65910.86kW·h, 64584.19kW·h, and 64283.8kW·h, respectively. It can be seen that the different insulation materials have little effect on the cooling load.

[0104] Through the above analysis, we found that increasing the thickness of the insulation layer can significantly reduce the heat load, but has little effect on the cold load. Both the hot and cold loads are negatively correlated with the thickness. As the thickness of the insulation layer increases, the building energy consumption gradually decreases, but the reduction rate gradually decreases and tends to be stable. Among the three insulation materials, the PU board insulation layer has the best energy-saving effect, but its price is also the most expensive, and as the thickness increases, its energy-saving effect gradually decreases. Therefore, blindly increasing the thickness of the insulation layer will be counterproductive. Appropriate selection of insulation materials and thickness can achieve the best energy-saving effect.

[0105] S43. Analysis and determination of economic thickness of different insulation materials

[0106] According to the simulation analysis results, different insulation materials have different effects on the cooling and heating loads of buildings. After the insulation material is determined, the thickness of the insulation layer becomes the main parameter affecting the insulation performance of the exterior wall structure. This paper adopts the full life cycle cost analysis model

[22] , study the impact of different materials and thicknesses on energy cost, material cost and total cost, and then determine the economic thickness value and the corresponding total operating cost per unit area.

[0107] In Changsha, air conditioning systems are used for both summer cooling and winter heating. The average daily usage time of air conditioning in residential buildings is more than 10 hours in both winter and summer. Formulas (4) and (5) are the calculation formulas for air conditioning power consumption per unit area for summer cooling and winter heating, respectively.

[0108]

[0109]

[0110] Where W A , W B —Electricity consumption of air conditioner per unit area in summer and winter, kW·h / m 2; CDD26, HDD18—cooling and heating degree days, respectively, according to the "Energy-saving Design Standard for Residential Buildings in Hot Summer and Cold Winter Areas", take 2205℃·d and 377℃·d respectively; COP, EER—the energy efficiency ratio of the air conditioning system in winter and summer, take 3.0 and 2.6 respectively

[17] .

[0111] During the entire life cycle, the total building operating cost per unit area is equal to the sum of the insulation layer investment cost and the air conditioning operating cost. Equations (6) to (9) represent the calculation relationship between them.

[0112] C=C in +C h (6)

[0113] C in =C i δ (7)

[0114] C h =PWF×C e (8)

[0115] C e =0.73×(W A +W B ) (9)

[0116] Where, C is the total operating cost per unit area, CNY / (m 2 a); Cin—investment cost per unit volume of insulation materials (material cost, installation cost), CNY / (m 3 ·a); Ch—total cost of electricity consumption per unit area of ​​air conditioning, CNY / (m 2 ·a); Ci—unit area cost of thermal insulation materials, CNY / (m 2 a); δ—thickness of thermal insulation material, m; Ce—power consumption per unit area of ​​air conditioning, CNY / (m 2 a), 0.73 represents the average unit electricity price in Changsha, CNY / kW·h; PWF—present value factor in the whole life cycle, which represents the future value of funds converted into present value, and is calculated to be 14.18.

[0117] Based on the above analysis, equations (2) to (9) are integrated to obtain the calculation formula (10) for the total operating cost per unit area of ​​the building. When the total cost per unit area of ​​the building is the lowest, the optimal economic thickness of the insulation material is calculated by equation (11).

[0118]

[0119]

[0120] Where Rwt is the total thermal resistance of the foundation wall (excluding the insulation layer), which is 0.357 (m 2 ·K) / W.

[0121] By calculating the above formula, Fig.11 (c) is the relationship between the thickness of PU insulation material and energy consumption cost, material cost, and total cost. It can be seen that the material cost of the insulation layer is positively correlated with the insulation thickness, and the building energy consumption cost is negatively correlated with the insulation thickness, but the total cost C and the insulation thickness δ are nonlinearly related in an inverse parabola shape. When δ < 40 mm, C decreases as δ increases; when δ > 40 mm, C increases as δ increases; when δ = 40 mm, the total cost C is the smallest. Fig.11 (d) is the relationship between the total cost per unit area of ​​the building and the insulation thickness under three different insulation materials, and Fig.11 Compared with (c) in Figure 1, different insulation materials have similar inverse parabolic nonlinear relationships with respect to total cost and thickness, but the economic thickness of different materials is different. Fig.11 In (a), for EPS material, the optimal thickness is 70 mm, and the unit area cost is about 68 CNY / m2; Fig.11 (b) For XPS material, the optimal thickness is 50mm, and the total cost per unit area is about 66CNY / m 2 ; For PU material, the optimal thickness is 40mm, and the total cost per unit area is about 71CNY / m 2 Compared with the annual total energy consumption of the standard insulation exterior wall, the walls with the best insulation thickness of the three materials saved energy by 31.78%, 31.27% and 31.27% respectively.

[0122] Through the above analysis, considering the influence of various factors such as material cost, energy saving rate, and total cost, the total cost per unit area of ​​the XPS sandwich insulation wall with a thickness of 50mm has the lowest total cost, which ensures its energy saving efficiency while ensuring low construction cost, which is in line with the original intention of this study. Secondly, with the development of the green building industry, green building materials will also be updated and iterated. Not only should we consider building energy saving, but we should also pay attention to the impact of buildings on the environment to achieve green and low-carbon. The life cycle assessment model integrated in this article can provide theoretical references for material selection and material thickness in building energy-saving design.

[0123] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A thermal insulation and energy-saving analysis method for a residential building exterior wall system, characterized in that: include: Acquire the climate characteristics of the residential building, process the exterior wall enclosure structure of the residential building based on the climate characteristics, and design several exterior wall structures; Constructing an energy consumption model of a residential building, and based on the energy consumption model, performing a year-round load analysis on the several exterior wall structures to obtain an optimal exterior wall structure; Based on the energy consumption model, analyzing the exterior wall heat transfer coefficient of several insulation materials of the optimal exterior wall structure to obtain the optimal insulation material; A life cycle model of a residential building is constructed, and an economic thickness analysis of the optimal thermal insulation material is performed based on the life cycle model to obtain the optimal thermal insulation material thickness. Based on the optimal thermal insulation material thickness, thermal insulation and energy saving of the exterior wall system of the residential building are achieved.

2. The thermal insulation and energy-saving analysis method for the exterior wall system of a residential building according to claim 1 is characterized in that: The process of treating the exterior wall envelope of a residential building includes: If the climate characteristics are high temperature and high radiation, reflective heat insulation treatment is applied to the exterior wall enclosure structure; If the climate is characterized by humidity and high rainfall, the exterior wall enclosure structure shall be subjected to hydrophobic thermal insulation treatment.

3. The thermal insulation and energy-saving analysis method for the exterior wall system of a residential building according to claim 1, characterized in that: The several types of exterior wall structures include: internal insulation exterior wall, frame self-insulation exterior wall and sandwich insulation exterior wall.

4. The thermal insulation and energy-saving analysis method for the exterior wall system of a residential building according to claim 1, characterized in that: The process of building an energy consumption model for a residential building: Based on the floor plan of the residential building, a three-dimensional building model was constructed using DeST software; The model parameters of the three-dimensional building model are obtained, and an energy consumption model of the residential building is constructed based on the model parameters.

5. The thermal insulation and energy-saving analysis method for the exterior wall system of a residential building according to claim 1, characterized in that: The process of performing annual load analysis on the several exterior wall structures includes: A reference exterior wall structure is obtained, and based on the energy consumption model, a cooling and heating load analysis is performed on the reference exterior wall structure and several exterior wall structures respectively, so as to obtain analysis results of energy consumption reduction of the several exterior wall structures.

6. The thermal insulation and energy-saving analysis method for the exterior wall system of a residential building according to claim 1, characterized in that: The optimal exterior wall structure is a sandwich insulation exterior wall.

7. The thermal insulation and energy-saving analysis method for residential building exterior wall system according to claim 1, characterized in that: The several types of thermal insulation materials include: polystyrene material, extruded polystyrene material and polyurethane material.

8. The thermal insulation and energy-saving analysis method for residential building exterior wall systems according to claim 1, characterized in that: The process of analyzing the heat transfer coefficient of the exterior wall for several kinds of thermal insulation materials of the optimal exterior wall structure includes: Based on the calculation formula of the exterior wall heat transfer coefficient and the calculation formula of thermal inertia, the wall thermal characteristics corresponding to different thicknesses of several insulation materials are calculated, and based on the wall thermal characteristics, the optimal insulation material is obtained, and the optimal insulation material is polyurethane.

9. The thermal insulation and energy-saving analysis method for residential building exterior wall systems according to claim 1, characterized in that: The process of obtaining the optimal insulation thickness includes: Based on the climate air conditioning electricity consumption calculation formula in the life cycle model, the air conditioning operation cost is obtained; Based on the operating cost of air conditioning, the optimal insulation material thickness when the total operating cost of residential buildings is lowest is calculated through the full life cycle cost calculation formula.

10. The thermal insulation and energy-saving analysis method for the exterior wall system of a residential building according to claim 9, characterized in that: The calculation formula of the air conditioning operating cost is: Where W A , W B are the air conditioning electricity consumption per unit area in summer and winter, CDD26 and HDD18 are cooling and heating degree days, COP and EER are the energy efficiency ratios of the air conditioning system in winter and summer respectively; The formula for calculating the total life cycle cost is: C=C in +C h , C in =C i d, C h =PWF×C e , C e =0.73×(W A +W B ), Among them, C is the total operating cost per unit area, C in is the investment cost per unit volume of thermal insulation materials, C h is the total electricity cost per unit area of ​​air conditioning, C i is the unit area cost of the insulation material, δ is the thickness of the insulation material, C e is the electricity consumption cost per unit area of ​​air conditioning, 0.73 represents the average unit electricity price in Changsha, and PWF is the present value factor in the whole life cycle, which represents the future value of funds converted into present value.

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