Optimal method to achieve energy efficiency in residential buildings in different climate regions of China

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Optimal method to achieve energy

efficiency in residential buildings in

different climate regions of China

Yuxin Wang

Master of Science Thesis

KTH School of Industrial Engineering and Management Energy Technology EGI_2016-086 MSC

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Master of Science Thesis EGI_2016-086 MSC Optimal method to achieve energy efficiency in residential buildings in different climate

regions of China

Yuxin Wang

Approved Examiner

Jaime Arias Hurtado

Supervisor

Peter Kjaerboe

Commissioner Contact person

Sammanfattning

Genom att energin är begränsad i världen och att byggsektorn kräver en mycket stor andel så är arbetet att effektivisera i denna sektor ett av de viktigaste målen i denna bransch.

Syftet med detta arbete är att finna en bra, effektiv, och billig metod för att snabbt nå målet med energieffektivitet för Kinas bostäder.

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Abstract

Due to the energy shortage situation of the world and building sector occupies the most significant particle of total energy consumption, promoting the energy efficiency in the buildings has become one of the most urgent goals for energy develop the profession.

The purpose of this project is to look for the most reasonable method, which is efficient and can be carried out in a short term with a lower investment, to reach the goal of energy efficiency in residential buildings in China.

Considering that China is a vast territory country, the whole mainland is separated into five parts according to the various climate types in order to research accurately. A base building has been modeled in five climate zones at the same time. The software Designbuilder is used to simulate the base scenario, the building envelope improved scenario and the HVAC system improved scenario. The final suggestion is given according to the comparison of these three scenarios.

Besides, some other technologies have been given in the thesis. These methods would take a longer time period or more investment, but still are good choices for residential buildings energy efficiency. They should be promoted in the future by the government support.

Keywords

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Glossary of Terms

GHG Green House Gas

UNEP United Nations Environment Programme HVAC Heating, Ventilating and Air Conditioning tce Tons of standard coal equivalent

EU European Union

kgce Kilogram of standard coal equivalence

CHP Combine heat and power generation

DHW Domestic Hot Water

VAV Variable Air Volume

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List of Tables

TABLE 1-1 THE GRAPHIC SYMBOL OF FIGURE 1-1 ... 12

TABLE 1-2 AVERAGE TEMPERATURE OF DIFFERENT CLIMATE ZONES ... 13

TABLE 1-3THERMAL DESIGN REQUIREMENTS IN DIFFERENT REGIONS ... 14

TABLE 1-4 RESIDENTIAL BUILDING CATEGORIES DIVIDED BY FLOORS ... 14

TABLE 1-5THE CHINESE PHASE OUT OF INCANDESCENT LAMP CIRCUIT DIAGRAM... 17

TABLE 2-1AREA RATIO OF WINDOWS TO WALLS ON DIFFERENT DIRECTIONS ... 21

TABLE 2-2BASIC INFORMATION OF THE WALL OF THE STANDARD BUILDING ... 24

TABLE 2-3DETAILS OF 200MM CONCRETE WALL ... 24

TABLE 2-4DETAILS OF THE WINDOWS IN THE STANDARD BUILDING ... 26

TABLE 2-5THE SCHEDULE OF LIGHT SYSTEM ... 26

TABLE 2-6DESIGN INDOOR TEMPERATURE IN HEATING CASE ... 27

TABLE 2-7DESIGN PARAMETERS OF INDOOR CLIMATE IN COOLING CASE ... 27

TABLE 2-8PARAMETERS OF STANDARD BUILDING ... 28

TABLE 2-9SAMPLE CITIES ... 29

TABLE 2-10CLIMATE OF CHANGCHUN ... 31

TABLE 2-11CLIMATE OF BEIJING ... 32

TABLE 2-12CLIMATE OF SHANGHAI ... 33

TABLE 2-13GUANGZHOU CLIMATE ... 34

TABLE 2-14KUNMING CLIMATE ... 35

TABLE 2-15CALCULATED VALUES OF EXISTING WALL ... 36

TABLE 2-16TOTAL ENERGY CONSUMPTION OF CHANGCHUN – BASE SCENARIO ... 37

TABLE 2-17ENERGY CONSUMPTION BY CATEGORIES OF CHANGCHUN – BASE SCENARIO ... 37

TABLE 2-18TOTAL ENERGY CONSUMPTION OF BEIJING – BASE SCENARIO... 37

TABLE 2-19ENERGY CONSUMPTION BY CATEGORIES OF BEIJING – BASE SCENARIO ... 38

TABLE 2-20TOTAL ENERGY CONSUMPTION OF SHANGHAI – BASE SCENARIO ... 38

TABLE 2-21ENERGY CONSUMPTION BY CATEGORIES OF SHANGHAI – BASE SCENARIO ... 38

TABLE 2-22TOTAL ENERGY CONSUMPTION OF GUANGZHOU – BASE SCENARIO ... 39

TABLE 2-23ENERGY CONSUMPTION BY CATEGORIES OF GUANGZHOU – BASE SCENARIO ... 39

TABLE 2-24TOTAL ENERGY CONSUMPTION OF KUNMING – BASE SCENARIO ... 39

TABLE 2-25ENERGY CONSUMPTION BY CATEGORIES OF KUNMING – BASE SCENARIO ... 40

TABLE 2-26TYPICAL PHYSICAL PROPERTIES OF XPS ... 41

TABLE 2-27THE PERFORMANCE OF IMPROVED EXTERNAL WALL ... 42

TABLE 2-28TOTAL ENERGY CONSUMPTION OF CHANGCHUN –ENVELOPE IMPROVED SCENARIO ... 42

TABLE 2-29ENERGY CONSUMPTION BY CATEGORIES OF CHANGCHUN... 43

TABLE 2-30TOTAL ENERGY CONSUMPTION OF BEIJING –ENVELOPE IMPROVED SCENARIO ... 43

TABLE 2-31ENERGY CONSUMPTION BY CATEGORIES OF BEIJING ... 43

TABLE 2-32TOTAL ENERGY CONSUMPTION OF SHANGHAI –ENVELOPE IMPROVED SCENARIO ... 44

TABLE 2-33ENERGY CONSUMPTION BY CATEGORIES OF SHANGHAI ... 44

TABLE 2-34TOTAL ENERGY CONSUMPTION OF GUANGZHOU –ENVELOPE IMPROVED SCENARIO ... 44

TABLE 2-35ENERGY CONSUMPTION BY CATEGORIES OF GUANGZHOU... 45

TABLE 2-36TOTAL ENERGY CONSUMPTION OF KUNMING –ENVELOPE IMPROVED SCENARIO ... 45

TABLE 2-37ENERGY CONSUMPTION BY CATEGORIES OF KUNMING ... 45

TABLE 2-38THE COST OF INSTALLING XPS INSULATION ... 46

TABLE 2-39THE PRICE OF RESIDENTIAL ELECTRICITY IN CHANGCHUN ... 47

TABLE 2-40THE PRICE OF RESIDENTIAL ELECTRICITY IN BEIJING ... 47

TABLE 2-41THE PRICE OF RESIDENTIAL ELECTRICITY IN SHANGHAI ... 47

TABLE 2-42THE PRICE OF RESIDENTIAL ELECTRICITY IN GUANGZHOU ... 47

TABLE 2-43THE PRICE OF RESIDENTIAL ELECTRICITY IN KUNMING ... 47

TABLE 2-44THE PAYBACK TIME OF EACH DWELLING ... 48

TABLE 2-45TOTAL ENERGY CONSUMPTION OF CHANGCHUN –HVAC IMPROVED SCENARIO ... 48

TABLE 2-46ENERGY CONSUMPTION BY CATEGORIES OF CHANGCHUN –HVAC IMPROVED SCENARIO ... 49

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TABLE 2-48ENERGY CONSUMPTION BY CATEGORIES OF BEIJING –HVAC IMPROVED SCENARIO ... 49

TABLE 2-49TOTAL ENERGY CONSUMPTION OF SHANGHAI –HVAC IMPROVED SCENARIO ... 50

TABLE 2-50ENERGY CONSUMPTION BY CATEGORIES OF SHANGHAI –HVAC IMPROVED SCENARIO ... 50

TABLE 2-51TOTAL ENERGY CONSUMPTION OF GUANGZHOU –HVAC IMPROVED SCENARIO ... 50

TABLE 2-52ENERGY CONSUMPTION BY CATEGORIES OF GUANGZHOU –HVAC IMPROVED SCENARIO ... 51

TABLE 2-53TOTAL ENERGY CONSUMPTION OF KUNMING –HVAC IMPROVED SCENARIO ... 51

TABLE 2-54ENERGY CONSUMPTION BY CATEGORIES OF KUNMING –HVAC IMPROVED SCENARIO ... 51

TABLE 3-1ENERGY SAVING IN THE ENVELOPE IMPROVED SCENARIO ... 52

TABLE 3-2ENERGY SAVING IN THE HVAC IMPROVED SCENARIO ... 53

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List of Figures

FIGURE 1-1TOTAL ENERGY CONSUMPTION OF THE WORLD IN 2014 ... 10

FIGURE 1-2CHINA CLIMATE ZONES MAP ... 13

FIGURE 2-1SCHEME OF METHODOLOGY ... 20

FIGURE 2-2LAYOUT PLAN OF MODEL DWELLING ... 21

FIGURE 2-3BUILDING OUTLOOK ... 22

FIGURE 2-4BUILDING BLOCK ... 23

FIGURE 2-5BUILDING BLOCK –TOP VIEW ... 23

FIGURE 2-6STRUCTURE OF 200MM CONCRETE WALL ... 25

FIGURE 2-7CONDENSATION ANALYSIS OF 200MM CONCRETE WALL ... 25

FIGURE 2-8SAMPLE CITIES ... 30

FIGURE 2-9STRUCTURE OF EXISTING EXTERNAL WALL ... 35

FIGURE 2-10XPS EXTRUDED POLYSTYRENE ... 40

FIGURE 2-11IMPROVED EXTERNAL WALL ... 41

FIGURE 3-1COMPARISON OF DIFFERENT CITIES –ENVELOPE IMPROVED SCENARIO ... 53

FIGURE 3-2COMPARISON OF DIFFERENT CITIES –HVAC IMPROVED SCENARIO ... 54

FIGURE 3-3ENERGY CONSUMPTION IN DIFFERENT CITIES ... 55

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1 Introduction

With the social development and the improvement of science technology, energy consumption increasing sharply in order to meet the requirement of human comfortable. Besides, the building sector occupies the most significant part of total energy consumption. At the same time, the building sector is the largest contributor to global GHG emission (United Nations Environment Programme, 2016). The data collected by UNEP shows that buildings use about 40% of global energy, 25% of global water, 40% of global resources, and they emit approximately 1/3 of GHG emissions (United Nations Environment Programme, 2016). Therefore, achieving energy efficiency in existing buildings has become one of the most urgent task for the world, especially for the energy workers.

The map below (Enerdata Offices, 2015) shows the total energy consumption all over the world,

Figure 1-1 Total Energy Consumption of the World in 2014

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management of building demolition. To strengthen the city lighting management, strictly prevent and correct the excessive decoration and lighting. (The Central People's Government of the People's Republic of China, 2011)

Comparing with the EU countries, they propounded a series policy during 2003 to 2003 such as The European Energy Performance of Buildings Directive (EPBD)(2002), Intelligent Energy - Europe (IEE)(2003), etc. China was focusing on measurement management, while new goals are better to set as improving the energy efficiency technology.

To achieving the goal of reducing the building energy consumption, various types of methods, such as using heat pumps or improving the HVAC systems, can be used. While, not all methods need to be used at the same time. There would have an optimization choice or a terrific combination can be found for buildings. The reduction of energy use in the built environment through optimizing building energy efficiency is a strategic research challenge (Chwieduk, 2003). This thesis is dealing with a standard model of a Chinese building and focus on finding out a top selection by scientific analyzation and consultant.

1.1 Background

1.1.1 Current situation of building energy efficiency in China

Sustainability is comprehensive therefore a complex subject (Ragheb, El-Shimy, & Ragheb, 2015). Achieving energy efficiency is an important step of promoting a sustainable world. As one of the largest countries, which have a great number of buildings, China has already recognized that some improvement measures should be introduced to cut down the energy consumption, which is caused by buildings. The process of promoting energy-saving technology has become one of the most crucial technologies in China. Hence, China has been developing and improving building energy efficiency policies since 1980’s (Shui & Li, 2012).

In 2011, the total energy consumption in China was 3.75 billion tce (National Bureau of Statistics of the People's Republic of China, 2014), and the total building energy consumption (except for biomass energy) is 0.756 billion tce (Building Energy Conservation Research Center, 2015). Thus, building sector contributes 19.5% of total energy consumption in China.

According to Chinese government documents, by 2015, the implementation rate of new green buildings in the urban area should achieve to 20%, the area of new green buildings is suggested reach 300 million square meters, completed 300 million square meters of existing residential building heating metering in northern area (General Office of the State Council, 2014).

Among all branches of energy consumption, the intensity of heating energy consumption in northern cities and towns is relatively large. To improve the heating system would be the dominating measure to achieve building energy efficiency in northern heating region consequently. In 2013, energy consumption of heating in northern cities and towns was 0.181 billion tce, occupied 24.0% of total building energy consumption (Building Energy Conservation Research Center, 2015). During 2001 to 2013, building area of the northern heating region has increased from 5 billion m2_{to 12. The rate of}

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Excluding heating energy consumption in northern district, total residential building energy consumption in China 2013 is 0.185 billion tce, separated energy using terminals as air conditioning systems, household electric appliances, hot tap water and etc. the average growth of household energy consumption intensity approximately 50% since 2001 (Building Energy Conservation Research Center, 2015). With the improvement of people’s living standard, the requirement on living comfortable is becoming higher and higher. Some districts who are located along Yangtze River basin and even southern starts to use heating devices to get a warmer indoor climate.

1.1.2 Regional areas

China is a vast territory country, 9.6 million square kilometres land covering a variety of climate zones. To simplify the research work, the Chinese government made a code separate total landing area into different regions and define them.

Building climate zoning system in China is divided into two levels: primary level division is divided into five categories, and the secondary division is divided into 20 areas (Ministry of Construction of the People's Republic of China, 1993). The main indexes are the average temperature in January and July, and the average relative humidity on July. The auxiliary indexes are annual precipitation, the number of days of the daily average temperature lower than or equal to 5 ℃ and the number of days of the daily average temperature higher than or equal to 25 ℃.

Figure 1-1 shows the climate zones system in China (China Architecture Design & Research Group(CAG), 2005). Table 1-1 below is the Graphic symbol of Figure 1-2

Table 1-1 the graphic symbol of Figure 1-1

Severe cold region

Cold region

Hot-summer and cold-winter region Hot-summer and warm-winter region

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Figure 1-2 China Climate Zones Map

The average temperature of different climate zones in January and July can be found in Table 1-2 below. The data is collected from Standard of climatic regionalization for architecture, which was published by the ministry of construction of the People’s Republic of China in 1993.

Table 1-2 average temperature of different climate zones

Regions Average temperature (℃)

January July

Severe cold region ≤ -10 ≤ 25

Cold region -10 ~ 0 18 ~ 28

Hot-summer and cold-winter region 0 ~ 10 25 ~ 30

Hot-summer and warm-winter region ＞ 10 25 ~ 29

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Due to the different climate feature in different region, the requirements of heating and cooling has to be considered separately according to regions, as shown in the table below (Ministry of Construction of the People's Republic of China, 1993), when design or transformation of construction.

Table 1-3 Thermal design requirements in different regions

Regions Requirement for winter heating Requirement for summer cooling Severe cold Have to be fully considered Do not have to be considered

Cold Need to be considered Proper consider in partial area

Hot-summer & cold-winter Proper consider Need to be considered

Hot-summer &

warm-winter Do not have to be considered Have to be fully considered Temperate Do not have to be considered Proper consider in partial area

1.1.3 Standard modelling selection

During the year of 2001 to 2013, a plenty of people relocate to urban areas from rural areas, urbanization rate grows from 37.7% to 53.7% (National Bureau of Statistics of the People's Republic of China, 2014). The rapid urbanization lead to the uprush of urban residential floor area, because of the shortage of urban land area per capita, the urban residential building has become one of the most extensive architectural forms. Thus, as the most commonly urban residential building, the department has been chosen as the pilot building style.

The residential buildings can be divided into 4 categories according to the floors, as shown in the following table (Ministry of housing and urban & rural development of the people's Republic of China, 2011).

Table 1-4 residential building categories divided by floors

Name Number of layers

Low layer buildings 1 ~ 3

Multilayer buildings 4 ~ 6

Upper layer buildings 7 ~ 9

Top layer buildings 10 and above

Although those better-developed cities like Beijing, Shanghai, Guangzhou and etc. have lots of top layer buildings, the sort of multilayer still are the most commonly residential buildings in China.

The building specifications have clear regulation in relative codes. For each dwelling unit, which composed of a bedroom(s), living room (hall), kitchen and bathroom, its size should not be less than 30m2_{, the story height of residential buildings is appropriate 2.8m (Ministry of housing and urban &}

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China is 3.35 (National Health and Family Planning Commission, 2015), the area of each dwelling should be around 100m2_.

According to the data above, the standard building, which would be used for modelling is a 6-floor apartment building that has 8 families, which can be separated into 4 units, on each floor. On the basis of Chinese building habits, the apartment would be located on north and south direction.

The area of each dwelling is 105.48m2_{, the length on north and south direction of each dwelling is 10.4m,}

and the length on east and west direction is 12.6m.

1.1.4 Status of urban residential building energy consumption

The data collected by building energy conservation research Centre of Tsinghua University shows the trend of urban residential building energy consumption during 1996 to 2011 (Building Energy Conservation Research Center, Tsinghua University, 2013),

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Figure 1-4 Trend of urban residential building energy consumption per household except for district heating

The energy consumption was more or less steady during 1996 to 2000, With China's sustained rapid economic development and the increasing residents income, the living standard of residents improve gradually, the ownership rate and usage rate of various types of home appliances increased substantially. Besides, energy using patterns of residents in China has changed as well. Various reasons leading the energy consumption surged.

The totally urban building energy consumption can be divided into six main sections as district heating, air conditioning, household electric appliances, domestic hot water, cooking, and lighting.

1.1.4.1 District heating

District heating part would be discussed in detail afterward.

1.1.4.2 Air conditioning

Citizens always use air conditioners for cooling in summer, and some of the people living in south China use air conditioners to warm the room in winter. The appliances like radiant heaters, electric oil heaters, electric heating boxes and electric blankets always are used to warm in south China as well.

At present, the prevalence rate of air conditioning in the urban residential building is very high. While fission air conditioning is locating in the dominant position in China, household central air conditioning still needs to be expanded. The prevalence of household central air conditioner is no higher than 5%, even in the new high-grade residential building in Beijing (Building Energy Conservation Research Center, Tsinghua University, 2013). The totally residential electric consumption on the air conditioner is 52.0 billion kWh, amount to 16.03 million tce, accounting for 10.4% of total residential energy consumption in 2011 (Building Energy Conservation Research Center, Tsinghua University, 2013).

1.1.4.3 Household electric appliances

The total electric appliances consume 110.6 billion kWh of electric, amount to 34.07 million tce, accounting for 22.2% of total residential energy consumption in 2011 (Building Energy Conservation Research Center, Tsinghua University, 2013).

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1.1.4.4 Household hot water

The main types of water heater are electric water heater and gas water heater, district heating and solar water heater are auxiliary types. The energy consumption of water heater is around 14.53 million tce in 2011, accounting for 9.5% of total energy consumption (Building Energy Conservation Research Center, Tsinghua University, 2013).

1.1.4.5 Cooking

The energy consumption of cooking is 47.7 million tce in 2011, accounting for 31.1% of total energy consumption (Building Energy Conservation Research Center, Tsinghua University, 2013).

1.1.4.6 Lighting

The energy consumption of lighting is 92.2 billion kWh, amount of 28.4 million tce, accounting for 18.5% of total energy consumption (Building Energy Conservation Research Center, Tsinghua University, 2013). Improving the energy efficiency is an effective method to reduce the energy consumption in China because the lighting efficiency still has a large space can be increased.

The National Development and Reform Commission & the Ministry of Commerce & the General Administration of customs & the State Administration for Industry and commerce & the State Administration of quality supervision & General Administration of China issued the Chinese phase out of incandescent lamp circuit diagram jointly on November 11th_{in 2011.}

Table 1-5 The Chinese phase out of incandescent lamp circuit diagram

Phase Term Target product Rated

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Mid-term evaluation and follow-up policy adjustment

5 10-01-2016 Gradual incandescent lamps ≥15W Ban the import and sale

The eventually banned goal products and time,

and whether it is prohibited to produce

depends on mid-term evaluation result

The Chinese phase out of incandescent lamp circuit diagram (The National Development and Reform Commission & the Ministry of Commerce & the General Administration of customs & the State Administration for Industry and commerce & the State Administration of quality supervision & General Administration of China, 2011) plays an important role of controlling the electric consumption on lighting part.

1.1.5 Status of heating energy consumption in northern urban area

Energy consumption in the northern region is relatively large, accounting for more than 40% of the total urban construction energy consumption (Shui & Li, 2012). The large proportion of the energy consumption in this branch is because of the usage of district heating system.

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Figure 1-5 Proportion of Heating Resources

The form and proportion of various heat sources in typical cities can be described by the bar graph below (Building Energy Conservation Research Center, 2015).

Figure 1-6 Proportion of Various Heating Sources in Typical Cities

The most seriously polluted heating form, coal-fired heating still dominate a large proportion of Chinese heating style, hence, this phenomenon can become one of the breaches to solving the problem of energy efficiency in North China.

CHP 42% Coil fired boiling

48%

Gas boiler 8% Others2%

CHP

Coil fired boiling Gas boiler Others 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Others

Industrial Waste Heating Gas Heating

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1.2 Objectives

Due to the atmosphere that is getting worse in China, and the building energy consumption contributes to the total energy consumption a lot. Looking forward to the approach to achieve building energy efficiency has become one of the most important industries in China nowadays. However, applying all of the existing methods in constructions in not only unreliable but also uneconomical. The objective of this project is to find out the optimal method or combined approaches to achieve the goal of building energy efficiency in different regions of China.

Obviously, optimal choices of different regions are related to the climate, economical level, living habit of inhabitants and so on. Thus, a standard building would be set and be modelled in different regions separately.

2 Methodology

In order to make sure the difference of energy efficiency between areas, the history data would be collected to work out the status of energy consumption, then figure out energy efficiency scheme and be compared side by side.

During the whole process, the software Designbuilder would be used to set up building modelling and energy analyzation.

The steps by the whole process should be as below:

Figure 2-1 Scheme of methodology

2.1 The Standard Building

According to the chapter 1, the area of each dwelling is 105.48m2_{, the length on north and south direction}

of each dwelling is 10.4m, and the length on east and west direction is 12.6m.

Step 1 Set up the standard building

Step 2 Building the modeling in Designbuilder

Step 3 Concluding common means of energy efficiency

Step 4 Select sample cities in different areas

Step 5 collecting data of energy consuption in sample cities

Step 6 Simulation the base senario in Designbuilder

Step 7 Simulation the energy efficiency senario in Designbuilder

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Figure 2-2 Layout plan of model dwelling

The standard building, which would be used for modelling is a 6-layer apartment building that has 8 families, which can be separated into 4 units, on each floor. Due to the story height of residential buildings is appropriate 2.8m (Ministry of housing and urban & rural development of the people's Republic of China, 2011), the additional value of cooling and heating load should be calculated when the height of the layer is more than 3.0m (Ministry of Construction of the People's Republic of China, 1993). The height of each layer of standard building is designed as 3.0m. On the basis of Chinese building habits, the apartment would be located on north and south direction.

For the area of windows, the standard GBT50176-1993 Thermal design code for civil building (Ministry of housing and urban & rural development of the people's Republic of China, 2011) has the following tips.

Table 2-1 Area ratio of windows to walls on different directions

Orientation Area ratio of windows to walls

North ≤ 0.25

East & West ≤0.3

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Thereby, the ratio of windows to walls on the standard building can be set to 0.25 on the north, east & west and south separately. The average area ratio of windows to walls of the whole standard building is 0.25.

In previous years, residential buildings were always built by brick walls, and the thick of brick walls were depends on where the building located in. 240mm thick brick walls are always be used in the temperate region, the walls of server cold region are always 490mm, and 370mm walls can be found in other area of China. While, since China has come to an energy efficiency age, the brick walls are going out of sight step by step. In the new buildings, the most common external wall is the 200mm concrete wall, which added by thermal insulation. Therefore, the 200mm concrete wall has been chosen as the external wall of standard building, and the thermal insulation of external wall would be added in the energy efficiency scenario.

2.2 Modelling

According to the basic information, the standard building has been modelling in the software Designbuilder, and the model can be shown as below.

In the figures, each zone represents a dwelling. On each floor, zone 1 and zone 2 has external walls on three directions (zone 1 has external walls on the north, south, and east, while zone 2 has external walls on the north, south, and west), and zone 3 to 8 has external walls on two directions (the north and south). Besides, the block 1 is the ground floor and the block 6 is the top floor.

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Figure 2-4 Building Block

Figure 2-5 Building Block – Top View

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Table 2-2 Basic information of the wall of the standard building

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Figure 2-6 Structure of 200mm concrete wall

Figure 2-7 Condensation analysis of 200mm concrete wall

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Table 2-4 Details of the windows in the standard building

The lighting system is working following the schedule below.

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Since the area of each dwelling is 105.48 m2_{, and the average number of persons per household in China}

is 3.35 (National Health and Family Planning Commission, 2015), the density of occupancy should be set as 0.03176 people/m2_{in the Designbuilder. Considering people always go to work or school at}

daytime, only stay at home to relax at home and only few time is used to clean the room or do some other light work, the activity in the room is set as seated quiet. Due to almost every family is consisting of man and women, some families have children, the metabolic factor is set to 0.9. The winter clothing and summer clothing are set to 1.00 and 0.50 separately.

For the DHW, the range of 25-70 l/person*day has been given in the Standard for water saving design in civil building (Ministry of housing and urban & rural development of the people's Republic of China, 2010). Besides, the research showed that the DHW in China is always 20-30 l/person*day nowadays (Estate Business of Sina, 2016), what’s more, as mentioned before, the average residential area per person in China is approximately 30 m2_{, the DHW water is around 1 l/ m}2 _*day.

The design parameter of indoor climate should be following the tables below which are concluded from Design code of heating ventilation and air conditioning of civil buildings (Ministry of housing and urban & rural development of the people's Republic of China and General Administration of quality supervision, inspection, and Quarantine of the people's Republic of China, 2012).

Table 2-6 Design indoor temperature in Heating case

Region Design indoor temperature (℃)

Severe cold region & Cold region 18~24

Hot-summer and cold-winter region 16~22

Table 2-7 Design parameters of indoor climate in cooling case

Parameters Level of indoor climate comfortable Temperature (℃) Relative humidity (%) Wind velocity (m/s) Winter case I 22~24 30~60 ≤0.2 II 18~21 ≤60 ≤0.2 Summer case I 24~26 40~70 ≤0.25 II 27~28

In order to fit the regular above, the heating set point temperature and the cooling set point temperature is set to 18℃ and 24 ℃ separately. The relative humidity is set to 50%. The minimum fresh air of residential building should be 10 m3_{/h*person (Ministry of housing and urban & rural development of}

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2.3 Energy efficiency technologies

2.3.1 Introduction of energy efficiency technologies

To reduce the energy consumption, many technologies can be used. These technologies always can be sorted into the following facts,

• HVAC, Water Heating, & Appliance • Windows & Building Envelope • Lighting

• Sensors & Controls • Building to Grid

Technical analysis has shown that heat pumps have the technical potential to save up to 50% of the energy used by conventional HVAC technologies in residential buildings. New-generation windows and building envelope technologies have a substantial technical potential to reduce energy consumption in buildings (Office of Energy Efficiency & Renewable Energy, 2016). LED is not only sufficiently but also more efficiency compare to Incandescent, and installing daylight channelling is become a new way to improve the lighting system. Sensors and controls can keep the system working in an efficiency way, working when it is needed and stop working if the indoor climate has reached to a good status.

2.3.2 Major research subjects

The most popular technologies that be vigorously promoted in China is adding external insulation. At the same time, the HVAC system is needs to be improved so far. Considering the target building is the residential buildings, which means not that much of sensors and controls are working in this range, and the power efficiency lightings has already be pushed well in China, improving envelopes and optimizing the HVAC system would be two important factors to be considered and be compared in the project.

2.4 Sample cities

2.4.1 Selection of sample cities

According to the geographical position and the economic situation, five sample cities have been decided as below:

Table 2-9 Sample cities

Regions Sample city

Severe cold Changchun

Cold Beijing

Hot-summer & cold-winter Shanghai

Hot-summer & warm-winter Guangzhou

Temperate Kunming

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Figure 2-8 Sample Cities

2.4.2 Basic information of sample cities

2.4.2.1 Changchun

Changchun is the capital of Jilin province, which located in the central part of Northeast area of China. The longitude and latitude of Changchun are North latitude 43 ° 05 ' ~ 45 ° 15' and longitude 124 ° 18 ' ~ 127 ° 05', which is covered by North temperate on mid-latitudes of North hemisphere (News China, 2006).

Changchun is located in the North temperate continental monsoon climate zone. In the national discriminate of wet and dry climate zone, Changchun is located in the transition zone from the humid area to the sub-arid area (Changchun government, 2016). The annual average temperature of Changchun is 4.8℃, the highest temperature is 39.5℃ and the lowest temperature is -39.8℃, the average temperature of the hottest month (July) is 23.1℃, the average temperature of coldest month (January) is -15.1℃. The average annual rainfall is 522 to 615mm. (China Meteological Administration, 2016).

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Table 2-10 Climate of Changchun

Month Average Lower Temperature (℃) Average Temperature (℃) Average Higher Temperature (℃) Extreme Maximum Temperature (℃) Extreme Minimum Temperature (℃) Precipitation (mm) Jan -19.9 -15.1 -9.8 4.6 -33 3.2 Feb -15.9 -10.7 -5.0 14.5 -28.1 4.5 Mar -7.6 -2.0 3.5 19.5 -27.4 12.3 Apr 1.9 7.8 14.1 28.3 -12.2 21.9 May 9.3 15.2 21.4 35.2 -3.1 49.9 Jun 15.4 20.6 26.1 35.7 4.5 99.7 Jul 19.0 23.1 27.6 34.5 11.1 161.1 Aug 17.3 21.6 26.4 34.3 6.3 121.6 Sep 10.1 15.4 21.3 30.6 -1.4 51.9 Oct 1.9 7.0 12.9 27.8 -13.4 28.9 Nov -7.8 -3.4 1.7 20.7 -24.7 10.3 Dec -16.1 -11.7 -6.6 11.7 -31.0 5.0 2.4.2.2 Beijing

Beijing is the capital of China, located in the east longitude115.7° ~ 117.4°, north latitude 39.4° ~ 41.6°, the centre point of Beijing is located in the east longitude 116°25′29″ and north latitude 39°54′20″, the area of Beijing is 16410.54 square kilometre (Beijing government, 2016).

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The details weather information of Beijing shows in the table below (Baidu Baike, 2016).

Table 2-11 Climate of Beijing

Month Average Lower Temperature (℃) Average Temperature (℃) Average Higher Temperature (℃) Precipitation (mm) Annual Sunshine Hours (h) Average Humidity (%) Jan -7.5 -3.1 2.0 2.7 189.0 43 Feb -4.5 0.2 5.7 4.4 192.1 42 Mar 1.3 6.7 12.3 9.9 228.2 42 Apr 8.8 14.8 20.7 24.7 244.5 44 May 14.8 20.8 26.7 37.3 267.9 50 Jun 19.6 24.9 30.5 71.9 238.2 59 Jul 22.5 26.7 31.4 160.1 202.7 71 Aug 21.5 25.5 30.3 138.2 209.3 73 Sep 15.8 20.7 26.2 48.5 215.3 66 Oct 8.6 13.7 19.4 22.8 211.5 59 Nov 0.3 4.9 10.2 9.5 182.0 53 Dec -5.2 -1.1 3.8 2.0 175.2 47 Annual 8.0 12.9 18.3 532.0 2555.9 54 2.4.2.3 Shanghai

Shanghai is locating in the east longitude 120°52′~ 122°12′, north latitude 30°40′ ~ 31°53′. The city is standing on the west bank of the Pacific Ocean, east of the Asian continent. It is the centre point of China's north and south coast. It is the confluence of the Yangtze River and the Huangpu River to the sea as well. (Shanghai Government, 2016)

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The details weather information of Shanghai shows in the table below (China Meteorological Administration, 2015). The data in the table is collected between the years of 1971 to 2000.

Table 2-12 Climate of Shanghai

Month Average Lower Temperature (℃) Average Higher Temperature (℃) Precipitation (mm) Annual Sunshine Hours (h) Average Humidity (%) Jan 1.1 8.1 50.6 123.0 75 Feb 2.2 9.2 56.8 115.7 74 Mar 5.6 12.8 98.8 126.0 76 Apr 10.9 19.1 89.3 156.1 76 May 16.1 24.1 102.3 173.5 76 Jun 20.8 27.6 169.6 147.6 82 Jul 25.0 31.8 156.3 217.8 82 Aug 24.9 31.3 157.9 220.8 81 Sep 20.6 27.2 137.3 158.9 78 Oct 15.1 22.6 62.5 160.8 75 Nov 9.0 17.0 46.2 146.6 74 Dec 3.0 11.1 37.1 147.7 73 Annual 12.9 20.2 1164.5 1894.5 76.8 2.4.2.4 Guangzhou

Guangzhou is the capital of Guangdong province, which is locating near to the most south area of China mainland.

The geographical position of Guangdong is between east longitude 112°57′~ 114°3′ and north latitude 22°26′ ~ 23°56′. The city centre is located on the point of east longitude 113°15′53″ and north latitude 23°6′32″. (Guangzhou Government, 2016)

Guangzhou is located in the subtropical coastlines, the tropic of cancer crossing the city on the south central part. The climate of Guangzhou belongs to a maritime monsoon climate of subtropical zone. The annual average temperature is 20-22℃. Guangzhou is one of the cities, which has the smallest average temperature difference in china. The hottest month of the year is July, with an average temperature of 28.7 ℃. The average temperature of the coldest month (January) is 9 ~16 ℃. The annual average relative humidity is 77%, and the annual rainfall is about 1720 mm. (Guangzhou Government, 2016)

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Table 2-13 Guangzhou Climate

Month Average Lower Temperature (℃) Average Temperature (℃) Average Higher Temperature (℃) Extreme Maximum Temperature (℃) Extreme Minimum Temperature (℃) Precipitation (mm) Jan 10.2 13.6 18.3 27.2 0.6 40.9 Feb 11.8 14.5 18.6 28.6 1.5 69.4 Mar 15.1 17.9 21.4 32.1 3.2 84.7 Apr 19.4 22.1 25.7 32.4 8.3 201.2 May 22.7 25.5 29.3 36.2 14.6 283.7 Jun 24.8 27.6 31.5 36.6 18.8 276.2 Jul 25.5 28.6 32.8 38.1 21.6 232.5 Aug 25.4 28.4 32.7 38.0 20.9 227.0 Sep 24.0 27.1 31.4 37.2 15.8 166.2 Oct 20.8 24.2 28.7 34.8 9.5 87.3 Nov 15.9 19.6 24.5 32.5 4.9 35.4 Dec 11.5 15.3 20.6 29.4 0.0 31.6 2.4.2.5 Kunming

Kunming is the capital of Yunnan province. The geographical position of Guangdong is between east longitude 102°10′~ 103°40′ and north latitude 24°23′ ~ 26°22′. The centre point of the city is located on the point of east longitude 102°42'31" and north latitude 25°02'11". (General Office of Kunming Municipal People's Government, 2016)

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The details weather information of Kunming shows in the table below (China Meteological Administration, 2016). The data in the table is collected between the years of 1971 to 2000.

Table 2-14 Kunming Climate

Month Average Temperature (℃) Average Higher Temperature (℃) Average Lower Temperature (℃) Extreme Maximum Temperature (℃) Extreme Minimum Temperature (℃) Precipitation (mm) Jan 8.1 15.3 2.2 22.4 -5.4 15.8 Feb 9.9 17.2 3.6 25.5 -2.9 15.8 Mar 13.2 20.7 6.4 27 -5.2 19.6 Apr 16.6 23.8 10 30.4 1 23.5 May 19 24.4 14.3 31.2 5.5 97.4 Jun 19.9 24.1 16.6 30.2 9.9 180.9 Jul 19.8 23.9 16.9 29.3 11.6 202.2 Aug 19.4 24.1 16.2 28.1 9.9 204 Sep 17.8 22.7 14.6 28.5 6.2 119.2 Oct 15.4 20.4 11.8 27.4 2.4 79.1 Nov 11.6 17.4 7.3 24.5 -2.9 42.4 Dec 8.2 15.1 3.1 25.1 -7.8 11.3

2.5 Base scenario

Following the most popular structure of external wall of existing Chinese buildings, the external wall of base scenario has been set as 200mm concrete wall which adding with phenolic foam layer as insulation layer.

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The U-value of the external wall of existing buildings is 0.472, and the details of each layers has showed in the table below.

Table 2-15 Calculated values of existing wall

The windows of base scenario are double glazed windows and the ratio of windows to walls is 25%. In the severe cold (Changchun) and cold (Beijing) regions, radiator-heating systems are in use. Boilers supply the domestic hot water, and the electricity from grid affords the power for the lighting systems. In the hot-summer & cold-winter (Shanghai), hot-summer & warm winter (Guangzhou) and temperate (Kunming) regions, VAV and air-cooled chillers are used in the air condition systems.

2.5.1 Changchun

The software Designbuilder has calculated the energy consumption of the modelled building in Changchun.

In the base scenario, energy consumption of the building is 283 kWh/m2_{. Due to Changchun is much}

colder than other cities in winter. The heating demand is much greater than other cities as well. Because of the cold winter, the heating demand is significantly more than cooling demand. The heating demand is almost 7.6 times of cooling demand.

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Table 2-16 Total energy consumption of Changchun – base scenario

Total Energy [kWh] Energy Per Total Building Area [kWh/m2_]

Total Site Energy 1266240.95 282.59

Net Site Energy 1266240.95 282.59

Total Source Energy 4193746.02 935.94

Net Source Energy 4193746.02 935.94

Table 2-17 Energy consumption by categories of Changchun – base scenario

Electricity [kWh] Cooling [kWh] Heating [kWh] Water [m3_] Heating 0.00 0.00 986778.03 0.00 Cooling 0.00 141505.51 0.00 0.00 Interior Lighting 44094.10 0.00 0.00 0.00 Water Systems 0.00 0.00 93863.30 1469.80

Total End Uses 44094.10 141505.51 1080641.33 1469.80

2.5.2 Beijing

The energy consumption of the building in Beijing base scenario has been showed below, the total site energy of the building is 211 kWh/m2_{, which is much lower than Changchun because of the more}

temperate climate.

Table 2-18 Total energy consumption of Beijing – base scenario

Net Site Energy 945379.54 210.99

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Table 2-19 Energy consumption by categories of Beijing – base scenario

Electricity

[kWh] Cooling [kWh] Heating [kWh] Water [m 3_]

Heating 0.00 0.00 529080.87 0.00

Cooling 0.00 278341.26 0.00 0.00

Interior Lighting 44094.10 0.00 0.00 0.00

Water Systems 0.00 0.00 93863.30 1469.80

Total End Uses 44094.10 278341.26 622944.18 1469.80

2.5.3 Shanghai

The energy consumption of the building in Shanghai base scenario is 122kWh/m2_.

Table 2-20 Total energy consumption of Shanghai – base scenario

Total Energy

[kWh] Energy Per Total Building Area [kWh/m 2_]

Net Site Energy 545013.36 121.63

The cooling and heating demand of Shanghai almost arrive a balance status, the energy consumption of cooling and heating are nearly equal to each other. The details data can be found in the following table.

Table 2-21 Energy consumption by categories of Shanghai – base scenario

Total End Uses 44094.10 262728.44 238190.82 1469.80

2.5.4 Guangzhou

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Table 2-22 Total energy consumption of Guangzhou – base scenario

Net Site Energy 589181.52 131.49

Guangzhou is located in the south part of China, and the climate there is hot in summer and warm in winter. Thus the cooling demand is much more than heating demand in Guangzhou. From the calculation, the result shows that the cooling demand is around 3.9 times of heating demand. The data of energy consumption by categories are showing below.

Table 2-23 Energy consumption by categories of Guangzhou – base scenario

Total End Uses 44094.10 433313.09 111774.33 1469.80

2.5.5 Kunming

Kunming is locating in the temperate region. The city has an alias named “spring city”. That is to say, the weather of the city is always like in the spring. That’s why the energy consumption of the city is so small, even only 46 kWh/m2_.

Table 2-24 Total energy consumption of Kunming – base scenario

Net Site Energy 204073.38 45.54

Total Source

Energy 658516.65 146.97

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Table 2-25 Energy consumption by categories of Kunming – base scenario

Total End Uses 44094.10 23141.33 136837.94 1469.80

2.6 Envelope improved scenario

Considering the U-value of the previous wall is 0.472, there still have a large space to improve the property. A new structure of the wall could be introduced.

XPS extrude polystyrene is a kind of advanced thermal insulation material which can be used on the building external wall. XPS was started to be a trail in China in recent years, and has not been promoted (China wallmaterials network, 2016). That would be a significant promotion to use XPS as insulation instead of traditional materials.

Figure 2-10 XPS extruded polystyrene

R – value is a measure of thermal resistance (Desjarlais, 2013). It is one of the most important parameters to evaluate the thermal insulation performance of a material. The formula of R – value is

𝑅𝑅 =∆𝑇𝑇 𝑄𝑄̇𝐴𝐴

In the formula, ∆𝑇𝑇 is the temperature difference and 𝑄𝑄̇_𝐴𝐴 is the heat transfer per unit area per unit time. A material with high R – value would welcome to become an insulation material, and the comprehensive effect of other elements should be considered as well.

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Table 2-26 Typical physical properties of XPS

Property Test Method

1/2" Nominal Thickness

3/4" 1"

Thermal Resistance, R-Value (ºF-ft²-h/Btu)

ASTM C 518 (@ 75ºF Mean Temperature)

3.0 4.0 5.0

Water Vapor Permeance (perm)

ASTM E 96

(Procedure A) 0.8 0.8 0.8

Water Absorption

(Max % by Volume) ASTM C 272 0.1 0.1 0.1

Fire Characteristics2 Flame Spread Smoke Developed ASTM E 84/UL 723 10 60-200 10 60-200 10 60-200

Max, Recommended Use

Temp. (°F) 165 165 165

An R-Value of 5.0 per inch of thickness makes it an excellent thermal insulator that increases the energy efficiency of buildings (Kingspan Group, 2016). The feature of high R – value means that, to achieve the same effect of thermal insulation, the thickness of insulation could be cut down than before. The lightweight coating of the building will save more space.

While the performance of low water vapor permeance means the technologies of dehumidification should be used well to prevent condensation on the wall.

The improved wall is consisting of 200mm concrete block, 200mm XPS extruded polystyrene layer, 53mm brickwork outer layer and 15mm plaster inner layer. The structure of the improved external wall is shown in the figure below.

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And the thermal performance of the improved external wall has been shown in the table below. The U – value of the improved external wall has optimized to 0.153.

Table 2-27 The performance of improved external wall

Besides, the triple glazed window is suggested to replace the double glazed windows. That will reduce the energy consumption through the windows.

2.6.1 Changchun

After improving the external walls and windows, the energy consumption of Changchun decrease to 236kWh/m2_{. The data of energy consumption of Changchun in the enveloped scenario has shown below}

in the tables.

Table 2-28 Total energy consumption of Changchun – Envelope improved scenario

Net Site Energy 993015.10 235.78

Total Source

Energy 3318361.81 787.90

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Table 2-29 Energy consumption by categories of Changchun – Envelope improved scenario

Electricity [kWh] Cooling [kWh] Heating [kWh] Water [m3_] Heating 0.00 0.00 765115.90 0.00 Cooling 0.00 98227.87 0.00 0.00 Interior Lighting 41445.70 0.00 0.00 0.00 Water Systems 0.00 0.00 88225.63 1381.52

Total End Uses 41445.70 98227.87 853341.53 1381.52

2.6.2 Beijing

The energy consumption of Beijing achieves to 178kWh/m2_{in the envelope improved scenario. The}

details are shown in the tables below.

Table 2-30 Total energy consumption of Beijing – Envelope improved scenario

Net Site Energy 751499.82 178.43

Total Source

Energy 2206959.95 524.01

Table 2-31 Energy consumption by categories of Beijing – Envelope improved scenario

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2.6.3 Shanghai

After improving the external walls and windows, the energy consumption of Shanghai decrease to 87kWh/m2_{. The data of energy consumption of Changchun in the enveloped scenario has shown below}

in the tables.

Table 2-32 Total energy consumption of Shanghai – Envelope improved scenario

Net Site Energy 367894.82 87.35

Total Source

Energy 922972.84 219.15

Table 2-33 Energy consumption by categories of Shanghai – Envelope improved scenario

Total End Uses 41445.70 151644.14 174804.98 1381.52

2.6.4 Guangzhou

The energy consumption of Guangzhou achieves to 95kWh/m2_{in the envelope improved scenario. The}

details are shown in the tables below.

Table 2-34 Total energy consumption of Guangzhou – Envelope improved scenario

Net Site Energy 398164.52 94.54

Total Source

Energy 751022.11 178.32

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Table 2-35 Energy consumption by categories of Guangzhou – Envelope improved scenario

Total End Uses 41445.70 261637.07 95081.75 1381.52

2.6.5 Kunming

The energy consumption of Kunming drop to 35kWh/m2_{in the envelope improved scenario. The details}

are shown below in the tables.

Table 2-36 Total energy consumption of Kunming – Envelope improved scenario

Net Site Energy 147731.46 35.08

Total Source

Energy 501333.62 119.04

Table 2-37 Energy consumption by categories of Kunming – Envelope improved scenario

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2.6.6 Payback time

In order to promote the development of the energy efficiency in China, the Chinese government has adopted a series of compensating measurement to encourage the improvement of the residential building envelope. In the building envelop improvement program, the government would afford 70% of the total expenditure and the residents themselves only need to afford 30% (The ministry of finance of the People's Republic of China, 2007).

In the case, there are 48 dwellings in the building and the area of each dwelling is 105.48m2_{. Besides,}

the area of the wall can be calculated according to the length of each side of the building and the ratio of windows to walls of the building, which is 2800m2_{. Each dwelling would afford 58.33m}2

(2800m2_{/48dwellings) in the program.}

The price of the labour and material XPS in China is shown in the table below. North and South area in the table means north Yangzi River area and south Yangzi River area, which refer to Changchun and Beijing in the north area and Shanghai, Guangzhou and Kunming in the south area separately.

Table 2-38 The cost of installing XPS insulation

Itemize Price (Yuan/m2_{) - North Area} _{Price (Yuan/m}2_{) - South Area}

Labour 25 ~ 60 25 ~ 60

XPS 75 ~ 150 50 ~ 100

Total 100 ~ 210 75 ~ 160

According to the table, 150 Yuan/m2_{and 120 Yuan/m}2_{in north and south area are reasonable. Thus, the}

initial cost of improving the insulation of the external wall of the north area would be 150 Yuan m_⁄ 2_{× 58.33m}2_{/dwelling × 30% = 2625Yuan/dwelling} And the initial cost of the south area would be

120 Yuan m_⁄ 2_{× 58.33m}2_{/dwelling × 30% = 2100Yuan/dwelling}

Due to the heat metering and charging method has not been implemented in China, in the north area, the expense saving only comes from reduced cooling load and the expense saving of the south area comes from the cooling and heating load together. The expense saving is embodied in the reduction of the electricity bills of residential.

The electricity consumption per capita is 526kWh/year (National Bureau of Statistics of the People's Republic of China, 2014), 3.35 residents per dwelling has been settled. Thus, the electricity consumption per dwelling is around 1762 kWh/year (146.8 kWh/month).

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Table 2-39 The price of residential electricity in Changchun

Class Annual electricity consumption (kWh/year) Price (Yuan/ kWh)

1st _≤2040 _0.525

2nd _{2040 ~ 3120} _0.575

3rd _≥3120 _0.825

Table 2-40 The price of residential electricity in Beijing

Class Annual electricity consumption

(kWh/month) Price (Yuan/ kWh)

1st _≤240 _0.488

2nd _{240 ~ 400} _0.538

3rd _≥400 _0.788

Table 2-41 The price of residential electricity in Shanghai

Class Annual electricity consumption (kWh/year) Price (Yuan/ kWh)

1st _≤3120 _0.617

2nd _{3120 ~ 4800} _0.667

3rd _≥4800 _0.917

Table 2-42 The price of residential electricity in Guangzhou

1st _≤260 _0.61

2nd _{260 ~ 400} _0.66

3rd _≥400 _0.91

Table 2-43 The price of residential electricity in Kunming

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2nd _{170 ~ 260} _0.50

3rd _≥260 _0.80

Thus, the payback time of each dwelling in different areas is shown below.

Table 2-44 The payback time of each dwelling

City Initial cost (Yuan) Payback time (year)

Changchun 2625 2.93

Beijing 2625 2.96

Shanghai 2100 0.92

Guangzhou 2100 0.91

Kunming 2100 4.02

The payback time of Changchun and Beijing both are around 3 years, Shanghai and Guangzhou need around only 1 year to achieve cost recovery, the longest payback time of these cities is Kunming, which is 4 years. Objectively, the payback time of envelope improvement project is not a long period, which means the measure is a reasonable method.

2.7 HVAC system improved scenario

2.7.1 Changchun

The heating system would be improved in Changchun to decrease the energy consumption. In the subject, considering the modeling building is a new building which would locate in different areas of China, the radiator heating system in the precious design would be instead by heated floor in new buildings. The heating cable spread all over the room floor, which can give a more evenly heating than radiator, thereby the room would have a better indoor climate. Besides, the usage of heated floor would reduce the temperature requirement of heat resource. Lower temperature resource could save a large amount of energy instead of higher temperature resource when radiators had been used.

The energy consumption of Changchun after HVAC systems been improved is showing in the tables below.

Table 2-45 Total energy consumption of Changchun – HVAC improved scenario

Net Site Energy 1198706.12 267.52

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Table 2-46 Energy consumption by categories of Changchun – HVAC improved scenario

Total End Uses 44094.10 98725.67 1055886.34 1469.80

2.7.2 Beijing

The heating system in the previous design, same as in Changchun, is heat radiator, and heated floor would be the substitution in order to reduce the energy consumption as well.

The improved energy consumption of Beijing has been shown in the tables below.

Table 2-47 Total energy consumption of Beijing – HVAC improved scenario

Net Site Energy 847530.77 189.15

Total Source

Energy 2547265.46 568.49

Table 2-48 Energy consumption by categories of Beijing – HVAC improved scenario

Optimal method to achieve energy efficiency in residential buildings in different climate regions of China