Achieving energy efficiency and thermal comfort through passive strategies and renewable technology. Wuhai demonstration center project as an application case

Abstract

Buildings are designed to meet and improve the quality of life of the occupants. During the last decades, standards on building construction have risen sharply to integrate new, ambitious demands regarding energy efficiency and thermal comfort in the design procedure. The importance of understanding the performance of a proposed building project is undeniable nowadays. This paper presents a building performance assessment of the proposed demonstration center in Wuhai. The analysis of this paper focus on thermal comfort and energy performance through the application of passive solutions and renewable technology. The purpose of this study is to predict energy efficiency and thermal comfort through an effective simulation assessment of a proposed project at the design stage. Using parametric study, it is concluded that in this well-designed project, when appropriate building parameters are used, very little amount of energy is required for heating and cooling to maintain a comfortable indoor temperature. Also, the total amount of energy generated through solar PV remains higher than the total energy consumption, which makes the building energy self-sufficient. Additionally, the same parameters result in a high level of thermal comfort, which improve the occupants’ comfort and well-being. The findings indicate that incorporating appropriate passive strategies and renewable technology during the design stage has a beneficial effect on the entire building performance. Some good practices have also been highlighted and documented in this study.

1 Introduction

Concerns about buildings’ environmental effect and the quality of their indoor environment have sparked debate over the role the design team should play in environmental design [1]. Passive design, often known as “bio-climatic design,” seeks to improve residents’ comfort and health by incorporating local climatic and site elements into architectural design and building technologies [2]. As defined by Olgyay in their early studies, the purpose of passive design is to heat, cool, and light buildings using new adaptive ideas and materials while reducing or even eliminating the use of any energy system [3]. Local builders have successfully adopted numerous passive design strategies, such as a north–south plan orientation to balance solar gains, window openings designed to promote natural ventilation from local winds, external overhangs to protect from direct sunlight in the summer, and courtyards to offer a filtering area with the surrounding environment [4, 5].

It is becoming increasingly recognized that, in the end, the performance of a building is largely determined by its “strategic” design as considered during the project’s early stages. For example, plan depth, orientation, fenestration (glazing) and natural ventilation, affect the amount of heating and cooling required. These early design decisions invariably have knock-on effects on plants and equipment, which have a significant impact on the entire building performance [6]. In recent years, much effort has been put into the development of efficient and cost-effective technologies, to ensure the sustainability of the built environment [7, 8]. However, in addition, to reduce energy demand while having sustainability concerns, buildings must also provide comfort for their occupants [9]. This may create a conflict between strategies that focus on the reduction of energy consumption and those to maintain a healthy and comfortable indoor environment. To achieve a balance between efficiency and comfort, synergies between building design, have to be established [10]. The present study set out for a parametric building performance simulation on the impact of passive strategies and renewable technology under the Wuhai climatic condition to predict energy efficiency and thermal comfort of a proposed project at the design stage.

2 Methods

The method of this paper is divided into two sections. The first section describes the project, including climate conditions, passive design implementation, and renewable energy application. The second section presents the simulation process with parametric concept analysis. The last section deals with energy performance and thermal comfort analysis.

2.1 Project description

2.1.1 The climatic condition of Wuhai

According to the Köppen climate classification, the climate on the Wuhai is a cold arid desert climate. This climate is characterized by freezing, dry winter, and hot summers [11]. The cold desert climate is also found in several regions outside western china such as Morocco, South Africa, and Turkestan. To be more specific, according to the Köppen climate classification, Wuhai climate is a cold arid desert climate (BWk) [12]. The map in Fig. 1 shows the regions that feature such a climate.

Fig. 1

Regions with a cold arid desert climate (BWk) according to the world map Köppen climate classification [12]

Table 1 presents the information on the Wuhai weather and denotes the period for the acquisition of original weather data. All-weather data used in the present study were taken from a meteorological database called weather base (www.weatherbase.com). Table 2 shows the monthly mean values of average high temperature, average relative humidity, the average length of the day, and wind speed.

Table 1 Information on the Wuhai weather as well as on the period the data acquisition (data source: weatherbase.com)

Table 2 Monthly and annual mean values of weather data for Wuhai, China (data source: weatherbase.com)

2.1.2 Project setting

The project is located in Wulannur Town, Wuda District, under the administration of Wuhai City, 18 km away from the downtown of Wuhai City, 13 km away from Wuda District, and 43 km away from Hainan District (Fig. 2), under the climate condition shown in Table 2. With renewable energy as the core, the Wuhai demonstration center design has combined the top teams in various fields such as planning, design, construction, planting, operation, management, and more, from both domestic and foreign expertise to form a cross-border consortium to come up with an appropriate design which could be replicable anywhere depending on the climate conditions.

Fig. 2

Site location of Wuhai city, a Google map showing the entire territory with Wuhai as the center. b Aerial view of the project site and accesses from the main road. c A close aerial view of the site for the agricultural demonstration park

The Demonstration center accommodates various functional spaces which come together to create a harmonious environment. The design was done in such a way that it could address healthy environmental issues by improving the quality of life of the occupants when completed. The Demonstration Center is designed on three floors and includes the following areas; colonnade space, exhibition area, exchange area, experience dining room, conference rooms, office area, accommodation area, and indoor garden. Table 3 below presents the project program and Fig. 3 shows subsequent floor plans.

Table 3 Demonstration center program

Fig. 3

Demonstration center floor plans

2.1.3 Passive design strategies

The cornerstone of passive design is based on natural energy sources, which combines building architecture and the surrounding environment to reduce heating and cooling loads of structures while minimizing operating and maintenance costs [13, 14]. One of the key aspects of the passive design approach to reducing energy use and increasing occupant thermal comfort is the correlation of local climate with building shape and thermal performance [15]. The passive strategies used at the Wuhai demonstration center rely on the local climate to maintain the thermal range of buildings within spaces, avoiding the need for mechanical heating, ventilation, and cooling. The key strategy was to design with the local climate in mind. For best production, the design team needed to blend passive techniques with the surrounding local climate.

Figure 4 presents the sun shading chart for winter and summer that was examined by the design team in order to fully utilize passive solar design features and maximize the energy efficiency, comfort.

Fig. 4

a Sun shading chart during winter b sun-shading chart during summer

The following sections present the various passive strategies and renewable energy technology adopted during the design stage of the Wuhai demonstration center.

2.1.3.1 Building orientation and shape

When designing, the orientation of the site as well as the building shape was taken into consideration, this influences the building design as it helps to maximize the effectiveness of other passive strategies. The design of the Wuhai demonstration center uses simple rectangular shape with longitudinal orientation, along the sun path to guarantee an efficient passive design as shown in Fig. 5. The rectangular shape allows (1) the roof to be the main heat gain element of the structure, (2) the south facade to collect sun all year round, (3) the north façade to enhance natural ventilation with multiple opening, and (4) The west and east façades to be the second most exposed element in the building with small openings.

Fig. 5

Shape development in response to sun path and wind direction

2.1.3.2 Shading potential

To maximize energy savings, shading devices should be included into the facade of a structure from the early design stage. This can be accomplished through the use of “conventional” design tools such as solar path diagrams and shading masks, or through the use of specialized computer algorithms that “generate” the optimal shading device shape based on a set of input parameters [16]. This information allows the design team to make meaningful hypotheses about the optimum geometry of the shading device. According to the solar shading chart in Fig. 6, horizontal shading devices installed at the Wuhai agricultural demonstration park during the winter should be set at 75° This is to maximize winter sun collecting in the south while shielding users from visual intrusion. The shading devices are set to 60° during the summer to provide a maximum of four hours of shade. Additional vertical strips are utilized to enhance indoor thermal comfort and provide enough shading.

Fig. 6

a Sun shading chart used to design vertical and horizontal shading devices during winter b sun-shading chart used to design vertical and horizontal shading devices during summer

2.1.3.3 Natural ventilation and daylight

Passive ventilation strategies in this project use naturally occurring airflow patterns around and in the building to introduce outdoor air into the space. The Demonstration center takes advantage of this feature through it north–south orientation and the operable windows, especially during the summertime. Additionally, to enhance the quality of light and assure appropriate distribution within spaces, a high window to wall area ratio at the south façade paired with high ceilings is provided. Extra features such as interior surface colors and finishes are also considered. Figure 7 shows the light admission during summer and winter.

Fig. 7

Light admission during summer and winter

2.1.3.4 Building envelope

The analysis from the Psychometric chart helps to easily engage in the process of passive heating and cooling, elements of the building envelop were set as follow: high-performance and operable windows with low wall area ratio on the north façade for winter sun exposure, High-performance window with high wall area ratio on the south façade for solar heat gain (Fig. 8). Appropriate shading devices were provided to shade the building on the south during summer. The wall and the floor slab are high thermal mass surfaces that store winter passive heat and summer night cool. The floor plans are designed to allow winter sun penetration into offices and outdoor spaces are protected with a large overhang with integrated roof shading.

Fig. 8

Psychometric chart to evaluate thermal comfort through appropriate design strategies

2.1.4 Renewable energies technologies

Because the project is located in a remote area, away from the main city grid. One of the simplest ways to be connected with constant energy is through renewable energy technologies which produce sustainable and clean energy from sources. Renewable energy has the potential to strengthen energy security, improve environmental quality and contribute to the widespread diffusion of energy availability [17]. For this project, the focus is on solar PV with a system that will ensure the transformation of solar radiation into electricity. To implement this system, the design team proceeded with an analysis of the solar path in view to provide solar panels where needed and make appropriate use of the sun as natural and renewable energy. Figure 9 shows the sun’s path as it affects the length of daytime experienced and the amount of daylight received along a certain latitude during the summer and the winter solstice.

Fig. 9

a Sun shade direction on the winter solstice, and b the winter solstice

2.1.4.1 Solar panel system

Architectural integration represents an interesting opportunity for photovoltaic since the installation of modules on the building envelope provides a variety of advantages, such as the use of the land surface already occupied by the building, the saving on support structures, the replacement of materials and components such as traditional roof elements and the possibility of the energy produced on-site. However, to obtain the best performance, careful planning is necessary. The placement and orientation of solar panels are just as important as which type of solar panel is used in a given situation. A solar panel will harness the most power when the Sun's rays hit its surface perpendicularly [18, 19]. Ensuring that solar panels face the correct direction and have an appropriate tilt will help ensure that they produce maximum energy as they are exposed to the highest intensity of sunlight for the greatest period [20]. Figure 10 shows solar PV location on the demonstration center.

Fig. 10

Top aerial view from the south-west showing a full display of the demonstration park covered with solar panels (in blue)

In the northern hemisphere, solar panels should face the south. Usually, this is the best direction because solar panels will receive direct light throughout the day [20]. The angle or tilt of a solar panel is also an important consideration. The angle that a solar panel should be set at to produce the most energy in a given year is determined by the geographical latitude. A general rule for optimal annual energy production is to set the solar panel tilt angle equal to the geographical latitude [21]. The Wuhai is located at the latitude 39.65°. Therefore the solar panels were all fixed at 39°. Figure 11 presents displacements of solar PV on different sections of the building.

Fig. 11

Sectional views of solar PV on demonstration park and smart greenhouse

2.2 Building performance simulation

2.2.1 Simulation method

A 3D conceptual model was first created in SketchUp, then the model was imported to Revit where walls, roofs, floors, door and windows assembly were properly adjusted. Next, the developed Revit model was exported in gbXML format for energy simulation in DesignBuilder software. The plan of the building was divided into various separate HVAC zones including Reception, Exhibition area, Multi-purpose area, Cooking and eating area, Conference room, offices, meeting room and accommodation area. The cooling temperature was set at 24 ℃, while the heating was set at 22 ℃. Simulations for the energy model were conducted in Wuhai, New Mongolia, china and the weather data provided by EnergyPlus for the location were used. Physical properties and parameters were defined as described in Table 4. Other model information settings for each space including material, occupancy schedule, Window and door materials, lighting power were adopted. Activity parameter was set according to ASHRAE 55. Once everything was set in place, we ran the simulation process for the demonstration center.

Table 4 Parameters of walls, roof as well as window (glazing) assemblies

2.2.2 Reference case-building model

A base case building model of the demonstration center was set up in DesignBuilder based on the assumption of a fully detached, cuboid-shaped, building, where all façades were fully exposed to solar radiation and each floor had a gross floor area of 1725 m². Assuming different geometry, construction and use for each floor, the full building has to be modeled. The whole building was modeled as a single zone having, therefore, only one operative room temperature. Table 4 shows the parameters of walls, roof as well as window (glazing) assemblies. Figure 12 displays the DesignBubilder model. Architecturally, the thermal transmittances of the external walls and the glazing were specified as 2.223 W/m² k and 7.121 W/m² k, respectively. The total solar energy transmittance (g) of all windows was defined as 0.81.

Fig. 12

Reference case (Designbuilder) model of the demonstration center

In the present study, the adaptive model of the ASHRAE 55 [22] was employed for assessing the thermal comfort of the demonstration center, which refers to buildings without mechanical means systems and with operable windows. In this empirically derived adaptive thermal comfort concept, the range of acceptable operative room temperatures is defined as a function of the running mean of the interior temperature. Based on ASHRAE standard 55 using PMV, the highest acceptable comfort temperature is 24.3 ℃ during winter and 26.7 ℃ during summer, while the lowest acceptable comfort is 20.3 ℃ for both periods [22]. Only office hours were used in this analysis. The operative room temperature is calculated in DesignBuilder as the mean value of the air temperature and the mean radiant temperature in the room. The latter is defined as the area-weighted mean surface temperature of the enclosures (walls, roof, and windows). The influence of other room parameters such as the relative humidity on the adaptive thermal comfort was not included in the model.

2.2.3 Parametric study

To better understand the impact of input variables on energy consumption and thermal comfort and test the robustness of results, a parametric study was performed. The present study also shows how sensitive the results are to a change of certain input variables. Starting from the reference case described in Sect. 5.8, a series of case scenarios methods were used to show the effect of the variation of the wall assembly, roof assembly, and window assembly on the level of energy-saving and thermal comfort that can be achieved. Input parameters were varied according to scenarios presented from table 5 to table 8. In scenario case 2, the external wall thickness was set to 0.2770 m, with a resistance limit of 1.302 m² k/W and a transmittance value of 0.768 W/m² k (Table 5). In scenario case 3, the concrete roof was set at a resistance limit of 1.949 m² k/W and a transmittance value of 0.513 W/m² k (Table 6). In scenario case 4, the window assembly was set to triple glazing (Tpl LoE (33) Bronze 6 mm/13 mm Air), with a total solar transmission (g) of 0.142 and a transmittance value of 1.999 W/m² k (Table 7). The last scenario case 5 is the one that combines scenarios cases 2, 3, and 4, where the wall, the roof and window assembly were all replaced (Table 8).

Table 5 Scenario case—2, wall assembly was replaced

Table 6 Scenario case—3, roof assembly was replaced

Table 7 Scenario case—4, windows (glazing) assembly was replaced

Table 8 Scenario case—5, wall, roof and windows assembly were replaced

2.3 Energy performance and thermal comfort analysis

2.3.1 Energy performance

The energy performance of a building depends on the quality of the properties of the building itself, it is a critical factor that determines how much energy the building consumes. Building performance relies on passive and active strategies applied during the design process. Table 8 (Case 5) outlined the optimized case scenario with an optimized building envelope of the Demonstration center building.

2.3.1.1 Energy production from solar panel

In terms of energy, the Wuhai agricultural demonstration park is designed to provide maximum energy to sustain its annual consumption. To help achieve this result, the buildings were all designed to facilitate the positioning of PV panels on their roofs which have a triangulated form and mostly face the south. Additional PV pods were provided on site to maximize energy collection. Table 9 presents the zoning with their respective spaces as well as the total PV collection surface and their yearly energy generation.

Table 9 Total energy generation from the entire agricultural demonstration park

2.3.1.2 Energy consumption

The focus of this analysis remains the demonstration center which is the main building of this project. It is a mixed-use building where various activities take place including, working, living, eating and recreational. Figure 13, Fig. 14, Fig. 15, Fig. 16 and Fig. 17 show the monthly energy consumption in electricity for lighting, heating and cooling of case 1, case 2, case 3, case 4, and case 5.

Fig. 13

Monthly energy consumption from case 1—base case

Fig. 14

Monthly energy consumption from case 2—efficient wall

Fig. 15

Monthly energy consumption from case 3—efficient roof

Fig. 16

Monthly energy consumption from case 4—efficient glazing

Fig. 17

Monthly energy consumption from case 5—efficient wall, roof, and glazing

Table 10 presents the annual comparative results for the total energy consumption per case scenario. Figure 18 shows the annual energy consumption for each case.

Table 10 Comparative results for energy consumption per case scenario

Fig. 18

Annually energy consumption (kWh) from cases scenario

2.3.1.3 Heating energy demand

Wuhai is located in a cold arid desert climate region. Therefore to maintain an appropriate temperature within the built environment, a heating system is required to complement heating energy demand. Table 11 shows the total heating energy demand per case scenario for the demonstration center throughout the year, while Fig. 19 presents the monthly variation according to each case.

Table 11 Total heating demand per case scenario for the demonstration center

Fig. 19

Monthly energy consumption from cases scenario

2.3.2 Thermal comfort

Thermal comfort is most likely the most significant and readily defined IEQ factor. The human body strives to keep its temperature around 37 ℃. The temperature is maintained via heat exchange between the human body and the surrounding environment via convection, radiation, and evaporation [22].

2.3.2.1 Heat balance

The heat balance consists of heat gains on one side and heat losses on the other. The heat losses consist of transmission, ventilation and infiltration, while the heat gains consist of solar loads, internal heat loads and heating systems. In this paper, only heat transmission causing heat to flow through the building envelope (wall, roof and windows) and solar load through the windows are addressed. To better understand the heat balance of the demonstration center, a simulation was carried out on the entire building with the main focus being on wall, roof and windows assemblies. The simulation was conducted throughout the year as presented in the figures below. Figure 20 shows the amount of heat loss through the wall when using parameters from case 1, case 2 and case 5, Fig. 21 shows the amount of heat loss through the roof when using parameters from case 1, case 2 and case 5 and Fig. 22 shows the amount of heat gain through windows when using parameters form case 1, case 2 and case 5.

Fig. 20

Heat loss through the wall when using parameters form case 1, case 2 and case 5

Fig. 21

Heat loss through the roof when using parameters from case 1, case 2 and case 5

Fig. 22

Heat gain through glazing when using parameters from case 1, case 2 and case 5

2.3.2.2 Indoor temperature

The indoor temperature denotes comfortable habitation for humans. Therefore, it remains a key factor in determining appropriate thermal comfort within a given space. To ensure that indoor temperature fluctuation is not affected by external conditions, parameters were set to the building envelope including wall, roof and windows, respectively represented as case 2, case 3 and case 4 while case 1 represents the base case model with standard parameters and case 5 represents a combination of case 1, 2 and 3. Table 12 presents the monthly indoor temperature for each case in comparison to the minimum and maximum comfortable temperature.

Table 12 Monthly indoor temperature per case scenario

To easily analyze the different outputs, and determine which case scenario provide better conditions in terms of indoor temperature, case 2, case 3 and case 4 were compared to case 1 and case 5. Figure 23, Fig. 24 and Fig. 25 show the monthly indoor temperature level when using case 1, case 2, case 3, case 4 and case 5 as compared to minimum and maximum comfortable temperature.

Fig. 23

Monthly indoor temperature level when using case 1, case 2 and case 5

Fig. 24

Heat gain through glazing when using parameters from case 1, case 3 and case 5

Fig. 25

Heat gain through glazing when using parameters from case 1, case 4 and case 5

3 Results and discussions

Building performance simulation (BPS) in the project was used to accurately evaluate the hypothetical building’s performance on energy efficiency and thermal comfort, being the direct result of the implementation of passive design strategies and renewable technology use. The indoor simulation took into consideration the energy analysis and Indoor environment quality analysis under various scenarios cases from which parameters on wall, roof and glazing were adjusted. The results of these analyses will be discussed in the sections below.

3.1 Energy performance

3.1.1 Energy production

Energy analysis shows that the total energy generated by the entire site is about 983,904 kWh with a total PV area of 4122 m². It can be seen that the demonstration center has a total PV area of 963 m² with an annual energy generation of 214,414 kWh. Table 13 presents Total energy generation from of the entire site.

Table 13 Total energy generation from the entire agricultural demonstration park with emphasis on the demonstration part

3.1.2 Energy consumption

With the input parameter set for the base scenario (case 1) throughout the year, the energy consumption is relatively high as compared to the remaining case scenarios. When parameters were set to case 2—efficient wall in Table 5, we observed a total energy consumption of 2% lower than that of the base case. When parameters were set to case 3—efficient roof in Table 6, we have an 8% reduction in the total energy consumption as compared to the base case. Furthermore, with the parameters in Table 7, case 4—efficient windows, the total reduction is only 3%. Finally, when the parameters were set to case 5—with the efficient wall, roof and window Table 8, a higher energy consumption reduction of 13% was observed. Table 14 below shows the total energy consumption and the percentage reduction as compared to the base case (case 1).

Table 14 Total energy consumption per case scenario and the percentage reduction as compared to the base case

3.1.3 Heating energy demand

Besides the total energy consumption per case scenario, the total heating demand was also estimated separately. The results show that during the winter, there is an important demand in heating. The base case heating energy demand is higher compared to other case scenarios as observed in Table 15. The maximum reduction of heating demand is achieved at 86% only when parameters are set to case 5 (Table 8) with the efficient wall, roof and windows.

Table 15 Total heating energy demand per case scenario and the percentage reduction as compared to the base case

The total energy produced by the PV system on the demonstration center is approximately around 214,414 kWh per year, meanwhile, the annual energy consumption achieved with the case 1—base case, case 2, case 3, case 4 and case 5 are respectively 168,662 kWh, 165,508 kWh, 155,481 kWh, 164,235 kWh and 146,766 kWh. It can be concluded that despite the significant reduction observed when parameters are set to case 5, which represents a total reduction of 13% as compared to case 1—base case, the demonstration center remains energy self-sufficient.

3.2 Thermal comfort

For this study, the results from thermal comfort will be limited to the heat balance and indoor temperature when the building is under different case scenarios.

3.2.1 Heat loss through the wall

The results from Fig. 20 were presented in Table 16 for better appreciation and a clear comparison of the case scenarios.

Table 16 Monthly heat loss through the wall for case 1, case 2 and case 5

The results show that when parameters are set to case 2—efficient wall, the reduction in heat loss is up to 56% as compared with case 1, however, when parameters are set to case 5—efficient Wall, roof and windows, the reduction in heat loss is up to 38%. We can observe that in this particular scenario, the case 2—the efficient wall has a better reduction in heat loss.

3.2.2 Heat loss through the roof

The results from Fig. 21 were presented in Table 17 for better appreciation and a clear comparison of the case scenarios.

Table 17 Monthly heat loss through the roof for case 1, case 3 and case 5

The results show that when parameters are set to case 3—efficient roof, the reduction in heat loss is up to 56% as compared with case 1, however, when parameters are set to case 5—efficient Wall, roof and windows, the reduction in heat loss is up to 77%. We can observe in this particular scenario, that case 3—the efficient roof has a better reduction in heat loss.

3.2.3 Heat gain through windows

The results from Fig. 22 were presented in Table 18 for better appreciation and a clear comparison of the case scenarios.

Table 18 Monthly heat gain through glazing for case 1, case 4 and case 5

The results show that when parameters are set to case 4—efficient window, the reduction in heat gain is up to 44% as compared with case 1, however, when parameters are set to case 5—efficient Wall, roof and windows, the reduction in heat gain is also to 44%. We can observe in this particular scenario, that case 4—efficient and case 5—efficient wall, roof and window have the same heat gain reduction.

The results from heat balance show that significant reduction in heat loss through the wall is achieved when parameters are set case 2—efficient while significant reduction in heat loss through the roof is achieved when parameters are set case 3—efficient roof. Furthermore, a similar reduction in heat gain is achieved when parameters are set in case 4—efficient glazing and case 5—efficient wall, roof, and glazing.

3.2.4 Indoor temperature

The results for Monthly indoor temperature for each case in comparison to the minimum and maximum comfortable temperature are presented in Table 19.

Table 19 Monthly indoor temperature of case scenarios and minimum and maximum comfortable zone

The results show that when parameters are set to case 2—efficient wall, the monthly indoor temperature level within the comfort zone account for 5 months in the years, respectively May 22.8 ℃, June 25.17 ℃, July 26.55 ℃, August 25.75 ℃, and September 22.60 ℃. During the 7 remaining months, from October to April, the indoor temperature is below the comfort zone.

When parameters are set to case 3—efficient roof, the monthly indoor temperature level within the comfort zone account for 7 months in the years, respectively April 20.77 ℃, May 23.09 ℃, June 25.43 ℃, July 26.49 ℃, August 25.88 ℃, September 23.45 ℃ and October 20.5 ℃. During the 5 remaining months, from November to March, the indoor temperature is below the comfort zone.

The results show that when parameters are set to case 4—efficient glazing, the monthly indoor temperature level within the comfort zone account for 5 months in the years, respectively May 22.36 °C, June 24.89 ℃, July 26.26 ℃, August 25.57 ℃, and September 22.49 ℃. During the 7 remaining months, from October to April, the indoor temperature is below the comfort zone.

When parameters are set to case 3—efficient roof, the monthly indoor temperature level within the comfort zone account for 7 months in the years, respectively April 21.95 ℃, May 23.50 ℃, June 25.31 ℃, July 26.17 ℃, August 25.78 ℃, September 23.97 ℃ and October 21.69 ℃. During the 5 remaining months, from November to March, the indoor temperature is below the comfort zone.

However, when we compare case 2, case 3, case 4 and case 5 to the base case 1, the results show that case 5 provides more time within the comfort zone, which means there will be no energy demand for cooling or heating. Furthermore, from November to March, where indoor temperature level falls outside the comfort zone, there will be less energy demand to maintain the balance since, during those months, the temperature is not less than 15 ℃ as compared to case 3 which also provide the same time within the comfort zone. It can be concluded that with the use of passive design strategies and when parameters are set to case—5, thermal comfort can be achieved for 7 months in the year.

4 Limitations

It is strongly recognized that thermal comfort is a key parameter of IEQ, but because of its wide coverage, the author intends to report its comprehensive assessment in future studies. Therefore, the author acknowledges a major limitation in this study that could be addressed in future research. The limitation is that this study did not account for the Predicted Mean Vote (PMV) index and the Predicted Percentage Dissatisfied (PPD) index. While the PMV index predicts the mean comfort response of a larger group of people according to the ASHRAE thermal sensation scale, the PPD index is a quantitative measure of the thermal comfort of a group of people in any thermal environment. These two parameters would be considered and estimated in our subsequent studies.

5 Conclusion

The thermal comfort and the energy efficiency of a building and its components are inherently connected. In this project, the design team was confronted with the interplay between aesthetical, functional and economical aspects, which interact with both the energy and the thermal quality performance. In this study, the results of the assessment of the energy performance and thermal comfort of the demonstration center located in Wuhai, were presented. The assessment of energy performance and thermal comfort was achieved by implementing passive strategies and renewable technology into the design to meet the appropriate requirement to achieve indoor comfort and energy conservation. The energy performance factors measured were energy production, energy consumption and energy heating demand and the thermal comfort factors measured were heat balance and indoor air temperature. A comprehensive parametric analysis based on simulations was conducted with the goal of demonstrating how passive design solutions can increase indoor comfort while lowering energy consumption at a demonstration facility in Wuhai, located in a cold dry winters and hot summers region. The following are the findings of this study:

• By implementing proper passive design measures, it is possible to extend the non-heating and cooling seasons.

• The best passive design solutions share several characteristics, including a north to south orientation, a well-insulated building envelope, and a north to south orientation. In the best case scenario, these features result in a 13% reduction in energy consumption and an 86% reduction in heating demand when compared to the base case, and it maintains a comfortable indoor temperature for up to seven months a year with minimal maintenance

• Significant reduction in heat loss through the wall (56%) and heat loss through the roof (77%) are achieved when appropriate parameters are set. Furthermore, a similar reduction in heat gain (44%) is also achieved with the same parameters.

• Mechanical systems are still required to maintain a comfortable indoor atmosphere throughout the hottest and coldest periods of the year.

The evidence from this current assessment revealed that the quality of the indoor environment of the demonstration center is relatively good, pointing to the need for good implementation during the construction and appropriate maintenance culture during the operation phase. This is the first study of its kind on the passive design of a demonstration center in Wuhai, China’s cold winter region.