Reference [8] introduced the difference of energy-saving techniques between China and Europe, and carried out the feasibility on the implementation of passive design in the severe cold region, cold region and hot summer/cold winter region of China. The results indicated that improving the design and construction level of energy-saving buildings in China could be realized through demonstration projects practiced in the above regions due to the huge energy efficiency potential. In this study [9] , the climatic parameters should be considered for the designing of energy-saving residential buildings in the hot summer/cold winter region. Several factors such as shape coefficient control and window-wall ratio were concluded as the crucial strategies for energy efficiency. Reference [10] demonstrated the concept, heat gaining and design proposal about the solar energy residences, summarized the methods of solar energy utilization on planning and design.

An experimental transformation of two apartment units in Beijing was demonstrated in the reference [11] how a passive ecological design can become a systematic tactics to transform a conventional residence to a green building by using local natural resources through sunlight room, solar thermal collectors, rainwater collection and interior ecological wall. Reference [12] presented a small low-energy green building located in the suburb of Hangzhou which was designed combining with active and passive methods such as solar energy technologies，enhanced insulation system of envelope and so on. According to the reference [13] , the first passive public building was constructed as a demonstrative project in Changxing county of Zhejiang province by using the “Passive house” standard of Germany for reference, which explored the potential of realizing the low-energy building practice in the hot summer/cold winter region and summarized the construction experience.

Computer simulation is a useful method for architects and engineers to simulate and analyze building performance earlier in the design process. The indoor thermal environment of the residences in Turpan District of Xinjiang was simulated and analyzed by using Ecotect software in the reference [14] to evaluate the thermal performance of primary scheme related to the solar radiation, heating consumption and indoor comfort level. Reference [15] carried out a simulation analysis of indoor hourly temperature towards a library building for the insulation material optimization.

Based on the above literature, there are very few studies on passive rural residential buildings design in response to the climate of hot summer/cold winter region. In this study, the “passive” design concept was considered firstly through appropriate plan arrangement, building shape optimization and construction materials selection to largely improve indoor thermal comfort and reduce energy consumption. Secondly, affordable technology equipments were integrated in this project for the purpose of gaining renewable energy actively, supplying energy to building and decrease the need of fossil energy. Furthermore, this project is not a real residential building while is an experimental model integrated with various adaptable energy-saving techniques to be studied and investigated or to be modified and changed into more advanced product in future.

The building Form Coefficient (FC) refers to the ratio of external envelope surface to volume, which influenced the energy consumption greatly. For this reason, FC

should be controlled at a relative low value to prevent additional heat loss. In terms of hot summer/cold winter region, FC is not so critical due to the less temperature difference, meanwhile over tight shape will impact on both architects’ creation and solar heat gains in winter. Therefore, the building models with different plans (see Figure 15) but the same floor area and height, were simulated and compared for the balance of heat transferring loss and solar radiation gains. According to the results (see Table 4), including the energy consumption, heating loss through envelope and solar energy gains, different building performance were visually reflected by the Figures 16-18.

Figure 16 and Figure 17 indicate that the annual energy consumption is expected to rise as the FC increasing. As shown in Figure 15, the form1 possesses the most simple shape so that the total annual loads is lower than others，while that of form6 is significantly high due to its relatively complex envelope (see Figure 17). For the other form, the annual energy consumption presents little difference because of their similar FC. Further simulating results about the ratio of passive solar radiation gains in heating season (i.e. from 1st Nov. to 30th Apr.) and cooling season (i.e. from 1st Jun. to 30th Sep.) together with that of the heating loss through fabric in heating season are shown in Figure 18. It can be observed that form1 obtain the lowest solar energy during heating season for the reason of the simplest shape. Although the FC of form 2, 3, 4 and 6 has an increasing tendency, the solar energy gains in winter are not expected so high due to the constant frontage facing to the sun. For the form 5, more compact shape does not contribute in reducing energy consumption because of its bigger deep compare to other models. In addition, it can be observed that the form 3 has relatively low annual loads and high solar heat gains (52%) in winter, while the solar energy obtained in summer is not so high (39.4%). Based on the above discussion, the form 3 was selected as the final plan considering the architecture style design, and the external shading can be provided in summer in case of preventing over solar radiation.

There are two types: In an earlier study [15] , the amount of astronomical solar radiation resulted from the TMY data base of Hangzhou was about 4329 MJ/m², namely 1202 kW∙h/m²∙a, where has been identified as the resource-poor area (i.e. between 1160 ~ 1400 kW∙h/m²∙a [15] ) of solar energy. According to the evaluation method indicated in the reference [17] , there were 273 days in Hangzhou area where has more than 6 hours sunshine duration in each day, taken as the indictor for assessing the value of solar resource utilization. Therefore, it can be observed that the period between May and September in Hangzhou conforms to the requirement. Based on the above discussion, the solar radiation data from TMY of Hangzhou was put into the basic model to

calculate the total solar radiation falling on the variable angles between 0˚ ~ 50˚, thereby determining the best degree inclination for the solar panel installation.

As shown in Figure 19, the amount of solar radiation falling on the sloped roof indicates an general increasing tendency as the changing degree of inclination: at the range of 0˚ ~ 5˚ angle, the solar heating gains (SHG) is decreasing firstly, and then rising gradually from 5˚ to 35˚ until reaching the peak value of 578.1. After 35˚, SHG appears declining slightly and starts to increase at 50˚. This finding presents that SHG (i.e. from 1st May to 30th Sept.) does not keep increasing constantly with the roof inclining, thus the best angle should be 35˚. Figure 20 illustrates the SHG profile as the angle changing of roof inclination during the whole year: it can be observed that SHG gradually rise from 0˚ ~ 30˚ and then increase suddenly at 32˚ where SHG begin to decline until the roof angle become 45˚. Thus it can be concluded that the best angle of roof for SHG between Jan. to Dec. should be 32˚. Generally considering the architecture style and construction, the roof inclined greatly will lead to the structure stability and un comfortable visual effect, so the angle of roof is determined to be 30˚ as the final plan.

The main envelope insulation system including external wall, roof and windows plays the important role on reducing thermal energy and improving indoor comfort. Considering the maximum energy efficiency and the minimum cost, the Ecotect software was used to simulate the variable tendency of annual heating and cooling loads which were the basic indicator of comparison among the wall and roof insulated by different thickness of materials, as well as the window designed various U-value (seen in Table 5). It was assumed that the thermal performance of other components remained unchanged while the any one of the components was investigated on influencing the energy loads during the process of simulation. Based upon the precondition, the appropriate U-value of the external wall, roof and window were determined according to the simulating results shown in Figure 21 and Figure 22.

Figure 21(a) shows that the energy consumption presents roughly decreasing tendency as the thicknesses of insulation layer constructed on the wall from 0 mm to 100 mm respectively: the heating demand of the external wall insulated by rock wool materials declines significantly by 14.2% (i.e. from 3275.7 kW∙h to 2810.3 kW∙h) compared to the cooling demand from 2278.5 kW∙h to 2190.5 kW∙h, only by 3.9%. It can be observed that total annual energy consumption mainly influenced by heating demand has a general reduction of 10% (i.e. from 5554.2 kW∙h to 5000.9 kW∙h), the profile of which is relatively obvious from 0 mm to 50 mm, but begins to level off after that.

From the simulation result (Figure 21(b)) about roof insulated by XPS board, the cooling demand changes obviously with a 24.6% reduction from 2278.5 kW∙h to 1717.3 kW∙h, relative to the heating energy consumption dropping down by 15.7% (i.e. from 3275. 7 kW∙h to 2761.0 kW∙h); it can also be seen that the annual total demand decreasing by 19.4% from 5554.2 kW∙h to 4478.3 kW∙h is influenced greatly by the cooling demand change, and the value begins to drop slowly when the insulation lay reaches to the thickness of 70 mm. According to the result, roof insulation is the main factor considered to defend solar radiation in summer, which can be explained by the fact that the most solar radiation access is accepted by horizontal plane in Hangzhou area.

The U-value changing profile of window , illustrated in Figure 22, show that the total demand variation is synchronized with that of heating demand: as the U-value changing from 5.4 to 0.5, heating demand falls very rapidly (i.e. with 37.1% reduction from3275.7 kW∙h to 2060.1 kW∙h) causing an overall decline of annual energy demand by 22.%. While the cooling demands profile has almost no change, only with a 2.5% reduction from 2278.5 kW∙h to 2220.5 kW∙h. Based on the figure, it can be concluded that the thermal performance of windows play an important role on the whole energy consumption, especially on reducing heating loss caused by the temperature difference in winter, but has no effect in summer.

According to the above analysis, the optimal thicknesses of insulation layer for wall and roof were decided as 50 mm and 70 mm respectively. In term of windows, the best U-value was considered as 2.5 processed by double glazing sandwich-type coated Low-E film, a 9 mm air gap layer enclosed between two 6 mm clear glass sheets and insulating aluminum profile.

Due to the reason that the thermal performance of residential building envelope was definitely regulated in hot-summer/cold-winter region [19] , the optimal values selected before and the those listed in the Table 6 were assigned to the model for simulating respectively, thereby comparing the energy demand level with each other. At the same time, the effectiveness of insulation design strategies was evaluated.

Figure 23 indicates that the total energy demand of design building insulated by highly efficient materials is obviously lower than that of standard building, falling down

by 14.2% relatively (i.e. from 3760.7 kW∙h to 3228.3 kW∙h). The heating demand profile represents a clear decreasing tendency with 20.7% from 2156.3 kW∙h to 1708.6 kW∙h, while the cooling demand has a slight change from 1604.4 kW∙h to 1519.7 kW∙h, only by 5.3%. The result determined that the objective progress was made in the design building compared to the current regulation.

Shading design is the important strategy on heat defending in summer of Hangzhou. Different directions should have corresponding shading measures, such as baffle devices for east or west windows, horizontal rectangular devices for south windows and surrounding shade with verticals for southeast or southwest windows.

In this project, the metal baffle shading devices made of adjustable horizontal shutters were designed for the east and west external window, shown in Figure 24. For the south window, the best shading devices should be the horizon sun shield due to the reason of Hangzhou location which is on the north of Tropic of Cancer. The size of shading shield can be calculated on the base of the solar altitude and azimuth angles. Firstly, the sun path and control in summer indicate that the horizontal size will be in the large value with solar altitude angle increasing when the sun moves at midday. Otherwise, the wing size of the shield could be decided by the directions of the solar rays, which is get longer as the sun set. In order to fit the facade configuration, the surrounding shade with verticals was selected in the phase of preliminary design, and then the detailed size will be get by using calculation software. For Hangzhou area, the hottest days in a year are usually from May to September when the maximum solar radiation of each day occurs at the range of 10:00 a.m. to 4:00 p.m. [17] . In Ecotect software, the minimum shading size was created automatically according to the input information including date range and time range mentioned above (see Figure 25). By the consideration of shading efficiency and architecture design, the final size of horizontal and vertical shield were both 450 mm, shown in Figure 26.

Normally, integrated shading coefficient of external window (SC) is the important indicator to evaluate the shading effect, relevant to the following factors: shading coefficient of external devices (SD), the shading coefficient of glasses (SCB) and the frame-window area ratio (FK/FC). The formula1 indicates the computing methods about the SC and SD. For the shading configuration designed for east or west window, SC can be calculated by the formula directly; but for the composed device, the value of SD should be the product of that get from horizontal shield and vertical shield respectively. The calculating results are shown in Tables 7-10.

After determining the shading devices style, Ecotect software was used to test the design effect through simulating the monthly cooling demand in TMY. The following design conditions were considered, and the results were shown in Figure 27:

The solar gain coefficient of glasses is 0.75, and has no any external shading devices;

Only east and west windows were provided with the metal baffle shading devices made of adjustable horizontal shutters, the value of SC seen in Table 10;

Only south windows were provided with integrated shading devices composed of horizontal and vertical shied , the value of SC seen in Table 10;

All the windows were considered with external shading devices, the value of SC seen in Table 10;

Otherwise, the monthly heating demand in TMY was also simulated under these two conditions, and the results were shown in Figure 28:

The solar gain coefficient of glasses is 0.75, and has no any external shading devices;

Only south windows were provided with integrated shading devices composed of horizontal and vertical shied , the value of SC seen in Table 10;

Figure 27 indicates that the annual cooling demand has an obvious decrease when only the east and west windows were designed with external shading devices comparing to that being installed outside the south windows only during May to September: especially in May, the cooling demand consumed by the former drops about 13.2% from 100.2 kW∙h to 87.1 kW∙h, while that consumed by the later only 2.4% (i.e. from 100.3 kW∙h to 98.0 kW∙h). When all the windows use the external sun-shading, the cooling consumption falls down by 14.7% from 100.3 kW∙h to 85.6 kW∙h. Even in July, the hottest month in Hangzhou, the cooling demand also has a declination of 8.6% under east and west shading consideration only, which can be seen that the eastern or western shading design is an important technological strategy in summer of Hangzhou.

In the heating season of Hangzhou, namely from November to next April, the

heating demand almost remain unchanged when south windows adopt fixes shading devices, shown in Figure 28: in January, February and December, the value of heating consumption increases slightly as solar energy gains are affected by the external shield, and that in other months rarely changes.

For the further analysis and comparison, the annual heating and cooling demand generated by different shading proposals were presented in Figure 29. When outside shading just used in east and west windows, the annual cooling demand drops by 10.2%

Data source: Design Standard Energy Efficiency of Residential Building in Hot Summer and Cold Winter Zone JGJ 134 - 2010.

a. SD=ax²+bx+1, x=A/B; b. the product of SD calculated for horizontal shield and for vertical shield respectively.

a. SC = SD × SCC, SCC = SCB × (1 − FK/FC); SCB = 0.75, FK/FC = 0.2, then SCC = 0.6

(i.e. from 1517.9 kW∙h to 1363.3 kW∙h), resulting in a 4% reduction of annual total energy consumption, which is more than prominently it is made by the south windows installed with external shield only, annual cooling consumption decreasing by 2.6% while the total annual energy consumption falling by less than 1%. The highest energy saving occur when all the windows possess the outside sun-shading and a significant difference between heating and cooling demand was illustrated that the former rises by 2.5% but the later drops by 12.6%.

Based upon those findings, in order to achieve the maximum energy efficiency through shading design in terms of Hangzhou climate, the external windows should have adjustable sun-shade devices. For the east and west window in this building, the metal baffle made of adjustable horizon shutters should be closed in summer season and open in winter time. On the other hand, the fixed shading shield is not appropriate for south windows. In this project, shading design could be modified as such way: the cantilever size of 450 mm with adjustable inside vertical shutters, which will either play a shading role effectively in summer or help to solar heating gains in winter.

The lighting quantity of the middle room was simulated and analyzed by using Ecotect software in order to demonstrate the effectiveness of the nature optical lighting system. Simulating conditions for lighting quantity was decided based on the Standard for Daylighting Design of Buildings (GB50033-2013), as shown in Table 11. According to the standard: Hangzhou city belongs to the IV daylight climate in China, the regulated average value of daylight factor should not be less than 1.1% under the top lighting condition, and the average illuminance of interior daylight should not be less than 165 lx. In terms of the following design conditions, the indoor day-lighting simulating was carried out: when no day-lighting windows on the external wall, the values of daylight factor and illumination were simulated as the changing of the metal optical tube diameter from 500mm to 1000mm with an increase of 100 mm, as shown in Table 12.

It can be seen in Table 11, the indoor average day lighting factor only add up to 0.66% as the tube diameter increasing from 500 mm to 1000 mm; on the other hand, oversize length will add the difficulty to the structure and influence the visual result. Therefore, single optical tubular system could not meet the requirement of the indoor day-lighting without the additional lighting openings. By overall consideration, the south wall was the only available component to be established with day-lighting opening, which was designed by 1500 mm wide and 500 mm high. The new simulated

results obtained from the modified model was shown as Figure 30: by comparison to the and the average illumination was 166 lx. Thus, the design of 1000 mm diameter optical model only designed tubular optical system, the average day lighting factor was 1.16% tubular system combined with 100 mm × 500 mm day-lighting opening would satisfy the standard.