Introduction
Northwest China has inclement ecological environment with backward economic environment. The severe problems of rural residential house in northwest China are as follows:
1) Too low indoor temperature in winter. The indoor temperature in most of the inquired households is about 10°C or even lower in winter day, which is far below the range of comfortable temperature stipulated by the Indoor Air Quality Standards.
2) Big energy consumption and high cost of heating in winter. Most of the famers use coal as the main fuel for heating. On the average, each household consumed at least 3.5 to 4.5 t of coal during the winter. A conclusion can be drawn that within one heating season, the average square meter in the farmer households can consume about 30 to 35 kg coal; it will be 1.5 or 2 times of the present energy consumption, which will be a heavy financial burden on most of the farmer households.
3) Renewable resources lack of effective application. Northwest China contains abundant renewable natural resources, such as wind energy, solar energy, and plants energy. These are unique advantages of sustainable development in the northwest. However, recently, these resources are used in high-cost technologies, such as photovoltaic and heat pump. In the vast rural areas, these resources lack of effective application.
To solve these inevitable problems in northwest China, appropriate architectural technologies should be developed according to the local conditions. Moreover, methods of utilizing natural resource with low cost should be explored.
Project description
The Jianfuqiao village in Yinchuan city, Ningxia Hui Autonomous Region, is an exploration of rural ecological residence in northwest China [
1]. The project is located at the east of Zhangzheng town, Xingqing district, Yinchuan city, Ningxia Hui Autonomous Region. The first phase of the project plans to occupies 5.64 ha and the residential land covers 2.4 hectares, which can accommodate 86 households (Fig. 1).
To construct ecologically energy saving village, the project actively adopts appropriate technologies and measures of ecology and manages to provide technological support for the future construction of energy saving, environment friendly, and human livable ecological residence.
In Jianfuqiao village, the average household income is less than 5,000 RMB per year. Considering the local technological conditions and the limit of rural construction cost, the technology in this demonstration village will mainly depend on passive means of low cost and easy popularization [
2].
Appropriate strategies
Architecture design
Site plan
The village is located at north latitude 38.5° and east longitude 106.2°. In winter, the most frequent wind direction here is north and in summer is southeast. Therefore, the best architectural orientation is the south or the scope of a 15° angle to the east/west, so as to make the buildings collect more sun radiation in winter. Moreover, the area of the side of the building facing the north wind should be reduced and at the same time; tracts of greening trees should be planted at the north side of the building to block or lead the airflow to improve the airflow conditions within the building groups to avoid the architectural heat being taken away by the cold north wind while dealing with the hot air in summer in this area.
Architecture design
The local newly built house is single house with one story. The building area is 103.34 m2, and the shape coefficient is bigger than high-rise buildings. To reduce the great energy consumption caused by the bigger shape coefficient, the building shape should be regular and compacted (Fig. 2).
To use the south wall as the section to collect heat and reduce the amount of heat losing by the other three walls, all the farmer houses face south and take the flat shape with longer east and west axis and shorter south and west axis. Moreover, the rooms in the house are distributed according to the discipline that the temperature is lower in north and higher in south. Therefore, the secondary rooms as toilet, kitchen, and store room occupy the north part of the house. However, the primary rooms will sit the south part so that the residents can stay longer there because the south wall collects direct solar radiation. Thus, the rooms in the north part function as the indoor buffer zone to protect the sitting room and bedroom at the south part.
The way of making openings for windows differs from one direction to another. In the south, direct-gain window and solar room will be built, and the area of the window is big enough to collect more solar energy; in the north, the window is to satisfy the basic needs for light collecting and ventilating, so the area of the window is small so as to reduce the heat loss in winter. In the east and west, there is no window, because of the huge amount of heat losing in such directions.
The part that loses the biggest amount of heat in the rural residence is the entrance. In winter, the rural life and working in the northwest cannot be totally carried out outdoor, so part of the activity will be moved into the house, which causes frequent opening and closing of the door. To solve this problem, the entrance should avoid the prevailing wind in winter-the north wind. The newly built house put the attached solar room as the entrance to avoid draft. By doing this, the direct blow of cold wind into the house can be avoided; the indoor heat loss caused by airflow under the wind pressure is reduced. At the same time, the solar room can also be used as the transitional space for temperature preservation.
Local ecological building materials
The agricultural industry in Yinchuan Plain where the project is located depends on the Yellow River’s gravity irrigation, and the staple crops are wheat, rice, and corn, so after harvesting, the straw can be used as the ideal ecological building materials.
In the practice of the project, taking consideration of the capability of the local construction team, brick-masonry and straw-bale house structure are adopted. The straw-bale will be filled between the tie columns of the nonbearing wall or be used together with the block masonry wall to just function as enclosing and filling materials but not load bearing. In construction, the roof should be built first in order to avoid the straw-bale being got damp or damaged. This structure is suitable for the houses with simple appearance in villages or towns and also economical and affordable (Fig. 3).
There is suspended ceiling in the house with pitched roof. Placing thermal insulation layer on the suspended ceiling can get high efficiency of heat insulation; the construction is simple, and the cost is low. The heat-preserving materials can be wheat bran, saw dust, or straw, and these materials can be directly put on the upper surface of the ceiling. This method is easy to operate and popularize in the farmers’ self-built house, and the materials are easy to get in the rural areas (Fig. 4).
Passive solar energy heating
Direct-gain solar energy by window
The traditional local residences are mostly adobe houses, and their windows are usually small to avoid heat losing in winter. Moreover, the area of an opening in the wall is limited when using adobe bricks as the load-bearing maintenance structure. All these defaults cause somberness and coldness in winter in the traditional residence.
The plan used in the practice of this project is increasing the size of the window facing south, using double-layer glass window and properly shortening the depth and lengthening the width of the south-facing house. To avoid the great fluctuation of indoor temperature, the adobe, which is made of the local raw-soil, is used to build the wall, because of its great heat-storing function. Besides, to improve its heat-storing function, raw-soil’s porous nature can function as an excellent regulator of the indoor air humidity. The plan has got good effect in real application, which makes the house filled with sunshine in the cold winter.
Attached solar room
The weather in Yinchuan restricts the outdoor activities; considering the local solar resource and economic situation, the attached solar room is an effective solution [
3].
The attached solar room sits at the south part of the house, its area is 12.5 m2, and its area of heat collecting is 24.26 m2. The room facing south has large area of glass and can be used as the porch or vestibule, at which the roof, an inclined glass, is placed (the inclination angle is 25°) to increase the amount of heat collection. In winter, sunshine will go inside the room, and most of the solar energy is turned into thermal energy to increase the indoor temperature. At the same time, a partition door or a detachable cotton wadded curtain should be placed between the attached solar room and the adjoining room to reduce the indoor heat loss through the big glass during night. In the specific construction operation, the glass wall in the solar room should not reach the floor, considering the local villagers’ habits of living and working. Between the glass wall and the floor, there is an adobe wall of 400-600 mm high, which can help avoid breaking the glass wall in the solar room when working or stacking sundries.
The attached solar room is welcomed by the farmers, because the indoor space is enlarged, and the indoor thermal condition is improved with only a little increased construction cost. The solar room has good effect in application, which makes the house filled with sunshine even in the cold winter (Figs. 5 and 6).
The evaluation of the project
Test on the physical environment of the building
The Jianfuqiao demonstration project was completed in early October 2008, and the research team had a winter test on the project from December 9, 2008 to December 13, 2008. To have a comparative analysis, an old traditional vernacular dwelling of equal area and household size was tested at the same time [
4].
The test days are all clear days. The indoor temperature test spot is at the central room where people stay longer. The outdoor temperature and humidity is recorded automatically by thermograph and hygrometer once half an hour. The detailed results are shown in Figs. 7 and 8, among which Table 1 is concluded in Fig. 7 and Table 2 in Fig. 8. The testing results illustrate the following:
1) Temperature in the newly built house is higher than that in the traditional house. In the traditional farm house, the average temperature is 13.5°C, and the heat-storing property is poor and is directly influenced by the solar radiation. Moreover, the temperature in the old house fluctuates greatly. At noon, when the indoor temperature reaches the peak, some residents open the window to decrease the temperature, which is a waste of energy.
However, the same day in the newly built house, without any means of heating, the average indoor temperature can reach 15.7°C. At the same time, the enlarging of the area of the lighting window in the south wall of the newly built house (using the direct-gain window) has no obvious influence upon the lowest indoor temperature, but in the typical winter climate, it can increase 2.4°C of the average indoor temperature.
2) The energy consumption of heating in the newly built house is obviously lower than that of the traditional house. Data from one of the winter testing days fully illustrate that the technology of passive use of solar energy is very effective. On the testing day, residents in the two houses begin to burn coal to heat the house; because of the residents’ habit of thriftiness, they only light the stove and heat the Chinese Kang, and at daytime, they only use the afterheat of the stove and the Chinese Kang. The changes of the indoor temperature can be seen in Fig. 7. During the period from 20 o’clock to 7 o’clock, temperature in the old house is a little lower, and residents in the two houses begin to burn coal to guarantee the indoor temperature. At 7 o’clock in the morning, the residents begin to cook, and after that, they will not continue the burning of coal.
As the solar radiation strengthens, the indoor temperature in the new house rises obviously. However, the indoor temperature in the old house falls. In the old house, at 7:00 am and 17:00, the indoor temperature clearly rises when the residents begin to cook. Therefore, the increase of the indoor temperature depends greatly on the consumption of coal; however, in the new house, the indoor temperature can be improved at daytime by using solar energy [
5]. According to the statistics, the average coal consumption per square meter in the heating season can be reduced to 15 to 20 kg.
3) The thermal stability in the newly built house is better than that in the traditional house. Though the wall maintenance structure in the old house is made of the adobes with higher thermal resistance and thermal inertia index, the cold bridges of the building, roof, and floor are poorly treated. According to the test results, the indoor temperature fluctuation in the old house can reach 8.7°C, and the humidity fluctuation reaches 28%; thus, the indoor comfort is poor. However, the new house has good thermal stability, and the heat loss through the outer wall is little, thus the temperature fluctuation is 5.1°C, which is close to the constant temperature. At the same time, the bigger outdoor humidity fluctuation is reduced in the new house, and the relative humidity in the new house is stable, which illustrates that the local ecological building materials have excellent ability of humidity adjusting.
Feedback of the questionnaire
Through site visit and questionnaire, we found that most of the farmers hold a positive attitude to the ecological appropriate technology popularized in this project. After one year’s use, they also fully realized the importance of the energy-saving measures. Their general responses are as the follows:
1) The indoor comfort is increased. The architectural technology used in the newly built house breaks through the traditional technology. The architectural plan layout conforms to the life habits and requirements of the modern farms’, and also, the function, physical sensation, and appearance of the new building are obviously improved. Especially the solar room not only reduces the penetration of the cold wind but also improves the indoor air quality. In addition, the indoor thermal environment in winter is clearly improved, which is of great importance for the farmers in the north to enjoy their winter ease.
2) The technology is easy to operate and popularized in rural areas. In the villages of the northwest, the construction level is very low. However, the appropriate technology is easy to put into practice and building materials as cinder, raw soil, and straw-bale can be obtained from the local place. Moreover, the cost is low, and the construction means that it can be easily adopted by the local farmers.
3) Some technologies cannot be fully adopted by the farmers. Although the obvious comfort and energy-saving effects of the newly built house have dispelled some of the farmers’ misgivings; some technological measures still cannot be accepted by the local farmers because of their intrinsic ideas. For example, painting the heat storing south wall into dark color is always regarded as unpleasant and thus is rejected. In addition, some farmers with better financial conditions want to follow the residential pattern in the city. They mistrust the local ecological building materials and heat preserving materials. To solve the problem, the subsequent work should be strengthened.
Project implementation and promotion
As an exemplary zone, the purpose of this project is to integrate and demonstrate the technologies for rural residence. Therefore, before the implementation of the project, the possibility of low-cost appropriate technologies and the flexibility of the composition of these technologies are taken into consideration so as to facilitate the promotion and application of the future technological achievements.
The benefits of integrating many technical schemes are to compare the practical effect on one hand and to provide more options for the farmers on the other hand. For example, the walls built with straw-bale, raw soil, and fly-ash brick respectively are demonstrated in different houses, and the heat collecting and storing wall will be built according to the farmers’ acceptance and with their own choice. Moreover, the place for the installation of the solar water heater is also reserved. Most of these schemes are either easy to implement, or the materials can be selected among the local materials; all of which can help the farmers to implement by themselves in the future. At the same time, the farmers are invited to participate in the construction. By doing this, not only can the farmers get technical support and supervise and investigate the construction themselves, but also the appropriate technologies can be promoted and publicized.
Conclusion
The rural area in northwest China has the advantage of vast space, relatively cheap labor, and rich renewable energy. By exploring and studying ecological architectural technologies suitable for countryside different from city and guiding countryside to build scientific pattern of developing and using energy resources, we can promote the development of the new countryside, speed up the pace of better-off life in countryside, and greatly relieve the pressure brought by the increasing energy consumption in our countryside.
Higher Education Press and Springer-Verlag Berlin Heidelberg
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