ENERGY SAVING INNOVATION IN CHINESE TRADITIONAL BUILDINGS. L. Zhu Nanjing University of Technology China

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1 Int. Journal for Housing Science, Vol.33, No.1 pp , 2009 Published in the United States ENERGY SAVING INNOVATION IN CHINESE TRADITIONAL BUILDINGS L. Zhu Nanjing University of Technology China ABSTRACT In Yangzhou, China, as part of an urban rehabilitation pilot project, an innovative energy-efficient design for traditional style houses is developed and implemented. The experimental building shows how energy saving measures and traditional building style can be combined to improve comfort and living quality for the residents while maintaining the unique character of the city. Key words: Energy saving, Chinese traditional style building, Renewable energy use. Background As part of the rapid urbanization in the past 20 years in China, a fundamental change of spatial, social and economic patterns of eastern Chinese cities has occurred. Old city areas -mainly with traditional courtyard buildings - are continuously disappearing due to demolition because of enormous economic pressure. But in the urban centre of Yangzhou, which is located at the junction of Grand Canal and the Yangtze River, 240 km north-west of Shanghai, a city with a development history of more than 2500 years, there still remains a substantial historical area of 5.1 km 2 with about 110,000 residents, characterized by 1 to 2 storey traditional style buildings with sequences of /01/ 35-43, 2009 Copyright 2009 IAHS

2 36 Zhu courtyards, narrow streets and lanes. The Yangzhou Municipal Government has discovered the historical and economic value of the old city and paid special attention to its preservation for years. Since 2002 German Technical Cooperation (GTZ) has been supporting the Municipal Government s efforts and introduced the concept of sustainable urban conservation that links heritage preservation with improvement of the residents living conditions in traditional neighborhoods by upgrading these areas and supporting self-help initiatives. One of the important issues in the conservation of the old city is that due to the low living comfort in most of these traditional residential houses, many young and higherincome residents choose to leave for living in the new town, which leads to the deterioration of the old city centre. Yangzhou is located in the lower reaches of Yangtze River Delta, at the northern edge of China s sub-tropical climatic zone. There is a high variation in temperature between summer and winter- muggy and hot in summer and cold in winter. While summer can see temperatures exceeding 39ºC, snow is not uncommon during winter. But most of the traditional residential buildings in the old city have poor thermal insulation. The old city residents usually have electric air-conditioners installed when income increases. For one thing, the outdoor air conditioner equipment damages the image of the old city; for another, energy consumption of these air-conditioners is very high for the poor thermal insulation of most traditional style buildings. To solve this problem, which is also universally valued for other historic cities, as part of a rehabilitation pilot project in the Wenhuali Neighborhood (see FIG.1), GTZ, in cooperation with the Yangzhou Municipal Government, designed and implemented in 2007 an experimental energy-efficient building in local Chinese traditional style. The primary objective of this experimental building is to show that traditional style buildings and modern energy saving concepts can be integrated to improve living comfort and quality of the residents while maintaining the unique character of the city and reducing energy consumption as well. Energy Efficiency Concept and Measures Considering the local weather of hot summer and cold winter, the expert team developed a comprehensive energy efficiency concept to reduce energy consumption for cooling in summer and heating in winter, and integrated the use of renewable energy. The design for this experimental energy-efficient building in Chinese traditional style began with some basic design principles. On the basis of the climate and land plot conditions, the shape and layout of the building, orientation, openings on the facade were fully considered to reduce its energy consumption need. After the initial design, a dynamic simulation was carried out (TRNSYS16.1to test the potential energy consumption of the house when integrated with possible energyefficient measures, according to the local data of temperature and global radiation,

3 Energy Saving Innovation 37 rainfall and air humidity, as well as geothermal conditions. Based on a quantitative analysis and comparison, the architectural design was improved and a comprehensive energy-efficient concept with optimized measures was then developed (see Figure 2). Figure 1 Location of the Building in Wenhua Li Neighborhood Architectural Design Located in the rehabilitation pilot block Wenhuali Neighborhood, this building has a total floor area of 160m 2, covering a land of 200m 2. on a former deserted factory warehouse plot. The Regulatory Plan for this area requires new construction should first take the form of the local traditional architecture, so the design adopts the layout of typical courtyard building style, with traditional bricks and tiles (see FIG.2 and 3). As the most important character of Chinese traditional style houses with wood frame structure, this building can be used for multiple functions. The main rooms face south, and those facing west and east are for washing rooms, storage and facilities. The building layout and shape, orientation, façade are considered for reducing heating and cooling needs, and the design is further optimized based on the dynamic simulation results of the building energy consumption. Above the courtyard, three tilted (convenient for natural ventilation and rainwater flowing) solar shading sails are used to protect the courtyard and adjacent rooms from the direct solar radiation in summer (see Figure 2, Point 3 and Figure 4). Vegetation such as flowers and small plants contribute to a cool and pleasant microclimate and reduce future cooling needs in summer.

4 38 Zhu Figure 2 Energy Efficiency Concept and Measures Figure 3 Facade/Entrance Figure 4 Courtyard and Shading Sail in Summer

5 Energy Saving Innovation 39 Thermal Insulation By means of improving the thermal insulation and air-tightness of the building envelope, the energy consumption requirement of heating in winter and cooling in summer of this building is minimized. Walls and Roofs: The walls and roofs of the entire building are covered by thermal insulate materials. Insulation systems are installed above wooden roof structures, on top of external brick walls and under the ground surfaces. Under the traditional roof tiles, 120mm thick PU (polyurethane) insulation panels are installed on the wooden roof structure; the exterior walls have a comprehensive and gapless thermal insulation system, mainly of 80mm thick EPS (expanded polystyrene) panel, installed with special plugs, above which brick coating is used to make the building appear like any other traditional building in the neighborhood, so as to conform to the traditional residential house style ( see FIG.3); under the interior traditional brick floor lay the foam glass insulation panel on hot bitumen coating. (See FIG.2, Point 1.1, 1.2 and 1.3) Doors and Windows: Thermal insulate PVC doors and windows with double glazing and low-e glass filled with argon are used instead of traditional wooden doors and windows for better sealing and air-tightness. 2-level rubber sealing in the window frames and windows being installed at the same level as the thermal insulation of the exterior walls further avoid any energy loss through any gaps. To solve the problem of PVC windows and doors not being in tune with the traditional form, traditional wooden doors with wire-mesh windows are installed from the outside of the building (see FIG. 5). During night time in summer when PVC windows are opened, there will be a natural ventilation system to circulate cooling breezes through the wooden wiremesh doors and windows and the air outlets near the roof ridges (see FIG. 2, Point 6.2).

6 40 Zhu Figure 5 Thermal Insulate Windows and Doors & Traditional Wooden Doors with Wire-mesh Windows. Figure 6 Solar Collector System: A. Solar Collectors; B. Buffer Tank; C. Solar Station; D. Control Panel Renewable Energy Use Earth heat exchange system for cooling in summer and solar collector system for heating in winter are used in this building. Earth Heat Exchange System for Cooling: In summer an earth heat exchange system guides cool air through PE pipes below the building s foundations to cool down the entire building (see FIG. 2, Point 5.2). 200mm-diametre PE pipes are placed for a total length of 60m along a clip-like ditch about 1.8m deep under the ground, with the inlet and outlet above the ground. An electric ventilator is installed on the outlet, which is then connected to the interior ventilation system. The warmth of the air is absorbed by the soil and ground water which cool down the air temperature. In summer day, when the ventilator is turned on, it draws in the cooled fresh air through the PE pipes. Air inlets near the floor direct cool breezes into the rooms while air outlets near the roof ridges expel hot air, thus a natural ventilation system is formed to assure that cooling breezes circulate through the rooms so that the entire building is cooled down. In summer night, turn off the ventilator, and open the PVC windows to make use of natural breeze to cool down the rooms while the soil temperature can be naturally restored. To reach the energy saving goal economically, the diameter, length, placement depth, the amount of the exchange air through PE pipes are determined after a thermal simulation calculation, and the power of the electric ventilator can be adjusted according to the temperature.

7 Energy Saving Innovation 41 In Yangzhou, humidity levels are very high most of a year, and the condensate due to heat exchange inside the PE pipes may accumulate and make the pipes moldy. Therefore, the installation ditch needs an overall angle of inclination of 3% towards a 2m deep condensation collection shaft in the middle of the yard (see FIG.2, Point 5.3). Besides, to guarantee the sanitary standard of the system, from time to time the pipe system will be cleaned inside with running water poured in through revision openings from both the air inlet and outlet. The functioning of the pump inside the shaft will be checked two to three times a year. Solar Energy Use for Heating: In winter, solar collectors capture the sunlight and convert solar radiation into thermal energy for heating. In Yangzhou winter is generally dry and sunny and there is long hours of sunshine. Global radiation even in the coldest December and January reaches kwh/m 2. These factors see Yangzhou as a perfect candidate for solar energy heating in winter, based on experiences from Germany. A solar collector of about 20m 2 installed on the south-facing roof capture sunlight and convert solar radiation into thermal energy. The heat from the collectors is then transferred to a 1,500-litre buffer tank where the thermal energy is stored. From there it is further distributed to heating radiators which warm up the building s interior. The buffer tank is completely covered with insulation to minimize any loss of thermal energy (see FIG. 6). To address the problem of insufficient global radiation when it is overcast or raining, an additional high-efficient electric heater is installed to the buffer tank. Also, a control panel is installed to automatically control the solar fluid circulation and allow manual settings depending on the individual requirements of the user. In this way, the energy consumption need for the heating and cooling of the entire building depends mainly on regenerative measures. The only conventional energy consumption for this end is the electricity used by the electric ventilator for earth heat exchange system and the additional electric heater for the solar collector system. Energy Saving and Demonstration Effect By adopting comprehensive energy efficiency concept with optimized measures and avoiding conventional electric air-conditioners, this building reaches a high-level living comfort with comparatively low energy consumption (see Table 1). Meanwhile, it also demonstrates the feasibility of integrating modern energy efficient concepts with Chinese traditional style buildings.

8 42 Zhu Table 1 Energy Saving Measures and Effects Energy Saving Measures Energy Saving Reference Buildings Thermal insulation 18,400 kwh/a Common buildings - 120mm thick PU insulation on roof without thermal structure insulation, heating and - 80mm thick EPS insulation on the envelopes cooling with electric airconditioners - 60mm thick foam glass insulation under floor surface - PVC windows and doors with thermal insulate glass of low- E filled with argon, with 2-level rubber sealing Solar collector system 2,000kWh/a Buildings with thermal insulation, heating with electric air-conditioners Earth heat exchange system 1,083kWh/a Buildings with thermal insulation, and with electric air-conditioners Note: The annual energy saving is based on the dynamic simulation of the building s energy consumption with TRNSYS In winter, the indoor temperature is supposed not to be below 19 C during working hours (from 8 to 20), and above 12 C during the offwork and weekend hours; in summer, the indoor temperature is supposed to be below 25 C during working hours, but when outdoor temperature above 38 C,the indoor temperature may be raised to that of 8 C below outdoor temperature. The cooling system will be turned off at night and on weekends in summer. (1) As the first energy saving building in traditional style in Yangzhou, it has attracted large groups of common old city residents and other visitors, thus reaching the anticipated effect for demonstration. Residents in the historic neighbourhoods show great interest in the energy efficiency measures of this courtyard building, similar to those resided by them. The residents, government decision-makers and developers are encouraged and stimulated to learn from the energy efficiency concept and measures adopted by this experimental building, to better rehabilitate historic neighbourhoods, and improve the living conditions in the historic buildings as well. The energy efficiency concept in this building may be applied to existing as well as new buildings in similar situations for other Chinese old cities. As a basic rule, passive and preventive measures should be applied first with regenerative measures added afterwards. China is concerned by the rapid growth in energy consumption in the building sector. Energy saving measures take a central position in China s National 11th Five-Year Plan (2006 to 2010), during which period such energy saving targets for buildings are clearly laid down in China Medium and Long Term Energy Conservation Plan issued by the National Development and Reform Commission

9 Energy Saving Innovation 43 (NDRC) in Nov. 2004: New buildings should strictly adhere to the design standard of 50% energy conservation; energy saving retrofits for existing residential and public buildings shall be conducted in combination with urban reconstruction. Large cities are to improve 25% of building areas, medium cities 15% and small cities 10%; and speed up application of solar and other renewable energies in buildings. (2) However the practices of energy saving of Chinese traditional style buildings are still very rare. The experience of this experimental building may be shared with those who wish to conserve their historic neighbourhoods in more sustainable way. References 1. GTZ, Energy Efficiency in Traditional Buildings, Yangzhou, Source of the Figures: GTZ Expert Team