Detailed inventory of energy-saving renovation of doors and windows

The significance of doors and windows in building energy conservation

Building doors and windows undertake the two contradictory tasks of isolating and communicating the indoor and outdoor environments. They are not only required to have good thermal insulation performance, but also have multiple functions such as lighting, ventilation, decoration, sound insulation, fire prevention, etc. Therefore, compared with other enclosure components, the technical treatment is more difficult and the problems involved are more complex. From the perspective of building energy conservation, on the one hand, the exterior window of a building is a component with high energy consumption, on the other hand, it may also become a heat-harvesting component, that is, it can obtain solar energy through sunlight penetrating into the room. Therefore, appropriate door and window materials, window types and corresponding energy-saving technologies should be selected according to the local building climate conditions, functional requirements, and other surrounding components, so as to achieve good energy-saving effects.

On the other hand, the thermal insulation performance of doors and windows is the worst among the four major enclosure components of building envelope, including doors and windows, walls, roofs and floors, which is one of the main factors affecting the quality of indoor thermal environment and building energy conservation. As for the current typical maintenance components in China, the thermal energy consumption of doors and windows is about 4 times of the wall, 5 times of the roof, and more than 20 times of the ground, accounting for 40%~50% of the total energy consumption of building envelope components. According to statistics, under the conditions of heating or air conditioning, the heat loss of single glass windows in winter accounts for about 30%~50% of the heat supply load, and the cooling consumption due to the solar radiation heat entering the room through the single glass windows in summer accounts for about 20%~30% of the air conditioning load. Therefore, enhancing the thermal insulation performance of doors and windows and reducing the energy consumption of doors and windows are important links to improve the quality of indoor thermal environment and the level of building energy conservation.


Energy-saving renovation methods of existing building doors and windows

Overall, the energy saving of doors and windows is mainly reflected in the improvement of thermal insulation performance of doors and windows. The energy conservation of doors and windows in cold areas in the north focuses on thermal insulation, while that in hot summer and warm winter areas in the south focuses on thermal insulation, while that in hot summer and cold winter areas should consider both thermal insulation and thermal insulation. The following aspects can be considered to improve the thermal insulation performance of doors and windows.


1. Strengthen sunshade measures inside and outside windows

On the premise of meeting the design requirements of the interior of the building, the addition of external sunshades and awnings and the appropriate increase of the length of the south-facing balcony can play a certain sunshade effect. A thermal reflective fabric curtain coated with metal film is set on the inside of the window, with decorative effect on the front, forming a space air layer of about 50mm thick with poor mobility between the glass and the curtain. This can achieve good thermal reflection and insulation effect, but the direct lighting is poor, so it should be made into a movable type. In addition, the shutter curtain with certain heat reflection function installed on the inner side of the window can also obtain certain heat insulation effect.


2. Improve the thermal insulation performance of doors and windows

Improving the thermal insulation performance of building exterior doors and windows mainly refers to improving the thermal resistance of doors and windows. Because the thermal resistance of single-layer glass window is very small, and the temperature difference between the inner and outer surfaces is only 0.4 ℃, the thermal insulation performance of single-layer glass window is very poor. The use of double or multi-layer glass windows or insulating glass can significantly improve the thermal insulation performance of windows by taking advantage of the large thermal resistance of the air interlayer. In addition, the selection of door and window frame materials with low thermal conductivity, such as plastic, metal frame materials after heat insulation treatment, can improve the thermal insulation performance of external doors and windows. Generally speaking, the improvement of this performance also improves the thermal insulation performance.


3. Strengthen the thermal insulation performance of doors and windows

Here we focus on the existing buildings in southern China, such as hot summer and cold winter areas and hot summer and warm winter areas. The thermal insulation performance of doors and windows mainly refers to the ability of doors and windows to block solar radiation heat from entering the room in summer. The main factors that affect the thermal insulation performance of doors and windows include the thermal and photophysical properties of door and window materials, inlay materials (usually glass), etc. The smaller the thermal conductivity of the door and window frame material, the smaller the conductivity of the door and window. For windows, using various special heat-reflective glass or heat-reflective film has a good effect, especially selecting reflective materials with strong infrared reflection ability in the sun, such as low-radiation glass. However, when selecting these materials, we should take into account the lighting of the window. We cannot improve the thermal insulation performance by losing the light transmittance of the window, otherwise its energy-saving effect will be counterproductive.


4. Improve the air tightness of doors and windows

Improving the air tightness of doors and windows can reduce the energy consumption generated by the heat exchange. At present, the air-tightness of exterior doors and windows of buildings is poor, and the air-tightness should be improved from the production, installation and addition of sealing materials. In the design, the determination of this index can be considered according to the sanitary air exchange rate of 1.5 times/h, that is, doors and windows are not necessarily required to be absolutely airtight. For buildings in the north, enhancing the air tightness of doors and windows has a great impact on reducing the heating energy consumption in winter.