The Shape Coefficient of Building (SCB) is an index that reflects the ratio of the external surface area of a building in contact with outdoor air to the volume it surrounds, and it is a quantitative parameter that characterizes the shape of a building. The formula for calculating the building size coefficient is as follows:
scb=\frac
Among them, $scb$ is the building size coefficient, $f 0$ is the external surface area of the building in contact with the outdoor air, and $v 0$ is the volume surrounded by the building. The external surface area does not include the area of the ground and the partition wall of the unheated staircase and the door, does not include the parapet wall, and does not include the wall of the stairwell and equipment room on the roof floor. The components that protrude from the wall, such as the air conditioning panel, are ignored in the calculation and can be calculated according to the complete wall.
The building shape coefficient reflects the complexity of the building shape and the heat dissipation area of the envelope structure, the larger the body shape coefficient, the more complex the body shape, the larger the heat dissipation area of the envelope structure, and the greater the heat transfer heat consumption of the building envelope, so the building shape coefficient is one of the important factors affecting the heat consumption index of the building, and it is an important index of building energy-saving design. At the same time, the building shape coefficient also reflects the aesthetics and functionality of the building, the smaller the body shape coefficient, the more concise the body shape, the more neat its appearance, the higher the aesthetics and functionality of the building, so the building shape coefficient is one of the important factors affecting the aesthetic effect and use effect of the building, and is an important index of architectural aesthetic design.
The steps to calculate the building size factor are as follows:
The first step is to calculate the external surface area of the building, that is, to add the areas of several surfaces that constitute the main body of the building, and pay attention to excluding the parts that are not counted, such as the ground, stair partition wall, parapet wall, etc.
The second step is to calculate the volume of the building, that is, multiply the base area of the building by the height of the building, noting that the base area should include all the projection areas, such as balconies, cornices, etc.
The third step is to calculate the building size coefficient, that is, divide the external surface area of the building by the volume of the building to obtain a dimensionless value.
Example of calculation of building size factor:
Suppose there is a building with a rectangular plan, 30 meters long, 20 meters wide, and 10 meters high, with two balconies, located on the east and west sides, each with an area of 5 square meters, and a cornice located on the south side, with an area of 10 square meters, no underground part, no overhead floor, no staircase partition wall and door, no parapet, no stairwell and equipment room with roof layer, and no components protruding from the wall. Then the calculation process of the size coefficient of the building is as follows:
The first step is to calculate the external surface area of the building, that is, to add the areas of several faces that make up the main body of the building to obtain:
f_0=2\times(30\times10)+2\times(20\times10)+30\times20+2\times5+10=1360(m^2)
The second step is to calculate the volume of the building, that is, to multiply the base area of the building by the height of the building, and get:
v_0=(30\times20+2\times5+10)\times10=6600(m^3)
The third step is to calculate the building size coefficient, that is, to divide the outer surface area of the building by the volume of the building to obtain:
scb=\frac=0.206
Therefore, the size factor of the building is 0206。
Building shape coefficient has a wide range of applications in architectural design, which can be used to evaluate the energy-saving performance and aesthetics of buildings, and guide the optimization of building shape and the selection of energy-saving measures. Here are some specific applications:
Evaluate the energy-saving performance of buildings. According to the climatic characteristics and energy-saving requirements of the area where the building is located, the building shape coefficient should meet a certain limit, otherwise corresponding energy-saving measures need to be taken, such as improving the thermal insulation performance of the envelope structure, increasing sunshade facilities, and using energy-saving equipment. Generally speaking, the smaller the building size coefficient, the better the energy-saving performance of the building, because the smaller the external surface area, the smaller the heat transfer loss, and the smaller the heat consumption. For example, China's "Design Standard for Energy Conservation of Civil Buildings" (JGJ 26-2010) stipulates the limits of the size coefficient of residential buildings in different regions, as shown in the following table:
Region |Size coefficient limit |
Severe cold area | 0.4 |
Cold Regions | 0.5 |
Temperate Regions | 0.6 |
Hot summer and cold winter areas | 0.7 |
Hot summer and warm winter area | 0.8 |
If the size factor of the building exceeds the limit, it is necessary to make a comprehensive judgment of the thermal performance of the envelope structure, or take other energy-saving measures to reduce the energy consumption level of the building.
Evaluate the aesthetics of the building. According to the function and style of the building, the building size coefficient should meet certain aesthetic standards, otherwise the shape and appearance of the building need to be adjusted to improve the aesthetics and coordination of the building.