The city is full of high-rise buildings, and under the beautiful appearance, do you know the difficulty of the work of the energy conservation officer?Exposed to the sun in the summer and cold in the winter, people thought of wrapping. However, in the process of use, in the face of temperature changes in different seasons and regional differences in climate, the actual energy-saving effect of curtain wall film is the opposite of the well-known market publicity effect.
In this context, we will comprehensively and scientifically understand the energy consumption of architectural glass film through professional literature research.
In this paper, the energy plus software is used to study the changes in the energy consumption of building glass film in cold areas (Beijing) and hot summer and cold winter areas (Shanghai). The object of the study is an old office building, with a construction area of 32,000 square meters, a total of 20 floors, a height of 4 meters, facing south, 40 meters long from east to west, and 40 meters long from north to south.
Simulating Building Parameters:
1. Enclosure structure.
The thermal parameters of the literature refer to the "Energy Conservation Design Standards for Public Buildings" promulgated in 2005, and the parameters are set according to the thermal requirements of different climate zones.
2. Interior design parameters.
3. Thermal parameters of the translucent envelope structure:
The single-layer white glass window and the medium blank glass window were respectively pasted with two energy-saving films, namely low-emissivity film and heat-reflective film, and the heat transfer coefficient U value, solar heat gain coefficient SHGC value and visible light transmittance of the two exterior window types after being coated with two different films were calculated to a certain extent.
1) Heat transfer coefficient U value: Compared with the medium blank glass window, the U value of the single-layer white glass window changes more obviously, and the U value of the low-emissivity film decreases by 25%.The heat reflective film dropped only 68%。
2) SHGC value of solar heat gain coefficient: compared with the medium blank glass window, the shading effect of the single-layer white glass window is more significant, and the U value of the low-emissivity film of the single-layer white glass window is reduced by 70%.Heat-reflective film decreased by 73%.
3) Visible light transmittance: According to the "Code for Energy-saving Design of Public Buildings" (GB50189-2015), the window-to-wall ratio of a single façade of Class A public buildings is less than 04. The visible light transmittance of the light-transmitting material should not be less than 06；Greater than 04. The transmittance of visible light should not be less than 04。The visible light transmittance of the glass will decrease constantly, and it is not adjustable, which is difficult to meet the requirements of the specification, which will affect the indoor light comfort.
4. Energy Plus software simulation results.
According to the simulation data, the energy-saving rate of single-layer white glass window paste low-emissivity film in severe cold areas (Beijing) is 21%, the energy saving rate of the heat reflective film is 05%；The energy saving rate of low-emissivity film is 06%, with heat reflective film energy saving rate of 01%。
The energy saving rate of single-layer white glass window pasted low-emissivity film in hot summer and cold winter area (Shanghai) is 29%。The energy saving rate of the heat-bearing reflective film is 19%；The energy saving rate of the low-radiation film is 06%。The energy saving rate of the heat-bearing reflective film is 03%。
The conclusions of the literature study are obvious:
After the low-emissivity film is applied to the medium-blank glass windows widely used in buildings, the energy-saving rate in Beijing and Shanghai is 06%, after the addition of reflective film, Beijing's energy saving rate is only 01%。Considering other factors such as air-conditioning equipment in the real life environment, there are still doubts about whether the actual energy saving rate of the blank glass window after the film can achieve the effect of the simulated data.
Finally, it is worth mentioning that, judging from the above-mentioned simulation data of the solar heat gain coefficient SHGC value, all the films block the outdoor sunlight heat from entering the room. In the process of practical application, it is an effective means to achieve building energy conservation by blocking sunlight heat from entering the room in summer and keeping sunlight heat entering the room in winter. This minimizes the energy consumption caused by the translucent envelope. Although the film can reduce the solar heat entering the room in summer and reduce the energy consumption of air conditioning, the reduction of sunlight heat into the room in winter will increase the heating energy consumption, and the two are offset, and the contribution rate of the glass film to the energy saving of the building is very limited.
To sum up, would you still choose film to solve the problem of building energy efficiency?The follow-up will take you to continue to interpret the energy saving of architectural glass film in different quarters, and see you in the next issue.
References: 1] Yu Ziwei. Simulation study on energy consumption of glass film in existing office buildings[D].Hebei University of Technology, 2022doi:10.27105/d.cnki.ghbgu.2020.000116.