Reasons for increased energy consumption caused by glass curtain walls

The main reasons for the increase in energy consumption caused by glass curtain walls include the following aspects:

Poor thermal performance

Small heat capacity: The heat capacity of glass curtain walls is much lower than that of solid walls, making them susceptible to weather changes, resulting in large fluctuations in indoor temperature and increasing heating and cooling loads.

High heat transfer coefficient: The heat transfer coefficient of single-layer glass can reach 5.7W/(m ² · K), which is several times that of ordinary walls, resulting in rapid heat loss in winter and a large amount of external heat input in summer.

The "thermal bridge" effect: Metal keel (such as aluminum alloy frame) is directly connected to the wall, forming dense heat transfer channels, intensifying heat transfer, and reducing insulation effect.

The sun radiates a lot of heat

Overheating in summer: Transparent glass curtain walls allow a large amount of solar radiation to enter the room, becoming the main load for air conditioning cooling. For example, in commercial buildings in Hong Kong, solar radiation accounts for over 50% of the air conditioning load.

Insufficient heating in winter: Although winter sunlight can partially compensate for heating energy consumption, the insulation performance of glass curtain walls is poor, resulting in overall energy consumption still higher than that of solid wall buildings.

Insufficient shading and ventilation design

Lack of external shading: It is difficult to install external shading devices on the glass curtain wall facade, which leads to direct sunlight indoors in summer and exacerbates the problem of overheating. Reasonable shading design can reduce air conditioning energy consumption by 16% -29%.

Natural ventilation is limited: Glass curtain walls are usually designed in a closed manner, relying on mechanical ventilation systems and increasing energy consumption. If an openable part or ventilation device is set up, it can improve thermal comfort and reduce energy consumption.

Airtightness and sealing issues

Defects in adhesive joint construction: poor bonding effect of sealant, inadequate sealing of rubber strips or structural deformation resulting in cracks, leading to the penetration of cold and hot air and increasing ventilation and heat transfer.

Frame gap air leakage: The existence of structural gaps between curtain wall frames causes airflow to penetrate the gaps, leading to heat transfer and further exacerbating energy consumption.

Material and structural defects

Improper glass selection: High performance materials such as Low-E coated glass and insulating glass were not used, resulting in poor thermal insulation performance.

Lack of insulation material: There is no effective gasket or insulation material between the curtain wall and the insulation layer, which reduces the overall insulation effect.

Chimney effect: The air flow between the curtain wall and the insulation layer forms a chimney effect, reducing the service life of the insulation structure and increasing energy consumption.

Design and construction issues

Excessive window to wall area ratio: In order to achieve transparency, the proportion of glass curtain wall area is too high, resulting in a sharp increase in heat transmission in summer and a large loss of heat exchange in winter.

Node method error: Failure to effectively set gaskets between components or improper connection of nodes, affecting air tightness and insulation performance.

Poor construction quality control: inadequate joint construction, aging sealant, and other issues lead to water leakage and breathability, further reducing the insulation effect.