Green building starts from "face"

In recent years, green buildings have become very popular and the market space of trillions of yuan has become the focus of attention. In the enclosing structure of a multi-storey building, the energy consumption of the roof accounts for 8% of the total energy consumption of the building, while in a single-span long-span building, the energy consumption of the roof accounts for 25% 40% of the total building energy consumption. The use of green roofing system technology has little impact on construction cost. Energy conservation, consumption reduction, environmental protection and material saving are obvious. Recently, the 11th China International Roofing and Waterproof Technology Exhibition held a green roof system technology theme forum, attracting many people in the industry to stop. The forum brought a new trend to the construction waterproofing industry and provided advice for the development of green roofing system technology.

Has good thermal insulation properties

Zhu Dongqing, chairman of the China Building Waterproofing Association, said that the green roofing system technology includes planting roofing, heat reflecting roofing, single-layer roofing, photovoltaic building integrated roofing and ventilation tile roofing systems, and it has energy conservation, environmental protection, ecology, and suppression of the urban heat island effect. Recyclable, extended roof life and coexistence with nature and other functions.

According to statistics, at present, the roof area of ​​various types of existing houses in urban areas in China is more than 7 billion square meters, and the roof area of ​​various types of existing houses in rural areas is approximately 18 billion square meters. More than 25 billion square meters of roofing, which is basically the traditional roof structure of flat roofs and slope roofs, is mostly made of traditional building materials. It only considers the basic functions of building shelter from wind and shelter from rain, and it has high energy consumption, many consumables, and roof insulation. The problems of poor insulation, serious leakage, short service life, lack of recycling, lack of environmental protection and beautification functions cannot meet the needs of sustainable development.

Zhu Zhiyuan, an expert of the China Construction Waterproofing Association, said that roofing is a kind of building external protection structure, which causes heat transfer between indoor and outdoor temperature and heat consumption, which is greater than the heat loss of the same area outside the wall or the ground. For example, in the envelope structure of a multistory building, the energy consumption of the roof occupies 8%-10% of the total energy consumption of the building, while in a single-span long-span building, the energy consumption of the roof occupies 25%-40% of the total energy consumption of the building. . In this sense, the energy saving potential of building roofs is huge, and the use of green roofing system technology has little effect on the construction cost, so the “green” benefits are significant.

Waterproofing of buildings is essential

The ecological effect of roof greening is remarkable, and it looks very green and comfortable. However, experts pointed out that the greening of the roof, the first is to ensure the safety of the building, mainly in the load, structure and waterproof. Taking water as an example, JGJ155-2013 "Technical Specification for Planting Roofing" stipulates that the roof greening and waterproofing layer shall meet the requirements of first-class waterproof and fortification, and the reasonable service life shall not be less than 20 years; a waterproof layer must be provided with a rooted puncture resistance Waterproof materials; In order to ensure the safety of the roof structure, the secondary roof shall be waterproofed on the original roof before the roof is greened.

Professor Han Lili, a professor at the Beijing Institute of Landscape Architecture, said that one of the key requirements for roof waterproofing is the waterproof material used for roof greening. Root puncture must be done before use. The waterproof material was placed in a scientific research institute for two years. Induced puncture with plant roots was performed. After two years, the results were found. If the penetration was thorough, the material was not qualified.

The Beijing Institute of Garden Science has been conducting waterproof puncture-resistant puncture experiments since 2006. At present, there are about 120 samples, and the experimental pass rate is very low. According to the standard regulations, waterproof materials suitable for roof greening basically have kinds and thickness requirements. For example, the modified asphalt polyester waterproof membrane (SBS) should have a thickness of not less than 4 mm; polyvinyl chloride (PVC) should not be less than 2 mm thick. The penetration rate of the water-resistant material for puncture resistance test is low, indicating that there is still much room for improvement in product quality. If manufacturers want to do something in this market, they must begin by improving product quality.

Green roof technology tends to mature

Zhu Zhiyuan said that the change in the value of heat flux throughout the roof of the green roof is extremely weak, and the insulation and heat insulation of the roof of the building roof is obvious. The average green room temperature in summer is 2°C-4°C lower than the unglazed roof room temperature; the room temperature in winter is 1°C-3°C higher than the unglazed roof room temperature in winter.

It is reported that the current domestic green roofing system technology has matured. Taking ventilation roof system technology as an example, it is mainly applied to tile roof systems in hot and hot summer and warm winter areas, and meets the requirements of GB50378 “Green Building Evaluation Standards” for thermal performance of enclosure structures, and can optimize the design of structural systems. Achieve material saving effect. At present, China has formulated relevant product standards and engineering technical specifications.

For single-layer roofing systems that can achieve waterproof and thermal insulation construction, the project specifications have also been established. Zhu Zhiyuan said that the materials used for single-story roofing, such as PVC, TPO, EPDM, and modified asphalt, all have current product standards. The Technical Regulations for Single-Layer Roofing Engineering has been submitted for approval and it is estimated that this year will be formally promulgated.

At present, many residential buildings in the city use solar systems to green roofs. The traditional method is a mounting type, which uses a large number of single-crystal silicon and polycrystalline silicon battery modules of a glass substrate and is mounted on the roof by means of a bracket. However, in the eyes of industry experts, this is not a real realization of PV building integration. Because the solar panel assembly is placed on the roof, it will cause some damage to the original roof and waterproof layer. In addition, the weight is heavy and the wind load is different from the original roofing system. Compared to the roofing system, it is much more demanding.

Photovoltaic building integration is the development direction of solar roofs, and thin-film solar photovoltaic modules of flexible substrates may be the preferred material. The flexible photovoltaic module can be laid directly like a waterproof membrane, completely fitting with the roof, and being lighter in weight, without any damage to the original roof structure.