Why Does Rooftop Solar Need High Molecular Weight Waterproof Membranes?

Product End: Original roof waterproof grades cannot match solar module lifespans, making system upgrades inevitable.

Under traditional waterproofing standards, the reasonable service life is only 10 years, with minimal quality degradation. From the above discussion, it’s clear that BAPV is mainly used in storage buildings, whose waterproofing lifespan is typically shorter due to lower standards. According to the current 'Code for Roof Engineering Technology', roof waterproofing is divided into three grades. Industrial buildings typically require Grade II waterproofing, with a reasonable service life of just 10 years. Once used beyond 10 years, replacing the waterproof layer impacts the economic viability of the solar system.

Solar modules have much longer lifespans—typically 25 years—with only a slight decline in power efficiency afterward. Their actual operational lifespan may exceed 25 years.

According to data from the German Fraunhofer Institute, the average lifespan of solar power plants has increased from about 21.5 years in 2007 to around 32.5 years in 2019. This indicates a severe mismatch between roof waterproofing lifespan and solar plant operational periods. Roof leaks not only increase maintenance difficulty but also severely impact factory production and residents’ daily lives.

In this context, the 'Technical Code for Roof Engineering of Photovoltaic Modules (Trial Version)' issued by the China Building Metal Structure Association in 2018 requires the design service life of roof materials to match the solar system's design lifespan. If unmet, a repair or replacement plan must be provided. In 2020, the Ministry of Housing and Urban-Rural Development issued the 'Code for Roof Engineering Technology (Departmental Revision Trial Version)', explicitly stating that the design service life of roof engineering should be no less than 20 years. With the advancement of industry standards in solar and building materials, upgrading waterproofing grades has become an inevitable trend.

The modules and systems themselves cannot achieve high-performance waterproofing independently. Waterproof membranes play a critical role in reinforcement and protection. Rooftop solar waterproofing adopts the 'drainage-first, with waterproofing as a complement' approach, commonly using W-shaped (vertical) and U-shaped (horizontal) drainage channels combined.

Distributed solar installations in China are concentrated in northern, central, and eastern regions, with provinces like Shandong, Anhui, and Zhejiang leading in installed capacity. These areas receive higher rainfall than the national average, making drainage systems prone to backflow and leaks during heavy rain or clogged channels. Moreover, complex installation procedures increase the risk of errors and accidents. Thus, relying solely on bracket waterproofing cannot guarantee the long-term performance of distributed solar systems, requiring additional rooftop waterproof membranes for added protection.

Therefore, waterproof membranes are fundamental components of first-class rooftop solar waterproofing systems. Under the trend of upgrading waterproofing standards, waterproof membranes are one of the main technical pathways and occupy a significant market share. According to the 'Technical Code for Roof Engineering of Photovoltaic Modules (Trial Version)', first-class solar roof waterproofing systems must include waterproof membranes in addition to the structural waterproof layer. This suggests that future module lifespans will continue to extend, waterproofing requirements will grow stricter, and the demand for waterproof membranes will rise accordingly.

Installation End: Current installation techniques still have room for improvement, and prefabricated accessories could help resolve existing pain points.

Current bracket installation methods often lead to leakage risks. Whether for concrete or metal roofs, brackets are generally categorized into two types: drilling-and-plugging fixation and clamp-supported fixation. Both can cause roof leaks. Drilling-and-plugging brackets require drilling into the original roof, potentially damaging the existing waterproof layer. To prevent leaks, waterproof tapes or grouted seals are typically used, but neither fully seals the drilled area. According to the 'EPDM Rubber Strip Durability Calculation Method (Public Version)', the natural aging time of EPDM rubber strips is 10–15 years, while the actual service life is shorter. Over time, they will inevitably crack and leak. Clamp-supported brackets are typically made of aluminum alloys, which differ electrically from steel sheets, accelerating galvanic corrosion of the steel roof.

After installing plug-in brackets, the roof must undergo waterproof maintenance. Long-duration work may cause secondary damage. Traditionally, to address leakage risks from drilling, individual bracket waterproofing is performed: after bracket installation, cover the bracket base with waterproof membrane and connect it to the original roof membrane using hot air welding. Then, use fine-mesh membranes to wrap the entire bracket, joining it seamlessly with the main membrane to form a complete waterproof system. This process is complex, time-consuming, and increases the risk of secondary damage due to prolonged on-roof work. Additionally, workers may deform the metal roof, causing edge loosening and further compromising waterproofing integrity.

Integrated prefabricated components can combine waterproofing and mounting functions, speeding up construction. To solve the issue of secondary damage caused by separate waterproofing and bracket installation, waterproof companies have developed integrated fixed prefabricated components. These components use waterproof membranes to fully encapsulate the posts, with the base plate pre-formed in the factory. During installation, the component is rotated 90 degrees and secured to the steel sheet substrate, providing adequate wind resistance and protection for distributed solar roofs.

2.2.2 BIPV: Modules must bear building material properties. Waterproof membranes are indispensable today.

Unlike BAPV, rooftop BIPV replaces the original roof. While BIPV generates electricity, its most important feature is its building functionality. BAPV’s waterproofing aims to meet solar module lifespan needs, whereas BIPV’s waterproofing is essential because it serves as a building material. Currently, due to technological limitations, BIPV cannot yet replace the roofs of concrete public buildings and often appears as a covered design. However, in commercial and industrial metal roofs and residential applications, BIPV products capable of replacing original roofs have emerged, such as insulated BIPV roofs for industrial use and solar glass for residential homes.

From a product structure perspective, transparent BIPV uses translucent modules, demanding higher installation requirements. However, waterproof membranes and sealants lack transparency, limiting their application space. In commercial settings, roofs are typically metal, and current BIPV products integrate PV modules, insulation materials, waterproof membranes, and color steel panels into a unified system, fulfilling both power generation and building functions—replacing original roofs. In residential applications, solar glass currently only replaces traditional glass and slate, but the underlying roof still requires a waterproof membrane layer at the base.

Examining closely, commercial BIPV roof systems use an integrated sales model, with waterproof membranes typically included within the system. In current commercial BIPV products, waterproof membranes are pre-integrated into the system and sold together—meaning their use is already confirmed at the product stage. During subsequent installation, the membrane material is usually positioned above insulation layers and below PV modules, and the integrated installation considers the combination of the waterproof layer and brackets, ensuring the overall waterproof integrity of the BIPV roof system.

In residential applications, solar glass only replaces traditional glass and slate, but the roof still requires a base layer of waterproof membrane. In traditional concrete and asphalt tile roofs, the waterproofing is mostly borne by the membrane layer beneath the tiles. Solar glass merely replaces conventional glass and slate without carrying significant waterproofing responsibilities. Moreover, after replacing the glass, the need for additional brackets often damages the original waterproof layer. In open-source solar glass installation guidelines, solar glass must be installed on a waterproof membrane layer provided by manufacturers specializing in concrete tile roofs. Therefore, in residential applications, using solar glass still requires a base waterproof membrane layer.