Potential of ETFE Film Membranes to Expand the Range of Architectural Expression

In the summer of 2020, Nissan Motor’s limited-time facility “Nissan Pavilion” opened in the Minato Mirai 21 district of Yokohama. This facility is a place where visitors can experience various images of the future mobility society envisioned by the company. Soft curved surfaces rhythmically interlock to form a circle that changes its appearance with the passage of time and the way the light hits it. What makes the pavilion stand out and unique is the membrane facade that surrounds the front of the building.

The material used is ETFE film, a high-performance fluoropolymer rolled into film form. It is characterized by its high durability and transparency, and is now attracting a great deal of attention in Japan and abroad as a material that expands the possibilities of architectural expression.

Characteristics of ETFE film membrane structure: As a transparent building material replacing glass

ETFE film membranes are transparent, lightweight, and can be easily formed into any shape. Overseas, ETFE film has been used in many advanced architectural projects, including the Eden Project, a huge environmental complex in Cornwall, England, and the Allianz Arena, the site of the World Cup finals in Germany. The unique form created from ETFE film is attracting a great deal of attention as a new architectural style.

Feature 1 Ultra-lightweight: Contributes to improved earthquake resistance and construction efficiency

One of the main characteristics of ETFE film membrane material is its light weight. Compared to other common building materials (steel plate (1.6mm) 12.6kg, aluminum (2mm) 5.4kg, glass (2mm) 5kg), it is extremely lightweight, thus reducing the load on the building frame and greatly contributing to improved earthquake resistance, as well as improving efficiency in material transportation, storage and construction. It also contributes to improving the efficiency of material transportation, storage, and construction. In addition, it also contributes to improving the efficiency of material transportation, storage, and construction.

Feature 2 Durability: Maintains high transparency over a long period of time

ETFE film membrane materials have excellent weather resistance to ultraviolet rays and rain, as well as high durability performance in terms of strength. The service life of ETFE film is more than 20 years, and the change in transmittance over time as measured by outdoor exposure tests has proven that ETFE film maintains its high transmittance over long periods of time with almost no yellowing, in contrast to vinyl chloride, which drops to 40% in 3 years, and polyolefin, which drops to 70% in 6 years. This high weatherability and durability also leads to a reduction in daily maintenance costs, such as eliminating the need for periodic cleaning required for glass buildings, even for the same transparent buildings.

Feature 3: Heat insulating and heat-shielding properties: Realizes the same thermal transmittance as glass

There are two major types of ETFE film membrane structures. One is the “tension method,” which consists of a single film supported by a frame or cable, as in conventional membrane structures. The other is the “cushion method,” which consists of multiple layers of film and inflates the interior with air.

Of the two structural types, the “cushion method” greatly expands the possibilities of architectural styles. A lens-shaped cushion inflated with air reduces the stress generated on the membrane surface to form a large grid. Complex designs can be expressed by combining the two. In addition, the internal air layer has the effect of suppressing heat release, achieving a thermal transmittance equivalent to that of glass. This allows for a wide range of applications, including large spaces such as stadiums and atriums, where livability and comfort are required.

An air blowing system automatically controls the internal pressure inside the cushion to withstand external loads such as wind. Tension force is also automatically managed for optimum performance through the same internal pressure control system.

Feature 4 Transparency: Flexible brightness by combination of films

ETFE film membrane materials maintain high light transmittance in all regions of ultraviolet, visible light, and infrared rays. In the case of transparent materials, visible light transmittance is over 90%. ETFE film is available in five types according to optical characteristics: transparent, pear-shaped, white, blue, and dot print. By combining these materials, the amount of light taken into the interior can be freely controlled.

Combining stadium comfort and turf growth issues

The high light transparency of ETFE film membrane structures is attracting attention in many architectural fields, but the focus of particular attention is on stadiums for soccer and rugby. However, the roof reduces the amount of sunlight that falls on the field, which can greatly inhibit the growth of turf grass. To solve this problem, conventional methods include seasonal turnover between summer and winter turf and artificial LED lighting to accelerate turf growth, but these methods have been a major burden on stadium management costs. In contrast, the high light transparency of the ETFE film membrane structure allows the roof to maintain a comfortable spectator environment while at the same time allowing sufficient sunlight to reach the turf, thereby greatly reducing the cost of turnover and other turf protection and cultivation. In addition, because sunlight can be secured even when the entire ceiling is covered, the stadium can be used for live music performances and various other events, regardless of weather conditions.

Feature 5: Light effects: Buildings are dressed in light.

昼間は高い透光性によって快適な明りを室内に導き、自然光による空間演出ができる一方、日没後の夜間は照明によってまったく違った印象を演出できるのもETFEフィルム膜構造の大きな特徴です。内部照明だけでも十分な光演出は可能ですが、ETFEフィルム膜構造はLED照明設備との親和性が高く、その組み合わせによって独創的で訴求性の高い夜間の光演出を行うことができます。

LEDの調色機能を活かし時間、季節、歳時などに合わせて変化させる。膜を通して広がる柔らかな光の拡散は、外部照射によるライトアップとは異なり、まるで建物が光の衣装を纏ったかのようになり、建築表現の可能性を大きく拡げ、アイコン、ランドマークとして建物の存在価値を大きく高めます。

Example of domestic construction: Combination of overseas construction experience and cultivated know-how of membrane construction

Although ETFE film membrane structures are being introduced overseas, there are not many examples in Japan, where ETFE film has been used on an experimental basis since around 2000, mostly for small-scale projects such as temporary structures for events.

Now that the legal framework has been developed, including the approval of ETFE film as a building material and membrane structure, it is expected that ETFE film membrane structures will attract even more attention in Japan in the future due to the many advantages of the material. While many possibilities as a construction material are expected, in order to take full advantage of the features of the ETFE film membrane structure, various innovations and know-how that have never been seen before are required in terms of design and construction. Taiyo Kogyo, through its overseas group companies, has a wealth of experience in design, processing, and construction, as well as a wealth of know-how in membrane structural buildings that it has cultivated over the years. Here we introduce some of the leading examples of ETFE film membrane structures in Japan that we, a leading company in membrane structures, have worked on.

Case Study 1: Repeatedly examining every detail to find the optimal solution: UNIQLO Shinsaibashi store

The pioneer of ETFE film membrane construction in Japan was the facade of the UNIQLO Shinsaibashi store (Osaka), which opened in 2010. At the time, it was not yet approved as a building material, so it was used as a “decorative surface material for fire-resistant exterior walls.
The cushion structure is made of ETFE film injected with air. With a design reminiscent of the company’s down jackets, the building exterior itself functions as an icon of the store, and at night, LED lighting creates a variety of different expressions, attracting the attention of people on the street. In designing and constructing the UNIQLO Shinsaibashi store, a full-scale mockup was created as the first full-scale building in Japan to use an ETFE film membrane structure. While viewing the prototype, we worked together with the designers to repeatedly examine every detail to find the optimal solution, including grid dimensions, packaging, transportation, and lighting methods.

1) Grid considerations

The design load is the wall load of the exterior material for use as a finishing material. The grid size was calculated to be 2.7m square per side as the maximum value to meet the designer’s image.

2) Detail

Flat type, V-shape type, V-shape + groove type, etc. were considered for the aluminum hardware to fix the ETFE film. The V type was adopted based on the designer’s intent.

3) Processing and manufacturing

Multiple film cutting patterns were considered to create a cushion with a natural curved surface. Repeated implementation of mockups led to the optimum values for a wrinkle-free, beautiful finish.

4) Lighting

Various production patterns were verified from the mock-up stage.

5) Packing and transportation

To prevent film from being scratched or folded during packaging and transportation, the film is covered with a paper tube and then transported in a wooden box specially designed for film.

6) Construction Procedure

All aluminum frames are dimensionally inspected during the manufacturing process to meet high precision requirements. Dimensional accuracy is set within ±2mm. In addition, the accuracy of the support frame is secured to accommodate on-site installation errors.

 

 

Case Study 2: High-Dimensional Fusion of Design and Technology: Shin Toyosu Brillia Running Stadium

Shin Toyosu Brillia Running Stadium, located in Toyosu, Koto-ku, Tokyo, is an all-weather exercise facility that opened in 2016, creating a beautiful tunnel-like form by creating surface rigidity with a steel frame structure that supports the ETFE and a network of timbers from within. The ETFE is the centerpiece of the design of the building, and the ETFE is a unique facility in the Toyosu area.

The ETFE membrane, the centerpiece of the design, is made of two layers of film and uses a cushioning system that sends air pressure into the interior. Unlike conventional roof construction, installation work cannot be performed on the roof itself. Therefore, careful design and construction plans were developed based on optimum tension, wrinkle-free beauty, and construction efficiency, and simulations were repeated several times in advance using mockups.
The high translucency of the ETFE film membrane is a key factor in the design of this facility, as it is used to cover the majority of the roof. However, when the majority of the building is covered, as is the case in this facility, internal temperature rise can be a problem. In this facility, silver dots are printed on the outside and white dots on the inside of the two-layer film to reduce the transmittance from approximately 90% for one film to approximately 35% for the two films combined. In addition, a ventilation function is provided at the top to maintain the optimum balance between brightness and indoor temperature.

The Shin-Toyosu Brillia Running Stadium, which was highly evaluated for its overall strength in terms of design, structure, design, and construction, received the 2019 Architectural Institute of Japan Award (Work), the Japan Structural Design Award, the Good Design Award, the BCS Award, and other major architecture-related awards in Japan. In addition, it was nominated for the DFA (Design for Asia), GRAND AWARD, and FRAME Award (Netherlands), and has received high acclaim both domestically and internationally.

summary

In 2014, it was added as a designated building material in the Building Standard Law for membrane structural films, and in 2015, the Ministry of Land, Infrastructure, Transport, and Tourism established a notification regarding fire prevention, expanding the scope of its application in construction, The adoption of membrane structures in stadiums, sports facilities, and atrium spaces is expected to expand in the future.

The ETFE membrane structure has many possibilities for architectural expression, including transparency, light weight, safety, durability, heat shielding, and other functions, as well as design and light effects. In the era of full-scale ETFE membrane structures in Japan, Taiyo Kogyo, as the top runner, will respond to all needs by adding the latest research and development to its accumulated know-how, and pioneer the future of membrane structure architecture.

 

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