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Mountains & Canyons in Midtown: The Jerde Partnership’s Namba Parks Green Roof

Interview with Jeri Oka, by Leslie McGuire, managing editor

The mid-day surface temperatures in August average 62 degrees cooler on Namba’s roof than on the surrounding asphalt surfaces. That’s why there are so many activities. It’s a nice place for people to gather socially. In urban areas there aren’t a lot of areas for young people to congregate, and Namba is especially romantic.
All Images courtesy of Hiroyuki Kawano

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Namba Parks—a rooftop park that crosses multiple blocks while gradually ascending eight levels—creates a new natural experience for Osaka that celebrates the interaction of people, culture and recreation. When the baseball stadium closed its doors, it opened the door to a prime redevelopment opportunity in a new commercial district adjacent to the Namba Train Station, the first stop from Kansai Airport.

Namba Park includes more than 300 different types of plants and there are approximately 70,000 individual plantings on Namba’s 1.3 acres of green. The overall roof is 2.8 acres with the other parts as gathering spaces and walkways or hardscapes.

Nature Intervenes

Given the location, owner Nankai Electric Railway asked The Jerde Partnership to create a gateway that would redefine Osaka’s identity. So Jerde conceived Namba Parks as a large park, a natural intervention in Osaka’s dense and harsh urban condition. Alongside a 30-story tower, the project features a lifestyle commercial center crowned with a rooftop park.

Jeri Oka did the initial conceptual work for this 8.3 acre park while at EDAW, and then went on to complete the design and implementation as Partner and Director of Landscape of The Jerde Partnership.

“The overall work is very keyed into the idea of nature, which becomes a large part of our reference since it’s a key component of how people interact with a place. Part of the philosophy is really about creating an experience. Even though it began as a retail venue, ultimately it became about how we actually captured the sense of the project and used nature as that kind of metaphor. We looked at the history, the context in nature and used it interdependently.

“We tried to get as much greenery as possible,” says Jeri Oka, “but there’s so much traffic coming through there it becomes somewhat of an impediment. Up to the other levels, you can go into the smaller garden spaces and those are much more park-like. There are also a lot of activities surrounding the plants, not just the standard annual color change outs. Since there are so many species, a whole program makes sure there’s something different to see all year round.”

“What is interesting about Namba Parks was the building, which was an old triple-A based stadium. In addition all the people going from the railroad station and the subway connection would pass through. When John Jerde saw the site, he realized it was all asphalt and said, ‘Wow there is no sense of greenery here.’ John has always felt that people need to get back to nature. That was the kernal of why we were asked to do the project and that was also the program of the client.

“They asked us to do a mixed-use project, but at that time it was primarily a retail and entertainment venue with a residential component to come. The park starts on the second level. The ninth level is the top part of the roof. The project is a rooftop park or garden which is used to get to the various interior retail levels. It was always realized as a park with the metaphor of a canyon that splits open.

“In addition Namba Parks acts like a botanical garden. There is signage that identifies each type and species of tree, flower and shrub. There’s quite a variety in the landscaping—with 84 species of tall trees alone measuring over 2.5 meters in height. People can go to the web site where there is a monthly calendar, which let’s them see what’s in bloom and what kind of plants they can see in each season. Another interesting fact about the park is that in Asia, parks are done more architecturally, and don’t use that kind of vocabulary. Namba has a more residential and botanical feel and people really enjoy that.”

In addition to providing a highly visible green component in a city where nature is sparse, the eight level sloping park connects to the street, welcoming passers-by to enjoy its groves of trees, clusters of rocks, cliffs, lawn, streams, waterfalls, ponds and outdoor terraces. Beneath the park, a canyon carves an experiential path through specialty retail, entertainment and dining venues.

A Very Grounded Sensation

Originally, the building was a baseball stadium with asphalt parking. That fact alone opens the discussion about the urban challenge that is required when you try to create a site in a highly dense urban area while introducing something that has nature. Even the planters give you the feeling that you’re on the ground. You feel as if you are within a garden, not just on a roof with planters. They tried to think of clever, easy ways to design the planters so people can also sit on them and interact with the plants.

Namba was Jerde’s first roof top park. They did another roof top park with a garden that also feels as if you are on grade because of the terraces. The other real challenge with the structured roof top gardens they deal with is the issue of shade. The buildings surrounding the rooftop create shade. Many different kinds of enclosures are created. “You have to cleverly plan your spaces so people get a diversity of planting. At Jerde we always take a look at that. Shade is very welcome because it is so humid in Osaka. We have to make sure we work with a local landscape architect to find out what plantings grow best in those conditions.”

The residential tower phase opened in 2007 creating a second portion to the project. The connective bubble element creates easy access from the residential area to the retail area. The bubble also creates another place of gathering. The large crystal dome acts as an anchor to the linear path that intertwines through the special garden areas.

They also had to deal with wind. By using trees as natural windbreaks, they can bring another sustainable gesture to protect people. The key requirement is to create comfort. A lot of the principles they bring are applicable internationally They try to create external environments that people aren’t used to. A lot of South Pacific people are sceptical about being outside, so they use lattice structures, trees and wind that allow people to be outside.

There are different types of hardscaped surfaces for the walkways and gathering spaces—with some use of reconstituted wood or decomposed granite. “Since we were trying to create the look of a natural park environment we also introduced other sustainable elements for the future,” says Oka.

Creating a Novel Retail Environment

If you take it one step further, you see they are creating a different kind of retail model—one that people like to go to. They can have outdoor dining, outdoor bars where people can sit outside and people-watch—and all by using the natural environment rather than a fabricated method. “Of course, we always want to use as many natural elements as possible. But sometimes we can’t,” says Oka.

The “canyon walls” hold up parts of the park, but they look soft and sensual as if it really is earth. The natural undulation of the surface makes people feel good. The canyon is granite, as if water had trickled through and eroded the surface. It can’t be shiny. In addition, the surfaces have to be a bit rough because otherwise, people would slip.

“We try to make it as natural as possible. People have an innate need to be connected to nature. Many times, what limits you are the structural conditions, especially of a roof. The height of building, the clearance height of the parking levels, as well as all the other uses have to be dealt with. You are also going to be bringing water up and you have to drain the walking spaces. When that level of plaza is way up in the sky, everything becomes an artificial envelope.”

“If we can get in on the design discussions early, we’re able to structure the project to handle the weight load of the vegetation. That structured weight load is a big reason why we can use a lot of vegetation. We use design to allow for much bigger specimens,” says Oka.

Adjusting the Weather

But in the long run it’s all about sustainability. An Environmental Benefits study of Namba Park was conducted in 2003-2005. The rooftop garden reduced the cooling load on the project’s top floor by 22.7 MJ (megajoules) per square meter. The sensible heat emitted into the atmosphere was 37.2 percent less than a similarly sized concrete surface.

And this is very important when the mid-day surface temperatures in August average 62 degrees cooler on Namba’s roof than on the surrounding asphalt surfaces. “A green roof cuts the cost of heating in the winter and air conditioning in high heat and humidity. It’s how people began and we’ve lost sight of that. The initial cost may be higher but, in the long run, you’re saving money. A green roof also deals with the urban heat island phenomenon.”

“What’s really very interesting about the Namba Roof Park,” Oka continued, “is that it is not just a contemplative garden. It also created a cultural space for the city, a place where activities can occur and it has become an event of its own. People use it as an amenity. They use it as their own back yard in a highly urban environment.”

In winter the garden changes and there are different kinds of events. Although there is some tree protection from wind, there is not as much sitting around when it’s cold. The plantings go through bloom phases with flowering dogwood, cherries, mountain peach and azaleas, as well as basic plant materials such as rosemary that survives nicely in winter. White oaks are evergreens as are bayberries. That foliage holds up well in a lot of the areas.

According to Oka, “We can create pits for the root balls and from a cost perspective we can isolate the expense of doing on-structure plantings because it is about two times more if you are using natural grade and creating an artificial planter and container of soil. You have the cost of the container and the structural cost of live loads.”

A Constructed Narrative

The garden also deals with senses. You can see, smell, hear and touch. Aspen or cottonwood’s leaves shimmer and bamboo groves have funny, spooky sounds giving a different, more spiritual sensation. There are seasonal and/or weekly programs, and there are always new things to discover. The way the spaces are intertwined allow people to discover and interact with the vegetation. On the whole, this constructed canyon is filled with natural events, sights and experiences that bring a whole new meaning to the world of roof gardens.

Namba Awards

  • Finalist, ULI 2006 Awards for Excellence: Asia Pacific, Urban Land InstituteGrand Award, 2005 Superior Achievement in Design and Imaging (SADI) Awards, Retail Traffic magazineBest New Open-Air Center, 2005 Superior Achievement in Design and Imaging (SADI) Awards, Retail Traffic magazineCertificate of Merit, Innovative Design and Construction of a New Project, 2005 ICSC International Design and Development Awards , International Council of Shopping Centers
  • 2004 Good Design Award, Architecture and Environment Design, Good Design Award (Japan)

Project Team

  • Landscape Concept Designer: EDAW (Jeri Oka was a principal for EDAW at the time.)Landscape Executive Architect, Phase I: HEADSLandscape Contractor, Phase I: Tsujimoto RyushoenLandscape Executive Architect, Phase II: E-Design
  • Landscape Contractor, Phase II: Namba Parks Landscape Dept.

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November 18, 2019, 10:40 am PDT

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