Natick's lush garden in the sky

Mall rooftop to host greenery for condos

An artist's rendering of Parc Nouvelle in Natick, soon to be the largest roof garden in New England. (NOUVELLE AT NATICK)

NATICK - Most mall rooftops look like dumping grounds for exhaust fans and industrial pipes.

Aaron Bartels, senior development director for General Growth Properties Inc., which opened the Natick Collection last year and is now completing an attached 215-unit luxury housing project called Nouvelle at Natick, said retail roof space has traditionally been "the most overlooked real estate in any building." Not any more.

Seventy feet above ground level, construction is set to begin on Parc Nouvelle, the largest rooftop garden in New England, a 1.2-acre experiment in residential living, energy conservation, and drought-resistant botany.

The garden has been planned for years, but its relevance seems heightened in this time of heightened environmental correctness, as well as a housing market that has slowed dramatically since the condos went on sale two years ago.

Once the garden is built, it may help boost Nouvelle condo sales, lagging in the moribund housing market. Only 30 Nouvelle units have sold so far - for prices ranging between $500,000 for below-garden, one-bedrooms to nearly $1.5 million for the largest upper-level units.

Planners hope to have most of the drought-resistance plantings - including flowers, trees, and native grasses showcased in beds of black river rocks - in place by November, just as the first wave of occupants is expected to move into their condominiums.

Three-quarters of the Nouvelle units are designed to look onto the gardens. The most expensive will also look out onto private landscaped terraces - and two small three-hole putting greens - from upper penthouse levels.

"This is their Central Park," Bartels said during a rooftop tour last week. Shortly before, workers had begun laying down egg-crate-like rubber insulation, a three-quarter-inch membrane that will hold and distribute water to the roots of the plants while protecting the upscale shopping galleries below from an estimated 3,000 tons of soil, water, planters, and greenery.

"With retailers like Tiffany and Gucci below us, you don't want any leaks," he quipped.

The garden is not only meant to be beautiful to look at and a pleasant place to stroll, sit, or entertain guests - it is also one of the most environmentally correct construction projects in the region, according to Bartels.

Layers of insulation and soil, moisture sensors, and drip irrigation reduces its water consumption to just 12,000 gallons per year, the amount used by the average American single-family home. Bartels said the same amount of land and plantings traditionally requires 1.2 million gallons per year.

Natick officials originally declined to give the mall permission to tap into municipal water supplies for irrigation, but reversed their position after learning how little water would be consumed.

General Growth attempted to drill wells on the mall property for the garden, but came up dry, said Robert Bois, Natick's environmental compliance officer. After the company made its case about how conservation-minded the garden would be, the Natick Planning Board, with support of the town Conservation Commission, decided to grant access to its water.

"It's a great project," said Bois. "It allows for use of a number of energy-saving measures that we hope will reduce greenhouse gases. We felt it set a standard that hopefully, other people will be able to replicate."

Rooftop gardens have long been popular among urban apartment dwellers craving a green spot in a cement jungle, but were not in demand in the suburbs, where there is more open space for plantings. But sprawl and congestion have led to the reinvention of vertical surfaces even in less-urban communities.

"Land getting scarce here," said Bartels. "The roof is the new ground plane."

Roof gardens have sprouted in recent years on many city buildings, including the Boston Marriott hotel, the Boston Children's Museum, and Massachusetts General Hospital. This summer, Dorchester restaurant dbar is growing tomatoes and herbs on its roof, and a upper level parking lot at Boston Medical Center is being used to plant 6,000 square feet of crops by the Food Project, based in Lincoln, which sells the produce at local farmers' markets and donates it to food pantries.

General Growth has retail-residential projects under development in Hawaii and Salt Lake City that are expected to incorporate rooftop garden ideas inspired by the Natick Collection project, Bartels said.

It isn't unfair that this first-of-its-kind roof garden is for private use only, he said.

"It's no different than someone having a great backyard. You can't just walk into their living room," he said. "This garden is someone's living room, and amenity for living at Nouvelle."

For future resident Michael Gould, Parc Nouvelle can't get planted soon enough.

Gould, 43-year-old regional sales manager, bought a one-bedroom, garden-level condo, and plans to spend a lot of time sitting on his small patio, enjoying the greenery.

The garden isn't the only reason he wanted to live at Nouvelle, which offers other amenities, he said.

"But I do want to enjoy a garden without having to do any upkeep," said Gould, who is renting nearby until his unit is finished. "And it's cool to be part of something that is so 'green.' My friends are definitely expecting me to throw a rooftop garden party when I move in."

Erica Noonan can be reached at enoonan@globe.com.