Texas Medical Center Features State’s Largest Green Roof

WEBSTER, Texas — The Houston metropolitan land market and simple long-run economics pushed Jacob White Construction to develop the three-story East Medical Center project around environmentally sustainable technologies that may win LEED gold certification with the largest living roof in the state, according to officials.

But company president Jeff Mickler also sees the project, which features two 48,000-square-foot medical buildings, as a marketing tool that can differentiate Jacob White in the market.

“We wanted to show the industry that there is a better way to build,” says Jeff Mickler. “We wanted to make a statement with this project and use it as a model.”

The economic realities of upwardly spiraling land prices and declining availability of affordable medical office space across the Houston area forced developers to adopt an unconventional design and construction approach that would make the medical center viable.

“Our goal was to develop a high-performance office building that would be affordable not only to build, but to occupy as well,” Mickler says. “It’s about dealing with the realities, overcoming challenges and moving forward in ways that are smart and sustainable, but also practical.”

The living roof system, which includes gardens, walking paths and lush landscaped spaces, promised significant reductions in resource consumption and improvements in building performance, while delivering lower operating costs. The system also offered a quick installation time with relatively low costs.

“It’s not just about doing the right thing and saving the environment; sustainability is a money maker,” Mickler says.

The 15,000-square-foot living roof, which sits atop the first of the complex’s two buildings, represents the project’s most visually impressive, but challenging, component.

The high front-end costs and lack of design flexibility of stock green roofing systems forced Mickler to go back to the drawing board to find a more workable solution for his development.

“You could say we were forced to invent a better mousetrap,” Mickler says. “In the end, we basically created our own system, using the local economy to incorporate individual elements from different systems.”

The rooftop vegetation works to reduce the heat island effect normally generated in urban concrete environments and the system provides a R-68 insulation rating with three distinct layers. “We’re seeing a 30 degree temperature differential between the roof surface, which might be 110 degrees, and the interior that would be roughly 75 degrees,” Mickler says.

A 4-inch layer of rigid foam insulation board with a protective coating is installed directly onto the concrete and steel roof structure, while a 40-mm reinforced waterproofing membrane is laid over the insulation, roof sidewalls and drain assemblies.

The system’s third layer features a drainage and water retention composite layer, which is installed on top of the loose-laid membrane before the addition of a 9-inch top layer of soil mixture.

“When you install a living roof, you’re eliminating the effects of all the usual elements that destroy traditional roofing systems, from UV to moisture to wind,” he says.

Manufactured by Colbond Inc. of Enka, N.C., for use in green roofing installations, the Retain & Drain composite layer provides the key to the whole roofing system and is designed to hold 10 to 12 times its own weight in water, officials say.

The layer consists of a post-industrial, recycled polypropylene drainage core, which is fused and molded into a square waffle pattern, before an absorbent water retention fabric is heat-bonded to the drainage core.

Approximately 75 percent of rainfall that strikes the living roof is retained to sustain vegetation. The remainder is directed to roof drains, which channel the runoff to an underground storage cistern.

A self-replenishing irrigation network, which comprises 700 feet of concrete culverts leading to the cistern, was built beneath the facility’s parking lot. The 175,000-gallon rainwater storage unit will fulfill the facility’s entire irrigation and grey water requirements, reducing water demand and consumption from the city.

“Our water bill is 70 percent less than the building beside us,” Mickler says.

Developers incorporated several other energy- and resource-efficient technologies and systems throughout the project in order to optimize operational costs, environmental impact and interior environmental quality.

“We knew we could save a tremendous amount of power, and we’re operating at 60 to 70 percent less than a more traditional building,” Mickler says.

The building features high-efficiency exterior walls with a high-performance heat-reflective glazing system that reduces energy consumption and waste by providing a solar/heat barrier.

The HVAC system, which is designed to reduce energy consumption, utilizes fresh air for facility air conditioning and features HEPA filters to improve indoor environmental quality. Developers also used low-VOC materials throughout the building.

Each of the facility’s individual sustainability components complement each other to create a robust overall building design.

“We feel like we’re setting an example and raising the bar for everyone around us,” Mickler says.

Mickler says Jacob White Construction has been incorporating green techniques into their buildings during the 1980s, before the current trend toward environmental sustainability.

With two more green projects planned for 2007, Mickler says the company is reorienting itself to focus more on green construction. “Everything we do in the future will have some flare of green to it,” he says.

In May, the building development and management company divested itself of the last of its non-green holdings.

“We’re redeveloping our portfolio to become entirely LEED-certified,” Mickler says.