Pre-Vegetated Tray Designed for Easy Transport and Installation

American Hydrotech introduces the InstaGreenGT-4 pre-vegetated trayAmerican Hydrotech introduces the InstaGreenGT-4 pre-vegetated tray, an expansion of the InstaGreen product line within the Garden Roof portfolio of assemblies. The GT-4 tray is one option for a storm water management plan by providing valuable green space as a best management practice on roofs to handle the first rains. It consolidates all growing media, drainage and vegetation in one convenient package for easy transport and installation by roofing professionals and landscape contractors.

According to the manufacturer, the tray is composed of 100 percent fully recycled content and its 12-inch-by-24-inch high performance format can hold up to 4 inches of media for optimum plant growth. It has a unique reservoir base design for increased water capacity and sustained plant growth in times of drought and perforated side walls to promote inter-tray root growth and water transfer. Integral connector clips are used to form a unified, seamless, vegetated surface and resist wind uplift forces. 

Vegetation options for the InstaGreen GT-4 tray are a standard sedum species blend designed to accommodate the rooftop conditions. A range of perennials can also be added to provide increased color, texture and habitat features for the pre-vegetated roof.

Green Roof Brightens the View for Patients at VA Hospital

At the Ralph H. Johnson VA Medical Center in Charleston, a modular green roof system was installed to improve the quality of life for patients in the extended care wing.

At the Ralph H. Johnson VA Medical Center in Charleston, a modular green roof system was installed to improve the quality of life for patients in the extended care wing.

Michael Whitfield was fascinated by the concept of green roofs, but he didn’t encounter many of them near his home in Charleston, S.C. He knew green roofs benefitted the environment, extended the life of roof systems and were aesthetically pleasing, so he was sure he could tap into the market in the Southeast as a green roof installer. When he couldn’t find a modular green roof system he liked, he designed his own. Whitfield is now the president and CEO of Green Roof Outfitters. Founded in 2009, the company manufactures components for green roofs installed all over the country. The company also installs green roofs itself, as was the case with a nearby hospital project.

After reading research studies that showed hospital patients recovered more quickly and needed less pain medication when they had a natural setting to look out on, Whitfield was inspired. He checked with local hospitals to see if there were areas that would be good candidates for green roofs. When the PR person at the Ralph H. Johnson VA Medical Center expressed an interest, Whitfield passed along the research material.

Months later he got a call asking him to submit a bid. While the hospital’s budget did not allow for a green roof to be installed on the entire building, there was a section of the roof that could be worked on right away. It was a 3,000-square-foot area on a wing for extended care patients, who looked out on a white TPO roof. “We put a green roof on that whole strip outside their windows so the patients would have something nice to look at,” Whitfield says.

Roof Materials

Construction took place on a weekend, when traffic would be lighter. A crane was used to load the material on the roof, including 4-inch-deep trays for the extensive modular green roof system and 2-inch-thick rubber pavers to go around the perimeter. Plants in the pre-grown mats included different varieties of sedum. Chives, prickly-pear cactus and other perennials were added later.

Green Roof Outfitters partners with growers around the country to provide pre-grown mats. Different varieties of plants are used in different parts of the country, but in most markets the company has had success with a blend using approximately 14 different varieties of sedum.

Whitfield believes the proper combination of plants is essential. “Two buildings that are right next to each other could have different microclimates, so you don’t know exactly what is going to work perfectly there and what is not,” he says. “We mix these plants with a variety—some do better in shade, some do better in sun. With the different tolerances they have, the strongest will survive, so we will always have something there. Many people make the mistake of planting one species they like with a certain pattern or color. But if you plant one species—a monoculture—and it doesn’t like it there, you’ll have a totally dead roof.”

Roof Report

The system does not require slip sheets for installation, but some roof manufacturers require them to maintain the warranty on the existing roof. In this project, a layer of 40-mil EPDM was placed on top the existing TPO roof. “We laid the modules on top of that,” says Whitfield. “We have rubber paver walk pads, which have feet on the bottom for drainage. We put those around the outside so we could have a nice-looking barrier and a walking area for the maintenance guys.”

Michael Whitfield was on hand to oversee the project at the VA medical center.

Michael Whitfield was on hand to oversee the project at the VA medical center.

“Many people don’t know this, but a green roof can help the roof last 200 percent to 400 percent longer by preventing UV degradation,” Whitfield says. “It shades the roof and protects it. During the day, exposed roofs get superheated in the sun, and cool at night, so they are constantly expanding and contracting. A green roof system keeps it at a constant temperature.”

Another benefit can come from creating functional space on the roof. “We wholesale a lot of systems that combine a green roof with pavers to add usable space,” he says, “We can supply ipe wood pavers or other pavers in different configurations on our pedestal system to make walkways and patios.”

Depending on the environment, an irrigations system is a common option. “Green roof are a low-maintenance systems, not a no-maintenance systems,” notes Whitfield. “We incorporated irrigation channels into the new design of our modules, so you can put in irrigation during the installation or after it is completed.”

Another change is a smaller module. “Our modules used to be 2-feet-by-2-feet, but they were really heavy for the roofers,” he explains. “Our new modules are half the size—one-by-two—so they are much easier to handle and put in place.”

As they become more comfortable with green roof systems, roofing contractors are finding out they can be a valuable add-on with roofing projects. “Once roofers are on the site with all of the equipment and labor, why not make double the money by installing roofing and a green roof?”

No special training is needed to install this tray system. “It’s easy to install,” Whitfield notes. “The modules come fully vegetated, 40 to a pallet. You just pick one up, put it down, and repeat. It’s like laying down dominoes, honestly.”

The modular system is also easy to move if roof maintenance is necessary. “Our system is so flexible,” he says. “If you need roof maintenance, you can just pick up a couple of trays, move them and move them back. This is such an easy, modern way to do it—and it’s very affordable.”

Team

Green Roof Manufacturer and Installer: Green Roof Outfitters

Photos: Green Roof Outfitters

Stanford Hospital Project Demands Versatility and Surgical Precision

The new Stanford Hospital is currently under construction in Palo Alto, Calif. The 824,000-square-foot facility connects to the existing hospital by a bridge and tunnel. The project includes a multi-level parking garage and with additional office buildings. Photo: Stanford Health Center.

The new Stanford Hospital is currently under construction in Palo Alto, Calif. The 824,000-square-foot facility connects to the existing hospital by a bridge and tunnel. The project includes a multi-level parking garage and with additional office buildings. Photo: Stanford Health Center.

Dennis Olson is used to dealing with large health care projects with multiple scopes of work, but the new Stanford Hospital project he’s currently working on might be the most challenging job he’s ever faced.

“I’ve never been involved with a project that’s been this complex and this difficult to roof and manage,” says Olson, the owner of Letner Roofing in Orange, Calif. “There are 16 different types of roofing and waterproofing systems, and each one is a little bit different at each location around the building.”

Located in Palo Alto, Calif., the new Stanford Hospital is an 824,000-square-foot facility that connects to the existing hospital by a bridge and tunnel. Olson is convinced his company is perfect for the job. He has been in the roofing industry for almost four decades, and he’s worked at Letner for more than 30 years. Olson worked his way up through the company as a foreman, project manager, and estimator before becoming the president and owner 15 years ago. “I have been estimating and managing health care projects for more than 25 years,” he says. “This job is right up our alley.”

The Company

Located in Orange, Calif., Letner Roofing specializes in commercial work including all types of roofing and below-grade waterproofing systems. “We are licensed with all of the major manufacturers to install their products,” Olson says. “We install basically every roofing and waterproofing system that’s available to the market. We have a sheet metal division that produces metal wall panels, roofing and general sheet metal.”

The new hospital features green roofs on the main hospital, central plant and parking structure. The garden roof section on level three of the main hospital building is shown here. Photo: Stanford Health Center.

The new hospital features green roofs on the main hospital, central plant and parking structure. The garden roof section on level three of the main hospital building is shown here. Photo: Stanford Health Center.

Olson believes the company’s success begins with its great alliances with top general contractors and owners. “Our strengths are our customer service and quality control, and our ability to get projects done efficiently and on time,” he says. “I think that’s why general contractors choose us. We do what we say we’re going to do, we do it efficiently, and we take a lot of pride in the finished product.”

Communication is the key, according to Olson. “We have weekly sales meetings where all of the project managers and sales staff get together,” Olson says. “We share information, which allows us to learn from our failures and successes. It’s a team atmosphere. There is no real competition between the sales guys other than the innate competition that you each have to be better. We don’t compete against each other; we all work together for the common goal.”

Keeping the lines of communication open with industry partners is a key part of the puzzle. “As far as communication with the general contractor, that’s pretty simple, but a lot of people miss that,” he says. “You have to return phone calls. You have to return emails. If you have an issue on a project, handle the issue efficiently. Bring scheduling problems or details issues to the attention of the general contractor early. Nobody like to be surprised. People like to be informed.”

Due to their expertise in design-build situations, members of the Letner team are often called in by general contractors at the design and budgeting stage to offer advice on the right materials and methods for a project.

That was the case with the new Stanford Hospital project and general contractor Clark/McCarthy—a joint venture of Clark Construction Co. and McCarthy Building Cos. “McCarthy is a contractor I’ve been dealing with for more than 25 years. I’ve done a lot of health care projects with them, so when Stanford came out, they certainly wanted our input and help developing the budgets,” notes Olson.

Underground, Overhead

For Letner, the project involved several scopes of work including roofing on the main hospital and below-grade and underslab waterproofing.

Below-grade work included a pre-applied blind-side waterproofing application by Cetco. Letner also waterproofed underground tanks for domestic water, fire suppression, and sewage with a hot rubber system by Gaco Western. “The hospital was built for the worst-case scenario,” Olson notes. “If there is a big earthquake, and services are interrupted, the hospital can sustain itself for a while.”

This aerial photo shows the new Stanford Hospital, which is currently under construction. When completed in 2018, the complex will showcase 16 different roofing systems on 12 different elevations. Photo: Stanford Health Center.

This aerial photo shows the new Stanford Hospital, which is currently under construction. When completed in 2018, the complex will showcase 16 different roofing systems on 12 different elevations. Photo: Stanford Health Center.

As the superstructure was being completed, the roofing work began. “As I said, there are 16 different roofing systems on this project. There are 12 different elevations,” notes Olson.

Systems range from urethane and urethane and polymethyl methacrylate (PMMA) coatings to split-slab and inverted hot rubber systems, PVC roof systems and hybrid dual waterproofing system. The largest roofing systems include a Sarnafil PVC roof on the main hospital and a hot rubber system by Cetco for use under the garden roofs. Letner is installing garden roofs on the third floor of the main hospital and another on the central plant building.

Both of these garden roofs were constructed over flat concrete decks. The first step was to provide positive slope for drainage. Cell-Crete Corporation of Hayward, Calif., provided lightweight insulating concrete (LWIC), which was used to create positive slope. After the LWIC cured, crews from Cell-Crete installed quarter-inch cement board over the LWIC.

The hospital’s surgery rooms are directly beneath the garden roof on the main hospital, so the system has to be bulletproof. “This roof area requires intricate detailing along with a Cetco hybrid dual waterproofing system,” Olson states. “After the lightweight concrete and cover board are in place, Letner will install 60 mils of Hydrofix urethane membrane, followed by Cetco Corflex, a unique combination of a re-enforced KEE membrane bonded to an active polymer core membrane. Both garden roof areas will be protected with an in-place leak detection system by Internal Leak Detection.”

The overburden at the hospital garden roofs will include insulation, drainage mats, various types of plants and trees and pedestal paver systems.

Letner installed PVC roof systems from Sika Sarnafil level three of the hospital and on the main roof of the hospital. The 60-mil PVC membrane was installed over insulation and DensDeck cover board. Insulation was a minimum of R-20 near the drains. Some sections of the PVC were topped by ballast rock.

On the adjoining multi-level parking deck, Letner installed PVC roofs on two office buildings. The rest of the roofing and waterproofing work on the parking structure, including another garden roof, was completed by Courtney Waterproofing and Roofing of Irvine, Calif.

Safety Precautions

Letner and the general contractor help ensure safety is always top of mind at the site. “On this project, like any other, the safety issues were extremely important,” notes Olson. “We have our crews stretch and flex daily, and everyone must wear the personal protective equipment required for each task. Fall protection is a concern at every elevation, and hot rubber is extremely hazardous activity that requires additional protection and monitoring.”

Elastizell lightweight insulating concrete from Cell-Crete was used to provide slope for drainage on the flat structural concrete decks. It was later topped with cement board. Photo: Cell-Crete

Elastizell lightweight insulating concrete from Cell-Crete was used to provide slope for drainage on the flat structural concrete decks. It was later topped with cement board. Photo: Cell-Crete

The perimeter walls were being constructed during the project, so extra precautions had to be taken at the roof edge. “We had to wear harnesses and be tied off at all times,” Olson says. “We are very concerned about safety. We have a safety manager, and he does a very good job of identifying possible hazards on each job. We identify those per deck and apply the proper safety measures required for each elevation.”

Waterproofing the tanks also required special care. “The domestic water, waste and fire tanks and are in the ground, so you have to have people certified to do that work with specialized equipment,” Olson states.

Challenging Schedule

Construction of the hospital is still underway. Work is expected to be completed in 2018. The sheer size and multiple scopes of work were obvious challenges on the project, but the schedule was also tight—and subject to change. Some roof details were changed and others were developed as the job progressed, so Letner’s crews had to make some adjustments on the fly. Letner continues to work with the consultant on the project, ABB, to iron out the details.

“Sometimes you have to adjust the schedule when you are coordinating the work with other trades,” Olson notes. “The schedule, coordinating with other trades and the number of changes on the job have been the biggest issues we’ve faced. It’s is still a challenge, as the work is ongoing.”

When it came time to stage equipment and materials, the large job site suddenly seemed small. “The site was kind of tight, so of course logistics came into play with loading and off-loading each different area,” he says. “Some areas were hard to get to, and sometimes we had to wheel the product through corridors to get to the decks. Not everything was easy to get to. Logistics were difficult, but we were able to overcome those problems. Clark/McCarthy helped out quite a bit with logistics and loading.”

Despite the complexity of the job, the installation work has gone smoothly, according to Olson. “As far as the application for our field crews, there’s not that much difficulty for them. They are all very talented at what they do,” he says. “It’s just a very difficult building, and there are a lot of details that are not typical.”

The key to overcoming difficulties? “It’s constant communication,” Olson says. “Our strengths are our management teams, from the field operations to office staff. We’re honest with our customers. They understand the level of customer service and quality we deliver. Our success is a testament to the service we provide to our customers. We are often praised for our service and workmanship, and we are very proud of our quality installations as well.”

On the adjoining multi-level parking deck, Letner Roofing installed PVC roofs on two office buildings. The rest of the roofing and waterproofing work on the parking structure, including another garden roof, was completed by Courtney Waterproofing and Roofing. Photo: Stanford Health Center.

On the adjoining multi-level parking deck, Letner Roofing installed PVC roofs on two office buildings. The rest of the roofing and waterproofing work on the parking structure, including another garden roof, was completed by Courtney Waterproofing and Roofing. Photo: Stanford Health Center.

TEAM

Architect:
Rafael Viñoly Architects in association with Lee, Burkhart, Liu Inc.

General Contractor:
Clark/McCarthy—a joint venture of Clark Construction Co. and McCarthy Building Cos.

Roofing and Waterproofing Contractors:
Main hospital building and offices: Letner Roofing, Orange, Calif.
Adjoining parking structure: Courtney Waterproofing and Roofing, Irvine, Calif.

LWIC Provider and Installer:
Cell-Crete Corp., Hayward, Calif.

Using Engineered Geofoam for Garden Roofs

For most of the past century, the rooftops of commercial and institutional buildings have largely been places to locate unsightly mechanical systems. Architectural treatments, such as parapets and screens, provide visual relief from such equipment. Now, roofing professionals and building owners increasingly look at the roof as “found space”—a place to be planted and used, instead of hidden.

Facebook’s Frank Gehry-designed MPK 20 building sports a 9-acre green roof using EPS geofoam from Insulfoam.

Facebook’s Frank Gehry-designed MPK 20 building sports a 9-acre green roof using EPS geofoam from Insulfoam.

Throughout the U.S., garden roofs (or living roofs) are growing in popularity with more than 5.5 million square feet installed in 2014, according to Green Roofs for Healthy Cities. Most of that total was for private rather than public projects, indicating this is not just a government trend. In addition to providing attractive and usable open space, garden roofs offer environmental benefits, such as helping to slow and filter urban run-off.

Some of America’s largest companies have installed green roofs. Ford’s Dearborn, Mich., truck plant final assembly building sports one of the world’s largest living roofs at 454,000 square feet. In 2015, Facebook opened its MPK 20 office building in Menlo Park, Calif., with a 9-acre living roof featuring a 1/2-mile walking trail and more than 400 trees.

If you haven’t worked on a garden roof yet, it is likely only a matter of time until you do.

Addressing the Challenges of Garden Roofs

Weighing a fraction of soil, EPS geofoam fill creates ultra-lightweight landscaped features on Facebook’s garden roof.

Weighing a fraction of soil, EPS geofoam fill creates ultra-lightweight landscaped features on Facebook’s garden roof.


Adding plants and park-like amenities to a roof increases the complexity of the roofing assembly. Garden roofs present two primary challenges for roofing professionals to solve: minimizing the dead load and preventing moisture intrusion.

The project team for the Facebook MPK 20 building’s green roof met this two-fold need—and more—with expanded polystyrene (EPS) geofoam.

Weighing considerably less than soil, EPS geofoam is an ultra-lightweight engineered fill that can be used to create contoured landscape features, such as hills and valleys. The material weighs from 0.7 to 2.85 pounds per cubic foot, depending on the product type specified, compared to 110 to 120 pounds per cubic foot for soil.

Despite its low weight, EPS geofoam is designed for strength and has better load bearing capacity than most foundation soils. Geofoam’s compressive resistance ranges from approximately 2.2 psi to 18.6 psi (317 to 2,678 pounds per square foot) at a 1 percent deformation, depending on the product.

The garden roof on Facebook’s MPK 20 building provides ample open space and a half-mile walking trail for employees.

The garden roof on Facebook’s MPK 20 building provides ample open space and a 1/2-mile walking trail for employees.

EPS geofoam is also effective at addressing the second challenge of garden roofs: managing moisture absorption. The moisture performance of the various components in a green roof assembly is critical; retained water imposes additional loads on the roof and increases the risk of water damage to the roof assembly. EPS geofoam meeting ASTM D6817 standards works well here as it only absorbs 2 to 4 percent moisture by volume, even over long-term exposure, and it dries quickly. The moisture performance of EPS has been demonstrated in extensive in-situ applications and real-world testing, including research conducted by the U.S. Army Corps of Engineers’ Cold Regions Research and Engineering Laboratory. After burying EPS in wetted soil for nearly three years, the lab found that the material absorbed only 1.7 percent moisture by volume.

In addition to enabling lightweight, durable landscape features and helping to defend against water, EPS geofoam provides thermal insulation in garden roofs. Roofing professionals have used EPS insulation in roof assemblies for decades because it offers the highest R-value per dollar among rigid foam insulations.

Expect More Demand

Although green roofs currently account for a small portion of the billions of square feet of roofs in the U.S., expect to see more demand for them given their aesthetic and environmental benefits. High-performance materials, like EPS geofoam, can help provide a long-lasting, durable green roof assembly.

PHOTOS: Insulfoam