Four Views From a 44th Floor Manhattan Green Roof

The green roof is a living ecosystem, and multiple species of sedum give it the best chance of success. The vegetative mat from ZinCo is pre-cultivated with about 12 to 16 hardy plant species.

SL Green Realty Corp., the largest commercial landlord in New York City, is working with tenants across its NYC properties to achieve a 30-50 percent reduction in greenhouse gas emissions over 10 years. Green roofs are playing a role in the effort, including one 44 stories up at 1185 Avenue of the Americas.

The 1.1 million-square-foot commercial office building is owned and managed by SL Green, a leader in urban sustainability. Among the many environmental advantages of green roofs, they reduce the urban heat island effect, ease storm water runoff, filter pollutants in rainwater and remove carbon dioxide, a greenhouse gas, from the air. In addition, by lowering building cooling demand, they can cut greenhouse gas emissions associated with producing electricity.

The roof replacement project was completed in the fall of 2017, and key participants shared their perspectives on the project, including representatives of four companies:

  1. SL Green, the property owner and management company
  2. CANY Architecture and Engineering DPC, the construction management firm
  3. Nations Roof LLC, the installer
  4. ZinCo USA, the green roof system consultant and manufacturer

1. The Realty Management Company

Daniel Huster, Senior Project Manager, SL Green Realty Corp.

How did this project get started?

Before the new Kemperol waterproofing membrane could be installed, the existing bituminous roof needed to be removed down to the concrete deck. Photo: Nations Roof LLC.

SL Green has an on-site team that manages 1185 Avenue of the Americas. I handle all the construction within the building and several others in our portfolio. The old (bituminous) roof was past its warranty. It had absorbed water, and we were showing signs of leaks in our mechanical room and the spaces below. We engaged CANY to put together a package to design and replace the roof system. They specified a reinforced waterproofing membrane from Kemper System America Inc. for the main roof, and we also asked CANY to bid with a green roof on top.

Green roofs are uncommon at such heights. What convinced SL Green?

When we originally put the RFP out for roofing renovation, we asked for the green roof as an alternative. After the group considered all the advantages and then saw the pricing, we made a collective decision that it was worthwhile to pursue.

SL Green already has two buildings in New York with green roofs — 100 Park Avenue and a vegetable garden at 1515 Broadway near Times Square. But those are setback roofs at much lower elevations. The roof at 1185 is essentially rectangular, so this was an opportunity. The floor plates spread the weight, and the green roof and pavers could cover roughly 4,500 to 5,000 square feet of the 14,200 square foot total. It took a while to work out the details on the elevation, but CANY and the green roof consultant from ZinCo figured out a design that could work.

2. The Construction Management Firm

Andrew Cucciniello, Project Manager, CANY

What was the condition of the existing roof?

The existing roof was a modified bituminous system — a torch-applied sheet on the concrete deck followed by layers of rigid insulation, topped with cover board and two more plies of the mod bit. Judging by the wear, it had been down about 20 years. We completed an investigation of the assembly, and found that it had failed in a number of locations and water had infiltrated the layers. This was one of the driving forces behind our recommendation for a full replacement aside from any repair.

What is involved with the investigation?

Typical with any investigation for us, we coordinate with an environmental consultant and an independent agent, who cuts holes into the main roof frame down to the structural deck so we can understand all the existing components. This also gives us an opportunity to do material sampling and test for asbestos-containing materials (ACMs). (There were none.)

Testing lets the demolition contractor know the extent of material removal. Also, the environmental consultant is required to submit a laboratory report and must notify the NY Department of Buildings before we can file for permits. The city wants to know there are no ACMs present, and if there are, the Department of Environmental Protection will receive notification about the abatement procedures.

What do you consider in specifying the green roof waterproofing assembly?

When we get a project like this, there are several different types of materials we can consider. We try to analyze the use of the roof and what kind of traffic it will experience in terms of mechanical equipment, people performing maintenance and repairs, etc. Also, for a protective roof assembly, there can be NY Energy Conservation Code requirements for insulation.

In this case, if we were to go with a built-up roof (BUR) it would require drainage at the surface, which would mean tapered insulation (likely a polyisocyanurate). Tapered insulation would drive our base flashing height halfway up the parapet, which we could not accommodate due to a scaffold track around the perimeter.

Nations Roof crews are acquainted with the challenges and procedures of working at height. In this photo, crew members are appropriately harnessed as they remove an old metal railing. Photo: Nations Roof LLC.

So we selected the liquid-applied Kemperol 2K-PUR reinforced membrane system, which is self-flashing and installs directly to the deck. Since it is a fully-adhered system that can withstand ponding water, we did not have to design for slope. A (non-tapered) rigid-styrene insulation board sits on top. Because the Kemperolmembrane is root resistant, a separate root barrier was not required. There were also ongoing discussions with Kemper System and ZinCo throughout our design process to assist with the final overburden components.

Are inspections conducted during the construction phase?

Our company performs QC inspections throughout the course of construction. From existing roof material removal and any preparation of substrates, as well as the new roof installation, flashing details, and the overburden placement. We have been involved with Kemper System for about two decades. With these roof assemblies which offer a 20-year warranty, we conduct periodic inspections with Kemper System to make sure the installation meets their warranty compliance requirements. We were the applicant of record with the NY Department of Buildings, though, and are on board until the project gets closed out.

3. The Installer

Michael Johannes, President, Nations Roof-East

Why was Nations Roof selected for this green roof rather than an architectural landscape company?

When a realty management firm first looks at us as a roofing and waterproofing company, they see our financial stability and our commitment to working safely. Nations Roof consistently ranks in the top five roofing contractors in the U.S. We are committed to delivering comprehensive roofing solutions. During any repair or construction project, we understand the need to protect employees, guests and valuable assets, and at the same time, to maintain business operations and service levels throughout the project. This project was completed working off-hours and through occupied spaces that needed to be ready for the next workday without interruption.  

Also, not a lot of landscaping companies are going to carry the required levels of insurance coverage without numerous exclusions for such things as building height. We work constantly on projects from eight to 50 stories in the air installing roofing systems both on new construction and renovations such as 1185 Avenue of the Americas.

What about the quality of the waterproofing installation?

1185 Avenue of the Americas in New York City earned a LEED Silver rating from the U.S. Green Building Council and is one of the most efficient commercial office buildings in the nation. The property features expansive views and a green roof on the 44th floor.

Landscape contractors are not generally authorized to install roofing and waterproofing systems. Our foreman, project managers and installers are employees and most have been with our company for years. Our crews are trained and experienced in installing leak-free systems. That includes certified training by Kemper System in the liquid-applied reinforced membrane system used on this project. Plus, ZinCo provided guidance on installing the garden components and the transitions to the interlocking paver walkways. We can supply a “finished turnkey green-roof” with all the components, and provide the owner with a warranted watertight installation.

Has Nations Roof installed other green roofs in New York City?

Actually, we’ve done many garden roof installations. For example, we successfully completed 100 Park Avenue with SL Green, which was a LEED Silver project, and Via Verde, an affordable housing complex in the Bronx.

New York and Chicago are at the front of the green roof trend. Via Verde was former N.Y. Mayor Michael Blomberg’s first initiative into green gardens back in 2010, and they caught on. Most new roof projects we do in the city now have some form of hardscape and softscape. It’s valuable space that in the past has gone unused for the owner and the tenants. If you live or work in one of these buildings, it’s nice to have a place you can go that is secure. When we go to Via Verde now, we see mothers with baby strollers sitting and reading books in what would have been just a roof a few years ago.

What do you see for the future of green roofs?

We believe the market will continue to be strong for livable roof space that improves the environment, and we will continue to be in the middle of that with big developers. It is also the commitment and leadership of property owners like SL Green to invest in these initiatives that will continue to drive success.

4. Green Roof System Consultant and Manufacturer

Nick Smith, National Account Manager, ZinCo USA

What are the primary issues with installing a green roof at this height?

Any green roof installed at 500 feet can invite potential problems with horticulture, erosion and exposure. Let’s focus on those three: To analyze exposure, we recommend a wind study and sun/shade study, and CANY performed these tests.

Wind uplift is a major issue with the physical properties of the green roof. We are concerned with getting the proper ballast. In this situation, a standard engineered-material assembly would not be heavy enough to protect against a worst-case scenario. The solution was to add significant weight to the assembly within the cups and the drainage elements. The engineered growing media is also a bit heavier than normal.

Wind scour, a horticultural issue, is the plant’s ability to stay vital with continuous wind. We know after looking at hundreds of studies that trouble spots most often occur around the perimeter and at corners, where you get microcurrents of fast-moving or swirling air. The conventional wisdom is that on a building over 500 feet tall that is going to withstand serious wind 24 hours a day, plants simply won’t grow at the perimeter and corners.

To combat erosion, we separated the vegetated area from the walkway deck in many areas with an aluminum angled-edge. The aluminum barrier acts as a separation for the way the wind moves. So we make sure the installer understands that at the edge angle, the depth of the growing media must be exactly compacted in the cup wells to 3 inches plus. A shallower depth may not be significant at the center, but at the edge you must have that specificity in quality control to safeguard against erosion.

Finally, once the plants are down, we place a “jute net” over the entire assembly. Our erosion blanket is a biodegradable coco-fiber. It is really important on the perimeter that the jute net is wrapped around the vegetation and under the soil profile at full depth to make sure the plants have the best chance. 

What were some other ways you adapted the green roof for this project?

One unusual thing is we infilled the drainage element with an aggregate. That’s not totally uncommon on a green roof assembly, but it is on sedum. We wouldn’t do that at a lesser height, but it served as ballasting. The mineral-based aggregates we use also wick the water saved in the cups up into the growing layer, which in this case had a slightly higher dry weight (28.9 pounds per square foot) than a traditional assembly, again primarily for ballasting.

Dry weight always compromises nutritional content in the media. That means you can’t think strictly about weight, or you lose plant vitality. This was a balancing act we performed with CANY — to make sure proper weight was maintained for ballasting without undermining the needs for plant life, while also keeping the fully saturated weight within the load-bearing requirements of the structure.

What about the installation?

Green roof design, engineering and global experience are important, but the success of a green roof also depends on the installation. We worked with Nations Roof on proper installation technique, both generally and specifically for this challenging installation, and they did a fantastic job.

TEAM

Building Management: SL Green Realty Corp., New York, www.slgreen.com

Construction Management: CANY Architecture and Engineering DPC, New York, www.cany.com

Installer: Nations Roof-East, Yonkers, N. Y., www.nationsroof.com
Green Roof Consultant: ZinCo USA, Stoughton, Massachusetts, www.zinco-usa.com

MATERIALS

Roof Waterproofing System: Kemperol 2K-PUR cold liquid-applied reinforced membrane system, Kemper System, West Seneca, N.Y., www.kemper-system.com

Green Roof: Custom Sedum System by ZinCo USA, Stoughton, Massachusetts, www.zinco-usa.com

Living Roof Helps Orcas Island Home Blend into the Landscape

This residence on Orcas Island is crowned with an extensive green roof from XeroFlor.
Photos: Terra Firma NW LLC

Orcas Island is a horseshoe-shaped island in the northwest corner of the state of Washington. With an area of 57 square miles, it’s the largest of the San Juan Islands, and accessible only by ferry. When a client approached him about building a custom home on the island, Justin Paulsen jumped at the chance. Paulsen is the owner of Terra Firma NW LLC, a general contractor located in nearby Eastsound, Washington. “We were hired directly by the owners to build the project from the ground up,” Paulsen notes.

The 3,400-square-foot home features 3,850 square feet of roof area, which is crowned with a living roof. The system specified for the project was a XeroFlor extensive green roof, which was installed on top of a PVC membrane roof manufactured by Versico.

The green roof system consists of a root barrier with a drainage composite, 1-1/4 inches of growing medium, and pre-vegetated sedum mats. The system was installed in the late fall in 2018, so many of the plants were dormant. Photos: Terra Firma NW LLC

“The roof system works well for the home, which is designed in the style of the Bauhaus school of design,” notes Paulsen. “The home features many linear design elements, and the green roof gives it a sense of blending in with the natural surroundings.”

It was only the second green roof Paulsen had been involved with, so he made sure to do his homework. He knew from experience that work on the island would pose logistical challenges, so he tapped a talented to team to help design and execute the project.

The Roofing Contractor

Paulsen wanted a skilled roofing contractor to install the waterproof layer beneath the green roof system. The Versico rep in the area, Ken Stillwell, recommended All Weather Rooftop Solutions, headquartered in Everett, Washington. The company, owned by partners Todd Severson and Greg O’Neill, typically focuses on commercial work, but this project was right in their wheelhouse. Severson knew the company had to plan ahead to ensure the everything went smoothly.

Crews from Terra Firma NW installed the green roof system. The sedum mats arrived on a pallet and were unrolled on top of the growing medium. Photos: Terra Firma NW LLC

“Working on the island was the biggest challenge of the whole project,” Severson notes. “We wanted to complete the project in one week, so we had to make sure we had everything ready to go. Everything had to be transported by ferry, so we had to schedule all of the trucks and make sure all of the material landed at one time. We just had to make sure we had all of the material and manpower on that ferry.”

The PVC roof system was installed over a plywood deck. Crews first installed two layers of 3.3-inch insulation to achieve an R-value of 38. Tapered insulation system was then added to ensure proper drainage. The insulation was topped with half-inch DensDeck Prime cover board, which was mechanically attached. A gray 60-mil PVC membrane from Versico was then fully adhered over the entire assembly.

All Weather crews also installed OMG SpeedTite roof drains with Vortex-breaker technology, as well as Solatube light tubes. The large skylight was installed by the manufacturer, CrystaLite.

All Weather Rooftop Solutions installed the PVC membrane to provide a waterproof barrier beneath the green roof. Photos: Terra Firma NW LLC

The sheet metal work was completed by All Weather on a second trip, with a smaller crew returning to complete the flashing and edge metal. The roofing portion of the project went smoothly. “Justin from Terra Firma was great work with, and our superintendent, Jeff Gale, did a great job quarterbacking it on our end,” Severson notes. “Everything went off without a hitch. It’s a pretty unique little structure.”

Paulsen agrees. “They did a great job installing the insulation and the membrane,” he notes. “The biggest thing we had to deal with after that was protecting the membrane from other trades. Our stonemason had to go back up on the roof and complete the chimneys.”

To preserve the integrity of the membrane after it was installed, Terra Firma crews cut a 20-mil pond liner pond liner into sections that were used to protect areas of the roof that had to be accessed by other trades.

Installing the Green Roof

After all the other work was completed on the rooftop, crews from Terra Firma installed the green roof system in the late fall of 2018. Paulsen had heard about XeroFlor from another contractor and did some research. He then contacted Clayton Rugh, director of XeroFlor America, to design and specify the system.

“I thought it was really top-notch system,” Paulsen notes. “I went to Clayton to document some other examples that had been installed in the area, and I pitched it to our client. Clayton did all of the functional engineering work on the green roof system and determined the soil requirements. The plantings by XeroFlor were sourced very close to the project site, which helps to ensure successful future growth.”

Photos: Terra Firma NW LLC

The extensive green roof system consists of a root barrier with a drainage composite, which is an open-flow zone of polymer coils with a bonded fleece fabric sheet. The drainage material was topped with 1-1/4 inches of growing medium, followed by 1-inch-thick pre-vegetated mats, which contained a mix of sedum succulents.

The pre-vegetated mats are installed just like sod. “They arrive rolled up on a pallet,” Rugh notes. “You just align the roll adjacent to the previously installed roll, abutting it tightly, and roll it into place.”

Terra Firma also installed the edge metal and rock ballast around the perimeter. “I was amazed at how simple it was to accommodate the green roof portion of the project,” Paulsen says. “Once the membrane was down, we knew we were rock solid and the house was well protected. The green roof portion was easy to install. I’d definitely do one again.”

Paulsen is proud to have this project under his belt. He can’t wait to see it in the spring, when the green roof is in its full glory.

“Terra Firma NW thrives on jobs that have complex and unusual requirements,” Paulsen says. “This job, from foundation all the way through the roof, presented numerous design challenges. We have a $2 million-dollar house under this roof. If I had to give advice to anyone doing a green roof, my advice would be: Don’t cut corners.”

TEAM

Architect:  Harlan Pedersen AIA, Orcas, Washington

General Contractor: Terra Firma NW LLC, Eastsound, Washington, www.tfnwllc.com

Roofing Contractor: All Weather Rooftop Solutions, Everett, Washington, www.allweatherroof.net

MATERIALS

Extensive Green Roof System: XeroFlor XF + GM Assembly, XeroFlor North America, www.xeroflornorthamerica.com

Roof Membrane: 60-mil PVC, Versico Roofing Systems, www.versico.com

Cover Board: DensDeck Prime, Georgia-Pacific, www.densdeck.com

Skylight: CrystaLite, www.crystaliteinc.com

Daylighting: Solatube, www.solatube.com

Roof Drains: SpeedTite roof drains, OMG Roofing Products, www.omgroofing.com

At The Wharf, Vegetative Roofs Play a Key Role in Storm Water Management

The Wharf is a riverfront community spanning nearly a mile of the Potomac River. The neighborhood features high-end hotels, luxury condominiums, retail shops, commercial offices and a music hall. Photos: The District Wharf

According to the Washington D.C. Department of Energy and the Environment, the District is home to more than 3 million square feet of vegetative roof assemblies (VRAs). A commitment to responsible storm water management has helped the nation’s capital rank first among U.S. cities when it comes to green roofs installed. From the massive 500,000-square-foot VRA atop the Douglas Munro U.S. Coast Guard headquarters (featured in the September/October 2018 issue of Roofing) to elegant boutique cocktail bars, VRAs are helping Washington, D.C., manage storm water runoff and providing unique vantage points for taking in national landmarks. The Wharf, in the District’s Southwest quadrant, represents a “neighborhood” approach to green roofs.

A riverfront community spanning nearly a mile of the Potomac River, The Wharf is a mixed use, public-private development, including high-end hotels, luxury condominiums, retail shops, commercial offices and even a 6,000-seat music hall. While the design and aesthetics of different buildings at The Wharf project a sense of diversity, VRAs are a unifying element. In addition to providing visual interest and elevated spaces for public gatherings, VRAs help The Wharf achieve its sustainability and water management goals.

Managing Storm Water, Supporting Sustainability

Water has long been a defining element of life in the District, whose neighboring waterways include not only the Potomac, but also the Anacostia River, Rock Creek and Chesapeake Bay. To help manage storm water runoff, the District makes use of a massive cistern system, permeable pavements, and extensive use of vegetative bio-retention supported by VRAs. The District of Columbia’s Department of Energy & Environment mandates measures that retain runoff from a 1.2-inch storm event through green infrastructure and capture reuse systems. Specific storm water retention rates are specified relative to a building’s footprint.

The vegetative roofs help tie together the diverse types of buildings in the area. Photos: The District Wharf

In addition to helping manage storm water runoff, protected roof membrane assembly (PRMA) systems at The Wharf also help to support the development’s sustainability performance goals, which started at the master planning stage. Sustainability objectives supported by The Wharf’s VRAs include reducing storm water discharge and improving thermal performance through the cooling and shading properties of soils and plantings — an important consideration in a region renowned for its humid summers. VRAs are also desirable in urban areas for the role vegetation can play in helping filter pollution and providing habitats for birds and other wildlife. Finally, VRAs offer an aesthetically pleasing environment for employees, occupants and visitors.

The Wharf development was designed to achieve LEED Gold, while individual buildings targeted LEED Gold or Silver. Constructed in phases, Phase One opened in 2017 and took nearly 15 years to complete. While the Great Recession slowed construction, an “upside” of the delay was that a proliferation of PRMA assemblies across the District helped inform the assembly of green roofs at The Wharf. Several high-profile buildings that employ similar roofing systems include the MGM Casino, the National Museum of African American History and the National Archives.

A PRMA Approach to Support Performance

More than half of the roofs in The Wharf make use of an Owens Corning PRMA that includes Owens Corning FOAMULAR 404 and 604 extruded polystyrene insulation (XPS) supplied by PPSI Maryland. XPS delivers unique water resistance and strength properties that differentiate it from other insulation products and make it ideal for VRA applications. In fact, the demanding conditions on rooftops helped prompt the National Roofing Contractors Association (NRCA) recommendation to use only XPS insulation for VRA applications. The innate water resistance of XPS helps a roofing system retain its R-value and energy-saving power while retaining its compressive strength to bear a significant amount of overburden. Strength is critical in a PRMA application, as the insulation must be able to withstand the weight of vegetation, rainfall, growing media, pavers and surrounding surface materials.

Sustainability objectives supported by The Wharf’s VRAs include reducing storm water runoff, improving thermal performance, and providing habitats for wildlife. Photos: The District Wharf

At the highest levels, the rooftop plants and vegetation help serve as a giant sponge to absorb the rainwater. In a PRMA roof, insulation under the plant layer, growing media and filter/drainage layer is placed above a waterproofing layer which directs water horizontally to a series of overflow vaults. A network of massive 700,000-gallon cisterns throughout the District collect and control the release of water.

In addition to water, wind was another consideration when planning VRAs at The Wharf. Rock curbs from Hanover Architectural Products help mitigate against winds coming in off the riverfront. Other roofing materials that help The Wharf PRMAs achieve performance include waterproofing membrane 790-11 Hot Rubberized Asphalt by the Henry Company, EMSEAL expansion joints to tie together air barriers, and Hanover Architectural Products pavers and sedum mats supplied by Sempergreen.

Contractor Coordination and Communications Are Key

As a community-focused development, The Wharf celebrated its grand opening with several public events. Hometown rock band the Foo Fighters performed for a sellout crowd at the Anthem music center on October 12, 2017. The enormous task of completing multiple buildings against a very tight timeline was a challenge felt by all of the contractor trades on site, according to Brian Davis, general superintendent at James Myers, the roofing contractor charged with installing green roofs at The Wharf. The immensity of the project required careful scheduling and logistics among roofers and other trades. Teams worked throughout the night and seven days a week as Phase One approached completion.

Photos: The District Wharf

As the countdown to the October 12 grand opening approached, construction teams followed tight schedules outlining exactly what team members would be working in what area at a particular time. The logistical demands of building nine buildings over six blocks made traffic bottlenecks an ongoing challenge throughout the project. Scheduling details had to consider not only the District’s notorious rush hour traffic but also events and attractions in the area. For example, the Washington Nationals baseball team played a number of weeknight baseball games at home. Trades working on The Wharf were required to clear the streets three hours before the first pitch of each Nationals home game. While navigating event schedules and a tight construction schedule, contractors also had to maintain high levels of safety and quality.

The public event commemorating the completion of Phase One celebrated a one-of-a-kind public space winding along one of the nation’s most historic riverfronts with an epic rock concert. More quietly, the completion of Phase One celebrated Washington’s role as a leader in the installation of VRAs while helping the District achieve sustainability goals and comply with storm water management mandates.

MATERIALS

Insulation: FOAMULAR 404 and 604 extruded polystyrene, Owens Corning, www.owenscorning.com

Waterproofing Membrane: 790-11 Hot Rubberized Asphalt, Henry Company, www.henry.com

Expansion Joints: EMSEAL, www.emseal.com

Sedum Mats: Sempergreen, www.sempergreen.com

Pavers: Hanover Architectural Products, www.hanoverpavers.com

At the Ace Hotel, Versatile Rooftop Terraces Capture the Imagination

Located in Chicago’s Fulton Market Historic District, the Ace Hotel features several vegetative roofs and a rooftop bar. Photos: Scott Shigley for site design group ltd.

The Ace Hotel is located in Chicago’s Fulton Market Historic District. It features 159 guestrooms and amenities including rooftop event spaces with stunning views of the city. The complex features several vegetative roofs, including a large fifth-floor terrace and a seventh-floor rooftop bar. The fifth-floor terrace incorporates a sculpture that visitors can climb on and areas that can easily adapt to host a variety of events, from corporate meetings to yoga classes.

The team at site design group ltd., the Chicago landscape architect on the project, worked closely with the lead architect, GREC Architects, and the Ace Hotel team to determine the key design goals for the rooftop spaces. Hana Ishikawa, design principal at site design group, notes the client was looking for an understated design. “In this project, what they really wanted was a prairie that kind of got left on the roof,” she says “So, that’s where the project got started.”

The fifth-floor terrace incorporates a sculpture created by artist Jonathan Nesci that visitors can climb on. An area topped with pavers is used to host a variety of events. Photos: Scott Shigley for site design group ltd.

On the fifth-floor terrace, the materials and plants chosen are meant to evoke a natural prairie landscape, while a section topped with pavers serves as a versatile event space. “We were really focused on creating a space that was super flexible,” Ishikawa says. “You’ll notice there’s a really large pavement area in the front, and they hold all kinds of interesting events there. That’s used pretty frequently, whether it be yoga or the little markets they hold up there. One of the primary functions we needed was a lot of flexibility, and that area works well for that.”

Other roof sections that were not open to the public had different needs. It took a talented team of design, manufacturing and construction professionals to turn the vision for the hotel’s rooftop spaces into reality — and provide the single-source warranty the architect and owner desired. 

A Versatile Roof System

The roof system specified for every roof level was a variation of Hydrotech’s protected membrane roof (PMR) assembly. According to Dennis Yanez, American Hydrotech’s national marketing manager, the foundation of the PMR assembly consists of Hydrotech’s Monolithic Membrane 6125, a hot fluid-applied rubberized asphalt membrane, which is applied directly to the deck and topped with Dow Styrofoam insulation. The system can then incorporate a variety of options including pavers, ballast, and extensive and intensive roof gardens. “The basics — the roofing/waterproofing membrane and the Dow Styrofoam — don’t change,” Yanez says. “One of the advantages of this system is once you apply the membrane and insulation in the field, you can mix and match all of these options and you aren’t changing the integrity of keeping that structure watertight.” 

Kevin Serena, Hydrotech’s garden roofing technical sales coordinator for the central region, worked with the building owner and design team to select the products and systems for each rooftop section. 

The materials and plants chosen for the roof terrace are meant to evoke a prairie landscape, with a trail leading to seating areas. Photos: Scott Shigley for site design group ltd.

“They have a few different roof levels, and there was a different design intent for each area,” Serena says. “There are a few upper roofs that only the occupants of adjacent buildings will see, so what they wanted there was low-maintenance vegetation with good coverage. They went with a sedum mat material. It’s pre-grown outside for over a year, so it’s a very hardy material, and once it becomes established it needs little to no maintenance. That was a goal of theirs for those upper roofs since not a lot of people would be accessing those areas.”

For the large podium deck that was open to the public, the owners wanted to add more interesting vegetation along with other features. “They integrated stone walkways, and they used a more expansive plant palette,” Serena notes. “They used the same sedum carpet as a base planting, and then added some different perennials and grasses throughout the mat to give it some vertical interest and add some biodiversity to the roof.”

Serena also worked closely with the roof system installer, Bennett & Brosseau Roofing Inc., of Romeoville, Illinois, an authorized Hydrotech applicator. “Bennett and Brosseau is one of the best contractors in the area,” Serena says. “They have taken a real interest in doing not only the membrane but all the way up through the growing media and vegetation. They are really into doing the green roof, so they are exciting to work with. They really like doing this type of work, and they do a great job.”

The Installation

Bennett & Brosseau Roofing installed all of the roof systems on the project, as well as the material for the garden roofs. The company also fabricated and installed four custom colors of sheet metal on the project. 

“We had grade-level to roof-level waterproofing on this project,” notes Jim Brosseau, CEO and owner of Bennett & Brosseau Roofing. “On the grade level, we installed pavers and drainage components. We also planted plants and trees in the planters on the plaza and at the grade level as well.”

Photos: Scott Shigley for site design group ltd.

The hotel was constructed at the site of a former cheese-making factory in the Fulton Market District. A part of the existing building was retained, including a wall with a historic mural, but the majority of the project was new construction with a concrete roof deck. “It was in a tight area where access was very limited at the jobsite,” Brosseau notes. “All of the roofs were new, but the owner wanted to tie into an existing wall for historical value.”

Bennett & Brosseau Roofing worked closely with Hydrotech to coordinate material deliveries, and access to the jobsite was eased by a couple of fortuitous events. “One of our vendors actually had some property behind the jobsite, so we were able to stage some material there,” Brosseau recalls. “They also closed the street for some work at a building across the street, so we took advantage of that and were able to stage some material on the street and lift it up with our hoists.” 

Elevators did not reach every level, complicating the logistics. “Safety was a challenge,” Brosseau says. “They had elevators at certain levels, but the rest we had to stage a second time for a double hoist. We had to have certified riggers and an approved lift plan. Every pallet is marked, and Hydrotech does an excellent job packaging material, so that helps the process.” 

Crews installed fall-protection barriers, which included the company’s own engineered bracket system with two-by-fours, as well as a Garlock safety rail system. Roofing work began on the penthouse roofs and the tops of the elevator shafts. “All of the roofs received Hydrotech’s hot fluid-applied rubber,” says Brosseau. 

Photos: Scott Shigley for site design group ltd.

The membrane is installed in two coats. The first coat is 90 mils with fabric reinforcement on top. The second coat is 125 mils, for a total of 215 mils. The hot rubberized asphalt, which is heated to 350-375 degrees, and cools as a solid, forming a monolithic membrane. “The membrane is adhered directly to the deck, and it forms one contiguous layer from parapet to parapet,” Yanez says. “They basically make a bathtub up on top of that roof, and then with all of the other design elements, you can do structural construction on top of the Styrofoam. It’s a much simpler, easier system, and the reality is there are fewer opportunities for it to fail because it’s a very simplistic approach.”

“Hydrotech’s system is easy to work with,” Brosseau notes. “The liquid is a very good product to work with on tough details. Another big advantage of the Hydrotech system, especially in this case, is that it isn’t temperature sensitive.”

Living Roofs

Sections of the roof with limited access were topped with an extensive vegetative system featuring Hydrotech’s InstaGreen sedum mat. River rock was applied as a perimeter border. “We’d get them watertight, and then we’d come back and install the garden systems after the other trades were done on the roof,” Brosseau explains. 

On the fifth-floor terrace, Bennett & Brosseauinstalled pavers, wood steppers and wood benches made from reclaimed Robinia. “We put down granite for pathways,” Brosseaunotes. “We had ballast, intensive garden, extensive garden, pavers, logs and the granite walkway. On Level 5, we had a lot going on.”

The material changes and the ground changes were designed to represent an actual prairie, according to Ishikawa. “There is a little trail that goes off and creates a little circle of seating,” she notes. 

Native grasses were chosen to provide visual interest and survive Chicago’s tough winters. These plants were plugged into the sedum mat to ensure the living roof would have complete coverage at the outset. “That was important to us so that the area wouldn’t be trampled while the native grasses and flora were emerging,” says Ishikawa.

Brosseau credits the support of the manufacturer before and during the project as the key to navigating all of the many details. “We regularly consult with Hydrotech’s technical department on non-standard details,” he says. “We’ll brainstorm to determine what the best solution is. There is also a value beyond that, and that is it helps the owner and the general contractor to see Hydrotech come out and recommend different ways to attack a problem.”

Bennett & Brosseau also installed edge metal, beam wraps, expansion joints, scuppers and downspouts. “The sheet metal was probably the most difficult part of it,” Brosseau says, “We custom fabricated everything in our shop. No two details were the same. For the bar area on Level 7, we fabricated a stainless-steel bar top for them as well.” 

It’s a Jungle Gym Out There

Crowning the fifth-floor roof area is a Nesci dome, a climbable sculpture created by artist Jonathan Nesci that has been likened to an “adult jungle gym.” According to Ishikawa, the blue metal design was inspired in part by the Louis Comfort Tiffany Dome in Chicago’s Cultural Center. “That one is an absolutely gorgeous Tiffany Dome with mosaic tile and glass,” Ishikawa notes. “This one is about the exact size and shape, so it’s kind of a reference of that cultural institution on top of the Ace Hotel. It’s meant to be a climbable, playful structure.”

“This roof is really exciting to us because it’s a very playful design,” Ishikawa continues. “Our firm in general believes that playful design also makes really loved landscapes. We were very excited to work on that part of it.”

Yanez points to the versatility and durability of the roof system as the key to a successful project that provides a long service life and the peace of mind of a single-source warranty. “We are happy to be able to give the market what it wants, and a lot of that hinges on the design creativity and pushing the envelope that the architects do,” he says, “We are very good at adapting to that and offering them a rock-solid assembly that, if applied correctly, should last the lifetime of that structure.”

TEAM

Lead Architect: GREC Architects, Chicago, Illinois, http://grecstudio.com

Landscape Architect: site design group ltd., Chicago, Illinois, www.site-design.com

General Contractor: Power Construction Company, Chicago, Illinois, www.powerconstruction.net

Roofing and Waterproofing Contractor: Bennett & Brosseau Roofing Inc., Romeoville, Illinois, www.bennettandbrosseau.com

MATERIALS

Roof Membrane: Monolithic Membrane 6125-EV, Hydrotech, www.hydrotechusa.com

Membrane Reinforcement: Hydroflex RB II-Hydrotech

Insulation: 60 PSI Extruded Polystyrene Insulation, Hydrotech/Dow, www.dow.com

Drainage Material: GR30 Water Retention and System Filter, Hydrotech

Flashing: Flex-Flash MB Granulated Flashing, Hydrotech

Growth Media: Litetop Intensive Media, Hydrotech

Vegetation: InstaGreen Sedum Carpet, Hydrotech

New NHL Practice Facility and Community Center Sports Vegetative Roof

The American Hydrotech Extensive Garden Roof Assembly was installed on two sections of the roof. The system was topped with pre-grown mats featuring mature sedum plants. Photo: American Hydrotech Inc.

The Chicago Blackhawks have captured the hearts of the city of Chicago along with three Stanley Cups in the last decade. The Blackhawks routinely lead the league in attendance at the United Center, and fans were excited when the team announced it would build a new 125,000-square-foot training facility and community center in downtown Chicago.

Completed earlier this year, the MB Arena features two NHL-sized ice rinks and other amenities including a fitness center, dining options, and spaces that can be rented for outings and events. The facility is the practice site for the Blackhawks and also hosts youth hockey, adult hockey leagues and public skating.

When plans for the project were unveiled, architects and planners mandated the facility meet or exceed all green and sustainable standards for the city. Chicago has been a leader in promoting vegetative roofs to help control storm water runoff, and this new construction project was no exception. The arena includes the construction of 24,000 square feet of green roof systems to complement the structure’s 68,000-square-foot main roof. A 60-mil TPO system manufactured by Carlilse SynTec was specified for the upper roof assembly, and plans called for an American Hydrotech Extensive Garden Roof Assembly to be placed on two lower sections of the roof.

The Garden Roof Assembly

Architect HOK worked with American Hydrotech during the design stage to select roofing components and plants that were optimized for the climate conditions and the building’s structural limitations.

According to Dennis Yanez, national marketing manager, American Hydrotech, and Kevin Serena, garden roofing technical sales coordinator for the central region, the structure’s metal deck necessitated a lightweight system.

The 125,000-square-foot facility 24,000 square feet of green roof systems that complement the structure’s 68,000-square-foot main roof. Photo: Chicago Blackhawks.

“Our 4-inch extensive garden roof system was ideal for this project,” says Yanez. “Since part of this project had a metal deck, there are more structural capacity concerns than with a concrete deck, so we were able to put together a lightweight, built-in-place system.”

The assembly consists of a hot-applied rubberized asphalt membrane, MM6125, which is applied to the roofing substrate to form a monolithic coating. It is topped with a root barrier and Dow Styrofoam insulation. The system also incorporates Hydrotech’s Gardendrain GR15, a molded polyethylene panel designed to retain water, filter fabric, lightweight growing media, and mature plants.

The plants are installed in the form of the InstaGreen Sedum Carpet, a pre-grown mat that comes in 25-square-foot rolls. It contains between nine and 15 different types of sedum and provides instant coverage when it is installed.

Key benefits of the system include reducing the urban heat island effect, purifying the air, and limiting storm water runoff, notes Yanez. “The Extensive Garden Roof Assembly is able to capture more than 1.5 inches of water on the roof, which plays a major role in storm water management,” he says.

The system also protects the membrane from ultraviolet (UV) degradation and damage from wind-blown debris. “Most importantly, for us, a garden roof is just another version of a PMR, or protected membrane roofing,” says Yanez. “Because the membrane is always in a PMR application, with Dow insulation over it, whatever ballast — whether it’s gravel ballast, or architectural pavers, or the garden roof assembly — is in place makes it literally impossible for the membrane to get damaged. It also mitigates the climate swings, keeping the membrane at a more constant temperature year-round.”

This system has a proven track record, according to Yanez. “We’ve been doing this going back 50 years on parking decks under regular topsoil, where weight wasn’t a concern,” he points out. “This is just a more modern version of that, but we’re putting it on the 4th, or the 14th, or the 99th floor.”

The Roofing Installation

All American Exterior Solutions, Lake Zurich, Illinois, is an approved applicator for both key manufacturers. The union contractor installed the Carlisle TPO system on the building’s main roof and the Hydrotech green roofs on the two lower roof levels.

Willie Hedrick, division manager at All American Exterior Solutions, notes that the TPO roof was installed first. “The deck was acoustic, so first we had to lay strips insulation in the flutes over the entire main roof,” he says.

The lightweight growth media was lifted to the roof in 2-yard totes. Photo: Christy Webber Landscapes.

Areas that housed mechanical equipment were reinforced with two layers of 5/8-inch DensDeck from Georgia-Pacific. Two layers of 2.6-inch insulation were then installed, followed by the 60-mil TPO, which was mechanically attached using the RhinoBond system from OMG Roofing Products. The attachment system uses induction welding technology to attach the membrane to the fasteners and plates that secure the insulation — without penetrating the membrane.

The main roof was originally designed as fully adhered system, but work began in January, and the temperature constraints ruled out some adhesives. “Once we made the switch to RhinoBond, we were able to install the membrane even though we did it during the winter,” Hedrick says.

Most of the TPO roof was surrounded by high parapet walls, and in other areas the safety perimeters were marked with flags. “At a few points at the highest points of the main roof we had to put up some the flags, and if you were outside of the flags you had to be tied off,” notes Hedrick. “The mid-roofs had short parapet walls, and on those roofs, we set up flags and had 100 percent fall protection outside the safety perimeter. For the lower green roof, we put guardrails up on the parapet to eliminate the fall hazard.”

The Garden Roofs

After the TPO sections were installed, work began on the extensive garden roof assemblies. The mid-roof had a metal deck, so the first step was to screw down 5/8-inch USG Securock cover board and strip in the seams. “At that point, we installed the liquid-applied membrane and the protection board,” Hedrick says.

The second green roof was installed over a concrete deck, so the application was a bit different. The membrane was applied directly to the concrete. A late change was made in the configuration of the lower green roof to take advantage of the space. “The owner decided to add a terrace to the lower green roof so people could walk out and see the roof and views of the city,” Hedrick recalls.

Before the growing media and plants were added, electronic field vector mapping (EFVM) was conducted by International Leak Detection to determine if there were any voids in the membrane. “You’ve got to confirm everything is 100 percent watertight before we start setting the components down,” Hedrick says. “We usually do the test and start putting the components down the next day to minimize exposure. The subcontractor we worked with to do the landscaping, Christy Webber, performed well. Since some of the components are loose laid, we worked with them to put down enough soil to hold everything in place. We worked hand-in-hand getting the all of the components and soil in.”

The Landscape Work

Jim Waldschmidt, project manager for Christy Webber Landscapes, Chicago, oversaw the installation of the lightweight growing media and sedum mats on the roof. Christy Webber is a full-service union landscaping company, and Waldschmidt notes that roofing work is a small but growing share of the company’s business. “We work with a few different commercial roofers,” he says. “This year we’ve done maybe 10 commercial projects.”

After the growing media was evenly spread out, the sedum mats were laid into place by crews from Christy Webber Landscapes. Photo: Christy Webber Landscapes.

Logistics at the site made for an easy delivery and setup — an unusual situation in downtown Chicago. “We were able to deliver the soil almost a week before we were scheduled to go out there, so we had everything on site and knew we wouldn’t have to worry about waiting,” Waldschmidt notes. “We just had to bring in a crane and lift up the soil bags. We had a pretty easy installation compared to other green roofs we’ve done.”

Growing media was lifted to the roof in 2-yard tote bags, which were cut open to disperse the contents. Three days after the growing media was in place, Christy Webber crews returned to install the sedum mats. “The sedum mats are delivered on pallets almost like the way a roll of sod would be delivered,” says Waldschmidt. “We just had to set the pallets on the roof, pull off the sedum mats and unroll them.”

A temporary irrigation system was set up to help the plants get established in the hot July temperatures. “Everything looks great now,” Waldschmidt says. “All of the sedum up there is thriving.”

Growth Sector

In this high-profile project, with a high-profile owner, making sure the system was error-free was critical, notes Serena. “Chicago is definitely the leader in vegetative roofs, and has been for more than 10 years,” he says. “This is another prime example. There was never a question whether this building would have a green roof on it. It’s a credit to Chicago, and it is a credit to the Chicago Blackhawks.”

Hedrick is proud to be part of the green roof movement. “I like the challenge, and I like the diversity,” he says. “When the Blackhawks went to the Stanley Cup championship and the blimp was hovering over the arena, I could see a couple of my projects on TV. It reminded me of all the time, effort, attention to detail, and collaborative hard work that it took to produce the final product. We’re turning typically unusable roof areas into useful space for amenities.”

The key driver of green roofs is storm water management, notes Yanez, but turning rooftops into useful space is another key benefit. “We’re seeing more and more city incentives for storm water management,” he says. “In urban areas, people are also taking advantage of existing space with green roofs. It’s a growing industry — pun intended.”

TEAM

Architect: HOK, Chicago, www.HOK.com
General Contractor: James McHugh Construction, Chicago, www.McHughConstruction.com
Roofing Contractor: All American Exterior Solutions, Lake Zurich, Illinois, www.AAEXS.com
Landscape Contractor: Christy Webber Landscapes, Chicago, www.ChristyWebber.com

MATERIALS

Garden Roof System:
Cover Board: Securock Gypsum-Fiber Roof Board, USG, www.USG.com
Membrane: MM6125 hot rubberized asphalt membrane, American Hydrotech Inc., www.HydrotechUSA.com
Protection Sheet: Hydroflex 30, American Hydrotech Inc.
Root Barrier: Root Stop, American Hydrotech Inc.
Insulation: DOW Styrofoam, DOW Chemical, www.Dow.com
Drain Board: Gardendrain GR15, American Hydrotech Inc.
Filter Fabric: System Filter fabric, American Hydrotech Inc.
Growing Media: LiteTop Engineered Growing Media, American Hydrotech Inc.
Plants: InstaGreen Sedum Carpet, American Hydrotech Inc.

TPO Roof System:
Membrane: 60-mil TPO, Carlisle SynTec, www.CarlisleSyntec.com
Cover Board: DenDeck, Georgia-Pacific, www.BuildGP.com
Attachment System: RhinoBond, OMG Roofing Products, www.OMGroofing.com

TPO System Delivers Energy Efficiency for Company Headquarters

TurnKey Corrections constructed a new 115,000-square-foot in facility in River Falls, Wis.

TurnKey Corrections constructed a new 115,000-square-foot in facility in River Falls, Wis.

If you want it done right, do it yourself. Company owners Todd Westby and Tim Westby take a hands-on approach to running TurnKey Corrections, the River Falls, Wisconsin-based company that provides commissary and jail management services to county corrections facilities nationwide. The Westby brothers also take pride in the fact that TurnKey manufactures the kiosks it provides to its clients and develops and owns the proprietary software used to run them.

So, it’s perhaps not surprising that, when building the company’s new headquarters, Todd Westby, the company’s CEO, founder and general manager, served as the general contractor. Or that he had definite ideas regarding the roofing system that would be installed. Or that he was more than willing to get his hands dirty during the installation process.

Founded in 1998, TurnKey Corrections helps corrections facilities streamline and lower the cost of delivering a variety services to inmates, including commissary, email and email-to-text communication, video visitation, law library access, and paperless intra-facility communication and documentation. Following several years of robust growth, the company had outgrown its three existing buildings. So, it constructed a new 115,000-square-foot facility to bring all operations, including 50,000 square feet of office space and a 65,000 square-foot warehouse where commissary items are stored prior to shipment to corrections facilities, under a single roof and accommodate future success.

“We wanted to be involved in the project from beginning to end so we knew what we were getting and how it was built,” Todd Westby says of the decision to keep construction management in-house. “We wanted to know about anything and everything that was being built for the company in this building.”

In planning the project, Westby initially set two key criteria for the roofing system: that the building would be made watertight as quickly as possible so concrete slab pours and other interior work could be completed, and that the roof would be covered by a warranty of at least 20 years. The design-build firm’s initial plans called for a ballasted EPDM roofing system, but Rex Greenwald, president of roofing contractor TEREX Roofing & Sheet Metal LLC of Minneapolis, suggested a white TPO system, noting that it would meet the quick installation and warranty goals while also enhancing the building’s energy efficiency. Westby was intrigued and, after some research, agreed to the recommendation. In addition to helping reduce cooling costs during summer months, the reflective surface would allow a blanket of snow to remain on the roof during winter months to provide additional insulation.

The TPO roofing system was constructed over a 22-gauge metal fabricated roof deck.

The TPO roofing system was constructed over a 22-gauge metal fabricated roof deck.

The Roof System

The TPO roofing system included a 22-gauge metal fabricated roof deck; two 2.5-inch-thick layers of Poly ISO insulation from Mule-Hide Products Co., with tapered insulation saddles and crickets to aid drainage; and 811 squares of 60-mil white TPO membrane from Mule-Hide Products Co. The insulation and membrane were mechanically attached using the RhinoBond System from OMG Roofing Products. Cast iron roof drains, designed and installed by a plumber, were used rather than scuppers and downspouts—a practice that the TEREX team strongly recommends to prevent freezing during the cold Upper Midwest winters. Walkways lead to the mechanical units, protecting the membrane from damage when maintenance personnel need to access the equipment.

The TEREX team finds the RhinoBond System to be the most efficient and economical attachment method for TPO systems. Specially coated metal plates are used to fasten the insulation to the roof deck and then an electromagnetic welder is used to attach the membrane to the plates. The membrane is not penetrated, eliminating a potential entry point for moisture. And while other mechanical attachment methods require the crew to seam as they go, the RhinoBond System allows them to lay the entire membrane (a task which must be completed in good weather conditions) at once and go back later to induction weld the seams and plates, which can be done when Mother Nature is slightly less cooperative.

Greenwald estimates that the switch from the originally specified ballasted EPDM system to the TPO roofing system and RhinoBond System shaved at least 10 percent off the installation time and reduced the roof weight by 10 pounds per square foot.

Having Westby on-site as the general contractor also sped up the project considerably, Greenwald notes. “He was a huge asset to all of the subcontractors,” he explains. “We could get construction questions answered quickly and could talk through issues and procedures on a timely basis.”

And the most memorable moment in the project for Greenwald was seeing Westby working side-by-side with his crew. “One day we had a delivery truck show up, and Todd jumped on the forklift and helped us unload the truck.”

As sought from the project’s outset, the roofing system is backed by a 20-year, no-dollar-limit labor and material warranty.

With one winter of use in the rearview mirror, the roofing system has exceeded Westby’s expectations. Warehouse space was doubled, but heating costs have been cut in half. The 10-unit heating system also is able to keep the warehouse a uniform temperature, without the cold spots that were common in the old building.

“It really is a beautiful, very efficient and organized-looking roof,” Greenwald says.

Green Roof Provides Learning Opportunities at the University of Iowa’s Pappajohn Biomedical Discovery Building

Established just 59 days after Iowa became a state in 1847, the University of Iowa, Iowa City, boasts a number of firsts. In 1855, it became the first U.S. public university to admit men and women; at that time, its enrollment consisted of 124 students—41 of which were women. In 1873, it was the first school to grant a law degree to a woman. In 1895, it became the first university to place an African American on a varsity sports team.

As such, the university’s new Pappajohn Biomedical Discovery Building was designed and built with sustainability in mind. PHOTO: Roof Top Sedums LLC

The university’s new Pappajohn Biomedical Discovery Building was designed and built with sustainability in mind. PHOTO: Roof Top Sedums LLC


In more recent years, the university has strived to lead via its environmental efforts. As a Green Power Partner of the Washington, D.C.-based U.S. Environmental Protection Agency, the university pledges to reduce the environmental impact of electricity generation through the use of renewables. In 2010, it established its first sustainability plan—2020 Vision UIowa Sustainability Targets, which contains the following goals:

  • Become a Net-negative Energy Consumer
  • Green Our Energy Portfolio
  • Decrease Our Production of Waste
  • Reduce the Carbon Impact of Transportation
  • Increase Student Opportunities to Learn and Practice Principles of Sustainability
  • Support and Grow Interdisciplinary Research in Sustainability-focused and Related Areas
  • Develop Partnerships and Advance Collaborative Initiatives, both Academic and Operational

Among the University of Iowa’s strategies to achieve its sustainability goals is ensuring all new construction and major renovations on campus achieve a minimum LEED Silver certification from the U.S. Green Building Council, Washington.

The 200,000-square-foot, 6-story building, which officially opened in October 2014, boasts many environmentally friendly attributes.

The 200,000-square-foot, 6-story building, which officially opened in October 2014, boasts many environmentally friendly attributes. PHOTO: Scott Nagel


As such, the university’s new Pappajohn Biomedical Discovery Building was designed and built with sustainability in mind. The 200,000-square-foot, 6-story building, which officially opened in October 2014, boasts many environmentally friendly attributes, including glow-emitting sealants, paints, carpet and other materials; water-efficient landscaping; and recycled content and regional materials. It also achieves an-other university first: three green roofs, one of which provides students the opportunity to grow medicinal plants.

Opting for Trays

Des Moines, Iowa-based landscape architecture firm Confluence has been completing projects at the University of Iowa for many years through its Iowa offices—Des Moines and Cedar Rapids. Confluence was hired by the project’s architect of record, Rohrbach Associates PC Architects, Iowa City, to complete landscaping around and on top of the Pappajohn Biomedical Discovery Building in the form of three green roofs that total approximately 6,440 square feet. Despite the building’s consider-able roof area, the design team opted to install the green roofs on lower roof areas upon which building occupants would be looking. The rest of the roof cover is a reflective membrane system.

Confluence provided the layout for a modular green roof on the three distinctive roof areas. Patrick Alvord, PLA, RA, LEED AP, a principal in Confluence’s Cedar Rapids office, notes the chosen tray system was off-the-rack, which is what made it appealing to him and his colleagues. “We spent a lot of time talking to the manufacturer and they were just great to work with,” Alvord says. “We had a number of case studies of work they had done in the Chicagoland area that had proven very successful, so we had a very high level of comfort right out of the gate.”

Alvord opted to use the 6-inch-deep tray model because it would provide some flexibility in the plant materials that could be specified. “We were able to specify different plant materials in the plan of the roof to coordinate with shade, densities and location,” he says. “In areas where the roof would be highly visible from floors above, we did some patterning with the plants. In areas where we had the opportunity to go deep, we planted deeper-rooting plants that will grow taller and provide a denser plant palette.”

The plants are a mix of native and adaptive Iowa plants, as well as recommendations from the green-roof supplier. “It’s a mix of perennials, grasses and forbs, ranging from sedums to liatris to a number of different things,” Alvord notes.

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