Douglas A. Munro Coast Guard Headquarters Boasts One of World’s Largest Green Roofs

The Douglas A. Munro Coast Guard Headquarters Building in Washington, D.C., has more than 550,000 square feet of green roof space. Photos: Owens Corning

Like a 550,000-square-foot sponge, the vegetative roof assembly (VRA) atop the Douglas A. Munro Coast Guard Headquarters Building in Washington, D.C., absorbs rainfall while managing its release into the city’s sewer system. Green roofs are a storm water management “best practice” in the nation’s capital, which boasts more than 3.2 million square feet of green roof space.

Gordon Contractors installed the green roof on the 11-level, 1.2-million-square-foot headquarters, which is also home to several independent field commands including the National Pollution Fund Center and Marine Safety Center. Key performance objectives included complying with D.C.’s stringent storm water regulations, as well as federal Environmental Protection Agency (EPA) rules requiring 95 percent of storm water to be collected onsite.

Beyond complying with local and federal storm water mandates, the project team creating the vegetative roof sought to create a rooftop habitat that supports biodiversity and helps birds and other wildlife thrive. The result of a careful and collaborative approach to moisture management is a high-performing roof that ultimately received LEED Gold certification from the U.S. Green Building Council. Working as a system, the roof’s components help reduce rainwater runoff while helping to reduce pollutant loads and protect natural resources such as the nearby Chesapeake Bay.

Numerous Challenges

As every roofer knows, no two projects are alike. The location of the Douglas A. Munro Coast Guard Headquarters on hilly terrain provided plenty of natural obstacles, including nine of the eleven levels being built into a hillside. The site

Gordon Contractors installed the green roof on the 11-level headquarters. Performance objectives included complying with D.C.’s stringent storm water regulations, as well as federal EPA rules requiring 95 percent of storm water to be collected onsite. Photos: Owens Corning

features a series of stair-stepped green roof terraces that help gradually move water from higher to lower levels and eventually into a pond through elevation changes of 120 feet. According to Steve Gordon, president of Preservation & Protection Systems Inc. (PPSI), the company providing design and installation support with the Owens Corning FOAMULAR extruded polystyrene insulation and Henry 790-11 Hot Rubberized Asphalt used in the VRA, the stair-step design required a complex approach to the roof’s varied elevations. To meet this challenge a complex network of expansion joints by EMSEAL tied together multiple air barriers within the system. Another challenge was the magnitude of the project, spanning more than a half-million feet across multiple levels and 176 acres. Timing was critical, as plants and vegetation required quick delivery and transplanting into their new environment, particularly during D.C.’s sweltering summers. These living materials couldn’t simply be covered with a tarp until better conditions prevailed, but had to be quickly transported, installed and irrigated.

The Douglas A. Munro Coast Guard Headquarters serves 4,000 occupants, so comfort and energy efficiency were important concerns. From the outset of the project, the integrated roofing team was tasked with designing a vegetative roof assembly that would help decrease the building’s heating and cooling energy usage, lower long-term maintenance costs and extend the life of the roof.

A Solution to Achieve Performance Goals

The project team selected a Protected Roof Membrane Assembly (PRMA) to deliver the water management required to meet storm water mandates, as well as deliver energy efficiency through R-value performance and strength to support vegetation requirements. The PRMA places the insulation layer above the waterproofing membrane, a reversal of traditional roof systems. PPSI recommended Owens Corning FOAMULAR 404 and 604 extruded polystyrene (XPS) insulations for use in the PRMA. The water resistance and compressive strength of the XPS insulation provided the integrity needed for long-term roof performance and helped the Douglas A. Munro Coast Guard Headquarters Building ultimately achieve LEED Gold certification.

The Douglas A. Munro Coast Guard Headquarters was built on hilly terrain, and nine of the eleven levels were built into a hillside. The stair-stepped green roof terraces help gradually move water from higher to lower levels and eventually into a pond. Photos: Owens Corning

Given the sheer size of the project, it was inevitable that the roofing team would encounter several scenarios requiring strategic problem-solving throughout the installation. For example, the team adjustedthe engineered soil specification to reduce the loads within the structural tolerances for the roof structure and carefully addressed a range of pH, moisture, organic matter and nutrient levels to support the variety of plants. Not only did such careful attention deliver strength performance, it’s also achieved the objective of attracting wildlife. The terraced landscape has welcomed not only birds and butterflies, but the occasional deer wandering onto a rooftop.

Evaluating Results

Since its completion, the VRA at the Douglas A. Munro Coast Guard Headquarters has attracted widespread attention from landscaping groups, engineering firms and organizations interested in sustainability. These groups are interested not just in the building’s unique design but in its resilience and performance. Steve Gordon of PPSI says the resilience of the headquarters’ roof is reflected in its record of no leaks. “We’ve had no leaks,” Gordon says. “The reason we use hot fluid applied waterproofing on green roofs is because we want to avoid any leaks in the building. At the end of the day, the biggest liability in a roof is water.”

After successfully navigating a range of challenges and opportunities, the U.S. Coast Guard Headquarters’ VRA epitomizes the convergence of aesthetics and performance and is recognizedas one of the largest green roofs in the world.According to the Landscape Performance Foundation, the headquarters’ vegetative roof retains up to 424,000 gallons of rainwater.

In a small way, the performance reflects the integrity of a hero an Act of Congress honored when naming the headquarters, according to Captain Will Smith, Commanding Officer U.S. Coast Guard Base NCR. Captain Smith noted, “The Coast Guard’s only Medal of Honor recipient, Douglas Munro earned the award for his selfless sacrifice as a landing craft pilot at Guadalcanal while evacuating marines from a beachhead under heavy fire from enemy forces.”

TEAM

Architect: WDG, Washington, D.C., www.wdgarch.com
General Contractor: Clark Construction Group, Bethesda, Maryland, www.clarkconstruction.com
Roofing Contractor: Gordon Contractors, Capitol Heights, Maryland, www.gordoncontractors.com
Independent Rep Agency: Preservation & Protection Systems Inc. (PPSI), Laurel, Maryland, www.ppsimd.com

MATERIALS

Insulation: FOAMULAR 404 and 604 extruded polystyrene, Owens Corning, www.owenscorning.com
Waterproofing Membrane: 790-11 Hot Rubberized Asphalt, Henry Company, https://us.henry.com
Expansion Joints: EMSEAL, www.emseal.com
Pavers: Hanover Architectural Products, www.hanoverpavers.com
Sedum Mats: Sempergreen, www.sempergreen.com

Roofing Industry Alliance for Progress Announces Additional Funding for Roofing Research

The Roofing Industry Alliance for Progress announces the addition of four members during 2016’s third quarter, adding $300,000 in funding for progressive roofing research that contributes to the ongoing advancement of the industry.

The Alliance’s newest members are:
Academy Roofing, Aurora, Colo., is one of Colorado’s premier roofing contractors providing commercial and residential roof system replacement and repair in addition to solar roofing, gutter installation and cleaning, new insulation and walkable deck systems. Academy Roofing joined the Alliance at the Governor level.

Bennett and Brosseau Roofing, Romeoville Ill., specializes in in low-slope, steep-slope, metal and green roof system design, construction and maintenance. As one of Chicago’s premier, full-service roofing contractors, Bennett and Brosseau Roofing has a commitment to sustainability and green building practices. Bennett and Brosseau Roofing joined the Alliance at the Governor level.

FiberTite Roofing Systems/Seaman Corp., Wooster, Ohio, manufactures an extensive line of membranes, systems and accessories. FiberTite Roofing Systems/Seaman joined the Alliance at the Regent level.

Georgia-Pacific Gypsum LLC, Atlanta, one of North America’s leading manufacturers of gypsum products and marketers of building products. GP Gypsum joined the Alliance at the Regent Level.

Through the generosity of its members, The Roofing Industry Alliance for Progress commits to the following:
Education and training — Develop programs and projects addressing current and future workplace issues ensuring a qualified and trained workforce for the roofing industry.

Technology — Engage collaborative industry segments to embrace innovation and use technology.

Sustainability — Advocate environmentally sustainable design.

Philanthropy — Enrich the well-being of the roofing community through scholarships, charitable gifts and endowments.

Alliance membership is reserved for those who commit their pledged amount during a three- to five-year period. All members are entitled to participate in the task forces established to guide the Alliance’s agenda, to attend the semiannual meeting of the full Alliance, and other Alliance activities scheduled throughout the year.

Roofs Are a Potential Solution for Urban Stormwater-management Issues

Can stormwater management using rooftops in urban areas be the financial solution to our growing urban stormwater problem? Will public-private partnerships with building owners help to provide a government service—stormwater drainage—in a more cost-effective manner? As cities struggle with the high administrative and procurement costs and time delays to manage stormwater, should we be looking up to roofs as part of the solution? Can we avoid more regulations and instead look to market-based solutions? These questions are beginning to be discussed and tested as new, innovative approaches to solving difficult and expensive urban stormwater-management issues.

Consulting and engineering firm Geosyntec Consultants is monitoring and controlling runoff from an existing New York City Parks and Recreation facility green roof.

Consulting and engineering firm Geosyntec
Consultants is monitoring and controlling runoff from an existing New York City Parks and Recreation facility green roof.

STORMWATER MANDATES

Many cities and counties are dealing with more stringent stormwater permits issued from the Washington, D.C.-based U.S. Environmental Protection Agency (EPA) and state environmental agencies that implement the federal Clean Water Act. Many communities are operating under federal court orders and administrative consent orders from EPA to reduce stormwater runoff into rivers, lakes and streams. In addition, there are 177 communities in the U.S. where stormwater and wastewater-collection systems are combined, known as combined sewer overflows (CSOs). These CSOs result in billions of gallons per year of combined untreated stormwater and wastewater discharged into waterways during large rainfall events. Funding crises have developed in many municipalities as they create programs, hire new staff, and design and construct new infrastructure to meet these regulatory requirements.

Many cities have spent billions of dollars separating stormwater drainage from wastewater-collection systems by installing new, costly drainage systems. In addition, large underground storage tunnels and vaults have been installed by many cities at the costs of billions of dollars per installation. These tunnels and vaults are designed to collect, hold and slowly release the stormwater into the treatment network. Increasing stormwater pipe sizes and creating tunnels and vaults is extremely costly. For example, Washington, D.C., just broke ground on the construction of two stormwater tunnels that are currently projected to cost $2.6 billion dollars to construct. Just one of the tunnels will be 13-miles long and hold 157 million gallons of combined stormwater and wastewater in 23-foot-diameter tunnels, 100-feet below the surface.

Green-infrastructure approaches to stormwater issues are included in most municipal stormwater permits and orders. For example, New York City is spending $187 million on green infrastructure for stormwater control in CSO areas to control the equivalent of 1 1/2 inches of runoff from impervious surfaces by December 2015. Public and private areas are under consideration for green-infrastructure solutions, and the city expects to spend $2.4 billion in green infrastructure during the next 20 years.

As cities address urban stormwater management, stormwater fees are being assessed on private-property owners to help fund the programs to solve urban stormwater issues. Close to 1,500 stormwater utilities are now in operation in the U.S., and the number is rapidly growing. These stormwater utilities typically are assessing stormwater fees based on the amount of impervious surfaces by property owner. The fees can range from a few hundred dollars per year to tens of thousands.

Roofs are considered an impervious surface because they are designed to shed stormwater through drainage networks into the collection system beneath city streets. For example, in New York City alone roofs make up 11.5 percent of the total area, or roughly 944.3 billion square feet, according to the city’s Department of Design and Construction’s Cool & Green Roofing Manual. Rather than looking at roofs as part of the stormwater problem in cities, they should be viewed as a possible solution.

DID YOU KNOW?

Baltimore enacted a stormwater fee
in 2013. Currently a building with a
200,000-square-foot roof would be
assessed $11,400 per year.

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From Green to Blue: Making Roof Systems Sustainable in Urban Environments

Municipal storm-water managers historically have focused on controlling runoff from ground-level impervious surfaces, such as roadways, sidewalks and parking areas. However, the next frontier in storm-water management is rooftops. In urban storm-water management, roofs are part of the problem and potential solution. An exciting new technology to control rooftop runoff is known as blue roofs. Over the next several years, New York City alone will spend several billion dollars on green infrastructure solutions to address its storm-water-control problem, and blue roofs will be a key part of these efforts.

Blue-roof trays are held in place with stone ballast and hold up to 2 inches of water. The tray systems resulted in a 45 percent reduction in roof runoff during rainfall events in a New York pilot project.

Blue-roof trays are held in place with stone ballast and hold up to 2 inches of water. The tray systems resulted in a 45 percent reduction in roof runoff during rainfall events in a New York pilot project.

Blue Roofs

The roofing industry has become very familiar with the use of vegetated, or green, roofs. The vegetative layer grown on a rooftop provides shade and removes heat from the air through evapotranspiration, ultimately reducing temperatures of the roof surface and the surrounding air. By reducing the heat-island effect, these buildings require less energy to cool in the summer and use fewer natural resources (oil or other fuel) in the process.

However, an even newer and less-well-known sustainable technology applicable to roofs is the blue roof. A blue roof temporarily stores rainwater in any of a number of types of detention systems on the roof. They are most applicable and provide the most benefit in highly urbanized cities that are serviced by combined sewers. Combined sewers handle sewage and rainwater runoff from roofs, streets and other impervious surfaces. On dry days, these combined sewers can easily handle the amount of sewage flowing through them to the local treatment plant. However, on days with heavy rain, these combined systems can easily overflow with rainwater and raw, untreated sewage. This combined sewer overflow, or CSO, can flow into local sensitive receptors, like streams, ponds and oceans, contaminating the natural resources and killing fish and other wildlife dependent on them.

The beauty of blue roofs is they can store much of this rainwater during and immediately after a rainstorm, temporarily preventing it from reaching the sewer system. In this way, CSOs are minimized and local natural resources are protected. When the storm is over and the sewer system has the capacity to handle it, the blue-roof retention materials are designed to slowly release the stored rainwater back into the storm-drain system.

This blue roof in New York uses a check dam to retain storm water.

This blue roof in New York uses a check dam to retain storm water.

NYC Pilot Program

Our firm, Geosyntec Consultants, along with environmental engineers Hazen and Sawyer and HydroQual and water-management firm Biohabitats, designed and implemented a groundbreaking blue-roof system in New York. The New York City Department of Environmental Protection (NYCDEP) retained the team to implement a sustainable green infrastructure retrofit pilot program to demonstrate how rooftops can reduce the frequency and volume of CSOs in the city. The objective was to design and install storm-water controls to quantify the benefits of sustainable approaches as a viable solution to reduce storm-water flows to the city’s CSO system. Rainfall of less than 1/2 inch can overload the system and result in untreated discharges. The use of sustainable green infrastructure, like blue roofs, to reduce storm-water inputs to the combined system is one of many approaches New York City is considering to help solve this problem.

Geosyntec’s role on the team was to design several storm-water pilot studies, including blue roofs. Our blue-roof designs included installing risers on rooftop outlets that would result in ponding of water around the outlets, small dams on the roof surface using check dams of angle-iron to create ponding and the most successful technique—blue-roof trays. We developed specially designed trays, held in-place with stone ballast, to hold up to 2 inches of water. The tray systems resulted in a 45 percent reduction in roof runoff during rainfall events. If blue-roof trays were installed on all roofs in an entire drainage area to a CSO, the results would be significant in solving the CSO problem. In addition, trays are more practical because they can be spaced around existing equipment on roofs and moved during repairs and maintenance of other rooftop systems.

Geosyntec Consultants designed a blue roof that included installing risers on rooftop outlets that would result in ponding of water around the outlets.

Geosyntec Consultants designed a blue roof
that included installing risers on rooftop outlets that would result in ponding of water around the outlets.

Roof-system Protection

Protecting the integrity of a roof membrane is an important consideration for roofing and building contractors that are considering installing a blue roof. Blue-roof-tray systems offer the best protection because they rest on top of existing membranes and ballast systems and do not result in any membrane perforations that require additional waterproofing. Other blue-roof systems, like check dams or new drain inserts, may require additional waterproofing. The bottom line is if the roof membrane is old, compromised or currently leaking, any type of blue roof would be problematic until a new membrane is installed.

In addition, during the pilot projects, we took great care to inspect and test the roofs for load-bearing support—a step that should be conducted for all blue and green roof systems.

As we look to the future, roofs in urban areas will most definitely become a major part of the storm-water solution, and blue-roof technologies will evolve to become a common practice.

Learn More

NYCDEP has posted information about blue roofs and other urban green infrastructure for CSO control on its website.
The U.S. Green Building Council offers an online course about blue roofs for storm-water management.

PHOTOS: Geosyntec Consultants

Several ‘Sandwich’ Roof Assemblies Mitigate Sound Transfer

We all want a roof over our heads to protect us from the cold winter months, hot summer months and precipitation year round. How much thought goes into the sound-control construction of a roof, though? Have you considered the acoustic properties of your roofing system? Admittedly, acoustics is not a topic that many roofing contractors think about. The construction of a roof, however, can have a significant impact on the sound quality of the building interior. While this may not seem important in every project, it can be a critical element of the design for concert halls, theaters, auditoria and even school classrooms.

Sound Isolation

The acoustics of a space depend on many criteria, including sound isolation, sound reflection, impact noise and sound transfer. In many cases, particularly in noisy, urban environments, there is a need to prevent loud outside noises, such as traffic, sirens and airplane noise, from entering quiet spaces. Sound isolation depends on the entire envelope of a space, including external walls, windows and roofs.

Green roofs, particularly the “intensive” version, which includes several inches of heavier-weight soil, can provide effective sound control.

Green roofs, particularly the “intensive” version, which includes several inches of heavier-weight soil, can provide effective
sound control.

Historically, roofs over sound-sensitive spaces have been built with fairly dense materials, such as concrete, which by themselves are relatively effective in blocking sound transfer. As construction methods have developed, however, more lightweight construction is being used. If thought and care are not given to the assembly, these lightweight construction methods can cause serious issues with acoustics. Rain noise, mechanical noise and other exterior sounds can all transfer readily through a thin, lightweight roofing system.

In an effort to use lighter-weight construction, a “sandwich” assembly may be used to mitigate sound transfer. Similar to an Oreo cookie, a sandwich assembly’s outer layers are comprised of a heavy, dense material, and the inner filling consists of insulation and/or airspace. The materials of this assembly can differ from concrete to roofing board, rigid insulation to fibrous insulation, gypsum board to acoustic ceiling tiles. The components can be combined in a variety of ways, each with varying levels of sound isolation.

One of the principle phrases often heard when discussing sound isolation is “mass air mass”, which refers to the separation of two bodies of mass by an air space. The greater the mass and the deeper the air space, the more sound isolation will result. For this reason, a heavy mass, such as 5-inch concrete, followed by a deep air space, such as an 18- to 24-inch ceiling cavity in which ducts are run, followed by a continuous layer of drywall ceiling will provide a high level of sound isolation. Additional steps, like adding sound-absorptive material to the air space and/or using resilient connections when supporting drywall, further improves the sound isolation of the assembly.

Sandwich Roof Assemblies

Several sandwich roof assembly approaches are possible, including:

Good: Multiple layers of dense roofing board (at 2.5 psf per board, a final density of 10 psf or four-ply is often recommended) on either side of insulation, which ideally would be a sound-absorptive fibrous fill, like mineral wool, can reduce sound transmission. This approach is similar to a “floating floor”, often used in interior spaces to isolate sound transfer from one room to another. (Equivalent Sound Transmission Class, or STC, ratings can range from low 50s to low 60s, depending on whether a ceiling is included below the deck.)

Drywall ceilings hung on resilient hangers in conjunction with a lightweight roofing system provide even greater sound isolation by virtue of the resilient connection or “decoupling” of the drywall layer from the rest of the building structure.

Drywall ceilings hung on resilient hangers in conjunction with a lightweight roofing system provide even greater sound isolation by virtue of the resilient connection or “decoupling” of the drywall layer from the rest of the building structure.

Good: Green roofs, particularly the “intensive” version, which includes several inches of heavier-weight soil, can provide effective sound control. These can be part of a sandwich approach with airspace or rigid insulation between soil and a more-dense roofing material, similar to the roofing board described in the previous example. The mass-air-mass combination is similar to the approach just mentioned, and the benefits of green roofs appeal to many building owners for a multitude of reasons, including minimizing urban heat islands and storm-water management.

Good: A 5-inch slab of normal-weight concrete (150 pcf) has a density of 62 psf. This tried-and-true method is still used regularly and often proves to be the most cost-effective method of enclosing a space. The best sound isolation will occur if this is used in conjunction with a ceiling below, but on its own it still provides a reasonable level of isolation in many environments. This isn’t technically a sandwich system unless paired with a ceiling below or a green roof above. (Equivalent STC ratings can range from low 50s to low 80s. The highest ratings require pairing a resiliently hung ceiling with the concrete, as described under “Multi-function Roof Assemblies”.) IMAGES: Threshold Acoustics LLC [Read more…]