Roofing Contractor Tackles Obstacles Both Seen and Unforeseeable

Clark Roofing installed nearly 40,000 square feet of TPO from Mule-Hide Products Co. on three buildings in Waco: the McLennan County Sheriff’s Office (lower center), McLennan County Records Management (upper right), and the McLennan County Courthouse Annex. Photos: Clark Roofing

When Clark Roofing of Waco, Texas, was selected to re-roof three McLennan County facilities in downtown Waco, they knew there would be challenges. The roofs were all 35-plus years old and leaked; one was notorious for ponding water. There was 95 tons of gravel ballast to remove. Product deliveries would require navigating busy streets, power lines and rooftop-mounted communication towers. The buildings’ historic features needed to be preserved.

What the crew could not have predicted were the added challenges of working during the early weeks of the COVID-19 pandemic and during protests for racial justice.

But attention to detail, determination, and a knack for finding creative solutions are deeply engrained in the Clark Roofing culture. The crew completed the work in just 20 working days, delivering new TPO roofing systems that will stand up to the Texas heat and hail. Most important, everyone remained safe.

The built-up roofing (BUR) systems on the McLennan County Sheriff’s Office, the McLennan County Records Management building, and the McLennan County Courthouse Annex were in rough shape. At 35 years old, 45-50 years old, and 45-50 years old respectively, each had significant leaks. They remained structurally sound, however, so recovering them, rather full tear-offs, was chosen.

Designed to Take What Texas Dishes Out

Waco is in “Hail Alley,” and average high temperatures top 90 degrees Fahrenheit from mid-June until mid-September. To create roofing systems that would withstand those conditions over the long haul and receive the desired 30-year no-dollar-limit system warranties, Clark Roofing looked to their go-to single-ply roofing system — 80-mil-thick standard TPO in white, fully adhered.

Nearly 400 squares of TPO from Mule-Hide Products Co. was installed on the three buildings.

The Records Management building was originally constructed in 1916 and expanded in the early 1950s. Its failing built-up roof was replaced with a fully adhered TPO system.

“In our experience, the thicker TPO is by far the best option in terms of durability and getting hail ratings and FM Global coverage,” says Clark Roofing General Manager Mike Anderson. “TPO can handle the Texas heat.”

The fully adhered systems also will withstand the hailstorms Waco experiences every year better than mechanically attached system would.

“If a large piece of hail strikes a plate or screw, it can damage the membrane,” Anderson explains. “With full adhesion, you’re only using fasteners on the perimeter to meet wind uplift or FM Global requirements.”

Full adhesion costs 10 percent to 20 percent more than mechanical attachment, but given the pounding that Texas roofs take, it is an investment that will be recouped in roofing system durability and longer lifespan, according to Anderson.

The key is the wrinkle-free installation that full adhesion provides. “To withstand hail, the roof needs to be very tight,” Anderson says. “If there are places where the membrane isn’t touching the substrate, hail has a better chance of puncturing it. You’re also less likely to have ponding water when the membrane is wrinkle-free.”

One of the signature features of the Records Management building is the clay tile parapet, which was preserved during the roof replacement project.

TPO Bonding Adhesive from Mule-Hide Products was used to adhere the membranes. “Solvent-based adhesives flash off faster than water-based adhesives, deliver a stronger bond, and can be used on cooler days,” Anderson says.

In each roofing system, a single layer of 1.5-inch-thick Mule-Hide Poly ISO Flat insulation was used as a top layer insulation and a separation board. The insulation was adhered using Helix Max Low-Rise Adhesive from Mule-Hide Products.

Heavy Lifting

But before the new roofing systems could be installed, 95 tons of gravel ballast had to be removed. To ensure proper adhesion of the adhesive, the substrate must be clean and dry before the adhesive is applied. Many contractors would have simply shoveled the gravel off, filling three dumpsters, and called it a day.

From their previous, off-the-jobsite experimentation, the Clark Roofing crew knew that extra attention paid to surface preparation would result in a stronger bond. So, after shoveling, they swept the surfaces with a motorized broom and blew away the remaining dust, filling 19 dumpsters.

On the roof of the Sheriff’s Office, Clark Roofing installed six TPO-clad troughs to drain water to the scupper outlets on the building’s perimeter.

All three rooftops were ballast-free and clean before installation of the first new roofing system began, ensuring that crew members cleaning one roof section did not track dirt onto newly installed TPO.

It took nearly two full days to complete the clean-up, but it paid off in a tight bond between the insulation and the substrate.

Eliminating Problems

The roof of the Sheriff’s Office building had been plagued by ponding water for years. The original project specifications called for using tapered insulation to remove the water. But Clark Roofing had another solution that cost approximately $40,000 less to implement. Six TPO-clad troughs — 12 inches wide and 200 feet long — were instead installed, each connecting to scupper outlets on the building’s perimeter to direct the water off the roof.

The Clark Roofing crew installs the TPO membrane on the Sheriff’s Office.

The roof of the Courthouse Annex building was littered with 40 obsolete, damaged or torn-off penetrations for exhaust fans, sewer fans and air-conditioning units. They created an obstacle course and were the source of many of the roof’s leaks.

The crew removed the penetrations, along with miles of unneeded conduit and wire, reducing the potential for future leaks and making navigating the rooftop far easier.

“When we started, you couldn’t walk 3 feet without bumping into something,” Anderson says. “Now you can go 10 or 15 feet without any trouble.”

Preserving History

The Records Management building, constructed in 1916 for the Texas Telephone Co. and expanded in the early 1950s, is an architecturally significant fixture in downtown Waco. One of its signature features is its clay tile parapet walls.

Following the standard practice of installing wood blocking, then plywood, and finally the TPO membranes would have taken away from the building’s historic look. So, the Clark Roofing crew stopped the TPO membranes short of the parapet caps and terminated them inside the walls, out of sight from the street. They then refilled the joints and applied Foxfire Matrix Pro SS-WB for waterproofing. The roof was watertight, with the building’s character preserved.

Challenging Roof Access

Busy streets and the presence of high-voltage power lines made material deliveries challenging at all three buildings. Crews blocked off streets as necessary, working quickly to minimize disruptions. Many deliveries were scheduled at night or on weekends when traffic was lighter.

The crew removed 40 obsolete, damaged or torn-off penetrations, along with miles of unneeded conduit and wire, as they installed the new roof on the Courthouse Annex building.

Deliveries at the Courthouse Annex required flawless communication between the crane operator and roofing crew. There was only a 15-foot area in which to work. Communication towers used by the Sheriff’s department and other county agencies are located on the building’s roof, anchored by big guidewires. The building’s parapet wall is 5 feet high.

The crane operator could not rely on visual signals from crew members on the rooftop to direct him, as he could not see them over the wall. So, they used two-way radios, with crew members verbally guiding the crane operator inch by inch.

“You have to really trust someone to do that,” Anderson says. “He was spot-on.”

Early Days of COVID-19

The COVID-19 pandemic arrived just as the projects were beginning. But the roofs had been leaking for months, so there was no thought of postponing the work.

A variety of protocols were followed to keep everyone safe, including:

  • A supervisor was always on the jobsite for quality control and safety. Sometimes two were there — one on the ground and one on the roof.
  • All meetings were conducted virtually.
  • To avoid going inside the buildings, crew members rode a manlift to the rooftops. It took a full hour to get the eight- to 12-person team in place, adding a full day to the job.
  • All crew members wore face coverings, safety goggles and disposable gloves and regularly sanitized their hands. The crew went through as many as 200 disposable facemasks each week, and gaiters reminded them not to touch their faces.
  • Social distancing was practiced. “We don’t even think about staying 6 feet apart anymore,” Andersons says. “It’s automatic.”
  • Hand tools were not shared. If equipment, such as welders, needed to be shared, it was sanitized before changing hands.
  • Crew members had their temperature taken multiple times a day, and anyone found to be running warm was required to get a COVID-19 test.
  • Disposable water cups were provided. No bottles or cans were allowed on the roofs.
  • At lunchtime, crew members left the roof and cleaned up before eating.

The precautions worked. There were no known cases of COVID-19 among the crew.

Protests for Racial Justice

Sheriff’s deputies shut down the Courthouse Annex jobsite on three occasions, having received word that protesters for racial justice were planning to assemble outside the building. The crew was ordered to get off the roof. Anything that could be used to cause injury or damage property — from sharp tools to the Sky Trak — was removed from the jobsite.

Approximately 95 tons of gravel ballast had to be removed before the new roof systems could be installed.

On one occasion, the crew had just removed the exhaust fans from the roof. Anderson says, “We told the deputies, ‘There are 3-foot openings in the roof. If it rains, the building will flood.’ They said, ‘Get off the roof. If it leaks, it leaks; we’ll take responsibility.’ Luckily, it didn’t rain.”

Thankfully, the protests were peaceful, with no injuries and no damage to property. The shutdowns ranged in length from one to three days and delayed completion of the job by four or five days.

Three roofs. Twenty working days. Four hundred squares of new hail-resistant TPO roofing installed. Challenges — from the expected to the unforeseeable — overcome. No leaks during the active hail season that followed. Just another day at the office for the Clark Roofing team.

TEAM

Roofing Contractor: Clark Roofing, Waco, Texas, clarkroofingtx.com

Roofing Materials Distributor: ABC Supply Co. Inc., Branch #040, Waco, Texas, abcsupply.com

Crane Operator: Wales Crane & Rigging Service, Woodway, Texas, walescraneandrigging.com

Equipment Rental: Equipment Depot, Waco, Texas, eqdepot.com

Gravel Disposal: Rise Up Refuse Dumpster Rental & Demolition, Waco, Texas, thetexasdumpster.com

MATERIALS

Membrane: 80-mil Standard TPO in White, Mule-Hide Products Co., mulehide.com

Roof Insulation: Mule-Hide Poly-ISO Flat insulation, Mule-Hide Products Co.,

Adhesives: TPO Bonding Adhesive (to adhere membrane) and Helix Max Low-Rise Adhesive (to adhere insulation), Mule-Hide Products Co.

Edge Metal: TPO-Coated Edge Metal with Attached TPO Skirt, Mule-Hide Products Co.,

Roof Drains: TPO-clad retrofit roof drains, Mule-Hide Products Co.

Tapered EPS Approach Protects Airline Facility’s Roof

When a 200,000-square-foot warehouse was converted into an airport network operation center, the roof system needed a complete overhaul. Photos: Insulfoam

Dubbed the world’s sixth busiest airport in terms of total passengers, Chicago O’Hare International Airport accommodated 84 million passengers and 900,000 arriving and departing flights in 2019. Naturally, nearly every domestic commercial airline carrier is represented at the international transportation hub. To ensure passengers arrive to their final destination safely and on time, each airline company is supported by a network operation center (NOC). From this offsite locale, hundreds of highly trained employees coordinate travel logistics and monitor day-to-day flight activity.

When it comes to designing a best-in-class NOC facility, a properly insulated roofing system plays an integral role in optimizing operating efficiencies and ensuring long-term protection overhead. So, when a major commercial airline carrier purchased a 200,000-square-foot warehouse space near O’Hare to house its new NOC, project designers turned their attention to the roof. Upon initial examination, the existing roof system was deemed subpar and the NOC project designers elected for a complete overhaul.

A Creative Roofing Solution

Challenged with sourcing a superior insulation material for the renovation, the project’s roofing company, Olsson Roofing, opted for tapered expanded polystyrene (EPS) from Insulfoam. Tapered EPS satisfies International Building Code (IBC) requirements across both new construction and re-roofing applications, while maintaining consistent thermal performance and long-term moisture resistance.

NOC project designers turned to this rigid foam insulation as a logical, cost-effective means of building up the pitch of the low-slope structure. Positive slope will reduce stress on the roof’s membrane by eliminating the risk of standing water, a serious threat to the integrity of the building system. Without adequate drainage, the building owners may face costly repairs down the road or premature roof failure. By employing the tapered EPS approach, NOC project designers will proactively avoid these issues and extend the lifespan of the roof system.

Moisture Resistance

Crews from Olsson Roofing installed flat and tapered EPS insulation and TPO membrane.

Long-term exposure to moisture can be extremely detrimental to a roofing system. But while the purpose of a tapered EPS approach is to keep pooling water at bay, moisture absorption is sometimes inevitable — particularly during Chicago’s winter months. To the NOC project designers’ advantage, EPS provides a high level of moisture resistance and breathability. A study by the Energy Materials Testing Laboratories (EMTL) has shown that EPS installed in a well-constructed roof does not absorb appreciable moisture, even under conditions characteristic of prolonged, cold, damp winters. The same amount of moisture absorbed (an average of 0.2 percent by weight) has little or no effect on its compressive or flexural strength, and the material retains between 95 and 97 percent of its thermal efficiency. With this level of ingenuity, NOC project designers can ensure the roof system is equipped to withstand Chicago’s harsh weather.

Customization

Because tapered EPS is available in large blocks up to 40 inches thick and can be cut to satisfy virtually any slope, it’s possible to achieve superior thermal efficiency — high R-values — without the added material or labor costs that are typically associated with building up multiple layers of insulation. Installed much like enormous puzzle pieces, the small crew hired to construct the NOC was able to easily adhere three layers of 4-inch tapered EPS, in combination with flat EPS, across the roof deck. The factory-cut pieces of material were installed quickly thanks to their ultra-lightweight composition. In application, the rigid foam material kept the project on budget by decreasing upfront material costs and minimizing the number of hours spent on the jobsite.

NOC project designers looked to tapered EPS not only for material and labor cost savings, but also for its stable thermal performance. EPS insulation delivers R-values ranging from 3.6 to 4.2 per inch. EPS rated at R-4 per inch can provide up to two times greater insulating effectiveness than other insulation materials of the same thickness. Much to the delight of NOC project designers, Insulfoam was able to deliver the desired R-25 designation in three layers of material, slimming the costs associated with building up the pitch. 

Further, third-party testing conducted in 2008 evaluated the field performance of EPS following a continuous 15-year installation period. The results demonstrated that EPS delivers 94 percent of its specified R-value after 15 years in use. Because the material does not experience off-gassing, the R-value remains stable over its entire service life.

Valley Panels

In addition to employing tapered EPS roofing insulation solutions, the NOC design team also opted for factory-cut EPS valley panels from Insulfoam. “Opting for pre-cut EPS valley panels was perhaps the biggest time saving element of the entire NOC renovation project,” says Kris Eschmeyer, Territory Sales Manager, Insulfoam. “Often with new sloped roofing systems, builders have to cut every valley in half diagonally and throw the unused piece away. It’s a big waste of time and materials.” To combat this, Insulfoam offers custom-made valley panels that can be tailored to meet exact project specifications. This level of customization reduces the amount of material waste on the jobsite. It also eliminates much of the field-cutting, which again supports labor cost-savings and accelerates the projects’ timeline.

High-Performance System

The roof membrane installed was a 90-mil, grey FleeceBACK TPO manufactured by Carlisle SynTec. The newly minted roof was completed in July of 2020 after two years of construction. By taking the tapered EPS approach, project designers were able to reap the benefits of the rigid foam material. They achieved a positive pitch in fewer layers of material, creating a slope for positive drainage and bringing forth a high R-value in twofold. In turn, designers kept material and labor spending in check, and ensured a high-performance roof system. Like a protective blanket, the well-insulated roofing system will safeguard NOC operations for years to come.

About the author: Tom Savoy is the technical director for Insulfoam, a division of Carlisle Construction Materials. He has worked in the EPS Industry for 33 years and in construction materials (manufacturing and testing) for 38 years. He actively participates in many trade organizations including ASTM, SPRI

TEAM

Architect: ROOFTECH Roof Technical Services Inc., Fort Worth and San Antonio, Texas, rooftechnical.com

General Contractor: Clune Construction, Chicago, Illinois, clunegc.com

Roofing Contractor: Olsson Roofing, Aurora, Illinois, olssonroofing.com

MATERIALS

Membrane: 90-mil grey FleeceBACK TPO, Carlisle SynTec Systems, carlislesyntec.com

Insulation: Insulfoam IX Flat and Taper Panels, Insulfoam, insulfoam.com

Restoring Warehouse District Complex Poses Re-Roofing Challenges

Five warehouse buildings constructed in the early 1900s were renovated into mixed-use space in 1980. The complex was topped with a new roof system in 2020. Photos: Central Roofing Company

In the trendy North Loop section of Minneapolis, the Warehouse District is anchored by Itasca Lofts condominiums. More than 100 years old, the converted warehouse is home to 71 units plus a restaurant, comedy club and commercial space on the first floor. Six stories tall, the structure’s old roof was failing until Encompass Inc. and Central Roofing Company stepped in to help.

Built in the early 1900s, Itasca’s five warehouse buildings were renovated into mixed-use space in 1980 by the Cuningham Group. Four decades later, age-related issues and leaks resulted in Itasca getting a new roof in 2020. The difficult project revealed layers of roofing challenges.

“We started by removing a built-up roof (BUR) that was probably 35 to 40 years old,” says Henri Germain, project manager with Central Roofing Company. “Once we got down to the original roof deck, we were surprised to discover it was made of old three-inch thick planks. Today’s roof decks are made of one-half-inch of plywood. These original planks were an old style of tongue-and-groove. It’s fascinating to really see the way structures were built more than a century ago.”

Forensic Roof Review

Before the Central Roofing team started the re-roofing process on the 30,000-square-foot roof space, Encompass was brought in to analyze the failures of the roof system and oversee the construction. Through a bid process they hired Central Roofing.

“There were various unknown elements and unforeseen conditions when the project started,” says Ben Sandvig, project engineer with Encompass, Inc. “Central Roofing’s experience was evident and critical to executing this project effectively.”

Rooftop Obstacles

Challenging aspects of the project included numerous penetrations, curbs, pavers and HVAC units on the existing roof.

According to Germain, the most challenging aspect of the project was working around dozens of different rooftop elements. A variety of penetrations, curbs, pavers and HVAC units exist on the condo’s roof. To help make the job easier, a Potain crane was brought to the site.

“We started by installing plastic on all the interior ceilings to protect the individual homeowner units,” says Germain. “Then our foreman Adam Freitche and superintendent Matt Tueffel led the effort to demolish all the wood decks and railings owned by top floor unit owners. After that, we removed flashing at the parapets between sections. Next, the old tar and gravel roof system was taken out down to the wood planks.”

Rebuilding the Roof

To start the rebuilding of the roof, the Central team used a variety of Johns Manville products. The fully adhered roof system includes 90-mil EPDM to reduce the potential of future leaks. Three-inch JM Enrgy 3 ISO insulation was installed along with a half-inch coverboard. The roof system included a JM Vapor Barrier SA.

As the weeks of work progressed, 17 Wasco and Velux skylights were installed, and curbs were raised to account for the height of the roof. At the roof entry doors, along with the base and top of the stairs, walkway pads and paths were installed to access HVAC units. Paths were also created for the top floor unit owners to reach their newly-built roof decks.

Working around the stand-out roof structures, the Central team installed Firestone Una-Clad 24-gauge sheet metal to provide a roof with a stunning appearance. Just over five months of re-roofing was completed in late August of 2020.

Team Effort

With the re-roof now complete, the leaks are gone and condo owners are once again enjoying their Warehouse District living space.

“The Encompass and Central Roofing teams really worked well together on this project,” says Brian Droske, association manager with FirstService Residential. “Our company has managed the homeowners association for Itasca Lofts for about 40 years. The top floor condo owners are especially pleased with the roof renovation.

“These owners have the ability to purchase a license agreement from the condo association, allowing them to build roof decks directly on top of their units. Some of these owners also have roof access staircases going from their unit to their rooftop decks that overlook the Mississippi River. The new roof and their roof decks make these condos all the more valuable for residents.

“Despite many challenges that everyone acknowledges, this project was completed successfully. Central Roofing’s experience was evident and critical to executing the project effectively given the various unknown and unforeseen conditions of the existing construction.”

TEAM

Architect: Cuningham Group, Minneapolis, Minnesota, cuningham.com

Roofing Contractor: Central Roofing Company, Minneapolis, Minnesota, centralroofing.com

Consulting Engineer: Encompass Inc., Minnetonka, Minnesota, encompassinc.com

MATERIALS

Membrane: 90-mil EPDM, Johns Manville, jm.com

Insulation: JM ENRGY 3 ISO, Johns Manville

Vapor Barrier: JM Vapor Barrier SA, Johns Manville

Edge Metal: Una-Clad 24-gauge sheet metal, Firestone Building Products, firestonebpco.com

Hybrid Design Rescues Roof at Virginia Hazmat Storage Building

Architects from Gauther Alvarado Associates designed a unique hybrid roofing solution for hazardous chemical storage building for the Virginia Department of Transportation in Cross Junction, Virginia. Photos: Dylan Francis Photography

Many people enjoy the splendor of Virginia’s Shenandoah Valley. The vistas, spectacular autumn colors, activities, history and generally temperate climate make the region a tourist destination and wonderful place to call home.

Except when it snows. While the region only receives an average of 19 inches of snow per year — well below the national average of 28 — driving can be risky. The peaks and valleys that make the region such a pretty-as-a-postcard setting also make for treacherous driving conditions in any snow or ice weather pattern, from a dusting to a full-bore blizzard. Interstate 81, a major north-south thoroughfare, travels through the heart of the region and links to West Virginia, Maryland and Pennsylvania in the north, and southern Virginia and Tennessee in the south.

The responsibility for making the road safe for travel falls on the Virginia Department of Transportation. The agency faced a complicated roofing issue at its hazardous chemical storage building in Cross Junction, where it keeps salt and de-icing products to help keep nearby roads safe for travel.

The building sits in a rural, hilly location and salt is distributed through roof hatches in the structure. The existing hatches, however, started to fail. Age, weather and corrosion from salt required VDOT to replace the entire roof, especially the hatches.

Working with architect and project engineer Gauther Alvarado Associates, general contractor Dinks Construction and Don Largent Roofing, VDOT approved a hybrid roofing solution that is expected to provide decades of service. The eventual design is efficient, cost-saving and durable, checking off three of the most important boxes on VDOT’s project requirements.

Narrow Project Scope

The scope of the project was not wide. The priority was to replace the roof hatches and the roof, which measured 1,960 square feet. The hatches, however, needed to be custom-built, corrosion-resistant, and structurally strong enough to support the weight of the salt during loading operations.

“In the early fall, salt is loaded into the building through three roof hatches accessible from the upper part of the site,” said Stephanie Stein, lead architect on the project for Gauther Alvarado. “During the winter, the salt stored in the building’s three bays is accessed on the lower part of the site as needed, in response to snow events.”

Crews installed three roof hatches from BILCO that were equipped with a liner to protect against corrosion caused by salt that is stored in the facility.

The top priority was to install roof hatches that could withstand the corrosive effects of salt. Architects selected three aluminum roof hatches manufactured by BILCO. The hatches are 3-feet, 11-inches wide and 11 feet long. They are manufactured with Type 316L stainless steel hardware, which is the most corrosion-resistant type of stainless steel. The roof hatch curbs were coated in an asphalt-based liquid coating to provide an additional layer of protection for the concrete inside the building.

“BILCO offers stainless steel roof hatches, but since this is a project that is designed and built on a government budget, we provided a more economical solution,” Stein said.

To protect the interior of the roof hatch that comes into contact with the salt, a team from Rhino Linings in Winchester, Va. installed a liner. Similar to the lining on truck beds, the spray-on material protects against corrosion while also providing excellent abrasion, impact and chemical resistance.

“With this solution, we combined the durability associated with the BILCO pre-manufactured aluminum roof hatches with the corrosion-resistant properties of the truck bed liner,” Stein said.

Dinks’ workers installed the roof hatches while the roofing team installed EPDM on the remainder of the roof. The durability of the roof hatches with the unique liner applied and the EPDM roofing material is expected to extend the roof’s durability up to 35 years.

Standing Up to Salt

The architectural team also designed another unique solution to protect the durability of the hatches.

“One of our prime concerns during the design phase was the additional force exerted on to the roof hatches during salt loading operations,” Stein said.

The time-saving design allows drivers to drop off loads of salt through hatches that are structurally reinforced. The roof hatches with the liner and a roof with an EPDM roofing membrane is expected to extend the roof’s durability up to 35 years.

They designed a structural steel bumper to provide additional support to the roof hatch. When the hatches are open prior to loading the building with salt, the roof hatch covers rest upon the bumpers. “The additional force applied to the roof hatch covers during the salt loading is then directly transferred to the steel bumpers to protect the structural integrity of the roof hatches,” Stein said.

The unique design of the building and the roof allows for a quicker, more efficient solution for storing the chemicals. For hazardous storage buildings without roof access, salt has to be moved by front-end loaders or some other type of conveyance. With the chemical storage facing more stringent regulations, the drop-and-go solution is much more favorable for the environment. Road crews access the salt from the lower part of the building.

Worrisome Corrosion

The corrosive nature of salt can impact almost any building material. When Dinks Construction started the project, workers found issues with decay in some concrete walls caused by salt corrosion. Teams tore out a portion of the wall and rebuilt it before replacing the roof.

Road salt can also cause paint corrosion on vehicles, and can even impact brakes, electrical systems and wiring. The American Trucking Association Foundation reported a direct correlation between increased magnesium chloride use and a significant escalation in truck corrosion and electrical system damage. Some states are even decreasing the use of sodium chloride in favor of magnesium chloride with added corrosion inhibitors.

“The building holds anti-icing, de-icing and snowmelt chemicals,” Stein said. “All of these chemical agents contain salt. Since this is a government project, longevity was a concern. As a result, any surface that comes into direct contact with the salt needed to be corrosion resistant to increase the lifespan of the building in this extremely corrosive environment. “

One additional concern was the increased weight of the roof hatch with the protective liner. BILCO provided a lift mechanism to handle the roof hatch and the protective lining.

Underappreciated Project

The tiny town of Cross Junction sits on the border of a small piece of West Virginia. The building is located several miles from the interstate, and is hardly the Lincoln Memorial in terms of an architectural masterpiece. Functionality in this project was more important than visual appeal. The structure is largely unnoticed by visitors to the region.

Yet, the building plays a key part in keeping drivers safe as they travel the region’s roadways. It might not be flashy, but drivers would certainly know if snow-covered roads were untreated as they attempt to navigate them. “It’s one of those buildings you don’t pay attention to until you actually need it,” Stein said.

The design and construction required ingenuity, attention to detail and creativity in solving some unique challenges. Every project has its own distinct and difficult equations, but the Cross Junction project posed questions that architects rarely see.

“This was a fun project because it was quite different,” Stein said. “This was our second roof and roof hatch system that we designed for VDOT. We had the opportunity to incorporate a few lessons learned from the first roof system replacement. It is our hope that we will continue to adapt this roof system prototype for additional VDOT sites in the future.”

About the author: Thomas Renner writes on building, construction, engineering and other trade industry topics for publications throughout the United States.

TEAM

Architect: Gauther Alvarado Associates, Fairfax, Virginia, gaa-ae.com

General Contractor: Dinks Construction, Linville, Virginia, dinksconstruction.com

Roofing Contractor: Don Largent Roofing Inc., Harrisonburg, Virginia, donlargentroofing.com

MATERIALS

Roof Hatches: Custom-made aluminum roof hatches, BILCO, bilco.com

Designing Resilient Single-Ply Membrane Roof Systems for Hot Climates

Photo 1: The Temple of Karnak, Luxor, Egypt: The ancients learned by experience that shade in association with ventilation provided comfort.

The growing popularity of increased thermal insulation, in association with code and standard mandates, assists in mitigating exterior ambient temperatures and heat flow migration influences on building interior environments. Some have tried to mitigate these exterior influences on the interior by roof surface color alone — an incorrect precept. Roof color alone, an attribute of a single roof system component, cannot mitigate exterior influence in and by itself. Insulation, roof system design, roof deck, etc., all have a role to play.

To make matters worse, HVAC designers have not been informed as to how roof system design can detrimentally affect HVAC performance. Increased air temperatures above the roof surface, high-temperature heating of rooftop piping, and the heating of rooftop units by reflection of the roof surface have all resulted in HVAC performance well below that for which it was designed.

Photo 2. The Greeks learned to use mass to mitigate high levels of solar radiation and resultant heat flow to maintain interior comfort. Shown here is the architecture on the Greek Island of Santorini.

The roof system is made up of various components, which can include some or all of the following: roof deck; substrate board; vapor and/or air barrier; thermal insulation layers; the insulation adhesive or mechanical fasteners; spray foam insulation sealer; cover board; cover board adhesive or mechanical fasteners; roof membrane; membrane adhesive or mechanical fasteners; and roof cover of ballast or coating. Thus, the function of the roof is not a single component effect, but the sum of the whole — all components working together in association with building type, interior use, and location.

Appropriate roof system design is the result of the architect, engineer and building owner working together, taking into consideration the function of the building and the effects of the climatic and environmental conditions expected to be experienced.

This article explains the effects of roof system design on HVAC design in hot climates from the perspective of a roof system designer. It is based on a paper I delivered at the 2014 ASHRAE International Conference on Energy & Indoor Environment for Hot Climates in Doha, Qatar. Its lessons are even more relevant today, with the increase in ambient temperatures worldwide. Concerns such as heat flow, reflected ultraviolet light effects, rooftop temperatures and their potential detrimental effects on HVAC performance will be reviewed. Design recommendations and detailing suggestions for achieving long-term roof service life performance in hot climates with single-ply membranes will be explored. Proactive design recommendations for HVAC designers on how to deal with roof-borne effects will also be provided.

Environmental Concerns Lead to Changes

Societal concerns for the environment, which led to the development of the Leadership in Energy and Environmental Design (LEED) program under the auspices of the United States Green Building Council (USGBC) promoted the use of “cool roofs” — now referred to as “reflective roofs” — as both a potential energy conservation and urban heat island reduction methodology. This movement led to legislative and code mandates that became drivers for massive changes in the roofing industry. Consequently, the use of reflecive roof membranes, which are defined by the U.S. Environmental Protection Agency’s Energy Star program as roof covers with an initial solar reflectance of 0.65 or greater, have become the code-mandated choice that architects have when designing low-slope roof systems. The specifying of reflective roof membranes — albeit with little forethought in their use and implementation into a roof system — resulted in unintended consequences, such as the formation of moisture below the membrane, excessive heat production to rooftop equipment and building components, and premature failure of some roof systems.

(FIGURE 1A) Figures 1A and 1B: A vented and ballasted roof system not only shades the roof cover, but provides a ventilation layer allowing warm air to rise and dissipate from the roof, thus reducing heat gain to the interior.
(FIGURE 1B)

The goal of cool roofing has moved over the past years from a potential energy-saving roof cover to an urban heat island mitigator. The challenge for the building design community is to realize that if energy savings is the goal, ballasted roofs are the best choice, as research shows that cool roofs actually raise the ambient temperature above the roof surface. Additionally, reflected UV rays are heating rooftop piping. Clearly in hot and sunny climates, reflective roofs are not in the best interest of the HVAC system performance.

As with any roof-cover material, the appropriate design and use of the material is required to achieve long-term success and a truly sustainable roof system. Roof-system design is equal in importance to structural, mechanical, plumbing and electrical design. Therefore, it is imperative that designers who utilize single-ply cool roof systems, especially those which fall within American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Climate Zones 4 through 7 (approximately from the state of Tennessee north), take extra care to achieve a properly functioning and sustainable low-slope roof system. Efforts have recently been made to raise the mandate for reflective roof surfaces to include ASHRAE Climate Zone 4. While this author firmly believes that the selection of a roof system (no matter the climate zone) should be the decision of the architect and owner, raising the mandate to Climate Zone 4 would be imprudent and result in little if any energy savings, with increased potential for roof system failures.

Optimal HVAC Performance in Hot Climates

HVAC cooling equipment design in hot climates often utilizes over-design to compensate for the building’s thermal gain and heat on the roof. Another often overlooked aspect of rooftop equipment is the drop-off in efficiency due to cooling loss in the ductwork and piping; as a result of solar gain, heat and exacerbation from cool roof surfaces that reflect rays back up at the piping can “superheat” the pipe/duct contents.

If the roof cover temperature can be reduced, and the roof’s effects on ducts and pipes can be reduced, the efficiency of roof op equipment will rise, units can be reduced in size, and operating costs will be reduced.

Roof System Requirements

Roof system design should take into consideration the climate and micro-climates in which the roofs are to be located. This is often not the case, with architects simply selecting a roof system by its warranty length and how many LEED credits it can procure. This lack of design methodology has kept many a forensic roof consultant busy, owners frustrated, and manufacturers unsettled, as failures are frequent and mitigation costly.

IMAGE: HUTCHINSON DESIGN GROUP LTD.

The need for climatic considerations is exacerbated when the roof system will be located in geographical areas of extreme weather: high winds, extreme cold, and extreme heat. For the purposes of this paper the climatic parameters to be considered are:

  • Extreme heat
  • Intense ultraviolet radiation
  • Sand erosion

Thus, to be successful, the roof cover (membrane) must resist these forces for the term of the desired service life. This author believes in designing with long-term service life in mind. Long-term service life is the essence of sustainability, and in this author’s opinion is a minimum of 30 years.

Heat aging and deterioration of roof membranes from ultraviolet radiation has been the bane of roof covers for decades. Premature end of service life as a result of these effects has been well documented by professionals, studied by researchers, and experienced by building owners.

The effects of windblown sand across, or accumulation upon, roof membrane is less understood, but as a rough-surfaced material moving across a pliable membrane it is intuitive that this action could be egregious to the long-term performance of the roof membrane.

Consequently, to achieve long-term performance in hot climates, the roof membrane, in addition to meeting all the needs of the building and roof system, must have a history of resisting long periods of high ambient temperatures, and high surface temperatures, and be resistant to the effects of ultraviolet radiation.

Lessons From History

Learning from historical examples from indigenous peoples who had to deal with the climate with fewer tools than are available today is both prudent and wise. Cultures in the Middle East have dealt with extreme heat is several ways. The first is through shade. While exposed to the sun, hot and arid ambient climates are almost unbearable. Indigenous people first protected their skin with “galabeyas,” a traditional garment. For structures, shade became a key design element. This can be observed in many of the ancient Egyptian structures that have been uncovered and are viewable today. The Temple of Karnak along the Nile in Luxor is one fine example. (See Photo 1.)

Photo 4: At Queen Alia International Airport in Jordan, architect Norman Foster utilized ventilation cavities below the metal roof systems to vent out any possible build-up of heat. Photo credit: Markus Mainka – stock.adobe.com

The Temple of Karnak also provides us with a second example of a method used as protection from the heat and sun, which is to cool via ventilation. The tall columns of the various halls provided needed structure, but also induced air movement. This concept was integral in the design of the Jeddah Airport in Saudi Arabia.

Wall and roof construction across the Mediterranean, not only in the European cultures, but also in the Asia Minor, Middle Eastern, and Northern African cultures, utilized thick, massive walls that could absorb the heat of the day and prevent it from moving to the interior — a cave above ground, if you will. (See Photo 2.)

Thus, we learn from history that the following were important design features in providing comfort in extremely hot and arid climates:

1. Shade

2. Ventilation

3. Mass

In translating the historical precedents in regard to roofing to today’s building needs and roof systems, the issue of shading needs to be given more consideration. In the United States, the current roof systems that offer shading are ballasted assemblies with river-washed gravel of approximately 1.5 inches in diameter (3.8 cm). Spread at a minimum of 10 pounds (4 kg) per square foot(30.5 cm2), the stone creates a shading layer over the roof membrane below. The stone ballast also creates a mass element that can absorb the sun’s energy. While the stones lying next to each other create voids and spaces, the ventilation element is small, but present. In order to achieve the ventilation element, a drainage mat (used in garden roof systems) is placed above the roof membrane and below the stone.

To complete the roof system, a roof membrane with a historical in situ record of exposure performance and resistance to UV is needed. EPDM satisfies this requirement with its carbon black component, as well as its proven performance, given this author’s experience with EPDM roofs designed 30 years ago which are still in service today. Thermal insulation layers should be multiple, and in the range of 3 inches (7. 5 cm) each.

This roof assembly can be seen in Photo 4 and is detailed in Figures 1A and 1B. It typically includes the following:

· Ballast to shade the membrane from solar heat gain and prevent reflection back at the walls and mechanical equipment. The aim is to provide a mass to gather the solar energy and not allow it to dissipate to the building interior, rooftop equipment, and/or the atmosphere.

· Drainage mat to provide a ventilation layer.

· EPDM to provide resistance to heat and UV radiation, and to provide a break in potential heat flow.

· Thermal insulation to “keep the hot out, and keep the cold in.”

There are several goals to this system, including:

1. Shade the roof membrane and thus provide a cooling layer.

2. Provide protection from the deleterious effects of heat and UV radiation.

3. Provide a ventilation plan to dissipate heat.

4. Eliminate the reflection on rooftop equipment.

5. Reduce cooling loads.

6. Provide a rooftop environment that will allow for the downsizing of rooftop equipment, and thus increase efficiency and lower energy usage.

7. Achieve a sustainable long-term roof system.

A roof system of similar concept was recently installed at the Queen Alia International Airport in Amman, Jordan, in which metal roof panels were elevated off the roof deck to form a cavity to vent any possible heat build-up. (See Photo 4.)

Design Recommendations

The goal of architects/designers should be to design roof systems to achieve sustainable and resilient long-term service lives. Today’s society is asking that roof systems provide more than just protection from the exterior environment. For extreme climatic areas of the world, the standard of care required to be exercised by the design professional has increased. For dry and hot climates interior comfort is paramount, and the roof system can be designed to assist rooftop HVAC systems in regard to performance, energy conservation, and efficiency, as well as extending the roof system service life.

Many of the required roof system design parameters apply, but for hot climates there are several key design elements that should be given consideration. Following are the design considerations that will provide a greater opportunity for successful roof systems in hot and dry climates:

1. Ensure collaboration and coordination with the HVAC system designer. The association between potential heat flow, resultant interior heat gain and cooling demand is so closely related that it would appear obvious that the coordination of the two building system designers should be a given. Unfortunately, this is far from reality.

2. Gain an understanding that heat energy is first and foremost transmitted by solar energy, and protecting the roof membrane’s surface from the “sun’s rays” will result in diminished heat gains. Use indigenous concepts to your benefit.

3. Use thermal insulation to provide a formidable barrier between the interior and exterior environments. It is not only about the cost of cooling that should be dictating the amount of insulation, but the loss of cool air and preventing heating. This author feels that the insulation amounts used on roofs of hot climates should be equal to those in cold climates.

4. Shading 1: Protecting the roof surface from direct contact by the solar radiation will provide enormous benefits.

5. Shading 2: The shading element typically will absorb (to the extent the solar radiation is not deflected), thus minimizing and/or absolving the effects of heat flow to the interior.

6. Specify roof membranes (roof covers) that have a history of in situ long-term performance in hot climates.

7. Specify roof membranes (roof covers) that have high resistance to ultraviolet radiation.

8. Specify roof membranes (roof covers) that have high resistance to heat aging.

9. Understand that the high base flashings are part of the roof system and will need to be designed appropriately. The should be protected with double layers of flashings.

10. Specify robust and durable materials: Increase the thickness of roof membranes and covers. If the membrane is reinforced, the thickness of material protection above the scrim is the critical dimension.

11. Design roof system components with the same care for the effects of the sun, solar radiation, and heat as you would the roof. For example, the use of no-hub couplings on roof drains will see the sun for several hours each day and will deteriorate over time, and will become attributable to one of those “hidden, mystery” leaks.

12. Use the historically proven method of heat disbursement: Provide a ventilation layer above the roof membrane (roof cover).

13. Design to protect rooftop HVAC equipment and walls from deflected solar radiation. Remember how you started a fire as a kid with a magnifying glass? This is the same concept.

14. When using metal components such as roof edge copings, realize that the temperature of the metal during daylight periods will work to heat age and deteriorate the roofing below. Try to incorporate a ventilation layer below the metal.

The Importance of the Roof

The design of roof systems has historically been given little forethought, and was often regulated to junior designers with little or no empirical experience, and armed with little more than a “canned” master specification that provided little more than a market-driven minimum of a roof system. Today’s buildings are much too expensive and sophisticated to allow poorly conceived and designed roof systems to prevail. With an increase in detrimental “climactic events,” roof systems demand the same level of consideration and design as do all other building systems: structural, mechanical, plumbing, communications, and building envelopes.

Hot climates are special and unique climatic environments, and as such, have special environmental conditions that need to be designed for. Using empirical and historical information, proven materials, and designing to particular in situ environmental conditions can produce roof systems that will reach sustainable levels of performance. With proper coordination with HVAC designers, the roof can rise above just a protection layer, and provide both raised interior comfort and greater HVAC cooling efficiencies. Greater emphasis on education on proper, innovative, and sustainable roof system design can be achieved if all stakeholders (manufacturers, contractors, architects, engineers and consultants) work together.

It is well past the time to move roofing system design to the forefront of building design and have it become a system that is appreciated for its crucial role in energy conservation and resilient construction.

About the author: Thomas W. Hutchinson, AIA, CSI, Fellow-IIBEC, RRC, is a principal of Hutchinson Design Group Ltd. in Barrington, Illinois. For more information, visit www.hutchinsondesigngroup.com.

Florida Stadium’s Metal Roof Intimidates, Alludes to Campus Architecture

The softball stadium on the campus of the University of Florida in Gainesville features a steeply pitched metal roof that frames an impressive gateway into the ballpark. Photos: Matt Horton, hortonphotoinc.com

The renovated Katie Seashole Pressly Softball Stadium on the campus of the University of Florida in Gainesville might have all the latest amenities, but its design pays homage to the school’s earlier days.

The facility’s steeply pitched metal roof in a signature orange-red finish is a clear reference to the buildings surrounding the stadium, and it also frames an impressive gateway into the ballpark’s friendly confines.

“The university is known for its collegiate gothic architecture and high-pitch, orange-red gable roofs,” says Joe Walker, AIA, president of Walker Architects, the local firm that designed the stadium. “This project ran with the roof as the character-defining element of the exterior, and the final design is a direct nod to the collegiate gothic style.”

The collegiate gothic roots most clearly are seen in the stadium’s signature entryway. In addition to tying the stadium to the surrounding campus, this two-story structure elevated on brick columns makes a statement all on its own for fans — as well as Gator opponents.

“From a fan’s perspective, the geometry of the roof signals the entryway and frames the impressive — and, for a visiting team, intimidating — first glimpse of the field,” Walker says. “For a player, when you look at the elevation of the facility from the field, the central gable is a centerpiece positioned directly over home plate.”

Approximately 10,300 square feet of PAC-CLAD Tite-Loc Plus panels in a Terra Cotta finish were installed as part of the project.

While officially a “renovation,” because the original 1996 field wasn’t altered, the upgraded facility has been largely rebuilt to include a new locker room, lounge training room and press box. According to Walker, the $15 million project is a tribute to the work head coach Tim Walton has done building the team into a national presence since joining the team in 2006. Since 2008, the Gators have made it to the Women’s College World Series eight times and have earned national titles twice.

Walker says metal roof panels were an obvious choice to create a visual link to the classic clay tiles that top many of the university’s older structures. “It was the product with the best look for the project price point and, aesthetically, it fit in well in this area of campus,” he says. “Plus, it has the benefit of being low maintenance and importantly, it does a great job of keeping water out.”

The architect specified 10,300 square feet of PAC-CLAD Tite-Loc Plus from Petersen in a Terra Cotta finish for the project. He says the choice of this particular profile was aided by advice from the company’s technical staff. “It was Petersen that suggested we use the Tite-Loc Plus product with striations, knowing it would be a better product for our project with respect to minimizing oil canning and damage from potential impacts.”

Jacksonville, Florida-based Thorne Metal Systems handled the roof installation, which posed a few challenges, according to the company’s office manager Cody Thorne. “It was a particularly tight site – we could only work around the perimeter because they were working on the field,” he says, adding that the roof’s steep pitch also called for some extra attention. “It was 10:12, so a little more caution and safety were involved.”

TEAM

Architect: Walker Architects, Gainesville, Florida, http://walker-arch.com

Roofing Contractor: Thorne Metal Systems, Middleburg, Florida

MATERIALS

Metal Panels: PAC-CLAD Tite-Loc Plus in a Terra Cotta, Petersen, www.pac-clad.com