RoofViews

Commercial Roofing

How Roof Uplift Testing Can Help Ensure System Performance

By Karen L Edwards

April 15, 2022

Wind sock on a windy day with bird flying in background

Strong winds can create pressure on the building envelope, potentially causing the roofing system to lift. However, conducting roof uplift testing on roofing systems can help predict how a roof will perform when subjected to strong winds.

What Is Wind Uplift?

Wind can exert three types of force on a structure—shear load, lateral load, and uplift load. Although all three load forces can damage a building, the uplift load most intensely affects the roofing system.

The NRCA defines wind uplift load as "The force caused by the deflection of wind at roof edges, roof peaks or obstructions causing a drop in air pressure immediately above the roof surface." However, the same lifting effect that enables airplanes to fly can be devastating for a roofing system. When wind flows under a roof, it pushes upward, elevating the roof membrane. As wind flows over the roof, it pulls the roofing system upward.

Understanding local wind zones and building codes will help determine the requirements needed for the roofing system to best protect the building. This is typically handled by an architect or roofing design professional. James R. Kirby, AIA, GAF building and roof science architect, writes in an article for the American Institute of Architects that the architect's responsibility is to provide wind pressures, whereas the manufacturer must determine the wind uplift capacity of the roofing system.

What Are Roof Uplift Testing Methods?

Professionals use two methods to perform wind uplift testing.

In-Facility Testing

Most manufacturers rely on unbiased, third-party testing labs that are accredited to determine wind uplift resistance of a roofing system. A few of the more well-known facilities include FM Approvals, Underwriters Laboratory, and Intertek. There are a number of industry-accepted testing standards for indoor test facilities, including ASCE-7, ANSI/SPRI, and ANSI/FM 4474.

During testing, these companies subject roof deck mockups (at least 10' x 10') to winds and conditions that mimic various wind speeds with increasing levels of pressure. The roof earns its certification based on its maximum wind performance rating—the level of wind speed that it was able to withstand without failure.

Although lab certifications are important, the building's location, use, occupancy, and wind zone can create unique conditions that may be difficult to replicate in a lab environment.

Field Testing

Roof uplift testing in the field involves placing a dome-like structure measuring 5' x 5' onto the roof surface that subjects the roof to negative pressure forces. The roofing system is observed at different levels of pressure to the point where the system is considered on the brink of failure. This point can vary depending on the criteria being followed—either specified by ASTM or FM Global.

The National Roofing Contractors Association (NRCA) has maintained that field testing is "inappropriate for use" to measure the quality of a membrane roof installation. The organization recommends that contractors avoid jobs that specify field testing as a condition of acceptable installation. A roofing system's ability to pass wind uplift testing relies on many more factors than just the contractor's installation. It's in the contractor's best interest to clearly spell out expectations; the NRCA offers suggested language to use in the project contract.

The NRCA says the most reliable way to determine the quality of a newly installed roof system is by having a "knowledgeable roofing professional" observe the installation. The International Institute of Building Envelope Consultants (IIBEC) agrees, stating in a technical advisory that they recommend observation by an IIBEC Registered Roof Consultant or Registered Roof Observer: "continuous installation monitoring allows for observing the entire assembly process and for corrective action of observed deficiencies as the roof is being installed."

Turn to the Experts

With the number of variables that go into ensuring a roofing system's performance during wind events, it can be challenging to determine the right system and installation method. Not every roofing project will have an architect or design professional behind the specification. In those cases, GAF is here to provide guidance on roofing system options where wind uplift pressures are an important consideration.

About the Author

Karen L. Edwards is a freelance writer for the construction industry and has a passion for roofing, having worked in the industry for 20 years.

Related Articles

Cold storage facility for fresh produce
Building Science

Is your Cold Storage energy use through the roof?

This piece is co-written by Jennifer Keegan, AAIA. The headaches of Cold Storage facility operations extend beyond making sure the ice cream doesn't melt. Owners and Operators are regularly challenged with: Selecting a cost-effective roof system that is going to be long-lasting Working around unsafe areas in the interior due to ice accumulation Struggling to reduce monthly energy bills For Owners who are looking to increase energy savings and safety records, your roof not only keeps the weather out, but can help resolve these operational issues. _____________ Cold Storage buildings are designed to maintain cold temperatures, much colder temperatures than a typical building. Cold storage facilities, such as blast freezers, may be required to maintain an interior temperature of minus 50 degrees Fahrenheit. Having a structure that is properly insulated and sealed to maintain the required temperature and minimize ice build-up is important not only for the products being stored inside, but also for potential energy savings over the life of the facility. How can roofing materials impact energy savings? Think of the walls of the Cold Storage facility as a jacket, and the roof as a hat. When it is cold outside, you want to make sure that you have a jacket and a hat to insulate and keep you warm. The same idea applies to a Cold Storage facility — the roof and walls of the structure insulate the products inside. But in this case, when it's warm outside, they keep the products inside cold. Not having enough insulation, on either the walls or the roof, will make your mechanical systems work harder to maintain the interior temperatures, which increases energy use, and can result in higher energy bills. The effectiveness of roof insulation is determined by its R-value. According to Energy Star, R-value is a measure of an insulation's ability to resist heat traveling through it. The higher the R-value, the better the thermal performance of the insulation and its effectiveness at maintaining interior temperatures. R-value is typically expressed as a value per inch of insulation, and the recommended R-value of Cold Storage spaces will vary based on the interior temperature, although they are much higher than typically recommended for a traditional building. For comparison, a traditional office building may require an R-value of 30. In the 2018 edition of the American Society of Heating, Refrigeration and Air Conditioning Engineers' ASHRAE Handbook – Refrigeration, there are suggested minimum R-values for Roof Insulation between 30 and 60, depending on the cold storage type. R-values will vary by product, including factors such as thickness and density. When calculating the total R-value of a multilayered installation, adding the R-values of the individual layers will provide the total R-value in the system. Particularly in Cold Storage, it makes sense to select an insulation that provides a higher R-value per inch, such as Polyisocyanurate (Polyiso, R-5.6 per inch), Extruded Polystyrene (XPS R-5.0 per inch), or Expanded Polystyrene (EPS R-3.8 per inch). While insulations come in many thicknesses, it is a best practice to install several layers of thinner insulation rather than one or two layers of thicker insulation in order to reduce thermal bridging. Thermal bridging occurs when insulation is discontinuous between joints, allowing for air and thermal movement between the joints or gaps between boards. During installation, the use of several layers of insulation allows for staggering and offsetting the insulation joints, and blocks the passages that allow for air to bypass the insulation. Limiting thermal bridging can increase energy efficiency as it limits air movement between insulation boards. Figure 1: Lower energy efficiency resulting from air movement between boards and fasteners acting as a thermal bridge. Adding the adequate amount of insulation will prevent uncontrolled loss of the interior conditioned air, as well as assist in maintaining the required interior temperatures. Better maintaining the interior conditioned temperatures means that the cooling systems are required to run less often, which can equate to energy savings. While there may be an additional upfront cost to install an additional layer of insulation to increase the overall R-value of the roof, the cost should be minimal compared to the long-term savings of the added insulation. Of course, energy cost savings are not guaranteed and the amount of savings may vary based on climate zone, utility rates, radiative properties of roofing products, insulation levels, HVAC equipment efficiency and other factors. What about the roof membrane? While there are many choices when it comes to the type of membrane, the most common discussion revolves around the color of the membrane. For a typical building, maintaining a comfortable space involves both heating and cooling, depending on the season. For the typical building, the color selection of the membrane has a greater effect when the interior of the building is being cooled. A highly reflective (light colored) roof membrane offers extra benefits when the interior is being cooled, because it will reflect heat from the sun. Similarly, for a Cold Storage building, it is beneficial to select a lighter-colored roof in order to reflect the heat from the sun to assist in reducing the already high costs related to cooling the building. Reflecting heat from the sun will decrease the heat radiating into the interior, which means the cooling equipment will not have to work as hard to maintain interior temperatures, and will ultimately work more efficiently. What about roof attachment? We discussed the concept of thermal bridging and how energy loss occurs at discontinuities between the joints of the insulation, but thermal bridging can also occur where there are fastener penetrations through the roof system, as seen in Figure 1. Fasteners are used to attach the insulation and the membrane to the roof deck, which is referred to as a mechanically attached system. A way to reduce the thermal bridging that occurs at fastener penetrations is to bury them in the system or eliminate them altogether and install an adhered roof system. An adhered roof system typically fastens the bottom layer of insulation to the deck level and then subsequent layers of insulation, membrane and coverboard, are adhered. By eliminating the fasteners, the path for air to travel into the roof system is also reduced. Figures 2 and 3 illustrate good and better scenarios, in terms of limiting thermal bridging and reducing air flow into the roof assembly. In Figure 2, labeled as the 'good' scenario, there are multiple layers of insulation, staggered and offset, but they are mechanically attached to the deck. While the staggered insulation layers limit some of the air flow into the roof assembly, air is still able to travel throughout the roof. In Figure 3, labeled as the 'better' scenario, only the first layer of insulation is mechanically attached and subsequent layers are adhered. By adhering the subsequent layers, air flow into the roof assembly is greatly reduced. Reducing air flow assists in maintaining interior temperatures, which can result in energy savings for the facility. Figure 2: "Good Scenario" with staggered and offset insulation and a mechanically attached roof membrane. Figure 3: "Better Scenario" with the first layer of insulation mechanically attached and subsequent layers of the roof system adhered, greatly reducing the air flow into the roof assembly. The Devil is in the Details The result of limiting air flow through the roof assembly of a Cold Storage facility is not a matter of occupant comfort, but a matter of occupant safety. In a traditional building, such as an office building, a poorly detailed roof termination could result in drafty offices or temperature complaints. In a Cold Storage facility, those same drafts condense due to the large temperature differential between the interior and exterior and the condensation can turn into ice. The ice can form on various surfaces including locations where air leakage is occurring, such as at roof-to-wall interfaces, but also on the Cold Storage floors where the surface of the floor is cooler than the air above it. When ice forms on the floors, it can cause slips, trips, or falls, and can also impact operations if a particular area of the facility has to be avoided. Ice formation inside a Cold Storage facility is the result of improperly designed or executed details. Details, such as those at the wall-to-roof interface, or sealing around penetrations, are crucial to not only keep out rain, but to conserve energy within the facility. Similar to the loss of energy created by thermal bridging, air flow through the roof created by poor detailing results in considerable loss of the cooled temperatures required in the space below. Additionally, air flow that condenses can collect within the roof assembly, including within the insulation, and freeze. Frozen insulation is a common side effect of a Cold Storage roof that is not functioning properly. Frozen insulation is exactly what it sounds like — insulation that has had moisture accumulate within it and then freezes. Frozen insulation has properties similar to wet insulation and is ineffective, since it provides virtually no insulating properties. A frozen roof is almost like having no insulation at all, and the energy used to maintain the interior temperatures goes through the roof! Proper detailing of a Cold Storage facility begins during the planning stage. Determining the type of interior spaces, the sizes, and the overall usage of the facility should be taken into consideration. Once the overall layout of the Cold Storage facility is decided, the construction materials, including the roof assembly, will need to be determined. Once the roof assembly is selected, design of the roof details is crucial. Typical details, including roof-to-wall interface and penetrations, must be meticulously thought out and designed. Roof-to-wall interfaces and penetrations must be sealed to prevent air from entering into the roof assembly. Even the smallest gap that allows air flow can have detrimental effects on the roof assembly. The most common method of ensuring sealed terminations and penetrations is the use of a closed-cell spray foam. Closed-cell spray foam is typically installed at the intersection of the exterior walls and the roof insulation at a width of one inch and extends from the deck level to the top of the insulation. At wall-to-steel deck intersections, it is also best practice to install spray foam in the deck flutes a minimum of 12 inches from the wall. The closed cell spray foam helps to seal the interface so air cannot enter into the roof assembly. Figure 4: GAF Detail 201C Coated Metal Roof Edge at Insulated Wall Panel Proper execution of the roof installation is critical and requires a contractor with Cold Storage construction experience. Having the right partner who understands the importance of their role in the project and collaborates with the team can make or break the project. A future article will dive into these details. In the meantime, for information on GAF-certified contractors, talk to GAF first. The benefits outweigh the risks. Seemingly insignificant decisions made during the design and construction of the roof of a Cold Storage facility can impact the functionality and energy usage of the building for the lifetime of the roof system, which is typically 25-35 years. Once air leakage occurs into a roof assembly, the damage that occurs is often irreversible. Ice accumulation on the floor can be a serious hazard for occupants and workers. The challenge of identifying where the breaches in the roof assembly occur, let alone remediation, can be difficult and costly. Remediation of the identified problems generally includes removal of frozen insulation as well as addressing the identified problem areas which are often attributed to detailing and air leakage. The associated consequence of a poorly designed and installed roof is the cost of the energy loss. Mechanical equipment having to work harder to maintain temperatures will result in higher costs due to an increase in energy use, and the effect of the equipment working harder often leads to premature mechanical failures. The benefits associated with designing and installing a proper Cold Storage roof far outweigh the risks. A properly designed and constructed roof will save energy, prolong the life of mechanical equipment, and protect both the building's occupants and the goods being stored inside the facility. Need to talk to an expert regarding Cold Storage roof design? Talk to GAF first. Email us at coldstorage.assistance@gaf.com for design questions, detailing assistance, and expert advice.

By Authors Kristin Westover

January 26, 2024

Carter Work Project team in front of house
In Your Community

Teaming Up to Build Skills and Shelter for the 2023 Carter Work Project

Work is getting underway in Greater Charlotte, North Carolina, as GAF supports Habitat for Humanity with the 2023 Jimmy and Rosalynn Carter Work Project. The five-day build event began in 1984 when former President Jimmy Carter and former first lady Rosalyn Carter led a group of Habitat for Humanity volunteers to New York, building alongside 19 families in need of safe, affordable housing. For 36 years, the Carters have worked side by side with professional builders and volunteers at locations around the world to build and raise awareness of affordable housing.From October 1st - 6th, more than 750 volunteers will cooperatively build 27 safe, affordable homes in Charlotte, where the homeownership rate of 26% falls far below the county average of 57%. A strong contingent of GAF team members will comprise the volunteer workforce, and the company is lending support in several other ways.Working Together to Build Better CommunitiesSince 2011, GAF has proudly partnered with Habitat for Humanity. For the 2023 Carter Work Project, GAF donated the roofing materials for all the homes built, offered training prior to the event, and will provide leadership while the work is being completed."We're focused on helping build more resilient communities, by making workforces, affordable homes, and ultimately families more resilient," says Jeff Terry, GAF vice president of corporate social responsibility and sustainability.The Carter Work Project has touched thousands of lives over the last few decades and means so much to all involved. "To know that we're making a small dent in the housing affordability crisis is something very near and dear to my heart," Hailey Von Dross, youth and young adult engagement coordinator for Habitat for Humanity of Charlotte, shared at a recent training session in Charlotte.Helping Leaders Grow While Doing GoodIn July, the high heat was no match for the great attitudes at the two-day, hands-on, on-the-roof training hosted by GAF CARE (Center for Advancement of Roofing Excellence) to prepare for October's construction work. The house and crew leaders who attended the GAF CARE training will use the roofing skills they learned to guide Carter Work Project volunteers and workers in proper shingle installation.Training these building leaders was a "really exciting opportunity" for the GAF CARE team, says Terry. "It ultimately gives them the tools to make these homes more resilient for the partner families who will be working alongside all of us and ultimately getting the keys to these homes."The GAF CARE training can also help shape future community leaders. Rachel Hurst, an AmeriCorps volunteer working with Habitat for Humanity, says, "GAF is here helping us learn the proper way to shingle a roof. It's actually really cool. It's really rewarding and shows volunteers that they have the ability to create something."The transformative power of these homes should not be underestimated. For example, Adam Hunter, new construction field manager for Habitat for Humanity of Charlotte, took a break from the GAF CARE training to reflect on his own journey with Habitat for Humanity. When he was five years old, his family bought a Habitat for Humanity home."That is still our family home," Hunter shares. "It's still the home we go home to every Christmas." Now, decades later, while helping prepare for the October 2023 build, he says, "When I look around, I see not only the work that's being done today, but I see the path that these new homes can set these families on."Honoring the Carters' Legacy of Service and ShelterThe 2023 Carter Work Project is particularly exciting, as construction is kicking off after a three-year hiatus between 2019 and 2022 due to the pandemic. This year's event also honors Jimmy and Rosalynn Carter, as it is the first project the couple won't participate in after retiring in 2019, following decades of humanitarian global service.Country music super-stars Garth Brooks and Trisha Yearwood will host the build event in Charlotte—while also celebrating their 13th year working on the Carter Work Project.Whether celebrities or volunteers, everyone is equal as they gather for this great event. The GAF CARE training is just one of many contributions from all those involved with the goal of building more resilient families and communities. That's why GAF is proud to support the Carter Work Project year after year."A good roof system means that a homeowner won't have to worry," Von Dross noted during the roofing training event in July. "It's quite literally a roof over their head, and we're making sure that roof will be strong and durable and won't leak."Getting Involved and Making a DifferenceWhile preparations are currently underway for the 2023 Carter Work Project, it's never too late to partner with your local Habitat for Humanity affiliate and support building safe and secure homes in partnership with families in your community. The GAF Habitat for Humanity Program works year-round to improve affordable housing and community resiliency. As part of the program, GAF Master Elite® and GAF Certified™ Contractors* donate their time and services to install GAF roofing materials donated by the company (complete with a GAF System Plus Ltd. Warranty).To learn more about how GAF is building resilient communities, read about their Community Matters initiative. There's always an opportunity to give back and help improve the quality of life of others—and as the Carters know, every bit helps.*Contractors enrolled in GAF certification programs are not employees or agents of GAF, and GAF does not control or otherwise supervise these independent businesses. Contractors may receive benefits, such as loyalty rewards points and discounts on marketing tools from GAF for participating in the program and offering GAF enhanced warranties, which require the use of a minimum amount of GAF products. Your dealings with a Contractor, and any services they provide to you, are subject to the GAF Contractor Terms of Use.

By Authors Annie Crawford

January 25, 2024

A smiling group of men and women gather in front of a red expo backdrop for a photo.
In Your Community

Supporting Latino Roofing Professionals at the 2nd Annual Latinos in Roofing Expo

Spirits were high at the second annual GAF Latinos in Roofing Expo, where more than 600 Latino roofing professionals gathered in Houston, Texas, for networking, business growth, and education seminars—all in Spanish. "To have a conference dedicated to Latinos, I love it," says Jorge Parada. "I'm sitting next to somebody that looks like me, that speaks the same language. It's a different experience from other conferences."Empowering Attendees at the Latinos in Roofing ExpoThe Latinos in Roofing Expo is one way GAF is working to level the playing field for Latino roofing professionals. Rather than take a one-size-fits-all approach, the expo provides education and resources that consider the Latino community's unique challenges. For example, industry experts taught classes in Spanish such as The Power of Latinos in Your Company's Culture, In-home Selling, Single Ply TPO, Coatings, and The Power of Content Creation for Roofing Companies.In addition to networking with other top-tier contractors, attendees received education in Spanish about the newest GAF contractor products, programs, and trainings designed to help roofers run—and grow—their companies. According to several attendees, these "culturally intended" business growth sessions, offered in Spanish, were one of the most valuable aspects of the conference.Many other conferences and training opportunities expect Latino roofing professionals to thrive with resources that cater to the non-Hispanic, English-speaking contractor community. In contrast, the Latinos in Roofing Expo empowered attendees through culturally intended offerings and shared language."The majority of these [Hispanic] contractors speak English, but it's also cultural. So, the way we do business has to feel culturally intended. Do business like Hispanics do business. Speak the language Hispanics speak," says Alan Lopez, GAF CARE training operations manager. Lopez has been a leading advocate for Latino roofing contractors at GAF and in the roofing industry as a whole.Improving Latino Roofers' Access to ResourcesMany Latino roofers have experienced disadvantages when rising in the roofing ranks because of language and/or cultural differences. For too long, the industry has pigeonholed Latinos into labor roles. As a result, Latinos are drastically underrepresented in roofing leadership, despite making up 57.7% of the roofing industry. Improving access to resources and cultural interactions is a sign of the roofing industry evolving."GAF is the front-runner in helping Latinos, because they have given us so many free resources and free seminars in Spanish," says conference attendee Junior Garcia, CEO. "They have allowed us to get to know what other [non-Hispanic] contractors already know." Some of the GAF culturally intended resources include:Spanish-language GAF website with the same user-friendly features as the English-language GAF website.Spanish-language GAF Document Library for Residential and Commercial GAF roofing products, including technical bulletins, warranty guarantees, data sheets, and more.Spanish-language GAF CARE trainings and resources, including business development courses, hands-on-trainings, and more—all taught with the needs of Latino contractors in mind.Spanish-language events, such as the 2023 GAF Latinos in Roofing Expo, designed to develop Hispanics in roofing leadership.Connecting with Latino ConsumersDeveloping Latino contractors also creates a powerful financial opportunity to serve Latino consumers. This benefits Hispanics in roofing and the roofing industry as a whole.Too often, Latino consumers are overlooked and underestimated. In fact, the Latino consumer base currently has unmet needs of more than $100 billion. Empowering Latino roofers to develop and grow as business leaders is one way to help bring change. "If you want to do business with the Latino community, you have to speak their language," says Hugo Saldaña, GAF territory manager in Houston, Texas.Speaking as a Latino professional in the roofing industry, Saldaña explains that people are at the heart of increasing a consumer base and growing contractor opportunities. "My parents preferred to do business with people who also spoke Spanish, their native language," says Saldaña. "Every day, when I go into work with these guys, it's like helping my dad or my mom. I think when you do that, and these guys know there's a caring relationship there, it goes a long way."Moving Towards the FutureLatinas in RoofingWhile the Latinos in Roofing Expo is a huge win, GAF and the roofing industry still have opportunities to grow. For example, GAF recognizes that female Latina roofing professionals may experience more challenges than their male counterparts. "There are a lot of challenges we [women roofing professionals] face, but there are opportunities for leadership. Now there are more resources and training and more opportunities to build our skills and build our knowledge, and be able to have the same opportunities as men," says Valeria Avila of Servi Express Roofing. GAF provides opportunities to empower women in roofing and recognizes the benefit of forming better bridges between women and the roofing industry.Resources for GrowthAlthough there is work to be done, the 2023 GAF Latinos in Roofing Expo is another step forward for the roofing industry. "Our company has done an amazing job—we now have a Spanish website and cater a lot to the Hispanic community, but there's still greater need," said Andres Beltran, a GAF CARE training manager based in Greenville, South Carolina.As the industry continues to evolve, Beltran encourages Latino roofers to connect with the free, Spanish-language training services and business development opportunities at GAF CARE Contractor Training Centers. "Whether it be from a marketing standpoint, financing, business development, leadership, insurance, and restoration—we can help Latino contractors to elevate their game," says Beltran.Learn more (in Spanish) about GAF resources and GAF certification opportunities today.

By Authors Annie Crawford

January 17, 2024

Don't miss another GAF RoofViews post!

Subscribe now