Specific building materials can enhance fire resistance and help with indoor air quality.

Design for Student Safety

As previously discussed, the safety of students and staff should always be at the forefront of any educational building design. For this course, we will take a closer look at how specification of building materials can enhance the safety of an educational building in the areas of fire and indoor air quality.

When evaluating building products and materials, there are many standards established specifically to address fire safety. For some commercial projects, simply adhering to the minimum expectations of code is adequate; however, for educational buildings, often the project will have enhanced requirements.

For the class of materials identified as strong candidates to address the challenges of designing and specifying for educational buildings, fiberglass-mat gypsum boards and related products perform well or above average in the previous standards. Gypsum boards are composed primarily of gypsum (calcium sulfate dihydrate), which is a naturally fire-resistant material. This composition inherently resists flame spread and smoke production. When combined with the inorganic and naturally fire-resistant fiberglass mat, boards of this type perform much better than those other materials for sheathing, roofing, and interior wall assemblies.

“Gypsum provides passive fire resistance,” says John Chamberlin, Senior Director of Product Management at Georgia-Pacific. “Every gypsum molecule has two water molecules in its chemical structure. Those water molecules will be released when exposed to a fire. This endothermic process helps delay the transmission of heat through the gypsum board. While the calcium sulfate dehydrates it continues to resist burning, forming an insulating layer to slow the spread of flames and heat.”

To evaluate building products and specify materials that will meet and exceed safety expectations, architects must have a strong working knowledge of the following industry-recognized fire standards.

UL Class A Fire Rating: A UL Class A fire rating is the highest classification given to materials for their ability to withstand severe fire exposure. This fire rating involves rigorous testing under standards set by Underwriters Laboratories (UL), including tests for flame spread, burn-through resistance, and structural integrity under fire conditions. Materials with a Class A rating are tested for their resistance to flame spread and their ability to resist severe fire exposure, as well as their capacity to prevent the spread of fire. To achieve a Class A rating, materials must score 0 - 25 for flame spread and 4 - 450 for smoke development. Materials that are better at maintaining structural integrity and slowing the spread of fire can provide extra time allows first responders more time to control fires, minimizing damage to the building.

ASTM C1177 (Fire Resistance): ASTM C1177 is a specification for glass-mat gypsum substrates used in the construction of fire-resistant wall assemblies. The standard outlines the requirements for the physical properties, performance characteristics, and testing procedures to ensure the material’s effectiveness in fire-rated assemblies. Products conforming to ASTM C1177 are evaluated for their fire resistance, moisture resistance, and overall durability, making them suitable for use in areas where both fire safety and long-term performance are critical.

UL 1256 (Under Roof Deck Fire Exposure): UL 1256 is a standard for fire tests of roof-deck constructions, specifically focusing on the resistance to fire from below the deck. The UL 1256 test simulates fire exposure from within the building, evaluating the roof deck’s ability to maintain its integrity and prevent fire penetration.

ASTM E84 (Flame/Smoke Developed): ASTM E84, also known as the “Standard Test Method for Surface Burning Characteristics of Building Materials,” measures the flame spread and smoke development of materials. This test is crucial for assessing the fire performance of interior finishes and insulation materials used in educational buildings. A low flame-spread index (FSI) and smoke-developed index (SDI) indicate that the material contributes minimally to fire spread and smoke production, enhancing the safety of the building’s interior environment. Materials with a score of 0/0 are considered exceptional in this standard classification. An FSI of 0 means that the material does not support flame propagation at all during the test and an SDI of 0 means that the material produces no measurable smoke during the test. In educational settings, slowing the spread of fire may provide more time for evacuation, and reduced smoke allows for greater visibility for occupants to escape.

UL723 (Roof Board Flame/Smoke Developed): UL 723, similar to ASTM E84, evaluates the surface burning characteristics of building materials, specifically roof boards in this context. For educational buildings, using roof boards with favorable UL 723 ratings may ensure that the roofing materials will not significantly contribute to the spread of fire or the production of harmful smoke. This is critical for maintaining the structural integrity of the building in the event of a fire.

ULC CANS102 (Roof Board Flame/Smoke Developed): ULC CAN-S102 is a Canadian standard akin to ASTM E84 and UL 723, focusing on the flame spread and smoke development of building materials, particularly roof boards. By adhering to ULC CAN-S102, architects can select roof boards that minimize fire spread and smoke production. The standard provides a clear benchmark for material performance, aiding in the design of buildings that are both safe and compliant with Canadian fire safety regulations.

ASTM E136 or CAN/ULC S114 (Interior Panel Combustibility): ASTM E136 and CAN/ULC S114 are standards for testing the non-combustibility of materials. These standards are crucial for ensuring that interior panels used in educational buildings do not contribute to fire spread. ASTM E136 is a widely recognized standard in the United States, while CAN/ULC S114 is its Canadian counterpart. Both tests involve subjecting materials to high temperatures and observing their combustion characteristics. Materials that pass these tests are considered non-combustible and suitable for use in fire-resistant construction.

ASTM C1396: ASTM C1396 focuses on the specifications and performance of gypsum boards used in construction, including regular gypsum board, gypsum sheathing board, water-resistant gypsum backing board, and gypsum core board. The standard specifies the requirements for the physical properties, performance characteristics, and testing methods for these materials. One of the key aspects of ASTM C1396 is the focus on fire resistance. Gypsum boards conforming to this standard must meet stringent fire-performance criteria, making them suitable for use in fire-rated assemblies. Materials that achieve a “Type X” classification are noted as having increased fire resistance beyond regular gypsum panels.

Severe damage to educational facilities can expose allergens, mold, mildew, and bacteria.

Shifting focus from fire to water, the other safety concern we will discuss is the need to create healthy IAQ for educational buildings. As stated previously, poor IAQ can impact not only the physical well-being of students and staff but also increase sick days and impair the ability of students to learn.

There are many contributors to poor IAQ in educational buildings. Aging HVAC systems that do not provide adequate filtration or appropriate air changes per hour can create stagnant spaces that students are stuck in for long periods of time. Allergens and pollutants, as well as volatile organic compounds (VOCs), are often introduced into educational settings as students, teachers, and staff go about the normal tasks of coming and going from school. While the architect has little control over the operational habits of the occupants, there are specific risks that the designer can address to help improve IAQ over the duration of the life of the building, such as water migration into the conditioned space.

Water poses many challenges to buildings but in terms of IAQ, the main risk is the development of mold, mildew, and bacteria. Mold and mildew are both fungi that thrive in damp environments and require organic materials for sustenance. They differ in appearance, but both have a negative impact on IAQ. Bacteria is a surface dweller too small to be observed but can trigger allergic reactions and exacerbate asthma, particularly affecting sensitive individuals and those with preexisting conditions.

Mold typically appears as black, green, or blue patches and can grow on various surfaces like walls, ceilings, and furniture. Mold releases spores into the air, which can trigger allergies, asthma, and other respiratory issues. Certain molds, like Stachybotrys chartarum (black mold), produce mycotoxins, posing significant health risks.

Mildew is usually white or gray and appears as a powdery or fluffy growth and specifically targets organic materials like paper, leather, cloth, and the organic matter on surfaces such as bathroom tiles, windowsills, and shower curtains. While generally less harmful than mold, mildew can still cause respiratory problems and allergic reactions, especially in sensitive individuals.

Bacteria require water to thrive because it is essential for their metabolic processes, nutrient absorption, and reproduction. In the presence of moisture, bacteria can rapidly multiply, particularly in environments with organic matter that serves as a food source. Bacteria can become airborne, forming bioaerosols that circulate through the building’s HVAC system. These bioaerosols can be inhaled by occupants, leading to respiratory issues, infections, and allergic reactions. Damp areas in educational buildings, such as water leaks through the building envelope, wet surfaces, and poorly ventilated spaces, can become breeding grounds for bacterial growth.

As with fire safety, there are standards architects can use to determine how effective a building material or product will be at reducing the proliferation of mold, mildew, and bacteria in educational settings.“Actual job site conditions always vary,” notes Chamberlin, “You can’t always be sure that a product’s mold resistance will produce the same results that were achieved in a controlled, laboratory setting. However, when used properly, fiberglass-mat gypsum panels can provide increased mold and moisture resistance compared to standard paper-faced boards.”

ASTM D3273 (Interior Panel Mold Resistance): ASTM D3273 is a standard test method for evaluating the resistance of interior panels to mold growth. The test involves exposing panels to high humidity and temperature conditions conducive to mold growth and assessing their resistance over time. Materials that perform well under ASTM D3273 testing may help prevent mold-related issues, which may lead to a safer and healthier learning environment. Architects use this standard to select interior panels that contribute to the longevity and healthiness of educational facilities.

ASTM D6329-98 (Microbial Resistance): ASTM D6329-98 is a standard guide for developing methodologies to evaluate the microbial resistance of materials. The guide provides procedures for assessing the resistance of materials to mold, bacteria, and other microorganisms. By using materials tested to ASTM D6329-98, architects can design buildings that are more resistant to microbial growth, thereby potentially enhancing the durability and healthiness of educational environments.

Is it a Roof or Cover Board?

Figure 1: The cover board is installed under the flat roof membrane while the roof board is secured just above the steel decking.

To the untrained observer, stacks of gypsum boards on a jobsite may all look the same. But knowing the difference between a roof board and a cover board is an important distinction when designing the build-up of the flat roof.

Roof boards are installed directly onto the structural deck. Depending on the type and style of board, they can help improve sound attenuation and help slow or limit the spread of heat and fire from within the building. For the roofing contractor, a roof board provides a good surface for a vapor control layer to be fitted to. And in the instance where the deck is fluted steel, it creates a flat surface that makes installation of the roof easier in general. Roof boards also can help improve wind uplift resistance by enhancing stability.

Cover boards are installed directly under the roofing membrane and over the layer of insulation. The primary function of the cover board is to protect the insulation from compression and impact damage. Though roofing membranes are the exposed component of the roof, the cover board is truly the first line of defense for the building. Cover boards can help mitigate the puncture risks posed by foot traffic during maintenance, and they need to be durable enough to withstand damage caused by an extreme weather event with hail or flying debris. A cover board is also a key feature to provide resistance to wind uplift.

It is important to note that specifying the appropriate type of cover board also impacts the durability of the building and the safety of the occupants. Gypsum cover boards provide excellent fire resistance and may slow the spread of flame compared to wood fiber cover boards. Some projects striving to maximize building energy efficiency may specify perlite, polyiso, or extruded polystyrene (XPS) boards. The trade-off to the building is that while these lightweight materials will improve the roof's R-value, they are not as durable, weather or foot-traffic-resistant as gypsum.