Extreme weather: Designing schools to withstand the forces of nature
April 24, 2019
April 24, 2019
Educational facilities must be a part of a community resiliency solution for natural disasters
When architects design education projects, keeping students safe is a priority, but communities often have even higher expectations for their education facilities. We expect the schools to be more resilient than other buildings in the community. In rural communities and beginning in the mid-20th century, we looked to schools as designated shelters, even as sites for Cold War fallout bunkers. Today, we see them used as aid-distribution centers, emergency shelters, and housing during natural disasters. This is logical, as schools are essentially mini cities with business, food, and wellness services all their own. And, in general, code requires that we design schools that are a notch above other buildings.
Because of these code requirements and the facility’s role as designated shelter, communities hold school designs to a higher standard. Some schools are even specified in emergency operation plans for communities. This means that authorities and school administration should be in close contact and aware of the emergency features in their facilities.
Today, the challenge of resiliency is more intense than ever. But if we focus on one threat or the last extreme weather event and design to just one, we may end up less resilient to others. The key is for us to take a holistic approach and consider all the potential threats that a school building may face. When we design an educational facility, it should complement operational resilience and work with community, law enforcement, and emergency services relationships.
Storms might be the most common natural weather event to impact schools. When inclement weather of any level hits, students, teachers, and staff should feel safe in the school’s storm shelter. Tornado shelters and hurricane shelters are more protective shelter types that are designed for more intense winds and for longer-term shelter.
Depending on where you are in North America, code requirements for educational storm shelters differ. In stretches of the US where tornadoes are common, the storm shelter must be able to withstand tornado-force winds. The 2018 IBC requires all education buildings that fall in the ICC 500 250-mph-windspeed map with an occupant load of 50 or more to have a storm shelter built to comply with ICC 500. This standard provides minimum design and construction requirements—structural design criteria, occupant density, critical support systems, and impact and pressure testing—to name a few. But users may expect much more.
What makes a good storm shelter? Protection and everything needed to maintain safety, communications, and comfort for a reasonable amount of time. When designing storm shelters for K-12 schools, there are three things to consider—location, critical support systems, and operations and maintenance.
1. Location: The school’s storm shelter may be free-standing (within 1,000 feet of the school by code), attached to, or within a building. And its location must be carefully analyzed for adjacent building collapse. In the case of a basement-level shelter with occupied floors, it must be designed to withstand the collapse of the structure above.
If we focus on one threat or the last extreme weather event and design to just one, we may end up less resilient to others. The key is to take a holistic approach and consider all the potential threats that a school building may face.
To use space and budget efficiently, it’s likely that schools will choose a portion of a new classroom wing or the gymnasium to double as the storm shelter. This means, however, that the gym or wing must meet requirements for occupant density, access, sanitation facilities, and impact-protective doors and windows. Recently, we designed a fine arts building with a band hall, choir, and black box theater to double as a storm shelter for a middle school, and a multi-classroom building extension as a storm shelter for an elementary school. Both are nearly impossible to distinguish but have features such as glass that meets impact requirements. A school in a dense area where land is expensive might build underground parking that doubles as emergency shelter.
2. Critical support systems: Critical support systems include structures, equipment, and components required to ensure the health, safety, and well-being of occupants over the short term—that is, when we can expect the structure to be occupied as a shelter.
Back-up power is key. If there’s a loss of power, uninterruptible power supply (UPS) or a generator is required to maintain emergency lighting, plumbing supply/waste systems or sump pumps, and mechanical ventilation. Natural ventilation is an option, since mechanical equipment is typically located on the exterior and difficult to protect against winds of up to 250 mph.
A tornado shelter requires critical support systems for two hours, while a hurricane shelter requires support for 24 hours, including functioning toilets, hand-washing stations, a fire extinguisher, a place for a first-aid kit, lights on back-up or battery power, and ventilation.
The most efficient shelters (which must have their own sanitation) function as classrooms or gymnasiums when not in use for emergencies.
3. Operations and maintenance (O&M): Operations and maintenance needs can vary. But considerations from the local emergency planning committee (LEPC) may be appointed by a school board, and FEMA’s outline of important factors (staffing, roles and responsibilities, access and entry, lockdown, and maintenance) for achieving “safe rooms” are a good place to start.
O&M needs can include communication systems, wireless access point, TV with cable connection, or a power-charging station with convenience outlets and back-up power to serve these items. Consider providing a control room for shelter equipment and emergency supplies, food, and bottled water.
O&M largely drives the design of these spaces. We recommend that owners form a collaborative planning team with architects to understand how the space will be used and develop the design and desired features around that.
Incorporating a storm shelter is a significant investment, spurred by changes in code, so school systems are keen to make the most of it. They want a secure space that can be used in lockdown situations. They want spaces that can be used by their students. It’s likely that these spaces are needed additions that can double as shelters—rather than standalone purpose-built shelters like the fallout shelter bunkers of the past.
In flood-prone areas, school buildings must be designed to withstand rising waters—and not just that of ordinary storms. A neighborhood may locate a sizable retention pond on school grounds to mitigate the effects of ordinary storms, but what happens to the school when it’s overwhelmed by extreme weather, like a tropical storm or other high-volume water event?
Here are five of our best practices for designing schools to withstand flooding brought on by extreme-weather events.
1. Higher floor elevations: Designing higher-floor elevations for schools (raising the lowest occupied floor above anticipated flooding level) is good practice for flood resilience. In coastal areas, this is standard. While regulations in an inland flood zone will define these for many schools, flood maps can change over time, necessitating new and higher elevations. Since the average lifespan of a school is 45 years or more, we design them to a higher standard.
As the City of Houston learned with Tropical Storm Allison, critical systems are extremely vulnerable during floods. A vast portion of the infrastructure for the Texas Medical Center was located below grade or at grade at that time and therefore failed during the storm-related floods. Elevating critical systems (power, HVAC, emergency generators) in our designs for new schools is essential. In retrofitting schools for resiliency, we must look for opportunities to elevate critical systems.
2. Wetable or waterproof materials: In new or existing buildings, we can anticipate which lower sections of the building may be prone to water intrusion during extreme weather and substitute “wetable” or waterproof materials for drywall in these interior areas, minimizing or reducing the possibility of damage and allowing for easy clean-up or replacement.
3. Critical back-up systems: Schools might be the main community center, place to go, or shelter in some communities. In these cases, it becomes even more important to build in those extra layers to help keep the building operational during periods of stress.
We design some schools as designated emergency-operations centers, where power, communications, and habitability will be maintained during a flooding emergency. Back-up generators, communications networks, and life-safety features like emergency lighting are critical. We must back up the things that will be needed in an emergency. Schools often link their freezers and coolers to back-up generators to ensure safe food storage during emergencies, an asset if the community seeks shelter there.
4. Consider the network: Maintaining the school building is one thing, but when we consider the school as part of a community network that must respond to emergencies another set of questions emerges. Does the community have a plan for emergencies and extreme weather? How will communications be maintained? What role will the school building and systems play, and which part(s) of the school does that involve? The facility must be able to accommodate the plan. We must make these emergency systems intuitive so that they are easy to operate in emergency conditions.
5. Take a “belt and suspenders” approach: Preparing for flooding requires a “belt-and-suspenders” approach to infrastructure and backups. That means preparing for the worst and then some. No matter how confident we might be in our primary system for dealing with floods, we should design a back-up feature as a safety net.
For example, for an existing facility in a highly flood-prone area or flood plain, we’ll design in flood gates and flood walls to keep the water out. That’s the “belt.”
Should those fail, all the materials behind those areas should be “wetable.” That is, if water gets through the first system, it will encounter waterproof materials, so damage will be minimal. That’s the “suspenders.”
Schools matter, and that’s especially true in times of emergency. They are often a focal point in the community—especially in more sparsely populated areas. They are an important piece of the social infrastructure that community members rely on. We must design them to perform and help people make it through whatever extreme weather events can throw at them.