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Storm Shelters’ Growing Importance in Minnesota Schools

Wold’s engineers & architects discuss storm shelter design and impacts of the 2020 ICC 500 code

In Minnesota, K-12 schools are developing solutions to respond to severe weather events. One of these solutions is storm shelters, which are buildings, structures or portions thereof designated for use during tornadoes, hurricanes, and other severe windstorms. Reliable storm shelters must include the mechanics and engineering necessary to ensure safety, comply with required guidelines, and create comfort during emergencies.

In May 2002, the International Code Council (ICC) and the National Storm Shelter Association (NSSA) initiated a joint project to develop the ICC 500 ICC/NSSA Standard for the Design and Construction of Storm Shelters, a standard that provides minimum design and construction requirements for storm shelters.

This structural engineering code, which was updated in 2020, contains design requirements for the main wind-resisting structural system, components and cladding of the shelters. It also provides basic occupant life safety and health requirements for shelters, including means of egress, lighting, sanitation, ventilation, fire safety and floor space.

Our architects and engineers have extensive experience designing storm shelters in K-12 schools and learning centers to create an imperative line of defense that protects work crews, staff and students during emergency situations. The ICC 500 code helps ensure our most vulnerable community members are protected when they need it most.

We spoke with education leaders Valerie Peterson, AIA, LEED AP, Associate, Paul Aplikowski, AIA, LEED AP, Partner, Brady Meister, PE, LEED AP, BD+C, Associate and Mechanical Engineer, and Mike Freeman, PE, LEED AP, Associate and Mechanical Engineer, to learn more about the process of creating shelters that protect occupants, address code requirements and integrate necessary components and features to meet clients’ needs.

Insights from our engineers

>> How have codes like the 2020 ICC 500 impacted storm shelter engineering and design?

Brady Meister:
These codes help provide a framework for required outcomes and strategies when designing storm shelters. Since codes like the ICC 500 often have incredibly strict structural requirements, they can have a major impact on other engineering systems serving the space.

Mike Freeman:
The requirements for meeting ICC 500 are related to the location of the building and building type. New buildings and additions for public buildings now have to budget additional funds for storm shelters. There are many requirements associated with storm shelter design, such as maintained services to buildings, increased structural requirements and maintained storm shelter rating, even if penetration occurs between the storm shelter and non-storm shelter portions of the building. The intent behind this code is to have a structure that protects occupants while safely maintaining ventilation, lighting and toilet room access, assuming that the non-storm shelter rated portion of the overall building is no longer standing.

>> What is Wold’s approach to designing storm shelters that meet Minnesota’s codes and guidelines?

There are many nuances to the specific design of each storm shelter, whether or not our team designs it. However, our approach to designing storm shelters is very much in line with our approach to any design. When we design a storm shelter, we make sure to engage the client as much as possible and understand how they want the shelter to function.

For example, one client may want a storm shelter to function without any human interaction, while another may elect to have specific occupants trained on how to operate features of the storm shelter during a severe storm. Discussions like these narrow down design approaches. Since Minnesota's adoption of ICC 500, we also have early conversations with code officials to verify that our proposals meet their interpretations.

We work with code officials to understand various interpretations of storm shelter code requirements. This collaborative approach has allowed us to meet the intent of the code during design and, as a result, our engineering team has experienced a streamlined plan review process. Understanding the structural implications and their extension to other disciplines, such as mechanical, has also been very beneficial.

We typically work to minimize the number of openings in the storm shelter envelope. However, we understand how to protect openings through the storm shelter with ICC 500 rated shrouds, louvers, roof drains and plumbing vents that have been coordinated with the structural engineer and the design team. We have used natural ventilation and mechanical ventilation with generator back-up to provide code compliant ventilation to the space(s) during a potential storm event.

>> What should districts keep in mind as they prepare for additions, renovations or new construction as it relates to storm shelters? What do they need to know about remaining compliant with Minnesota requirements?

When considering additions, renovations or new construction of storm shelters with school districts, the first question is usually whether one is required. In Minnesota, it depends on the building's location, occupancy class and number of occupants. In general, additions and new constructions in central and southern Minnesota will require a storm shelter. Renovations, on the other hand, may not require the addition of a storm shelter. When planning for storm shelters, consider the following:

  • Plan for the shelter to have as many exterior walls as possible. This is helpful for the ventilation system(s) that will serve the space, whether natural or mechanical ventilation is used.
  • Try to locate the storm shelter with close proximity to a domestic water utility. A dedicated domestic water service may be required for sanitation purposes.
  • If using mechanical ventilation, a generator protected by an ICC 500 structure is required, and any fuel serving the generator also will need protection. This includes the natural gas meter if it's being used for the generator.

Mike: Under the current code, a renovation of a public building alone will not enable the storm shelter requirement. However, when you add square footage, especially when it is tied to additional occupants, adding a storm shelter is required. This also means that any new public building that meets the criteria will likely need to include a storm shelter plan. When the size of an addition gets large enough, it is required to become a storm shelter - not just for the addition itself, but also to serve the entire building that is under renovation.

Insights from our architects

>> What design challenges has the implementation of the 2020 ICC 500 code presented for schools across the state?

Valerie Peterson:
To achieve the prescriptive requirements of the MN Code, consideration must be given to design. Learning environments have evolved into more vibrant, transparent and interactive spaces in contrast to former “institutional” feeling spaces that included masonry hallways lined with lockers and minimized windows in the fenestration. We aim to provide a design that feels seamless and unnoticeable by users when they cross the threshold of the storm shelter portion of the building.

Paul Aplikowski:
When the code was adopted, much of the design work in progress was budgeted prior to the code change, so it presented a funding challenge when the state mandated the code be applied to current projects.

Now that the code is in place, the storm shelter requirement will hinder clients’ ability to implement projects that expand capacity at schools. This is particularly pronounced at smaller additions where we may be adding just a few classrooms. The code requires you to allocate all of the square footage of the addition until you reach enough capacity to hold all occupants on campus during a storm event.

>> How does Wold ensure storm shelters are both functional and secure without feeling like students and staff are in bunkers?

In reality, school districts cannot afford to build a dedicated storm shelter at the size required. The storm shelter then becomes part of the daily utilization of the school where learning or programming takes place. To create seamless flow, Wold ensures consistent architectural language, details, materials and colors between the storm shelter and non-storm shelter areas. The integration of outside windows with storm shutters and/or ballistic glass ensures the interior environment feels open and connects occupants to their environment. Large interior openings with storm shutters can also create openness and connections with the adjacent, non-rated areas.

>> How has Wold successfully integrated storm shelters into school design?

In new facilities and school building additions, Wold has incorporated storm shelter design through various solutions based on the building scope, including in gymnasiums, classrooms and locker rooms.

In addition to the design elements Valerie mentioned, carefully stitching the line between storm shelter and non-storm shelter is critical to successful integration. There is a significant cost to reinforce facilities for tornado requirements. The shelter cannot be significantly larger than needed, but placing the boundary thoughtfully can help set the massive structure out of sight and allow for more openness within the learning environment.

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