Demystifying DoD Blast Mitigation

Above: Tulane University’s recently completed Tulane Commons includes an eatery, study area and event spaces. Located at the heart of campus, the three-story building features YKK AP America’s YHC 300 SSG Cassette Curtain Wall which meets impact requirements for the coastal region. 

Contrary to perception, blast mitigation glazing is not inherently complicated. More than 80% of injuries in blast events are caused not by building collapse, but by flying glass fragments. Glass shards can travel between 68 and 135 miles per hour, turning standard glass into hazardous projectiles. The purpose of blast mitigation for most buildings, therefore, is not to prevent glass breakage entirely, but to control glass behavior, keeping fractured glass attached within the frame, or within a few feet, to prevent hazardous debris.  

Most, or perhaps all, Department of Defense (DoD) building projects contain requirements for blast mitigation, but the way materials are specified changed significantly in 2018. After many years of increasingly stringent performance-based specifications, after 2018 buildings had to instead meet  prescriptive requirements only. While this change  was designed to streamline the compliance process, the shift resulted in some contractors incorrectly referencing both old and new standards.  

Prescriptive standards and UFC 4-010-01 

As stated, before 2018 DoD building projects were held to performance-based specifications, meaning the system could be approved based on testing and analysis, not based on prescribed parameters for the building materials. For blast mitigation, performance-based testing required the fenestration supplier to design and configure the building system to provide a level of protection to survive a specific size of the explosive charge weight (measured as a TNT equivalent) placed at a certain minimum distance from the building to be protected, known as the Standoff Distance.  

In 2018, DoD requirements moved to prescriptive standards, meaning blast mitigation systems must be built to specific parameters, and analysis and special engineering need for performance-based specifications are not required. 

The intent for this change from performance-based analysis to prescriptive standards was to make a distinction between low-risk and high-risk buildings. After 2018, low-risk buildings are built to the specifications of the UFC 4-010-01 standard, which requires only laminated glass and silicone glazing—no blast testing or analysis is required. Without the added cost of performance-based testing, more resources and dollars were then freed up to be used to protect higher-risk buildings where there is a specified threat, such as large gathering places or areas conducting confidential research. 

Common specification challenges 

While the move from performance-based to prescriptive standards for some projects was meant to simplify building and offer greater protections to higher-risk projects, the change has resulted in some confusion for builders. Specification inconsistencies remain one of the most frequent issues in blast-related glazing projects. Copy-and-paste from old specifications is typical in building products and is not limited to DoD projects. The  potential problems were just amplified with DoD since moving back to prescriptive standards was such a large philosophical changein approach to specifications. Typical problems include: 

Mixing UFC 4-010-01 prescriptive criteria with performance-based requirements. This often occurs when sections of old specs are copied and pasted into a new spec. Example: Use of UFC 4-010-01 is specified, but another section still refers to static analysis per ASTM F 2248, which is no longer required.   

• Incorrect sealant bite dimensions (e.g., ½ inch instead of the prescribed ⅜ inch) 
• Overly conservative assumptions leading to unnecessary curtain wall substitutions where storefront would meet requirements at a much lower cost.   

These errors contribute to cost escalation, bid disparities, RFIs, and schedule delays. Since the intent of changes in UFC 4-010-01 was to simplify and reduce cost, any duplication from old standards will increase cost. A clear understanding of the applicable standard prevents overdesign and improves bid accuracy. 

A simple path forward  

The reintroduction of prescriptive DoD standards has simplified compliance for most facilities. UFC 4-010-01 provides prescriptive requirements only. If there is a specific threat to the building, a different standard will be referenced. Glazing contractors who understand these requirements are positioned to participate confidently in secure facility work and avoid costly specification misunderstandings. The key for the glazing contractor is to act immediately if there is a problem with the specs. If there is a problem, glaziers should immediately call, email or do a formal Request for Information to get clarification.

However, glaziers may have to complete the bid before getting clarification. In that case, they should consider these two choices: 

• Bid the job to meet all specifications. The risk here is that someone else could underbid the glazier by only quoting prescriptive requirements, which may result in the glazier losing out. 
• Bid the job to meet prescriptive requirements only. The risk here is that the submission is rejected. The worst case scenario would be that the price of the bid can’t increase, but the glazier would have to meet the specs as written.