Blast Mitigation Demands Careful Attention

tax breaks for investments in energy-saving technologies. Then the 2007 Energy Independence and Security Act gave added impetus to the use of renewable energy systems.

The greenest renovations

According to Michael Binette, AIA, NCARB, and principal of The Architectural Team, Chelsea, MA, in some projects it’s possible to recycle on a very large scale—redeploy entire buildings, existing materials, structure, and MEP systems—saving money and resources in the process. Some of these adaptivereuse projects for historical factories open the door for adding modern cogeneration systems or even reviving hydroelectric capabilities. They can also accommodate renewable energy, using their large, flat roofs to support new photovoltaic panels and solar thermal collectors and by drilling geothermal wells below. Existing buildings usually can be reconnected to the grid more easily than most greenfield sites, too.

“When evaluating the best gains, look for simple answers first,” Binette said. “We work often with historic mills, where new insulation offers the biggest benefit at the lowest cost. We have achieved thermal barrier values as high as R-23 with medium-density spray foams in combination with cellulose insulation on century-old masonry structures.” One such case was the Oliver Lofts in Boston, an adaptive reuse, mixed-income residential property that was formerly a brewery warehouse.

The return on energy-related upgrades is well established. For green buildings and sustainability retrofits, there is a growing body of information underscoring the financial benefits of upgrades focused on occupant health and well being, lower toxicity, and occupant productivity. One study of hundreds of LEED-rated buildings by the Univ. of San Diego and the real-estate data company CoStar, Washington, showed rents increased by more than $11 and resale values jumped more than $170/sq. ft. for green buildings, compared with their non-green neighbors.

This value can be captured for long-term property holders, too. For example, the Haverford School, Haverford, PA, undertook a $28-million restoration and expansion for an upper school and administration building to meet the educational needs of information-age students within and adjacent to a historical 1903 hall. The Svigals + Partners, New Haven, CT. transformation of a corporate complex in New

with a visioning session For the Haverford School, MGA Partners restored the 1903 Wilson Hall, designed by noted architects Fred Furness and Allen Evans, and paired it with in the earliest part of the planning phase to establish a sophisticated modernist expansion for a major a description of a futurenew academic building certified LEED Gold. state based on shared values among the various stakeholders,” Brotman explained. For WXY’s work on the Drawing Center, the client’s planned expansion strategy led to a feasibility study. The cultural group had long considered a highprofile new building at the World Trade Center site, and compared that with another site several blocks away. The museum leadership eventually decided to stay at its existing, and iconic, location, said Layng, based on the favorable ROI of an LEED Gold landmark facility is also a teaching extensive renovation including new gallery interiors, tool for environmental responsibility, according MEP systems, skylights, and stairs for the 19thto Daniel F. Kelley, FAIA, senior partner with MGA century loft building. Partners, Philadelphia, and lead designer. Behind the decision was a careful

“The project incorporates many strategies accounting of organizational needs and longto minimize the building’s carbon footprint and term vision, followed by a detailed analysis of create a healthy environment for learning,” said design options and associated costs. “From Kelley. “It has launched the school’s heightened these granular details come the inspiration commitment to sustainable practice across and foundation of truly great projects, where campus.” One example: an array of specialized their unique attributes fully serve the core of meters and controls that give students and teachers each organization’s goals,” said Brotman. “But real-time feedback on energy and water usage. this is only the case if the planning phase has More than mere looks generate something larger from them.” Other retrofit and renovation projects are geared Kelley of MGA Partners, a firm that has toward aesthetic and performance upgrades, such expertise in university live-learn environments, as exterior recladding and overcladding. A numagreed. “Often our challenge as the architect and ber of school districts and healthcare providers planner is to help shape a new organizational are adding continuous exterior insulation, or CI, to system while adapting physical spaces to existing buildings by overcladding. In addition to accommodate how they work.” a renewed look, it’s an effective technique for imThe many different approaches to successful proving acoustics and the effective R-value while renovation boil down to extensive planning that controlling condensation and air infiltration. involves everyone with a horse in the race. That

Yet some renovation approaches don’t work key element, however, may be just about the well. In many cases it’s because the old building only thing any given group of renovations has can’t support the kinds of renovations envisioned, in common. As the saying goes, if you’ve seen leading to costly added work. But usually projects one renovation, you’ve seen one renovation. fall short of expectations because the goals and Each project brings enough challenges and the design vision are out of alignment, said Jay M. opportunities to keep the entire team on their toes Brotman, AIA, a partner with the architecture firm for the duration.

“We use a process of lab planning called Chris Sullivan is principal of C.C. Sullivan, Phusion that is ideal for these complex renovation a Montclair, NJ, marketing firm specializing projects,” said Brotman, who recently led the in the commercial-building market. thoroughly nurtured these granular details to Haven, into the W-B 24 scientific research hub for free information, CIRCLE 1 for Yale Univ.’s growing West Campus Integrated and visit our digital magazine at Science & Technology Center. “Phusion begins www.cbpmagazine.com/digital/julaug2013.

The Sarasota Police Headquarters is an example of a whole-building solution. It features an impact-resistant curtain wall and entrances, including the 1600 Wall System1 curtain wall and 350 IR medium-stile entrances from Kawneer

North America. Photo by Greg Wilson Group.

Well-planned blast mitigation protects buildings and saves lives.

Donnie Hunter, Kawneer North America

Threats to our national security are everpresent in today’s global society. Within seconds, buildings can be irreparably damaged and landscapes can change. Increasing the safety of building occupants and preserving human life is the primary goal of blast protection. The demand for blast-mitigation products is increasing in new and retrofi t building applications, giving architects a unique opportunity to safeguard human lives.

Determining which fenestration solutions and systems to specify for blast mitigation is a formidable responsibility. Making the right decision lies in understanding how the products are produced and what they’re designed to do. Developing high-performing blast-mitigation solutions involves several interdependent steps to ensure the effectiveness of the products.

Step One: Understanding Blasts. According to the Oxford Dictionary, a blast is “a destructive wave of highly compressed air spreading outward from an explosion.” Hazards resulting from a blast include fl ying glass shards, building components, shrapnel, dirt, rocks, and debris, leading to possible structural damage and/or building collapse. Fenestration

products cannot provide complete protection from an explosion, but in the unlikely event of a blast in or near a building, products designed to address blast hazards can help reduce the damage.

When looking at the nature of a blast there are two elements to understand: the charge weight and the standoff distance. The charge weight is the amount of explosives used (TNT equivalent), while the standoff distance is the distance of the point of detonation from the target. Ultimately, the greater the standoff distance, the slighter the explosive threat to the building or target.

Step Two: Assessment and Testing. According to the American Architectural Manufacturers Association (AAMA), Schaumburg, IL, the conditions for blastmitigating fenestration systems include limiting fl ying shards, glass preservation, frame support, and wall integrity. These criteria are all taken into consideration during product evaluation.

The fi rst step to any blast-mitigation project is a thorough threat assessment by a third-party consultant to determine the estimated size and nature of the potential explosive device, as well

Kawneer’s 350 IR medium-stile entrances and IR 500/501 framing system, shown on the Tarpon Springs, FL, public-safety building, can offer

protection from explosions. Photo by Gordon Schenck, Jr.

as the standoff distance. The consultant will evaluate issues such as the likelihood of an attack and how close a vehicle or carrier can get to a building. Risk-analysis software and site surveys help blast consultants determine the answers to those questions and more. Whatever the method, this step is critical and the results must go to the design team as the foundation for the project design.

After the initial threat assessment, several test methods that simulate the effects of an explosion can measure blast resistance. These methods include: • Static testing, an economical method that employs the conventional static-testing methods used to test fenestration products. • Shock-tube testing, a moderate-cost method that uses a compressed-gas charge or a live explosive device to achieve the positive pressure of an explosion. However, this kind of test usually lacks negative-phase effects. • Open-air arena testing in which an actual explosive charge is positioned at the projected standoff distance. The most realistic and costly method, it produces positive- and negative-phase blast effects.

The blink of an eye

The blast duration of a large explosive device is typically in the range of 28 to 42 milliseconds, which is roughly an eighth of the time it takes for an eye to blink. Destruction can vary greatly based on distance and the size of the explosive, so thorough testing can provide vital insight.

The shock-tube and arena-test methods use a number-zoned “witness chamber” to help measure the effects of debris entering the room as a result of the blast. The performance of the glazing system is determined and given a performance condition or hazard rating relative to the testing standards.

Building blast-resistance requirements, known as blast mitigation standards (BMS), are driven by the size of the explosive device and distance to the target. The BMS is typically expressed in pounds/square-inch•milliseconds (psi-msec) of refl ected pressure and psi-msec of impulse. Without these elements, the BMS is incomplete and the building is likely to be inadequately protected.

During this process, testers evaluate the building and wall assessment/reinforcement, addressing design and product options as

well as the blast resistance of the products and attachment methods. The evaluation and assessment must look at the products as a system and examine how the various elements work together. Key factors to consider include: • The glass can break but cannot send fl ying shards into the room. • The glass lite must stay in the frame, along with all interior window components. • The frame must remain anchored to the wall. • The wall must resist the load and retain the frame.

Depending on building and construction methods, materials, and construction, several wall-anchoring options are offered: • Basic trim and clip, usually suitable for lowblast-load applications • Expansion and adhesive anchors • High-performance grout-fi lled anchors, particularly effective in retrofi t applications where support for high blast loads requires tying together unrelated construction elements or deep anchoring.

Highly skilled glazing contractors and window installers are essential to the overall process and critical to assuring proper