Ensuring occupant comfort and safety with smoke vents

by Thomas Renner

Photos courtesy Hale Centre Theatre
Photos courtesy Hale Centre Theatre

The architects responsible for designing a state-of-the-art theater in Utah between 2015 and 2017 faced a unique challenge in trying to limit noise intrusion. An adjacent interstate and planes arriving and departing from
a nearby airport made for noisy neighbors for patrons attending events at the Hale Centre Theatre in the city of Sandy.

“The sound issue was pretty intense,’’ said architect Lyle Beecher. “We knew noise was going to be an issue.”

Beecher’s firm, Utah-based Beecher Walker, designed the $80-million Hale Centre Theatre, which opened in November 2017. A critical element of the solution for Beecher and his team was the installation of 20 acoustical smoke vents to guard against noise intrusion. The vents feature a sound transmission class (STC) rating of 46. This figure denotes how well a building partition attenuates airborne sound and roughly reflects the decibel reduction in noise a building component can provide.

STC ratings are included on the doors, windows, partitions, and even floors. They are generally much lower than 46 on doors and windows—a hollow door can have an STC rating of around 20 to 25, while windows are usually in the STC 26 to 28 range. Most smoke vents that are not acoustically rated have an STC value of 30 or less. The vents used at the Hale Centre Theatre include 75-mm (3-in.) thick fiberglass insulation, exceeding the 25-mm (1-in.) thickness of many smoke vents and helping contribute to their acoustic performance.

Construction materials limiting noise are particularly important at theaters and other performance venues, where interference from external forces can ruin events for guests who sometimes pay exorbitant prices to watch shows.

Acoustic smoke vents were installed in the construction of the Hale Centre Theatre in Utah.
Acoustic smoke vents were installed in the construction of the Hale Centre Theatre in Utah.

“In this instance, there are even helicopters that fly directly overhead,’’ Beecher said. “The air traffic was one of the primary concerns we had when we discussed which roofing components to use. Those acoustical smoke vents are the only thing stopping noise from the outside at the loading level. We could not have any noise infiltrating the building.”

The smoke vents are also supported by other acoustical elements, including 0.6-m (2-ft) thick concrete walls with carpeting installed. Additionally, the door bottoms included acoustical treatments.

The acoustical smoke vents atop the Hale Centre Theatre do more than limit noise intrusion. They are also a crucial safety feature in a venue that can host more than 1300 guests in its two auditoriums. Vents enable the escape of smoke, heat, and gases in a burning building.

“Vents will allow for the removal of heat and smoke and potentially slow the spread of fire,’’ said Steve Martin, battalion chief for the Columbus Fire Department in Ohio. “They will also permit firefighters to see and enter the building to possibly extinguish the fire early, preventing the entire building from becoming a loss.”

The vents used at the Hale Centre Theatre include gas spring operators that open the covers in snow and wind. They also have built-in dampers to ensure smooth opening and eliminate the possibility of operational, roofing, or structural damage.

“The vents solved a tremendous challenge for us,’’ Beecher said. “The most important thing is to make sure people are safe. Those vents create a passive smoke-ventilation system that leads up through the loading level. It keeps the smoke out of the theater so everyone can exit safely.”

The scoop on smoke vents

Regulations for smoke vents in commercial structures are outlined in National Fire Protection Association (NFPA) 204, Standard for Smoke and Heat Venting. This standard provides calculations to determine the required dimensions and spacing of smoke and heat vents. The number of smoke vents depends on the size of the building or area protected, the height of the ceilings, and the depth of the expected smoke layer, according to Robert Solomon, PE, division director for NFPA. The number of smoke vents required is also determined by local building and fire codes and the type of commercial structure.

In one example, fire destroyed a building owned by Dick Cold Storage, a business in Columbus, in 2016. More than 400 firefighters rushed to the blaze, but the building did not have smoke vents.

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