Energy efficient buildings are so well air-sealed it makes it difficult to replace exhausted air causing depressurization of the building environment and vents can’t draw out air, because there is not enough air in the environment.
Simply put, air needs to be replenished “make-up air” or compensated for the air lost through ventilation.
Building codes require air replenishment systems to compensate for the air exhausted through the hood and bathroom vents, or other means. This is accomplished using an in-line damper vent duct system that is controlled with a pressure regulator pulling outside air in. Keep in mind that this system and ductwork are placed in the above ceiling open plenum spaces in residential or commercial spaces.
So what does this have to do with elevator noise?……….
Make-up air or utility chases alongs with above-ceiling plenum spaces usually doesn’t include any insulation to provide some level of sound absorption. This creates a reverberant sound environment with the reflecting sounds building up and actually increasing overall sound level intensity.
The location of the air replenishment intake can greatly influence the amount of sound entering an occupied spaces whether it’s in close proximity to a rooftop chiller or as in the case of a recent project survey pulling air from the vertical rise plumbing chase.
Per U.S. Gypsum (USG) the commonly used UL U529 elevator shaft wall system has a sound rating of only STC39. This rating is comparable to a simple 2”x4” stud, 1/2” gypsum, and 2” sound blanket wall assembly of STC40. The wall sound rating requirements of machine room wall is at least STC50. For conversational purposes you may look at a rating difference of 10 equating to being either half or twice as loud at 500 Hz.
Low standard wall sound ratings may be acceptable for some building environments; however, a chase running along the counterweight wall allows migration of both airborne and structure-borne sound into the chase.
Airborne sounds from the moving elevator car and counterweights with the structure-borne sounds migrating through the guide rail anchoring points then into the chase where they will migrate via the air intake or any poorly sealed plumbing wall penetrations.
Are you experiencing elevator equipment sound disturbance complaints? Give us a call to learn how we can quiet your projects noise disturbance.
C.E. Electronics – Acoustics Group is the only sound control company dedicated to solutions for elevator equipment and their environments.
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CQuiet |ˈsē ˈkwī-ət | verb: to have the ability to see quiet