Top MEP considerations when designing for elevator systems
Designing multistory buildings requires architectural teams to carefully plan elevator systems that meet current safety standards as well as address the unique needs of the space. This whitepaper will discuss mechanical, electrical, plumbing, and fire protection considerations for designing a safe and efficient elevator system.
In recent years, there has been a growing trend toward architectural projects that focus on building upward instead of sprawling outward. When land is limited, particularly in urban areas, this is the most efficient use of space and resources. In Chicago alone, the number of active high-rise construction sites more than doubled (from 14 to 34) from October 2014 to January 2016.
Designing multistory buildings requires architectural teams to carefully plan elevator systems that meet current safety standards as well as address the unique needs of the space. This whitepaper will discuss mechanical, electrical, plumbing, and fire protection (MEP/FP) considerations for designing a safe and efficient elevator system.
Types of elevators
Hydraulic vs. traction elevators
When designing for an elevator system, it is important to first determine which type of elevator suits the project's needs. Hydraulic and traction elevators have different requirements and specifications, and building height is a major factor in which one is appropriate for a project.
Pumps that are generally 30 to 40 hp move hydraulic fluid under a piston to raise this type of elevator and then return fluid back into the tank to lower the elevator. Hydraulic elevators are advisable for shorter buildings, up to 5 stories. They also contain flammable liquid and must feature appropriate fire alarm and protection devices.
Traction elevators, on the other hand, are suspended by tensile cable and balanced by counterweights equal in weight to a half-loaded elevator. They are raised and lowered by moving the cable. Traction elevators are commonly installed in buildings that have more than 5 stories and use motors that are generally 15 to 20 hp.
Traction elevator machinery has traditionally been located in penthouse spaces above the elevator shaft; however, "machine roomless" elevators are now available for buildings up to 150 ft tall. This centralizes all machinery within the shaft, saving the client the cost of building a dedicated penthouse space.
Smoke control and pressurization
Modern buildings are designed to contain a fire to the location where it starts, and floor plates generally are rated to prevent movement of smoke and growth of a fire. For this reason, care must be taken with shafts that penetrate multiple floor levels, because they are susceptible to collecting smoke from a fire or transferring smoke from floor to floor.
Smoke control normally is operated automatically by the fire alarm system, but firefighters need the ability to override the system. Because of this, smoke control is required to be annunciated and manually operated from a firefighter's smoke control panel.
In the past, hoistway ventilation was the main approach to smoke control. When smoke was detected in an elevator shaft or lobby, vents in the top of the shaft would open to discharge smoke. Hoistway ventilation is becoming less preferable because it can exacerbate problems through stack effect, drawing smoky air from the fire floor through the shaft.
Pressurization is an alternative smoke control solution, which begins when a building's fire alarm system is activated. It works by positively pressurizing the hoistway and pushing air outward through any opening, avoiding smoke infiltration.
Emergency power is a primary concern in new building design, especially since high-rise buildings are becoming more commonplace, and they are simply not accessible without elevators.