Hotel Elevator Hoistway Venting

Summary:The IBC requires the top of all elevators to be vented to the outside. The size of this vent is important because in many cases it is routed through the elevator machine room.

 
The IBC requires the top of all elevator hoistways to be vented to the outside.  Since almost all hotels have  elevators, this is a feature the architect will ask the mechanical engineer for help sizing.  Therefore, this article is intended to be a quick reference.  The purpose of the vent is to allow smoke removal from the shaft in the event of a fire.   As an aside, I have also heard the argument that the vent provides relief from the piston effect of the elevator, but I have not seen this reason confirmed in writing anywhere.  Of course, if the piston effect reason was actually true, then there should be a corresponding relief opening at the bottom of the shaft, and the code does not address a vent at the bottom.
 
The vent size is determined by IBC Section 3004.3, which requires the area of the vents be not less than 3.5% of the area of the hoistway, but not less than 3 square feet for each elevator car. Dumbwaiters hoistways are also included in this requirement with a minimum of 0.5 square feet per dumbwaiter.
For hydraulic type elevators, the top of the elevator shaft is generally at or above the roof and providing this vent is simple. However, for elevators with machine rooms at the top, access to the outside is often through the machine room. This is accomplished done by routing a duct through the machine room in a rated enclosure. Routing of the duct and shaft involves close coordination with the elevator machine equipment layout and the associated working clearances.
The code allows up to 2/3 of the area of the opening covered with annealed glass. In mild climates, this is not generally required. However, in extreme cold climates, the glass can reduce the heat loss from cold air coming into the hoistway.
The table below shows typical vent sizes required for elevator shafts with one, two, and three cars. Obviously, there is no single size for an elevator. However, the table below can be useful during schematic design to quickly assess vent sizing requirements. Note that for two and three car banks with a common hoistway, the sizing criteria is dominated by 3 sf per car rule rather than the 3.5% rule. Therefore, estimating for multiple car hoistways is quite easy.
Table:
Shaft Size (Ft2) Number of Cars Vent Size Free Area (Ft2) Louver size (in) with 50% free area (nominal)
80 1 3 30X30
90 1 3 30X30
100 1 3.5 36×30
110 1 3.85 36×36
120 2 6 48×36
130 2 6 48×36
140 2 6 48×36
150 2 6 48×36
160 2 6 48×36
170 3 9 48×60 (close to 48×48)
180 3 9 48×60
190 3 9 48×60
200 3 9 48×60

 

 

Code:
  • 3004.1 Vents Required

Hoistways of elevators and dumbwaiters penetrating more than three stories shall be provided with a means for venting smoke and hot gases to the outer air in case of fire.

  • 3004.2

Vents shall be located at the top of the hoistway and shall open either directly to the outer air or through noncombustible ducts to the outer air. Noncombustible ducts shall be permitted to pass through the elevator machine room, providing that portions of the ducts located outside the hoistway or machine room are enclosed by construction having not less than the fire protection rating required for the hoistway. Holes in the machine room floors for the passage of ropes, cables, or other moving elevator equipment shall be limited so as not to provide greater than 2 inches (51mm) of clearance on all sides.

  • 3004.3 Area of vents.

Except as provided for in section 3004.3.1, the area of the vents shall not be less than 3.5% of the area of the hoistway not less than 3 square feet(0.28 m2) for each elevator car and not less than 3.5% not less than 0.5 square feet (.047 m2) for each dumbwaiter car in the hoistway, whichever is greater. Of the total required vent area, not less than one-third shall be permanently open. Closed portions of the required vent area shall consist of openings glazed with annealed glass not greater than 0.125 in (3.2 mm) in thickness.

 

Leave a Reply