Mechanical floor
Encyclopedia
A mechanical floor, mechanical penthouse, or mechanical level is a storey
of a high-rise building that is dedicated to mechanical
and electronics
equipment. "Mechanical" is the most commonly used term, but words such as utility, technical, service, and plant are also used. They are present in all tall buildings including the world's tallest skyscrapers with significant structural
, mechanical
and aesthetics
concerns.
While most buildings have mechanical room
s, typically in the basement
, tall buildings require dedicated floors throughout the structure for this purpose, for a variety of reasons discussed below. Because they use up valuable floor area (just like elevator shafts), engineers try to minimize the number of mechanical floors while allowing for sufficient redundancy
in the services they provide. As a rule of thumb
, skyscrapers require a mechanical floor for every 10 tenant floors (10%) although this percentage can vary widely (see examples below). In some buildings they are clustered in groups that divide the building into blocks, in others they are spread evenly through the structure, while in others still they are mostly concentrated at the top.
Mechanical floors are generally counted in the building's floor numbering (this is required by some building code
s) but are accessed only by service elevators. In some legislations they have been excluded from maximum floor area calculations, leading to significant increases in building sizes; this is the case in New York City
. Sometimes the building's designer has arranged a mechanical floor to be located on the thirteenth floor
, to avoid problems in renting the space due to superstitions about that number
.
Some skyscrapers have narrow building cores that require stabilization to prevent collapse. Typically this is accomplished by joining the core to the external supercolumns at regular intervals using outrigger
trusses. The triangular shape of the strut
s precludes the laying of tenant floors, so these sections house mechanical floors instead, typically in groups of two. Additional stabilizer elements such as tuned mass damper
s also require mechanical floors to contain or service them.
This layout is usually reflected in the internal elevator
zoning. Since nearly all elevators require machine rooms above the last floor they service, mechanical floors are often used to divide shafts that are stacked on top of each other to save space. A transfer level or skylobby
is sometimes placed just below those floors.
Elevators that reach the top tenant floor also require overhead machine rooms; those are sometimes put into full-size mechanical floors but most often into a mechanical penthouse
, which can also contain communications gear and window-washing equipment. On most building designs this is a simple "box" on the roof
, on others it is concealed inside a decorative spire
. A consequence of this is that if the topmost mechanical floors are counted in the total, there can be no such thing as a true "top-floor office" in a skyscraper with this design.
, and other services. They contain electrical generator
s, chiller
plants, water pump
s, and so on.
In particular, the problem of bringing and keeping water on the upper floors is an important constraint in the design of skyscrapers. Water is necessary for tenant use, air conditioning
, equipment cooling
, and basic firefighting through sprinkler
s (especially important since ground-based firefighting equipment usually cannot reach higher than a dozen floors or so). It is inefficient, and seldom feasible, for water pump
s to send water directly to a height of several hundred meters, so intermediate pumps and water tanks are used. The pumps on each group of mechanical floors act as a relay to the next one up, while the tanks hold water in reserve for normal and emergency use. Usually the pumps have enough power to bypass a level if the pumps there have failed, and send water two levels up.
Special care is taken towards fire safety on mechanical floors that contain generators, compressors and elevator machine rooms, since oil
is used as either a fuel
or lubricant
in those elements.
Mechanical floors also contain communication and control systems that service the building and sometimes outbound communications, such as through a large rooftop antenna (which is also physically held in place inside the top-floor mechanical levels).
Modern computerized HVAC control system
s minimize the problem of equipment distribution among floors, by enabling central remote control.
Most mechanical floors require external vent
s or louver
s for ventilation
and heat rejection along most or all of their perimeter, precluding the use of glass window
s. The resulting visible "dark bands" can disrupt the overall facade
design especially if it is fully glass-clad. Different architectural style
s approach this challenge in different ways.
In the Modern
and International
styles of the 1960s and 1970s where form follows function
, the vents' presence is not seen as undesirable. Rather it emphasizes the functional layout of the building by dividing it neatly into equal blocks, mirroring the layout of the elevators and offices inside. This could be clearly seen on the World Trade Center
twin towers and can be seen on the Willis Tower. In the IDS Tower in Minneapolis, the lowest mechanical floor serves as a visual separation from the street- and skyway
-level Crystal Court shopping center and the office tower above; the upper mechanical floor (above the 50th and 51st floors, the uppermost occupied floors) serves as a "crown" to the building.
Conversely, designers of the recent postmodern
-style skyscrapers strive to mask the vents and other mechanical elements in clever and ingenious ways. This is accomplished through such means as complex wall angles (Petronas Towers), intricate latticework
cladding
(Jin Mao Building
), or non-glassed sections that appear to be ornamental
(Taipei 101
, roof of Jin Mao Building).
Storey
A storey or story is any level part of a building that could be used by people...
of a high-rise building that is dedicated to mechanical
Mechanics
Mechanics is the branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment....
and electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
equipment. "Mechanical" is the most commonly used term, but words such as utility, technical, service, and plant are also used. They are present in all tall buildings including the world's tallest skyscrapers with significant structural
Structural engineering
Structural engineering is a field of engineering dealing with the analysis and design of structures that support or resist loads. Structural engineering is usually considered a specialty within civil engineering, but it can also be studied in its own right....
, mechanical
Mechanical engineering
Mechanical engineering is a discipline of engineering that applies the principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the production and usage of heat and mechanical power for the...
and aesthetics
Aesthetics
Aesthetics is a branch of philosophy dealing with the nature of beauty, art, and taste, and with the creation and appreciation of beauty. It is more scientifically defined as the study of sensory or sensori-emotional values, sometimes called judgments of sentiment and taste...
concerns.
While most buildings have mechanical room
Mechanical room
A mechanical room or a boiler room is a room or space in a building dedicated to the mechanical equipment and its associated electrical equipment. Unless a building is served by a centralized heating plant, the size of the mechanical room is usually proportional to the size of the building...
s, typically in the basement
Basement
__FORCETOC__A basement is one or more floors of a building that are either completely or partially below the ground floor. Basements are typically used as a utility space for a building where such items as the furnace, water heater, breaker panel or fuse box, car park, and air-conditioning system...
, tall buildings require dedicated floors throughout the structure for this purpose, for a variety of reasons discussed below. Because they use up valuable floor area (just like elevator shafts), engineers try to minimize the number of mechanical floors while allowing for sufficient redundancy
Redundancy (engineering)
In engineering, redundancy is the duplication of critical components or functions of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe....
in the services they provide. As a rule of thumb
Rule of thumb
A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination...
, skyscrapers require a mechanical floor for every 10 tenant floors (10%) although this percentage can vary widely (see examples below). In some buildings they are clustered in groups that divide the building into blocks, in others they are spread evenly through the structure, while in others still they are mostly concentrated at the top.
Mechanical floors are generally counted in the building's floor numbering (this is required by some building code
Building code
A building code, or building control, is a set of rules that specify the minimum acceptable level of safety for constructed objects such as buildings and nonbuilding structures. The main purpose of building codes are to protect public health, safety and general welfare as they relate to the...
s) but are accessed only by service elevators. In some legislations they have been excluded from maximum floor area calculations, leading to significant increases in building sizes; this is the case in New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
. Sometimes the building's designer has arranged a mechanical floor to be located on the thirteenth floor
Thirteenth floor
Thirteenth floor is a designation of a level of a multi-level building that is often omitted in countries where the number is considered unlucky...
, to avoid problems in renting the space due to superstitions about that number
Triskaidekaphobia
Triskaidekaphobia is fear of the number ; it is a superstition and related to a specific fear of Friday the 13th, called paraskevidekatriaphobia or friggatriskaidekaphobia.The term was first used by Isador Coriat in Abnormal...
.
Structural concerns
Outrigger
An outrigger is a part of a boat's rigging which is rigid and extends beyond the side or gunwale of a boat.In an outrigger canoe and in sailboats such as the proa, an outrigger is a thin, long, solid, hull used to stabilise an inherently unstable main hull. The outrigger is positioned rigidly and...
trusses. The triangular shape of the strut
Strut
A strut is a structural component designed to resist longitudinal compression. Struts provide outwards-facing support in their lengthwise direction, which can be used to keep two other components separate, performing the opposite function of a tie...
s precludes the laying of tenant floors, so these sections house mechanical floors instead, typically in groups of two. Additional stabilizer elements such as tuned mass damper
Tuned mass damper
A tuned mass damper, also known as an active mass damper or harmonic absorber, is a device mounted in structures to reduce the amplitude of mechanical vibrations. Their application can prevent discomfort, damage, or outright structural failure...
s also require mechanical floors to contain or service them.
This layout is usually reflected in the internal elevator
Elevator
An elevator is a type of vertical transport equipment that efficiently moves people or goods between floors of a building, vessel or other structures...
zoning. Since nearly all elevators require machine rooms above the last floor they service, mechanical floors are often used to divide shafts that are stacked on top of each other to save space. A transfer level or skylobby
Skylobby
A sky lobby is an intermediate floor where people can change from an express elevator that stops only at the sky lobby to a local elevator which stops at every floor within a segment of the building...
is sometimes placed just below those floors.
Elevators that reach the top tenant floor also require overhead machine rooms; those are sometimes put into full-size mechanical floors but most often into a mechanical penthouse
Penthouse apartment
A penthouse apartment or penthouse is an apartment that is on one of the highest floors of an apartment building. Penthouses are typically differentiated from other apartments by luxury features.-History:...
, which can also contain communications gear and window-washing equipment. On most building designs this is a simple "box" on the roof
Roof
A roof is the covering on the uppermost part of a building. A roof protects the building and its contents from the effects of weather. Structures that require roofs range from a letter box to a cathedral or stadium, dwellings being the most numerous....
, on others it is concealed inside a decorative spire
Spire
A spire is a tapering conical or pyramidal structure on the top of a building, particularly a church tower. Etymologically, the word is derived from the Old English word spir, meaning a sprout, shoot, or stalk of grass....
. A consequence of this is that if the topmost mechanical floors are counted in the total, there can be no such thing as a true "top-floor office" in a skyscraper with this design.
Mechanical concerns
Besides structural support and elevator management, the primary purpose of mechanical floors is heating, ventilation and air-conditioningHVAC
HVAC refers to technology of indoor or automotive environmental comfort. HVAC system design is a major subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer...
, and other services. They contain electrical generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
s, chiller
Chiller
A chiller is a machine that removes heat from a liquid via a vapor-compression or absorption refrigeration cycle. This liquid can then be circulated through a heat exchanger to cool air or equipment as required.-Use in air conditioning:...
plants, water pump
Water Pump
Water Pump is one of the neighbourhoods of Gulberg Town in Karachi, Sindh, Pakistan. It is near main Water Pump that supplies fresh water to the city of Karachi....
s, and so on.
In particular, the problem of bringing and keeping water on the upper floors is an important constraint in the design of skyscrapers. Water is necessary for tenant use, air conditioning
Air conditioning
An air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...
, equipment cooling
Cooling
Cooling is the transfer of thermal energy via thermal radiation, heat conduction or convection. It may also refer to:-Techniques:* Air conditioning* Air cooling* Computer cooling* Cryogenics* Conduction * Infrared solar cells* Laser cooling...
, and basic firefighting through sprinkler
Fire sprinkler
A fire sprinkler system is an active fire protection measure, consisting of a water supply system, providing adequate pressure and flowrate to a water distribution piping system, onto which fire sprinklers are connected...
s (especially important since ground-based firefighting equipment usually cannot reach higher than a dozen floors or so). It is inefficient, and seldom feasible, for water pump
Water Pump
Water Pump is one of the neighbourhoods of Gulberg Town in Karachi, Sindh, Pakistan. It is near main Water Pump that supplies fresh water to the city of Karachi....
s to send water directly to a height of several hundred meters, so intermediate pumps and water tanks are used. The pumps on each group of mechanical floors act as a relay to the next one up, while the tanks hold water in reserve for normal and emergency use. Usually the pumps have enough power to bypass a level if the pumps there have failed, and send water two levels up.
Special care is taken towards fire safety on mechanical floors that contain generators, compressors and elevator machine rooms, since oil
Oil
An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....
is used as either a fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...
or lubricant
Lubricant
A lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...
in those elements.
Mechanical floors also contain communication and control systems that service the building and sometimes outbound communications, such as through a large rooftop antenna (which is also physically held in place inside the top-floor mechanical levels).
Modern computerized HVAC control system
HVAC control system
-Direct digital control:Central controllers and most terminal unit controllers are programmable, meaning the direct digital control program code may be customized for the intended use. The program features include time schedules, setpoints, controllers, logic, timers, trend logs, and alarms...
s minimize the problem of equipment distribution among floors, by enabling central remote control.
Aesthetics concerns
Vent
Vent may refer to:*Vent , a slit up the back of a jacket or coat*Vent , a valve fitted to the top of a submarine's ballast tanks*Vent , a 2001 album by Caliban...
s or louver
Louver
A louver or louvre , from the French l'ouvert; "the open one") is a window, blind or shutter with horizontal slats that are angled to admit light and air, but to keep out rain, direct sunshine, and noise...
s for ventilation
Ventilation (architecture)
Ventilating is the process of "changing" or replacing air in any space to provide high indoor air quality...
and heat rejection along most or all of their perimeter, precluding the use of glass window
Window
A window is a transparent or translucent opening in a wall or door that allows the passage of light and, if not closed or sealed, air and sound. Windows are usually glazed or covered in some other transparent or translucent material like float glass. Windows are held in place by frames, which...
s. The resulting visible "dark bands" can disrupt the overall facade
Facade
A facade or façade is generally one exterior side of a building, usually, but not always, the front. The word comes from the French language, literally meaning "frontage" or "face"....
design especially if it is fully glass-clad. Different architectural style
Architectural style
Architectural styles classify architecture in terms of the use of form, techniques, materials, time period, region and other stylistic influences. It overlaps with, and emerges from the study of the evolution and history of architecture...
s approach this challenge in different ways.
In the Modern
Modern architecture
Modern architecture is generally characterized by simplification of form and creation of ornament from the structure and theme of the building. It is a term applied to an overarching movement, with its exact definition and scope varying widely...
and International
International style (architecture)
The International style is a major architectural style that emerged in the 1920s and 1930s, the formative decades of Modern architecture. The term originated from the name of a book by Henry-Russell Hitchcock and Philip Johnson, The International Style...
styles of the 1960s and 1970s where form follows function
Form follows function
Form follows function is a principle associated with modern architecture and industrial design in the 20th century. The principle is that the shape of a building or object should be primarily based upon its intended function or purpose....
, the vents' presence is not seen as undesirable. Rather it emphasizes the functional layout of the building by dividing it neatly into equal blocks, mirroring the layout of the elevators and offices inside. This could be clearly seen on the World Trade Center
World Trade Center
The original World Trade Center was a complex with seven buildings featuring landmark twin towers in Lower Manhattan, New York City, United States. The complex opened on April 4, 1973, and was destroyed in 2001 during the September 11 attacks. The site is currently being rebuilt with five new...
twin towers and can be seen on the Willis Tower. In the IDS Tower in Minneapolis, the lowest mechanical floor serves as a visual separation from the street- and skyway
Skyway
In an urban setting, a skyway, catwalk, sky bridge, or skywalk is a type of pedway consisting of an enclosed or covered bridge between two buildings. This protects pedestrians from the weather. These skyways are usually owned by businesses, and are therefore not public spaces...
-level Crystal Court shopping center and the office tower above; the upper mechanical floor (above the 50th and 51st floors, the uppermost occupied floors) serves as a "crown" to the building.
Conversely, designers of the recent postmodern
Postmodern architecture
Postmodern architecture began as an international style the first examples of which are generally cited as being from the 1950s, but did not become a movement until the late 1970s and continues to influence present-day architecture...
-style skyscrapers strive to mask the vents and other mechanical elements in clever and ingenious ways. This is accomplished through such means as complex wall angles (Petronas Towers), intricate latticework
Latticework
Latticework is a framework consisting of a criss-crossed pattern of strips of building material, typically wood or metal. The design is created by crossing the strips to form a network...
cladding
Cladding (construction)
Cladding is the application of one material over another to provide a skin or layer intended to control the infiltration of weather elements, or for aesthetic purposes....
(Jin Mao Building
Jin Mao Building
The Jin Mao Tower is an 88-story landmark supertall skyscraper in the Lujiazui area of the Pudong district of Shanghai, People's Republic of China. It contains offices and the Shanghai Grand Hyatt hotel. Until 2007 it was the tallest building in the PRC, the fifth tallest in the world by roof...
), or non-glassed sections that appear to be ornamental
Ornament (architecture)
In architecture and decorative art, ornament is a decoration used to embellish parts of a building or object. Large figurative elements such as monumental sculpture and their equivalents in decorative art are excluded from the term; most ornament does not include human figures, and if present they...
(Taipei 101
Taipei 101
Taipei 101 , formerly known as the Taipei World Financial Center, is a landmark skyscraper located in Xinyi District, Taipei, Taiwan. The building ranked officially as the world's tallest from 2004 until the opening of the Burj Khalifa in Dubai in 2010...
, roof of Jin Mao Building).
Examples
These are examples of above-ground mechanical floor layouts for some of the world's tallest buildings. In each case, mechanical penthouses and spires are counted as floors, leading to higher total floor counts than usual.- Taipei 101Taipei 101Taipei 101 , formerly known as the Taipei World Financial Center, is a landmark skyscraper located in Xinyi District, Taipei, Taiwan. The building ranked officially as the world's tallest from 2004 until the opening of the Burj Khalifa in Dubai in 2010...
: Floors 7–8, 17–18, 25–26, 34, 42, 50, 58, 66, 74, 82, 87, 90–91, and 102 in the penthouse (total 17/102, or 17%). The official count of 11 corresponds to the number of groups in the office section. Floors 92–100 contain "communications equipment" and so are not typically counted as mechanical since they do not service the building itself.
- World Trade CenterWorld Trade CenterThe original World Trade Center was a complex with seven buildings featuring landmark twin towers in Lower Manhattan, New York City, United States. The complex opened on April 4, 1973, and was destroyed in 2001 during the September 11 attacks. The site is currently being rebuilt with five new...
Twin Towers: Floors 7–8, 41–42, 75–76, and 108–109 (total 8/110, 7%). The 110th Floor of 1 WTC (North Tower) housed television and radio transmission equipment. Some sources erroneously mention 12 floors, in groups of 3, due to the height of the vents (actually the ceilings there were higher) and because levels 44 and 78 were skylobbiesSkylobbyA sky lobby is an intermediate floor where people can change from an express elevator that stops only at the sky lobby to a local elevator which stops at every floor within a segment of the building...
which in many buildings sit directly on top of the mechanical floors. However the twin towers had one occupied office floor under each skylobby, accessible through escalatorEscalatorAn escalator is a moving staircase – a conveyor transport device for carrying people between floors of a building. The device consists of a motor-driven chain of individual, linked steps that move up or down on tracks, allowing the step treads to remain horizontal.Escalators are used around the...
s.
- Willis Tower: Levels 30–31, 48–49, 64–65, 104–108, and 109–110 in the penthouse (total 13/110, 12%).
- Petronas Towers: Floors 2–7, 38–40, 43, 84, 87–88 (total 13/88, 15%) (New York Times, Elevator World magazine)
- Jin Mao BuildingJin Mao BuildingThe Jin Mao Tower is an 88-story landmark supertall skyscraper in the Lujiazui area of the Pudong district of Shanghai, People's Republic of China. It contains offices and the Shanghai Grand Hyatt hotel. Until 2007 it was the tallest building in the PRC, the fifth tallest in the world by roof...
: Floors 51–52, and 89–93 in the penthouse (total 7/93, 7.5%) (SkyscraperPage)
- Burj Khalifa: Floors 17–18, 40–42, 73–75, 109–112, 136–138, 155, and 160–168 in the penthouse (total 25/168, 15%)
External links
- Case study for Hong Kong's Central Plaza by the Department of Architecture of Hong Kong University, Energy Features section