BUILDING PRESSURIZATION CONTROL TO MINIMIZE STACK EFFECT

Field of the Invention [0001] This invention generally relates to controlling air pressure within buildings.

Description of the Related Art

[0002] There are a variety of situations where airflow management and air pressure management within a building is desirable and necessary. Various building configurations require controlling airflow between the building interior and the space outside of the building, for example, to prevent undesirably large airflows through passageways (i.e., doorways) that provide access to the building. In some circumstances, the differences in temperature between the inside and outside of the building and the building configuration results in a pressure differential between the inside of the building and the outside environment that results in undesirably large drafts or even gusts between the building interior and the outside, surrounding environment. Such drafts undesirably alter the heat load of the building and may interfere with comfortable passage through a doorway, for example. [0003] One example of undesirable airflow through a passageway between a building and an outside area may occur in a high rise building that includes a tall shaft such as an elevator hoistway or a stairwell. Such shafts allow for the so-called stack effect when there are differences between the indoor and outdoor temperatures. The stack effect results in large drafts of air through passageways (i.e., doorways) that provide access to the building when such passageways are open. The difference in pressure between the building interior and the outside environment and the stack effect cause such airflow.

[0004] For example, colder air outside of a building during a winter season is heavier than the warm air inside the building. The outside pressure is higher than the inside pressure at lower levels of the building. At upper levels of high rise buildings, the outside pressure is lower than the inside pressure under many circumstances. Accordingly, when there is an opening (such as at a doorway at a lobby entry level of a building) air tends to infiltrate into the building at the lower levels. The air tends to flow toward the top of the building. As airflow tends toward a path of least

resistance, the outside air entering the building tends to rise through a vertical shaft such as an elevator hoistway or stairwell toward the top of the building.

[0005] One example patent showing a stack-effect-reducing arrangement is shown in the Japanese Patent Publication No. 07-330247, which was published in December, 1995. That document proposes adding cool air to an elevator shaft using suction to draw in outdoor air. That arrangement has limitations.

[0006] A typical approach to address undesirable airflow between a building and the surrounding outside environment is to attempt to seal the building from the outside environment. Sealing passageways between the building interior and the outside typically is accomplished using revolving doors. There are various shortcomings and drawbacks associated with that approach. For example, revolving doors tend to limit the number of individuals that can pass through a doorway at any given time. To increase the potential traffic flow, larger revolving doors with larger motors have been introduced. This approach is not ideal because the larger equipment introduces additional cost and requires additional space.

[0007] Another drawback associated with revolving doors is that individuals desiring to pass through an automatically moveable door tend to become anxious about timing their entry into the passageway based upon the motion of the door. In many situations, an individual is not allowed to move slowly or to stop once they enter the vicinity of the revolving door or they may be bumped by one of the moving door panels.

[oooδ] There is a need for an improved arrangement that minimizes the occurrence of the stack effect to improve airflow management associated with the interior of a building. Additionally, it would be beneficial to be able to eliminate the requirement for revolving doors at building entrances. This invention addresses those needs while avoiding the shortcomings and drawbacks discussed above.

SUMMARY OF THE INVENTION

[0009] An exemplary method of managing a stack effect in a building includes maintaining an inside air pressure on at least one level of the building near a ground elevation outside of the building within a selected range of an outside air pressure at the ground elevation.

[00010] One example includes maintaining the inside air pressure above the outside air pressure. One particular example includes maintaining the inside air

pressure above the outside air pressure within a range from approximately 10 to 30 Pa.

[00011] One example includes maintaining a pressure of at least one vertical shaft within the building approximately the same as the inside air pressure on the at least one level of the building. One example includes maintaining approximately equal pressures between portions of the shaft and corresponding levels of the building along a height of the shaft.

[oooi2] The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[00013] Figure 1 schematically shows a building within which an example embodiment of pressure control designed according to this invention is useful for managing a stack effect.

[00014] Figure 2 schematically illustrates selected components of an example system for managing stack effect according to one embodiment of this invention.

DETAILED DESCRIPTION [00015] This invention includes pressurizing a building such that the largest pressure differential between the inside of the building and the outside occurs near the top of the building, which is typically a portion of the building that is well sealed from the environment. By keeping the inside air pressure of building levels near the ground elevation at least equal to or slightly above the outside air pressure at the ground elevation, the stack effect typically associated with vertical shafts such as elevator hoistways and stairwells within buildings can be controlled or minimized, which results in less undesirable airflow between the inside and outside of the building.

[00016] Figure 1 schematically shows a building 20 including a plurality of levels A, B, C, D...YY and ZZ. In this example, the level A corresponds to a ground floor having main building access points (e.g., at least one doorway) 30. The illustrated example also includes an elevator lobby 32 on the building level A.

[00017] In the illustrated example, a plurality of heating, ventilation and air conditioning (HVAC) devices 34 provide desired temperature control of the building

levels in a known manner. The HVAC devices 34 are also capable of adjusting the air pressure on the various levels of the building based upon airflow rates, for example.

[00018] At least one vertical shaft 40 extends along a height of the building 20 to provide access to at least selected ones of the building levels A-ZZ. In the illustrated example, the shaft 40 extends along the entire height of the building 20. One example shaft 40 comprises an elevator hoistway. Another example shaft 40 comprises a stairwell. Although only one vertical shaft 40 is shown for discussion purposes, a plurality of such shafts may be provided in a building. The pressurization techniques of this description can be used in a single vertical shaft or multiple vertical shafts, depending on the needs of a particular situation. Given this description, those skilled in the art will be able to apply the principles of this invention to meet the needs of their particular situation.

[00019] In Figure 1, there are a plurality of air moving devices 42 and 44 associated with the vertical shaft 40. In one example, the air moving devices comprise fans that draw air into or out of the shaft 40, depending on the needs of a particular situation. The resulting air flow may be between the shaft 40 and one or more levels of the building 20 or between the shaft 40 and the outside environment, for example. The illustrated example includes air movers near the opposite ends of the shaft 40 to control the amount of air introduced or vented at various locations within the shaft 40.

[00020] As schematically shown in Figure 2, a controller 50 controls operation of the HVAC devices 34 to achieve a desired air pressure on the various levels of the building 20. In this example, the controller 50 gathers information from an outside pressure indicator 52 to determine what the air pressure is in the vicinity of the ground elevation of the building 20 or another location where the air pressure corresponds to the air pressure near primary building access points or passageways. In one example, the outside pressure indicator 52 comprises a pressure sensor. In another example, the outside pressure indicator 52 provides temperature information to the controller 50. Based on the location of the building and the known elevation relative to sea level, the controller 50 in one example uses predetermined relationships between outside temperature and air pressure to determine the outside air pressure without a direct pressure measurement.

[00021] In one example, the controller 50 maintains an inside air pressure of at least one level of the building near the ground elevation (e.g., at least level A in

Figure 1) to be at least equal to the outside air pressure. In one example, the controller 50 always maintains the inside air pressure near the ground level elevation at least slightly above the outside air pressure. This example greatly reduces the changes of air infiltration from outside of the building to the inside of the building especially during colder outside temperatures.

[00022] In Figure 2, a plurality of inside pressure sensors 54 provide information to the controller 50 regarding the inside air pressures at various levels of the building 20. The controller 50 utilizes information from the pressure sensors to determine whether a current relationship between the inside air pressure within the building and an outside air pressure is within a selected range. If the inside pressure is not sufficiently high, the controller 50 operates at least a selected one of the HVAC devices 34 to increase the inside air pressure to achieve a desired result.

[00023] In one example, the controller 50 maintains a pressure within at least a portion of the shaft 40 so that it corresponds to the inside pressure of at least a selected one of the building levels (e.g., level A in Figure 1) within a selected range. In one example, the controller 50 seeks to equalize the air pressure within the shaft 40 and the inside of the building on the various building levels. The example arrangement of Figure 2 includes pressure sensors 56 and 58 that are strategically located within selected positions of the shaft 40 to provide inside shaft pressure information. Based upon such information, the controller 50 controls operation of the air movers 42 and 44 to adjust the pressure within the shaft 40 as needed.

[00024] In one example, the entire building is pressurized to achieve an essentially equal pressure throughout the building interior including the shaft 40. In another example, the lower levels (e.g., A-D) and the lower portion of the shaft 40 will have a higher air pressure than the upper levels (e.g., YY and ZZ) and the upper portion of the shaft. In either case, keeping the pressure in the shaft close to that on corresponding level of the building and keeping the levels near the ground elevation at least slightly above the outside air pressure at the ground elevation provides the advantage of essentially eliminating or at least minimizing the stack effect. [00025] One example includes balancing or equalizing a temperature within the shaft and the inside temperature of the building levels.

[00026] In one example, when the outside temperature is lower than the inside temperature within the building 20 and the inside air pressure is at least slightly above the outside air pressure near the ground elevation, there will be a significant pressure

difference between the inside air pressure and the outside near the top of the building 20. In such an example, the upper levels of the building include an arrangement for preventing air exchange between the inside of the building and the outside of the building. Appropriate sealing of the upper levels will achieve this in many circumstances. Where there is no need for provide access to the outside from such upper levels of a building, at least one example includes not providing any access points to the outside.

[00027] In examples where access to the outside of the building is required or desirable (e.g., such as a desire to have roof access) a closer 60 (e.g., a door) of at least one access passage to the outside at the upper levels of the building is designed to withstand a pressure difference between the inside and outside in a range from approximately 250 Pa to about 400 Pa. Such an arrangement will be able to withstand the significant pressure differentials that may occur near the top of a building when a pressure control strategy according to an embodiment of this invention is implemented within the building. By having the largest pressure differential concentrated near the top of a building and sealing off the top of the building from the outside, the stack effect typically associated with vertical shafts such as elevator hoistways or stairwells can be minimized or effectively eliminated in some examples.

[00028] On days where the outside temperature is higher than the inside temperature within the building 20, the controller 50 will effectively depressurize the building to keep the inside pressure of one or more levels of the building near the ground elevation approximately equal to or slightly above the outside air pressure. Even on such relatively warmer days, it is preferable in some examples to maintain the inside air pressure at least slightly above the outside air pressure to minimize or prevent the stack effect that can result in a flow of air between the inside and outside of the building, for example. During hotter days, the pressure within the building may be below the outside pressure on some levels of the building (e.g., the upper levels) even though the inside air pressure may be slightly above the outside air pressure near the ground elevation. [00029] When the shaft 40 is an elevator hoistway, maintaining pressure within the shaft 40 within a selected range of the inside air pressure on the building levels serviced by the hoistway serves the purpose of minimizing pressure on the hoistway doors.

[00030] The preceding description is exemplary rather than limiting in nature.

Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.