Patent Publication Number: US-2015079894-A1

Title: Positive pressure ventilation in enclosed housings

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. provisional application No. 61/878,582, filed Sep. 16, 2013, and U.S. provisional application No. 61/984,650, filed Apr. 25, 2014, which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     Enclosed housings provide shelter and a controlled environment through which unfavorable environmental conditions can be mitigated. Enclosed livestock housings, for example, provide animals with shelter from the climate, protection from preditors, as well as airborne pathogens and contaminants. Similarly, enclosed greenhouses can be useful where the growing season is short, light levels are poor, or environmental conditions are marginal for plant growth. Although enclosed housings provide shelter and can be useful as high production facilities for plants and animal husbandry, when poorly ventilated, enclosed housings can be susceptible to odor and moisture buildup, as well as elevated levels of air pollutants such as dust, viruses, bacteria and pollutant gases including ammonia, hydrogen sulfide, carbon monoxide and methane. This can contribute to the spread of diseases or lead to decreased production. 
     SUMMARY OF THE INVENTION 
     The invention provides a positive pressure ventilation system that utilizes a pressure differential between two chambers within the housing to promote ventilation and limit entry of air-borne pathogens. The invention provides a substantially closed housing having at least two chambers: an overpressure chamber which is maintained at a high positive static pressure, and at least one living chamber which is maintained at a lower positive static pressure relative to the overpressure chamber. The overpressure chamber is in communication with the living chamber through one or more interconnecting air passages that allow for controlled airflow from the overpressure chamber to the living chamber. The pressure differential between the chambers enable unidirection airflow from the overpressure chamber to the living chamber thereby enabling ventilation of the living chamber, and the overall positive static pressure prevents or minimize entry of contaminated external air into the housing. Thus, the invention provides a method for ventilating a substantially closed housing, a ventilation system for a substantially closed housing, as well as a substantially closed housing having positive static pressure and at least one overpressure chamber supplying ventilation air to at least one living chamber through a pressure differential between the chambers. 
     In some embodiments of a method of the invention, the overpressure chamber is maintained using one or more fans that blow air into the overpressure chamber, the fans being regulated using a controller in response to the pressure in the overpressure chamber. In some embodiments, the pressure in the living chamber is maintained by (1) regulating airflow from the overpressure chamber into the living chamber through the one or more interconnecting air passages, and (2) adjusting airflow out of the living chamber through one or more outlets in an external wall separating the living chamber and the exterior of the housing. In some embodiments, airflow through the one or more interconnecting air passages is regulated through inlet dampers in the interconnecting air passages, the inlet dampers being regulated using a controller in response to temperature in the living chamber. In some embodiments, airflow through the one or more outlets is regulated through use of outlet dampers, the outlet dampers being regulated using a controller in response to pressure in the living chamber. 
     In some embodiments of a method of the invention, the pressure differential between the overpressure chamber and the living chamber is between about 0.05 to about 0.125 inch of water column. In some embodiments, the pressure differential between the overpressure chamber and the living chamber is about 0.1 inch of water column. In some embodiments, the pressure in the overpressure chamber is maintained at about 0.2 inch of water column. In some embodiments, the pressure in the living chamber is maintained at about 0.1 inch of water column. 
     In some embodiments of a method of the invention, the air blown into the overpressure chamber is filtered air. In some embodiments, the filtered air is substantially free of a disease-causing agent. In some embodiments, the air blown into the overpressure chamber is cooler than the air concurrently existing in the living space. In some embodiments, the air blown into the overpressure chamber is warmer than the air concurrently existing in the exterior of the housing. 
     In some embodiments of a method of the invention, the substantially closed housing further comprises a slanted roof and gable defining an attic space, and at least one overpressure chamber comprises attic space. In some embodiments, the one or more fans that blow air into the overpressure chamber are disposed at one or more inlets in the gable. In some embodiments, at least one interconnecting air passage terminates in the ceiling of a living chamber. 
     In another aspect, the invention provides a substantially closed housing having an overpressure chamber, a living chamber, a first closure means, a second closure means, an optional, first air filter device, an optional, second air filter device, an optional, air heating device, an optional, an air cooling device, and an electrical system with a controller for regulating the function of the electrical fan, first and/or second closure means, optional first air filter device, optional second air filter device, optional air cooling device, optional air heating device, or any combination thereof. In these embodiments, the overpressure chamber has a wall or ceiling that includes at least one air inlet and at least one electrical fan at each inlet in electrical communication with a controller for pressurizing the chamber to at least about 0.1 inch of water column. The overpressure chamber further includes at least one air outlet in a wall, floor or ceiling for the egress of air from the overpressure chamber. The living chamber includes a wall, floor or ceiling that has at least one air inlet in communication with at least one air outlet of the overpressure chamber, the outlet of the overpressure chamber and inlet of the living chamber forming respective ends of an air passage interconnecting the overpressure chamber and living chamber. The living chamber further includes at least one air outlet for the egress of air to the exterior of the housing. The first closure means is disposed at the overpressure chamber outlet, living chamber inlet, interconnecting air passage or a combination thereof in electrical communication with the controller for affecting airflow through the interconnecting air passage. The second closure means is disposed at the living chamber outlet in electrical communication with the controller for affecting airflow from the living chamber to the exterior of the housing. The optional, first air filter device filters air prior entry into the overpressure chamber, and the optional, a second air filter device filters air prior to egress from the living chamber to the exterior of the building. The optional, an air-heating device and/or air-cooling device adjust the temperature of the air prior to entry into the overpressure chamber. The electrical system includes the controller for regulating the function of the electrical fan, first or second closure means, optional first air filter device, optional second air filter device, optional air heating device, optional air cooling device, or any combination thereof. The electrical system also includes: (i) a pressure sensor in the overpressure chamber in electrical communication with the controller thereby enabling the controller to affect the function of the electrical fan in response to pressure in the overpressure chamber, (ii) a pressure sensor in the living chamber in electrical communication with the controller thereby enabling the controller to regulate function of the first or second closure means in response to pressure in the living chamber, (iii) a temperature sensor in the living chamber in electrical communication with the controller thereby enabling the controller to regulate the volume of airflow into the living chamber in response to the temperature in the living chamber, and (iv) optionally, a temperature sensor in the living chamber in electrical communication with the controller thereby enabling the controller to regulate the function of the heating or cooling device in response to temperature in the living chamber. As used herein, components in the electrical system are in electrical communication when they are electrically connected so as to enable the transmission of information between the components, for example, between a component sending information and a component receiving the information, thereby enabling the function of the component receiving the information to be affected by the information received. 
     In some embodiments of a substantially closed housing of the invention, the electrical controller receives user input through the internet. 
     In some embodiments, the substantially closed housing includes a slanted roof and gable defining an attic space, and at least one overpressure chamber includes the attic space. In some embodiments, at least one air inlet and fan are disposed in the gable. 
     In some embodiments, the substantially closed housing further includes one or more air filters that operate to supply filtered air to the air inlet and fan. In some embodiments, the substantially closed housing further includes an evaporative cooling system that operates to supply cooled air to the filters. In some embodiments, the substantially closed housing further includes an evaporative cooling system that operates to supply cooled air to the air inlet and fan. In some embodiments, the substantially closed housing further includes one or more air filters that operate to supply filtered air to the evaporative cooling system. 
     In some embodiments of a substantially closed housing of the invention, at least one overpressure chamber outlet is disposed in the floor of an overpressure chamber and at least one living chamber inlet is disposed in the ceiling of a living chamber, the overpressure outlet and living chamber inlet forming respective ends of an air passage interconnecting the overpressure chamber and living chamber. 
     In one aspect, the invention provides a method for ventilating a substantially closed housing having at least one overpressure chamber and at least one living chamber in communication through one or more interconnecting air passages. The method involves maintaining a pressure differential between the overpressure chamber and the living chamber, wherein the pressure in the overpressure chamber is higher than the pressure in the living chamber and the pressure in the living chamber is higher than the pressure at the exterior of the housing. 
     In some embodiments of a method of the invention, the pressure in the overpressure chamber is maintained using one or more fans that blow air into the overpressure chamber. In some embodiments of a method of the invention, the fans are regulated using a controller in response to the pressure in the overpressure chamber. 
     In some embodiments of a method of the invention, the pressure in the living chamber is maintained by regulating airflow from the overpressure chamber into the living chamber through the one or more interconnecting air passages. In some embodiments, airflow through the one or more interconnecting air passages is regulated through adjusting the openings of the air passages. In some embodiments, the openings of the air passages are regulated using a controller in response to temperature in the living chamber. In some embodiments, the pressure in the living chamber is further maintained by adjusting airflow out of the living chamber through one or more outlets in an external wall separating the living chamber and the exterior of the housing. In some embodiments, airflow through the one or more outlets is regulated through use of outlet dampers. In some embodiments, the outlet dampers are regulated using a controller in response to pressure in the living chamber. 
     In some embodiments of a method of the invention, the pressure differential between the overpressure chamber and the living chamber is between about 0.05 to about 0.125 inch of water column. In some embodiments, the pressure differential between the overpressure chamber and the living chamber is about 0.1 inch of water column. In some embodiments, the pressure in the overpressure chamber is maintained at about 0.2 inch of water column. In some embodiments, the pressure in the living chamber is maintained at about 0.1 inch of water column. 
     In some embodiments of a method of the invention, the air blown into the overpressure chamber is filtered air. In some embodiments, the filtered air is substantially free of a disease-causing agent. In some embodiments, the air blown into the overpressure chamber is cooler than the air concurrently existing in the living space. In some embodiments, the air blown into the overpressure chamber is warmer than the air concurrently existing in the exterior of the housing. 
     In some embodiments of a method of the invention, the substantially closed housing further includes a slanted roof and gable defining an attic space, and wherein at least one overpressure chamber comprises attic space. In some embodiments, at least one interconnecting air passage terminates in the ceiling of a living chamber. In some embodiments, the substantially closed housing further includes a slanted roof and gable defining an attic space, and wherein at least one overpressure chamber includes attic space. In some embodiments, the one or more fans that blow air into the overpressure chamber are disposed at one or more inlets in the gable. In some embodiments, at least one interconnecting air passage terminates in the ceiling of a living chamber. 
     In another aspect, the invention provides a method for ventilating a substantially closed housing having at least one overpressure chamber and at least one living chamber in communication through one or more interconnecting air passages. The method involves blowing air into the overpressure chamber to achieve a pressure above about 0.1 inch of water column and adjusting the effective opening of the one or more interconnecting air passages to allow airflow from the overpressure chamber to the living chamber so as to achieve a pressure differential between the overpressure chamber and the living chamber between about 0.05 to about 0.125 inch of water column and to achieve a pressure in the living chamber above the pressure exterior of the housing. 
     In some embodiments of the method, the air blown into the overpressure chamber is filtered to remove a disease-causing agent. In some embodiments, the air blown into the overpressure chamber has a lower temperature than the temperature existing concurrently in the living chamber. In some embodiments of the method, the substantially closed housing further includes a slanted roof and gable defining an attic space, and wherein at least one overpressure chamber comprises attic space. In some embodiments, the air is blown into the overpressure chamber using one or more fans disposed at one or more inlets in a gable. In some embodiments, at least one interconnecting air passage terminates in the ceiling of a living chamber. 
     In another aspect, the invention provides a substantially closed housing that includes: (a) one or more overpressure chambers, each having a wall or ceiling that has at least one air inlet and at least one electrical fan at each inlet effective to pressurize the chamber to at least about 0.1 inch of water column, each overpressure chamber also having at least one air outlet in a wall, floor or ceiling for the egress of air from the overpressure chamber; (b) one or more living chambers, each having a wall, floor or ceiling that has at least one air inlet in communication with at least one air outlet of an overpressure chamber, the outlet of the overpressure chamber and inlet of the living chamber forming respective ends of an air passage interconnecting the overpressure chamber and living chamber, each living chamber also having at least one air outlet for the egress of air to the exterior of the housing; (c) first closure means at the overpressure chamber outlet, living chamber inlet, interconnecting air passage or a combination thereof for affecting air flow from the overpressure chamber to the living chamber; (d) second closure means at the living chamber outlet for affecting air flow from the living chamber to the exterior of the housing; (e) optionally, an air filter device for filtering air prior entry into the overpressure chamber; (f) optionally, an air heating or cooling device for adjusting the temperature of the air prior to entry into the overpressure chamber; and (g) an electrical controller for regulating the electrical fan, first closure means, second closure means, optional air filter device, optional air heating device, optional air-cooling device, or any combination thereof. 
     In some embodiments of a substantially closed housing of the invention, the electrical controller is in electrical communication with one or more temperature sensors, pressure sensors, or temperature and pressure sensors. In some embodiments, the substantially closed housing further includes a pressure sensor in the overpressure chamber in electrical communication with the controller thereby enabling the controller to regulate the function of the electrical fan to maintain pressure in the overpressure chamber. In some embodiments, the substantially closed housing further includes a pressure sensor in the living chamber in electrical communication with the controller thereby enabling the controller to maintain pressure in the living chamber by affecting the function of the second closure means. In some embodiments, the substantially closed housing further includes a temperature sensor in the living chamber in electrical communication with the controller thereby enabling the controller to regulate the volume of airflow into the living chamber in response to the temperature in the living chamber. In some embodiments, the substantially closed housing optionally includes a temperature sensor in the living chamber in electrical communication with the controller thereby enabling the controller to regulate the function of the heating or cooling device in response to temperature in the living chamber. 
     In some embodiments, the substantially closed housing includes a slanted roof and gable defining an attic space, wherein at least one overpressure chamber comprises attic space. In some embodiments of the substantially closed housing, at least one air inlet and fan are disposed in the gable. In some embodiments, the substantially closed housing further includes one or more air filters that operate to supply filtered air to the air inlet and fan. In some embodiments, the substantially closed housing further includes an evaporative cooling system that operates to supply cooled air to the filters. In some embodiments, the substantially closed housing further includes an evaporative cooling system that operates to supply cooled air to the air inlet and fan. In some embodiments, the substantially closed housing further includes one or more air filters that operate to supply filtered air to the evaporative cooling system. In some embodiments of the substantially closed housing, at least one overpressure chamber outlet is disposed in the floor of an overpressure chamber and at least one living chamber inlet is disposed in the ceiling of a living chamber, the overpressure outlet and living chamber inlet forming respective ends of an air passage interconnecting the overpressure chamber and living chamber. 
     In another aspect, the invention provides a ventilation system for a building that includes: (a) one or more electrical fans for blowing air into a first chamber of the building; (b) one or more air passages interconnecting the first chamber with a second chamber to enable air flow from the first chamber to the second chamber, the air passages having a first closure means for affecting airflow through the passages; (c) one or more outlets for the egress of air from the second chamber to the exterior of the building, the outlets having a second closure means for affecting airflow to the exterior of the building; (d) a controller for regulating the function of the one or more electrical fans, first closure means, second closure means, or any combination thereof; and (e) at least one pressure sensor in each of the first and second chambers and at least one temperature sensor in the second chamber, each of which is in communication with the controller to enable the controller to maintain selected pressures and temperature in the first and second chambers. 
     In some embodiments, the ventilation system is effective to maintain a pressure differential between the first and second chambers of about 0.05 to about 0.125 inch of water column. In some embodiments, the ventilation system is effective to maintain a pressure differential between the first and second chambers of about 0.1 inch of water column. In some embodiments, the ventilation system is effective to maintain pressure in the first chamber at about 0.2 inch of water column. In some embodiments, the ventilation system is effective to maintain pressure in the second chamber at about 0.1 inch of water column. 
     In another aspect, the invention provides an assembly having one or more electrical fans operably connected to one or more air filters, one or more evaporative cooling systems, or a combination thereof, so as to draw filtered, cooled, or filtered and cooled air from the one or more filters, evaporative cooling systems or combination thereof. 
     Any feature or combination of features described herein is included within the scope of the present invention provided that the features included in any such combination are not mutually inconsistent as will be apparent from the context, this specification and the knowledge of one of ordinary skill in the art. 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting. Although methods and materials similar or equivalent to those described herein can be used to practice the invention, suitable methods and materials are described below. 
     All patents and publications referenced or mentioned herein are indicative of the levels of skill of those skilled in the art to which the invention pertains, and each such referenced patent or publication is hereby incorporated by reference to the same extent as if it had been incorporated by reference in its entirety individually or set forth herein in its entirety. Applicants reserve the right to physically incorporate into this specification any and all materials and information from any such cited patents or publications. 
     Other features and advantages of the invention will be apparent from the following detailed description and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a diagram representing partial sectional view of an embodiment of the invention illustrating the configuration of the air intake end of positive pressure housing  1 . 
         FIG. 2  is a diagram representing a partial top plan view of an embodiment of the invention illustrating the configuration of the air-intake system of housing  1 . 
         FIGS. 3A-3C  are diagrams representing several views of living chamber air outlet  90 , including a vertical sectional view ( 3 A), an exterior elevation view ( 3 B) and an interior elevation view ( 3 C). 
         FIG. 4  is a diagram representing a top plan view of an embodiment of the invention illustrating positive pressure housing  1  from end to end. 
         FIG. 5  is a diagram summarizing the interaction of various components in a positive pressure housing of the invention. 
         FIG. 6  is a plan diagram of a sow site design employing three livestock housing of the invention: gestation barn  1000 , gestation barn  2000  and farrowing barn  3000 . 
         FIG. 7  is a diagram representing a partial top plan view of the air intake system at a gable end of gestation barn  1000  and  2000  (dotted line indicates center line of the air intake system). 
         FIG. 8  is a diagram representing a partial top plan view of the air intake system at a gable end of farrowing barn  3000 . 
         FIG. 9  is a plan diagram of a sow site that includes a livestock housing ventilated using air intake systems situated at a monoslope dormer as well as at the gable ends of the housing. 
         FIG. 10  is a diagram representing a partial top plan view of an air intake system that includes fourteen fans that can be used at a gable end of a livestock housing of the invention. 
         FIG. 11  is a diagram representing a partial top plan view of an air intake system that includes ten fans that can be used at a gable end of a livestock housing of the invention (dotted line indicates center line of air intake system). 
         FIG. 12  is a diagram representing a partial top plan view of an air intake system that includes eight fans that can be used at a monoslope dormer of a livestock housing of the invention. 
         FIG. 13  is a diagram representing a partial top plan view of an air intake system that includes nine fans that can be used at a gable end of a livestock housing of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention provides a positive pressure ventilation system for a housing that utilizes a pressure differential between two chambers within the housing to promote ventilation and limit entry of air-borne pathogens. The invention provides a substantially closed housing having at least two chambers: an overpressure chamber which is maintained at a higher positive static pressure relative to at least one living chamber which is maintained at a lower positive static pressure relative to the overpressure chamber. The overpressure chamber is in communication with the living chamber through one or more interconnecting air passages that allow for controlled airflow from the overpressure chamber to the living chamber. The pressure differential between the two chambers allow for unidirection airflow from the overpressure chamber to the living chamber thereby enabling ventilation of the living chamber, and the overall positive static pressure prevents or minimize entry of contaminated external air into the housing. Thus, the invention provides a method for ventilating a substantially closed housing, a ventilation system for a substantially closed housing, as well as a substantially closed housing having positive static pressure and at least one overpressure chamber supplying ventilation air to at least one living chamber through a pressure differential between the chambers. 
     Overpressure Chamber and Living Chamber 
     The invention relates to ventilating a substantially closed housing having at least two chambers in communication through one or more interconnecting air passages. As used herein, the term “substantially closed” in reference to a housing means to be closed from the external environment such that temperature or pressure in the interior of the housing can be maintained primarily using a mechanical ventilation system. The housing of the invention has at least one overpressure chamber and at least one living chamber. The overpressure chamber can be pressurized using a one or more air intake system that includes one or more fans that blow air into the chamber to achieve or maintain a higher positive static pressure environment relative to one or more living chambers in the housing. The living chamber can be pressurized through controlled airflow from an overpressure chamber to the living chamber through one or more interconnecting air passages to achieve or maintain a lower positive static pressure environment. 
     A positive pressure housing of the invention provides a substantially closed environment in which entry of external contaminants, as well as plant, animal or human pathogens are limited. Thus, a positive pressure housing of the invention is useful where minimal environmental contamination is desirable, for example, in agriculture, in the food industry or in medicine or surgery. A positive pressure housing of the invention can be used as production facilities, for example, in plant or animal husbandry, in food or drug production, for steril equipment production or storage. A positive pressure housing of the invention also can be used for performing medical or surgical procedures or the like. 
     Examples of a positive pressure housing of the invention include greenhouses for growing flowers, vegetables, fruits and transplants including tomatoes, marijuana, leafy greens, microgreens, spinach, peppers, herbs, cucumbers, squash, citrus fruits, grapes, peaches, strawberries and raspberries, as well as livestock housings such as barns for growing pigs, cattle, or poultry, including, for example, a gestation barn or a farrowing barn. The housing can include an attic space above the production room (or living chamber), the attic space being separated from the production room by the ceiling of the production room. The attic space can be pressurized using one or more fans installed at one or both gables of the housing and/or at a dormer. The fans can be configured to blow air, e.g. filtered air, into the attic space to achieve an overpressure attic having a high, positive static pressure, for example, 0.2 inch of water column (in. wc). The production room or living chamber can be pressurized or ventilated by controlling air movement from the overpressure attic into the production room and controlling air egress from the production room to the exterior through one or more outlets. As such, the production room, i.e. living chamber, can be maintained at a lower positive static pressure relative to the overpressure attic, for example, at 0.1 in. wc. 
     A housing of the invention can have more than two chambers, for example, two or more living chambers, two or more overpressure chambers, or two or more living chambers and overpressure chambers. The housing can have one overpressure chamber supplying ventilation air to one or more than one living chamber. A housing of the invention can have two or more overpressure chambers supplying air to two or more living chambers. Where a housing of the invention has two or more overpressure chambers, each overpressure chamber can supply air to one or more than one living chambers. Where a housing of the invention has a plurality of overpressure chambers supplying air to a plurality of living chambers, the housing can be zoned to enable different ventilation rates to different living chambers. 
     Inlets &amp; Outlets 
     An overpressure chamber of the invention is in communication with at least one living chamber through one or more air passages or ducts that allow air to flow from the overpressure chamber to the living chamber to pressurizing the living chamber. The overpressure chamber can have one or more outlets in a wall, floor, ceiling or any combination thereof, that allow air to flow out of the overpressure chamber, through the interconnecting air passage, to an inlet in the ceiling, wall, floor or any combination thereof, of the living chamber. Thus, the interconnecting air passage includes an overpressure chamber outlet on one end, a connecting duct, a living chamber inlet on the other end, and optionally, one or more air filters at the outlet end, inlet end, in the connecting duct, or any combination thereof. Outlets, interconnecting air passages, inlets or a combination thereof can be insulated and/or sealed. Air flow through the interconnecting air passage can be modulated by altering the opening of the passage through dampers disposed at the overpressure chamber outlet, within the interconnecting air passage, at the living chamber inlet, or combination thereof. 
     The living chamber includes one or more inlets allowing for the ingress of air from an overpressure chamber as discussed above, as well as one or more outlets for the egress of air from the chamber to the external environment. The number of inlets in the living chamber can be selected based on the size of the building, size or number of chambers, and/or desired ventilation rate. The number of outlets from the living chamber can be selected based on size of the living chamber and/or selected ventilation rate. Air inlets and outlets in the overpressure chamber and living chamber can be placed on one or more walls, ceiling or floor as needed for efficient airflow. Living chamber outlets are generally located on an outer wall of a living chamber. At least one outlet can be located on an outer wall of each living chamber, the size, quantity and location of which are selected to achieve uniform airflow and air quality as determined by those of skilled in the art. 
     Air inlets and/or outlets can include dampers, which can be placed at the inlet, outlet or both. Inlet dampers can be adjusted to modify ventilation rate automatically based on temperature change if used in combination with an electrical controller in electrical communication with the dampers and a temperature sensor as further discussed below. Outlet dampers can be adjusted to regulate living chamber pressure. Air inlets, outlets and dampers are known to those skilled in the art, see, for example, swine inlets, poultry inlets, tunnel doors, Bi-Flow ceiling inlets, and curtain and baffle machines, in AgHort Ventilation Accessories, at http://www.munters.us/en/us/Products—Services/Aghort-US/AgHort-Ventilation-Accessories/(last visited Jan. 22, 2014). Examples of inlets that can be used in the invention include the Munters&#39; swine inlets such as the Air Manager, Bi-Flow ceiling inlet, MI4 air-actuated modular inlet, AeroBaffle Sidewall Center inlet, or plastic ceiling inlet. See Swine Inlets Product Information, Aerotech Ventilation Systems, Munters Corporation, Aerotech, May 2011 (available at http://www.munters.us/upload/Related%20product%20files/inletspigsliterature.pdf). A living chamber outlet can include a door or an adjustable curtain that automatically adjusts the opening of the outlet so as to maintain desired room pressure. In addition, a backdraft protection system such as a Z Wall shutter wall can be used to reduce the risk of entry of unfiltered or contaminated air as illustrated in  FIG. 3A-3C . 
     The one or more living chamber inlets and outlets are adjusted to maintain a select lower positive static pressure in the living chamber relative to the overpressure chamber. 
     Air Intake System 
     The overpressure chamber can be pressurized using one or more air intake systems in the ceiling of the overpressure chamber, in one or more walls of the overpressure chamber, or a combination thereof. For example, an air intake system can be situated in the gable at one or both ends of the housing, as well as at a dormer of the housing. The air intake system of the invention includes one or more fans, optionally, an air-filtration system, and optionally, an air-cooling system. 
     The one or more fans can be any type of fans, for example, mechanical fans such as axial-flow fans, centrifugal fans or cross flow fans, that are effective to create the desired volume of airflow. The fans can be powered by electric motors, hydraulic motors or internal combustion engines. The fans can be conventional fans or high performance fans so long as the one or more fans are capable of achieving the airflow requirements for a housing of a particular size. Where a plurality of fans is used, the fans can be of the same model. Any fan capable of achieving airflow requirements for a select static pressure can be used including, without limitation, a high efficiency/low maintenance M drive fan. A fan that has an EC motor with reduced energy cost and no belts or bearing to service can be used. An example of a fan that can be used in the invention include Munters Drive fans available at www.munters.us (last visited Jan. 23, 2014), see also Munters Drive Product Sheet, Munters Corporation, July 2012 (available at http://www.munters.us/upload/Related%20product%20files/munter_drive_literature.pdf (last retrieved Jan. 22, 2014). Agricultural ventilation fans are available from a variety of sources and their performance and efficiencies and selection considerations are known to those skilled in the art. For example, the Agricultural Ventilation Fans, Bioenvironmental and Structural Systems Laboratory (BESS) website at www.best.illinois.edu (last visited Jan. 22, 2014) provides fan selection information, performance data, as well as manufacturer contacts for hundreds of commercially available ventilation fans of a variety of sizes. In addition, general livestock housing design considerations are well known to those skilled in the art. See for example, D. D. Jones &amp; W. H. Friday, Environmental Control for Confinement Livestock Housing, AE-96, Prudue University, Cooperative Extension Service. 
     Where more than one fan is used in the air intake system of the invention, the fans can be arranged in any configuration, for example, positioned singly or arranged linearly or in an array or other configuration at one or more inlets in a wall, ceiling or a combination thereof of the overpressure chamber. The fans can be placed downstream of one or more air filters, i.e. between one or more air filters and the overpressure space. The fans can be supplied with filtered or unfiltered air and can be in a “clean” space, not subject to dust, corrosive gasses or moisture. 
     The air intake system of the invention can include an air filtration system, an air cooling system, or a combination thereof to supply filtered air, cooled air, or filtered and cooled air to the fans. An air filter wall as shown in  FIG. 1  or inclusion of one or more filters at each air inlet adjacent to the one or more fans, as well as inclusion of one or more filters upstream of a cooling system can be utilized. Where both air filters and cooling systems are employed, external air can be cooled by passage through a system such as an evaporative cooling tower prior to being filtered and supplied to the fans; external air can be filtered, then cooled before being supplied to the fans; or external air can be filtered, cooled and then filtered again prior to entry to a housing of the invention. Air filters and cooling systems such as evaporative cooling systems are well known to those skilled in the art. An example of an evaporative cooling system that can be used in the invention include the CT &amp; CN evaporative cooling system available through Munters Corporation at www.munters.us (last visited Jan. 22, 2014), see CT &amp; CN Evaporative Cooling System Product Sheet, Munters Corporation, Munters AB, 2013 and ExpressCool Technical Specifications, Munters Corporation, June 2013, available at http://www.munters.us/upload/Related%20product%20files/expresscoolliterature.pdf (last retrieved Jan. 22, 2014) and http://www.munters.us/upload/Related%20product%20files/expresscooltechspecs.pdf (last retrieved Jan. 22, 2014), respectively. Air filters that can be used in the invention include microbial filters suitable for reducing viral and/or bacterial particles. Particulate air filters made of fibrous materials for removing solid particulates such as dust, pollen, mold and bacteria can be used. In addition, chemical air filters made of an absorbent or catalyst for removing airborne molecular contaminants such as volatile organic compounds or ozone can be used. Air filters can be made of paper (e.g. pleated paper), foam (e.g. oil-wetted polyurethane foam), cotton (e.g. oiled cotton gauze), oil bath, sand, or any combination thereof. Methods of selecting filters are known to those skilled in the art. See, for example, Filter Selection: A Standard Procedure, May 19, 2000, Engineered Systems (available at http://www.esmagazine.com/articles/print/filter-selection-a-standard-procedure-june-2000) (retrieved Mar. 23, 2014). 
     Where utilized, cooling systems such as cooling towers  10  and  101 - 106  illustrated in  FIGS. 2 ,  7 - 8  and  10 - 13  can be supported by studs  3   c  positioned at intervals between ends of external wall  3  of the enclosed housing as known to those of skilled in the art. Thus, regularly occurring studs  3   c  provides support to the cooling towers that extend between ends of external wall  3  in  FIGS. 2 ,  7 - 8  and  10 - 13 . Similarly, a plurality of filters forming a filter wall can be supported by studs  3   d  distributed as known to those of skilled in the art and shown in  FIGS. 2 ,  7 - 8  and  10 - 13 . 
     Pressure Differential 
     The invention utilizes a pressure differential between at least two chambers to enable airflow from the overpressure chamber to the living chamber, thereby pressurizing and/or ventilating the living chamber. By regulating the function of the one or more fans, as well as living chamber inlets and outlets as discussed herein, the pressure differential between an overpressure chamber and a living chamber can be established or maintain at a constant level. The pressure differential between an overpressure chamber and a living chamber can be between about 0.05 to about 0.3 in. we or more, for example, about 0.05, about 0.055, about 0.06, about 0.065, about 0.07, about 0.075, about 0.08, about 0.085, about 0.09, about 0.095, about 0.1, about 0.105, about 0.11, about 0.115, about 0.12, about 0.125, about 0.13, about 0.135, about 0.14, about 0.145, about 0.15, about 0.155, about 0.16, about 0.165, about 0.17, about 0.175, about 0.18, about 0.185, about 0.19, about 0.195, about 0.2, about 0.205, about 0.21, about 0.215, about 0.22, about 0.225, about 0.23, about 0.235, about 0.24, about 0.245, about 0.25, about 0.255, about 0.26, about 0.265, about 0.27, about 0.275, about 0.28, about 0.285, about 0.29, about 0.295, about 0.3, about 0.305, about 0.31, about 0.315 and about 0.32 in. we or more. 
     To achieve the pressure differential between the overpressure chamber and the living chamber, while maintaining an overall positive static pressure system, the overpressure and living chambers can be maintained at a static pressure greater than 0 in. wc. The overpressure chamber can be maintained at a static pressure greater than about 0.05, for example and without limitation, about 0.055, about 0.1, about 0.15, about 0.2, about 0.25, about 0.3 or more in. wc, as achievable without compromising the integrity of the housing as known to those of skill in the art. The living chamber can be maintained at a static pressure greater than 0 in. wc, for example and without limitation, about 0.005, about 0.1, about 0.15, or about 0.2 in. wc. 
     Table 1 provides nonlimiting examples of static pressure (S.P.) and pressure differentials useful in practicing the invention. As indicated in Table 1, various positive static pressure levels and pressure differentials can be achieved in the overpressure chamber and living chamber using a conventional or a high performing fan. The ventilation rate is determined by the pressure differential between the overpressure attic (intake) and living room—the higher the pressure differentials, the higher the rates of airflow per living chamber inlets. More specifically, as pressure differential increases, air velocity (feet/minute) at the living chamber inlet increases, and the volume of airflow (cubic feet/min) increases. Since ventilation rate is determined by pressure differential between the overpressure chamber and the living chamber, ventilation rates can be modified through adjusting static pressures of the chambers. In addition, although as pressure increases, the performance of the fan decreases (see fan capacity), both conventional and high performance fans can be used effectively to achieve a variety of static pressures in the attic and living chambers. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 FAN AND INLET PERFORMANCE VERSUS STATIC PRESSURE 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Fan capacity* 
                 Fan capacity* 
                 Fan capacity* 
               
               
                   
                   
                 (test 120675) 
                 (test 02387) 
                 (test 07105) 
               
               
                   
                 Inlet Capacity 
                 High performance fan 
                 Common fan A 
                 Common fan B 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Static Pressure 
                 Velocity 
                 cfm/ 
                   
                 cfm/ 
                   
                 cfm/ 
                   
                 cfm/ 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 attic 
                 room 
                 differential 
                 (ft/min) 
                 sq ft 
                 fan cap 
                 fan cfm 
                 watt 
                 fan cap 
                 fan cfm 
                 watt 
                 fan cap 
                 fan cfm 
                 watt 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 0.00 
                 0.00 
                 0.00 
                 0 
                 0 
                 100% 
                 34,800 
                 20.5 
                 100% 
                 31,000 
                 22.6 
                 100% 
                 30,700 
                 21.2 
               
               
                 0.05 
                 0.00 
                 0.05 
                 400 
                 400 
                 96% 
                 33,300 
                 18.6 
                 94% 
                 29,200 
                 20.4 
                 98% 
                 30,000 
                 20.2 
               
               
                 0.10 
                 0.05 
                 0.05 
                   
                   
                 92% 
                 31,900 
                 17.0 
                 88% 
                 27,400 
                 18.4 
                 92% 
                 28,200 
                 18.3 
               
               
                 0.15 
                 0.10 
                 0.05 
                   
                   
                 87% 
                 30,400 
                 15.6 
                 82% 
                 25,300 
                 16.6 
                 86% 
                 26,300 
                 16.5 
               
               
                 0.20 
                 0.15 
                 0.05 
                   
                   
                 82% 
                 28,700 
                 14.2 
                 75% 
                 23,100 
                 14.7 
                 78% 
                 23,900 
                 14.7 
               
               
                 0.25 
                 0.20 
                 0.05 
                   
                   
                 77% 
                 26,700 
                 12.8 
                 66% 
                 20,400 
                 12.8 
                 66% 
                 20,400 
                 12.3 
               
               
                 0.30 
                 0.25 
                 0.05 
                   
                   
                 70% 
                 24,500 
                 11.2 
                 53% 
                 16,500 
                 10.4 
                 52% 
                 16,000 
                 9.5 
               
               
                 0.10 
                 0.00 
                 0.10 
                 900 
                 900 
                 92% 
                 31,900 
                 17.0 
                 88% 
                 27,400 
                 18.4 
                 92% 
                 28,200 
                 18.3 
               
               
                 0.15 
                 0.05 
                 0.10 
                   
                   
                 87% 
                 30,400 
                 15.6 
                 82% 
                 25,300 
                 16.6 
                 86% 
                 26,300 
                 16.5 
               
               
                 0.20 
                 0.10 
                 0.10 
                   
                   
                 82% 
                 28,700 
                 14.2 
                 75% 
                 23,100 
                 14.7 
                 78% 
                 23,900 
                 14.7 
               
               
                 0.25 
                 0.15 
                 0.10 
                   
                   
                 77% 
                 26,700 
                 12.8 
                 66% 
                 20,400 
                 12.8 
                 66% 
                 20,400 
                 12.3 
               
               
                 0.30 
                 0.20 
                 0.10 
                   
                   
                 70% 
                 24,500 
                 11.2 
                 53% 
                 16,500 
                 10.4 
                 52% 
                 16,000 
                 9.5 
               
               
                 0.15 
                 0.00 
                 0.15 
                 1100 
                 1100 
                 87% 
                 30,400 
                 15.6 
                 82% 
                 25,300 
                 16.6 
                 86% 
                 26,300 
                 16.5 
               
               
                 0.20 
                 0.05 
                 0.15 
                   
                   
                 82% 
                 28,700 
                 14.2 
                 75% 
                 23,100 
                 14.7 
                 78% 
                 23,900 
                 14.7 
               
               
                 0.25 
                 0.10 
                 0.15 
                   
                   
                 77% 
                 26,700 
                 12.8 
                 66% 
                 20,400 
                 12.8 
                 66% 
                 20,400 
                 12.3 
               
               
                 0.30 
                 0.15 
                 0.15 
                   
                   
                 70% 
                 24,500 
                 11.2 
                 53% 
                 16,500 
                 10.4 
                 52% 
                 16,000 
                 9.5 
               
               
                 0.20 
                 0.00 
                 0.20 
                 1300 
                 1300 
                 82% 
                 28,700 
                 14.2 
                 75% 
                 23,100 
                 14.7 
                 78% 
                 23,900 
                 14.7 
               
               
                 0.25 
                 0.05 
                 0.20 
                   
                   
                 77% 
                 26,700 
                 12.8 
                 66% 
                 20,400 
                 12.8 
                 66% 
                 20,400 
                 12.3 
               
               
                 0.30 
                 0.10 
                 0.20 
                   
                   
                 70% 
                 24,500 
                 11.2 
                 53% 
                 16,500 
                 10.4 
                 52% 
                 16,000 
                 9.5 
               
               
                 0.25 
                 0.00 
                 0.25 
                 1400 
                 1400 
                 77% 
                 26,700 
                 12.8 
                 66% 
                 20,400 
                 12.8 
                 66% 
                 20,400 
                 12.3 
               
               
                 0.30 
                 0.05 
                 0.25 
                   
                   
                 70% 
                 24,500 
                 11.2 
                 53% 
                 16,500 
                 10.4 
                 52% 
                 16,000 
                 9.5 
               
               
                 0.30 
                 0.00 
                 0.30 
                 1500 
                 1500 
                 70% 
                 24,500 
                 11.2 
                 53% 
                 16,500 
                 10.4 
                 52% 
                 16,000 
                 9.5 
               
               
                   
               
            
           
         
       
     
     Electrical System and Devices 
     The operation of the one or more fans, as well as living chamber inlet and outlet dampers, optional heating or cooling devices, filters or filtration systems, or any combination thereof can be regulated using an on-site or remote electronic controller as known to those of skill in the art. The controller can be in electrical communication with the fans, living chamber inlet and outlet dampers, as well as various pressure and/or temperature sensors in the overpressure or living chambers. For example, pressure in the overpressure chamber can be determined using a pressure sensor in electrical communication with a controller that is programmed to turn on or off, or up or down regulate the one or more fans as needed to maintain a select positive static pressure in the overpressure chamber. Thus, the fans can be regulated using a controller in response to pressure in the overpressure chamber so as to maintain a select pressure in the overpressure chamber. Similarly, pressure of the living chamber can be determined using a pressure sensor in electrical communication with a controller that is programmed to open, close or adjust the opening of the living chamber outlets, for example, by adjusting the outlet dampers, as needed to maintain a select static pressure in the living chamber. The temperature of the living chamber can be determined using a temperature sensor in electrical communication with a controller programmed to open, close or adjust the opening of the living chamber inlets, for example, by adjusting the position of the inlet dampers, as needed to maintain a select ventilation rate in the living chamber. An electrical controller for use in the invention can be located anywhere, for example, on-site or remotely. In some embodiments, the electrical controller can be internet-accessible allowing for user input from remotely. Examples of controllers that can be used to practice the invention include entire climate controllers or control computers manufactured by Fancom such as the Fancom F20 or F21 entire climate control computers and Fancom Lumina 20 or Lumina 21 climate controllers (see http://www.fancom.com/uk/downloads/ or http://www.fancom.com/upload/downloads/1395671359 — 120 — 121%20factssheet_gb.pdf (retrieved Apr. 23, 2014). 
     The controller can also coordinate the functions of the fans, inlets and outlets with a chamber cooling or heating system to maintain desired living chamber temperature. A chamber cooling system can be utilized to reduce living chamber temperature, and a chamber heating system can be used to increase living chamber temperature as indicated in  FIG. 5 . The cooling and/or heating system can be in electrical communication with the controller, which can be programmed regulate the activity of heating or cooling systems in conjunction with the fans, inlets and outlets as needed. 
     Thus, the controller can include a processor programmed to receive temperature and pressure information from temperature and pressure sensors, compare the data received with temperature and pressure values inputted by a user and respond by affecting function of the one or more fans, dampers, cooling and/or heating systems or devices, as well as filters or filtration systems as described above or known to those of skilled in the art. The electrical system for implementing the invention described herein or portions thereof therefore can include one or more devices such as on on-site or remote controller or computer, temperature sensors and pressure sensors, which operate with the electrical fans, as well as inlet and outlet dampers as described herein. Software, data, information and instructions transferred between devices can be in the form of an electronic signal, electromagnetic signal, optical signal, or other signals capable of being provided by a communications path implemented through wire or wirelessly, for example, using wire or cable, fiber optics, a phone line, a cellular phone link, an RF link or other communications channels. 
     Specific embodiments of the invention are described in the following examples, which do not limit the scope of the invention described in the claims. 
     EXAMPLES 
     Example 1 
     Positive Pressure Ventilation of an Enclosed Housing 
     An embodiment of the invention is shown in  FIG. 1 , which provides a sectional view of an enclosed housing having a positive pressure ventilation system. In  FIG. 1 , housing  1  includes living chamber  80  at one level; overpressure chamber  60 , a highly pressurized attic space in communication with living chamber  80  through interconnecting air passage  70 ; air chamber  40 , which supplies cooled and filtered air to the one or more of fan  50 ; and air chamber  20 , which contains air that has been cooled by passage through cooling wall  10 . 
     The direction of airflow through housing  1 , represented by the arrows (a), (b), (c), (d) and (e) in  FIG. 1 , is as follows: (a) external, unfiltered air at ambient temperature is cooled by cooling wall  10  during passage into chamber  20 ; (b) cooled air in chamber  20  is filtered as it passes through air filter wall  30  into chamber  40 ; (c) cooled and filtered air in chamber  40  is drawn into overpressure chamber  60  by one or more of fans  50 ; (d) cooled and filtered air, i.e. ventilation air, from overpressure chamber  60  flows into living chamber  80  to the extent one or more of interconnecting air passage terminating in living chamber ceiling air inlet  70  is opened; and (e) air from living chamber  80  flows out to the exterior of enclosed housing  1  through living chamber outlet  90 . Living chamber  80  includes outlet  90 , an opening fitted with outlet damper  92 , which can be an adjustable curtain or door, for the egress of air as needed to maintain constant room pressure and provide an outlet for metabolic gasses and moisture. Outlet  90  also includes, on the interior side, a Z wall or backdraft shutters  94 , to prevent pressure drop in windy conditions. 
     Airflow through housing  1  is controlled by an electrical controller (not shown) in electrical communication with: (1) pressure sensor P1 in overpressure chamber  60 , (2) one or more of fan  50  that blow air into overpressure chamber  60 , (3) pressure sensor P2 in living chamber  80 , (4) outlet  90  used to maintain constant pressure in living chamber  80 , (5) temperature sensor T1 and T2 in living chamber  80 , (6) closure means or dampers in living chamber ceiling inlet  70  used to modulate the volume of vent air entering living chamber  80 ; and (7) one or more cooling and/or heating device (not shown) for cooling or warming living chamber  80 . 
     The electrical controller stages one or more of fans  50  to maintain the static pressure of overpressure chamber  60  at a select positive value in response to input from pressure sensor P1. The electrical controller receives pressure input from pressure sensor P1 in chamber  60  and responds to the pressure detected by turning on or off one or more of fan  50  or increase or decrease their output, e.g. speed or ventilation rate, as appropriate to maintain the static pressure of overpressure chamber  60  at a constant and higher positive value relative to that of living chamber  80 . The electrical controller also stages outlet  90  to maintain constant static pressure in living chamber  80  in response to input from pressure sensor P2. The electrical controller receives pressure input from pressure sensor P2 in chamber  80  and responds to the pressure detected by modulating the dampers at outlet  90 , i.e. opening or closing or increasing or decreasing the opening thereof as appropriate, to maintain the static pressure of living chamber  80  at a constant and lower positive value relative to that of overpressure chamber  60 . The electrical controller stages living chamber ceiling inlet  70  to regulate volume of vent air entering living chamber  80  in response to input from temperature sensor T1. The electrical controller receives temperature input from temperature sensor T1 in chamber  80  and responds by modulating the opening of living chamber ceiling inlet  70 , i.e. opening or closing or increasing or decreasing the opening thereof as appropriate, to adjust the airflow into living chamber  80 . The electrical controller also receives temperature input from temperature sensor T2 in chamber  80  and responds by staging heating and cooling devices as needed to maintain desired temperature in living chamber  80 . 
     Enclosed housing  1  is maintained at a constant positive pressure using one or more of fan  50  that blows air from air chamber  40  into overpressure chamber  60  to establish a space with a constant, high and positive static pressure and then regulating the amount of airflow from this space to living chamber  80  to achieve a constant, lower positive static pressure environment in living chamber  80 . An electrical controller electrically connected to pressure sensor P1 can turn on, off, adjust the airflow of, duration of output of one or more of fan  50  as needed to maintain a select high positive static pressure in overpressure chamber  60 . The electrical controller electrically connected to pressure sensor P2 can open, close, adjust the opening of living chamber ceiling inlet  70  so as to modulate airflow into living chamber  80  as needed to maintain a lower positive static pressure in living chamber  80 . 
     In sum, housing  1  of the invention is maintained at a constant positive pressure to eliminate infiltration of contaminated, unfiltered air. Positive pressure ventilation is accomplished by maintaining overpressure of the attic space/overpressure chamber  60 . The higher positive static pressure in the attic/overpressure chamber  60  relative to production room/living space  80  limits the entry of toxic gases or moisture generated in production room/living space  80  into attic/overpressure chamber  60 . The attic/overpressure chamber  60  is pressurized as a function of air demand from production room/living chamber  80  with static pressure override. Pressure fans  50  provide ventilation air, production room/living chamber inlets  70  provide regulated ventilation rate to production room, and outlet  90  maintain desired pressure in production room. Pressure differential between overpressure attic  60  and living chamber  80  determines rate of airflow from the former to the later, further adjusted by electrical controller as discussed in response to pressure sensor P2. The constant positive static pressure in housing  1  limits infiltration of contaminated, unfiltered air. Constant positive static pressure in living space  80  limits entry of contaminated air from the external environment though a crack, gap or other opening in the structure of housing  1 . 
     Example 2 
     Positive Pressure End Wall Configuration 
     A diagram representing a partial plan view of an end wall configuration used in an embodiment of the invention is illustrated in  FIG. 2 . In this embodiment, a plurality of fan  50  for blowing air into overpressure chamber  60  is mounted to building end wall  5  adjacent fan access platform  9 . Two air spaces, air space  40  and air space  20 , separate the one or more of fan  50  from the exterior of the housing. Air space  40 , which occurs between building end wall  5  and filter wall  30 , supplies cooled and filtered air to the plurality of fan  50  for ventilation of overpressure chamber  60 . Air space  20 , which is between filter wall  30  and evaporative cooling wall  10 , houses cooled air from the exterior of the housing. Cooling wall  10  separates cooled air in space  20  from the exterior of the housing. Filter wall  30 , disposed between building end wall  5  and cooling wall  10 , is formed using a plurality of filters arranged at least about five feet from end wall  5  and at least about four feet from cooling wall  10 . 
     The size of cooling system is determined based on capacity required by total airflow. Similarly, number of filters or size of filter wall  30  is determined by airflow capacity as dictated by total fan capacity, and the quantity and size of fan  50  are determined by ventilation needs based on the size of the housing. 
     Example 3 
     Exterior Wall Structure of a Living Chamber Outlet in a Positive Pressure Housing 
     Living chamber air outlet  90  for the egress of air from living chamber  80  is illustrated in  FIG. 3A-3C . Outlet  90  is disposed above housing base wall  3   b  and includes damper  92  and shutter wall  94 . Outlet damper  92  is a 48-inch roll seal or insulated curtain wall outlet damper mounted on the exterior side of the building outlet above base-wall  3 .  FIG. 3B , which provides a view of outlet  90  from the exterior of the building, shows the insulated curtain/roll seal outlet damper  92  half opened. Shutter wall  94  is a 45-inch ID Z Wall shutter wall located within the opening of outlet  90  above base-wall  3   b  to provide backdraft protection.  FIG. 3C , which provides a view of outlet  90  from the interior of the building, shows that shutter wall  94  is coextensive with the opening of outlet  90 , thereby providing an added barrier to infiltration of external air. Base wall  3   b  is a 48-inch insulated concrete or EPS panel that form the lower half of the external wall, i.e. below outlet  90 . 
     Example 4 
     Positive Pressure Housing 
     A diagram representing a top plan view of housing  1  of the invention is shown in  FIG. 4 . Housing  1  has air intake systems at both ends, each including cooling wall  10 , filter wall  30  and one or more of fan  50  drawing air from the exterior of the housing into the interior. Cooling wall  10  can be an evaporative cooling system commonly used for livestock housing. Filter wall  30  can consist of hospital-quality air filters placed downstream of the cooling wall  10  for removing disease-causing viruses such as PRRS or swine flu virus. One or more of fan  50  located in the gable area is used to blow cooled and filtered air into the attic space to establish or maintain an overpressure chamber having a high positive static pressure. A plurality of passages interconnecting the attic space or overpressure chamber with the living chamber and represented by inlet  70  is distributed along the length of the housing. The plurality of inlet  70  located in the ceiling of the living chamber allows cooled and filtered air to ventilate the living chamber. A plurality of air outlet  90  along each longitudinal sides of the housing provides relief valves for the egress of pressurized air from the living chamber to the exterior. Thus, air space in the living chamber of housing  1  is pressurized using filtered air from the overpressured chamber or attic space, and as a result, entry of contaminated air from the exterior is minimized or prevented. 
     Example 5 
     Positive Pressure Operational Function 
     A summary of the interactions among various components in a housing of the invention is provided in  FIG. 5 . The environmental control  100 , i.e. the electric control, serves to regulate all components to maintain correct ventilation rate and can be internet-accessible. Room inlet  70  adjusts to maintain desired room temperature and air quality. Room outlet  90  includes outlet dampers that adjust to maintain desired living room static pressure, while ventilation fans  50  modulate to increase or decrease air volume to maintain constant attic pressure, the combination serving to maintain a constant pressure differential. The air filters  30 , and optional cooling wall  10  (not shown), filters and optionally cools air entering the facility to reduce risk of viral infection of livestock. 
     When living room temperature increases above a select desired room temperature (DRT) at  200 A, two processes are triggered: (1) cooling system is turned on at step  210 A to bring room temperature down to the select temperature; and (2) room inlets  70  opens at step  220 A to increase ventilation rate to living room. The increase in ventilation rate to the living room triggers the opening of outlet  90  at step  230 A to maintain constant pressure at the higher ventilation rate, which in turns leads to an increase in the speed or ventilation rate of fans  90  at step  240 A to maintain constant attic pressure and airflow. The increase in speed or ventilation rate of fans  90  at  240 A leads to an increase or decrease in the volume filtered air moving through filter  30  at step  250  based on capacity of ventilation fans  50 . In contrast, when living room temperature decreases below a select temperature (DRT) at  200 B, two processes are triggered: (1) heating system is turned on at step  210 B to bring room temperature up to the select temperature; and (2) room inlets  70  closes at step  220 B to decrease ventilation rate to living room. The decrease in speed or ventilation rate to the living room triggers the closing of outlet  90  at step  230 B to maintain constant pressure at the lower ventilation rate, which in turns leads to a decrease in the speed or ventilation rate of fans  90  at step  240 B to maintain constant attic pressure and airflow. The decrease in speed or ventilation rate of fans  90  at  240 B leads to increase or decrease in the volume of filtered air moving through filter  30  at step  250  based on capacity of ventilation fans  50 . 
     Example 6 
     Positive Pressure Sow Site 
       FIG. 6  illustrates the combination of three positive pressure housings of the invention, in particular, barn  1000 ,  2000  and  3000  at a sow site. Positive pressure barns  1000 ,  2000  and  3000  are connected by tunnel  810  and include living chambers such as rooms  820 , which are biosecured and pressurized with filtered air supplied by a ventilation system that includes fans  501  and cooling and filter system  1030 . Barns  1000 ,  2000  and  3000  include airlocked entry/egress, which can be disposed at any convenient location, as well as a biosecured emergency exit at each filter wall (not shown). 
     Gestation barn  1000  and  2000  are similarly constructed, each with an overpressure chamber (attic) that is pressurized through an air intake system of the invention disposed at the gable ends of the housing. The air intake system of the invention blows filtered air, and optionally cooled air, into the overpressure chamber using a plurality of fans. The overpressure chamber is interconnected with and supplies vent air to one or more living chamber or production room. 
     Gestation barn  1000  and  2000  are each about 160 ft. wide×458 ft long×8 ft high and can accommodate about 3,300 animals between about 375 pounds to about 400 pounds. Gestation barns  1000  and  2000  have gable ends, the cross-section of each being about 1,600 sq. ft (about 160 ft wide, roof pitch of 3, and total rise of 20 ft). Each gable end provides about 1,200 sq ft of attic air inlet space (2,400 sq ft per barn), of which at least 952 sq ft (1,904 sq ft per barn) are used to maintain a free air velocity of about 500 ft per minute or less. 
     Each barn can be maintained at a comfortable living environment, for example, at about 70° F., using a positive pressure ventilation system that includes ventilation fans  501  for blowing air into the barn and cooling and filter system  1030  for providing cooled and filtered air to the fans. Thirty-two primary ventilation fans  501 , each having a capacity of 28,700 CFM, can be used to achieve a total of ventilation rate or ventilation system capacity of 918,400 CFM (about 278 CFM/pig). Ventilation rate is selected based on a minimum ventilation of 18.8 CFM/pig, a maximum ventilation of 305 CFM/pig for full ventilation based on air exchange. 
     A plan diagram illustrating a portion of the gable end of gestation barn  1000  and  2000  is provided in  FIG. 7 , which illustrates various components of the air intake system of the invention. Each gable end includes 16 of fan  501  (VX51 M Drive fans, 56.25 inches wide×57.75 inches high; cone OD 68 inches) for a total of 32 fans per barn spaced 12 inches apart and occupying about 106.7 sq ft of space at each end.  FIG. 7  shows that the plurality of fan  501  is offset from barn endwall  51  forming fan access platform  91 . Cooling and filter system  1030  at each gable end includes an evaporative cooling system having two 8 ft×75 ft cooling modules  101 . The evaporative cooling system of each barn is about 2400 to about 2500 sq ft total (1200 sq ft at each end) and has a cooling potential of about 10° C. to 25° C. depending on the local climate condition. Cooling and filter system  1030  at each gable end of gestation barn  1000  and  2000  also includes filter wall  301  exterior to the barn end wall  51  through which cooled air from the evaporative cooling system is filtered. Filter wall  301  includes a plurality of orthogonal sections, each section consisting of multiple filters. For example, filter wall  301  can consist of 1152 filters of 2 ft by 2 ft dimensions, arranged in sections consisting of 12 or 18 filters stacked three across and four or six high to form wall sections of about 103 in. or 154 in. high that are parallel or perpendicular to end wall  51 , respectively. The filters are selected to accommodate a ventilation capacity of about 918,400 CFM (about 797 CFM per filter). Filter wall  301  and evaporative cooling system  101  are positioned from the fans so as provide about a 5-foot minimum distance between filter wall and fans for movement of filtered air to the fans and about a 4-foot minimum distance for movement of cooled air from the evaporative cooling system  101  to filter wall  301 . 
     Each of gestation barns  1000  and  2000  also includes ceiling inlets (not shown) between the overpressure attic and living chamber that are arranged in 40 rows of 8 inlets for a total of 340 ceiling inlets with inlet capacity calculated at about 2800 CFM for each inlet. 
     To accommodate a ventilation system capacity of about 918,400 CFM (about 278 CFM/pig), gestation barn  1000  and  2000  are constructed with 12 of outlet  901  on their external walls, each outlet configured with a damper and effective outlet area of about 81 sq feet (about 30 ft×3 ft) and 8 Z-wall shutters (about 4 ft×4 ft) (total 96 Z-wall shutters/barn). See  FIG. 6 . The size and quantity of outlets are selected to achieve desired airflow using principals and methods known to those of skill in the art. 
       FIG. 6  shows that gestation barn  1000  and  2000  are connected to farrowing barn  3000  through interconnecting tunnel  810 . Farrowing barn  3000  also utilizes a plurality of fans to blow cooled and filtered air into an attic space to establish or maintain an overpressure chamber having a constant and highly positive static pressure. In farrowing barn  3000 , cooled and filtered air from the overpressure chamber is used to maintain a constant and lower positive static pressure in a plurality of living chambers, e.g. the farrowing rooms  820 , tunnel  810 , and positive pressure rooms  840 . The pressure differential between the overpressure attic and plurality of living chambers promotes unidirectional movement of air from the overpressure attic to the plurality of living chambers, while the positive static pressure in the entire sow site minimizes or prevents the ingress of unfiltered exterior air. 
     Farrowing barn  3000  consists of thirteen 96-crate rooms and one holding room and can accommodate about 1,344 animals of about 400 pounds. Farrowing barn  3000  is about 210 ft wide×452 ft long×8 ft high, with two gable ends of about 2,756 sq ft cross-section each (about 210 ft wide, roof pitch of 3, and total rise of 26.3 ft). Each gable end of farrowing barn  3000  can provide about 2,067 sq ft of attic air inlet space (4,134 sq ft total) to maintain a free air velocity of about 500 ft per minute or less. 
     The barn can be maintained at a comfortable living environment, for example, about 70° F., using a positive pressure ventilation system that includes ventilation fans  501  for blowing air into the barn and cooling and filter system  1030  for providing cooled and filtered air to the fans. Thirty-four primary ventilation fans  501 , each having a capacity of 28,700 CFM, can be used to achieve a total of ventilation rate or ventilation system capacity of 975,800 CFM (about 726 CFM/pig). 
     A plan diagram illustrating a portion of the gable end of farrowing barn  3000  is provided in  FIG. 8 . Each gable end includes 17 of fan  501  (VX51 M Drive fans, 56.25 inches wide×57.75 inches high, cone OD 68 inches) for a total of 34 fans spaced 12 inches apart and occupying about 113.3 sq ft of space at each end.  FIG. 8  shows that the plurality of fan  501  is offset from barn endwall  52  forming fan access platform  92 . Cooling and filter system  1030  disposed at each end of the barn includes an evaporative cooling system having two 8 ft×80 ft cooling modules  102 . The evaporative cooling system of each barn is about 2500 to about 2600 sq ft total (1280 sq ft at each end) and has a cooling potential of about 10° C. to about 25° C. depending on the local climate condition. Cooling and filter system  1030  at each gable end of farrowing barn  3000  also includes filter wall  302  exterior to the barn end wall  52  through which cooled air from the evaporative cooling system is filtered. Filter wall  302  includes a plurality of orthogonal sections, each section consisting of multiple filters. For example, filter wall  302  can consist of 1,200 filters of 2 ft by 2 ft dimensions, arranged in  100  orthogonal sections, each of which consists of 12 filters stacked three across and four high to form wall sections of about 103 inches high. The filters are selected to accommodate a ventilation capacity of about 975,800 CFM (about 813 CFM per filter). Filter wall  302  and evaporative cooling system  102  are positioned from the fans so as enable a 5-foot interval for movement of filtered air to the fans and a 4-foot interval for movement of cooled air from evaporative cooling system  102  to filter wall  302 . 
     Farrowing barn  3000  also includes ceiling inlets (e.g. model B128M, not shown) between the overpressure attic and living chamber. In general, farrowing barn  3000  has 378 inlets arranged in 42 rows of 9 inlets, each inlet having a capacity of 2800 CFM. Each 96-crate room is ventilated using 27 inlets (3 rows of 9 inlets) for a total of 351 inlets serving the 13 farrowing rooms. The remaining 27 inlets serve the ancillary spaces. 
     To accommodate a ventilation system capacity of about 975,800 CFM (about 726 CFM/pig), farrowing barn  3000  is constructed with 14 of outlet  901  on their external walls, each outlet configured with a damper and effective outlet area of about 81 sq feet (about 30 ft wide×3 ft high) and 8 Z-wall shutters (about 4 ft×4 ft) (total 112 Z-wall shutters per barn). See  FIG. 6 . 
     Example 7 
     Gestation Barn with Dormer 
       FIG. 9  illustrates a sow site that includes an enclosed housing in which positive pressure ventilation is achieved through the gable ends, as well as through a side dormer. The barns at the sow site illustrated in  FIG. 9  are constructed with air intake system at one or both gable ends. The air intake systems include one or more of fan  50 , as well as cooling and filter system  1030  that are used to establish and/or maintain an overpressure chamber (attic space) for supplying vent air to one or more living chambers or production rooms according to the invention. Gestation barn  4000  also includes a similar air intake system at monoslope dormer  4  situated along one side of the barn. The air intake system at dormer  4  also includes one or more of fan  50 , as well as cooling and filter system  1030  for establishing or maintaining overpressure in the attic space that supplies vent air to one or more living chambers. Thus, the overpressure chamber of gestation barn  4000  is pressurized by air intake systems at monoslope dormer  4 , as well as at the gable ends. 
     Gestation barn  4000  is about 154 ft wide×655 ft long×8 ft high and can accommodate about 5,248 animals between about 300 to about 400 pounds. Gestation barn  4000  has two gable ends, the cross-section of each being about 1,482 sq ft (about 154 ft wide, roof pitch of 3, and total rise of 19.3 ft), and monoslope dormer  4  with a cross-section of about 1,600 sq ft (about 160 ft wide, roof pitch of 1.5, and total rise of 10 ft). Each gable end provides about 1,112 sq ft of attic air inlet space (about 2,223 sq ft total) with a maximum air flow capacity of about 556,000 CFM, and monoslope dormer  4  provides about an additional 1,200 sq ft of attic air inlet space with a maximum airflow capacity of about 600,000 CFM. At least about 2,870 sq ft of the available attic air inlet space are used to maintain a free air velocity of about 500 ft/minute or less. 
     Gestation barn  4000  can be maintained at a comfortable living environment using a positive pressure ventilation system having an air intake system that includes ventilation fans  50 , as well as cooling and filter system  1030 . Fifty primary ventilation fans, each having a capacity of about 28,700 CFM, achieve a total ventilation rate or ventilation system capacity of about 1,435,000 CFM (about 273 CFM/pig). Ventillation rate is selected based on a minimum ventilation of about 15 CFM/pig, a maximum ventilation of about 264 CFM/pig for full ventilation based on air exchange, and about 50 CFM/pig for natural ventilation barns. Of the 50 primary ventilation fans,  16  are situated at each gable end, and  18  are situated at monoslope dormer  4 , the fans being spaced 12 inches apart and occupy about 320.8 sq ft of space total. (Each gable end can accommodate about 19-20 fans and the dormer can accommodate about 20-21 fans as determined based on CFM capacity or physical dimension.) As such, the actual ventilation capacity and air velocity at each gable end and monoslope dormer  4  are about 460,000 CFM and about 413 ft/minute, and about 517,000 CFM and 431 ft/minute, respectively. 
     Cooling and filter system  1030  includes an evaporative cooling system exterior to the fans so as to provide cooled air to the fans. Uncooled air is supplied to gestation barn  4000  through a collective of about 2,392 sq ft of inlet opening at the gable ends and monoslop dormer  4 . The uncooled air is supplied to an 8 ft×150 ft evaporative cooling system at each gable end and an 8 ft×160 ft system at monoslope dormer  4 . The cooling system at the gable ends and dormer form about 3827 sq ft system with cooling potential of about 10° C. to about 25° C. depending on local climate conditions. 
     Cooling and filter system  1030  also includes a filter wall situated between the fans at the barn end wall and the evaporative cooling system through which cooled air from the evaporative cooling system is filtered. The filter wall includes a plurality of orthogonal sections, each consisting of multiple filters. For example, 31 orthogonal sections form the filter wall at each gable end, and 35 orthogonal sections form the filter wall at monoslope dormer  4 , each section consisting of eighteen 2 ft by 2 ft filters stacked three across and six high. The filters are selected to accommodate a ventilation capacity of about 1,435,000 CFM (1746 filters at about 822 CFM/filter). 
     Gestation barn  4000  also includes 520 ceiling inlets between the overpressure attic and living chamber for the movement of vent air between the attic and the living chamber, and 4 outlets at external walls of the living chamber for egress of air to the exterior. Each of the 520 inlets is configured with a filter of about 24 inches×20 inches and has an inlet capacity of about 277 CFM/animal. And each of the 4 outlets is configured with a damper (about 120 ft×4 ft) and 30 Z-wall shutters (about 4 ft×4 ft) (total 120 Z-wall shutters). Each outlet has an effective outlet area of about 360 sq ft and a capacity of 360,000 (1000 CFM/sq ft). 
     Example 8 
     Additional Embodiments of the Invention 
       FIGS. 10-13  illustrate air intake systems that can be incorporated into a gable end or a monoslope dormer to achieve positive pressure ventilation in barns of various sizes.  FIG. 10  is diagram representing a top plan view (left side) of an air intake system that includes: (1) fourteen of fans  503  (VX51 M Drive fans, 56.25 in wide×57.75 in high, cone OD: 65 inches) disposed below fan access platform  93  (accessible through stairway  333 ) that blow filtered air in chamber  403  into attic space  603 ; (2) filter wall  303  (102.5 ft high+stem wall,  41  orthogonal sections of 492 filters stacked 4 high×3 across) that filters cooled air passing from chamber  203  to chamber  403 ; and (3) evaporative cooling system  103  (8 ft×140 ft cooling cell) that cools air as it passes from the exterior into chamber  203 . Wall  53  separates overpressure chamber  603  from cooled and filtered air chamber  403  and is airtight and biosecured, thereby limiting the movement of air through other than through fan aperture. Optional winter inlet  73  on the sides allow for winter air entry into chamber  203 . 
       FIG. 11  is a diagram representing a top plan view (left portion) of an air intake system that includes: (1) ten of fans  504  situated below fan access platform  94  (accessible through stairway  444 ) that blow filtered air from chamber  404  into attic space  604 ; (2) filter wall  304  (102 ft high+stem wall,  29  orthogonal sections of 324 filters stacked 4 high×3 across) that filters cooled air passing from chamber  204  to chamber  404 ; and (3) evaporative cooling system  104  (8 ft×100 ft cooling cell) that cools air as it passes from the exterior into chamber  204 . Wall  54  separates overpressure chamber  604  from cooled and filtered air chamber  404  and is airtight and biosecured, thereby limiting the movement of air through other than through fan aperture. Optional winter inlet  74  on the sides allow for winter air entry into chamber  204 . 
       FIG. 12  is a diagram representing a top plan view of an air intake system that includes: (1) eight of fans  505  situated below fan access platform  95  (accessible through stairway  555 ) that blow filtered air from chamber  405  into attic space  605 ; (2) filter wall  305  (102.5 ft high+stem wall,  23  orthogonal sections of 276 filters stacked 4 high×3 across) that filters cooled air passing from chamber  205  to chamber  405 ; and (3) evaporative cooling system  105  (8 ft×75 ft cooling cell) that cools air as it passes from the exterior into chamber  205 . Wall  55  separates overpressure chamber  605  from cooled and filtered air chamber  405  and is airtight and biosecured, thereby limiting the movement of air through other than through fan aperture. 
       FIG. 13  is a diagram representing a top plan view of an air intake system that includes: (1) nine of fans  506  beneath fan access platform  96  (accessible through stairway  666 ) that blow filtered air from chamber  406  into attic space  606 ; (2) filter wall  306  (102.5 ft high+stem wall,  27  orthogonal sections of 324 filters stacked 4 high×3 across) that filters cooled air passing from chamber  206  to chamber  406 ; and (3) evaporative cooling system  106  (8 ft×85 ft cooling cell) that cools air as it passes from the exterior into chamber  206 . Wall  56  separates overpressure chamber  606  from cooled and filtered air chamber  406  and is airtight and biosecured, thereby limiting the movement of air through other than through fan aperture. 
     OTHER EMBODIMENTS OF THE INVENTION 
     While the invention has been described in conjunction with the detailed description, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the claims. Other aspects, advantages, modifications and variations are within the scope of the following claims. Under no circumstances may the patent application be interpreted to be limited to the specific examples or embodiments or methods specifically disclosed herein. 
     The terms and expressions employed herein are used as terms of description and not of limitation. There is no intent in the use of such terms and expressions to exclude any equivalent of the features shown and described or portions thereof. 
     The invention has been described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the invention. As used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural reference unless the context clearly dictates otherwise.