Patent Publication Number: US-2012028563-A1

Title: Energy efficient building environmental control apparatus and method

Description:
BACKGROUND 
     1. Technical Field 
     This disclosure generally relates to the field of building construction and, more particularly, to energy efficient buildings. 
     2. Description of the Related Art 
     There is ever increasing concern regarding energy consumption. Reducing energy consumption may provide numerous benefits. For example, such may reduce the costs paid by individual consumers. Such may reduce the infrastructure costs incurred by energy suppliers, for example reducing the number of new generation facilities required. Such may also reduce negative environmental effects, for instance the generation of greenhouse gases or spoilation of the natural environment. In light of such concerns various governmental agencies or departments are promulgating new rules and regulations regarding energy conservation. Various private individuals and business are proposing new approaches and new technologies to address these concerns. 
     The heating and cooling of buildings is one of the major uses of energy. Many residential and commercial buildings require heating, particular during winter months to maintain a comfortable interior climate. Likewise, many residential and commercial buildings require cooling, particular during summer months to maintain a comfortable interior climate. Various approaches to heating and cooling are used. Most such approaches are active approaches using, for instance using furnaces and air conditioners, which rely on a variety of energy sources, including electricity, natural gas, coal. 
     Many building owners or managers, particularly owners and managers of commercial buildings, are expending large sums of money and time to achieve greater energy efficiency and/or “green” certification. Some such approaches employ solar insolation, for instance to heat water or generate electricity. Other such approaches are more passive, for instance improved insulation and specialty glazing. Some approaches are more suitable for new construction, while other approaches are suitable for both new and existing construction. 
     While numerous improvements in energy efficient buildings have been made, yet still further gains are desirable. 
     BRIEF SUMMARY 
     A building includes exterior walls that form spaces which are selectively vented under control of a control system. Vents are operated to retain trapped air or exhaust trapped air to improve the energy performance of the building. Vents with selectively operable dampers may be located proximate a top of a wall or wall section of wall. Vents may also be located proximate a bottom of a wall or wall section to allow drainage of liquid and circulation of air. Various specific wall constructions provide for an air gap between layers of exterior sheathing of the exterior wall. The air gap may be in addition to a space between interior and exterior sheathing, which space may include a thermal insulation material (e.g., fiberglass batting). 
     An environmental control system for a building having at least one exterior wall may be summarized as including at least one lower vent positioned proximate a bottom portion of at least one exterior wall portion of the exterior wall of the building and which provides fluid communication between an exterior environment outside of the building and at least one space in the at least one exterior wall portion, the at least one space formed between at least a first exterior wall member and at least a second exterior wall member, the first and the second exterior wall members which form at least a portion of the at least one exterior wall portion of the exterior wall of the building, the first exterior wall member spaced interiorly of the second exterior wall member; an upper vent positioned proximate a top of the at least one exterior wall portion of the exterior wall of the building and which provides fluid communication from the at least one space in the at least one exterior wall portion of the building; and a vent actuation system configured to selectively open or close the upper vent to allow air to exhaust out of the upper vent from the at least one space of the at least one exterior wall portion when open and to trap air in the at least one space of the at least one exterior wall portion when closed. The upper vent may, for example provide fluid communication with the exterior environment outside of the building or may provide fluid communication to an interior space within the building, for example an attic. The vent actuation system may include at least one of an electric motor or a solenoid coupled to open and close the upper vent; and a controller coupled to the at least one of the electric motor or the solenoid. The vent actuation system may include at least one temperature sensor communicatively coupled to the controller provide signals indicative of temperature. The temperature sensor may be posited to sense a temperature in the exterior environment outside of the building and the controller may be configured to open the upper vent in response to the sensed temperature in the exterior environment exceeding a first threshold temperature. The vent actuation system may be communicatively coupled and responsive to at least one of an independent heating or air conditioning system of the building which is distinct from the environmental control system of the building. The vent actuation system may be communicatively coupled and responsive to at least one of a user actuated input device, a timer, a wireless communications device or an external computer system. At least a portion of the upper vent may form a Venturi shaped conduit or passage. 
     The environmental control system may further include a fan fluidly coupled to the at least one space of the at least one exterior wall portion and selectively operable to cause air to flow from the at least one lower vent to the at least one upper vent. A first one of the at least one exterior wall may be opposed across the building to a second one of the at least one exterior wall, each of the first and the second exterior walls having respective exterior wall portions having at least one lower vent and at least one upper vent, and the vent actuation system may be configured to selectively open or close the at least one upper vent of the exterior wall portion of the first exterior wall separately from the at least one upper vent of the exterior wall portion of the second exterior wall. 
     The environmental control system may further include the at least one exterior wall, wherein the at least one exterior wall portion of the at least one exterior wall further comprises a lath separating the first and the second exterior wall members to defined the at least one space therebetween. 
     The at least one exterior wall portion of the at least one exterior wall may further include at least one outer flexible web material positioned proximate an interior facing face of the second exterior wall member. The at least one outer flexible web material may be a Kraft paper retained by the lath. 
     The at least one exterior wall portion of the at least one exterior wall may further include at least one inner flexible web material positioned proximate an exterior facing face of the first exterior wall member. The at least one inner flexible web material may be a building wrap or paper adhesively or mechanically secured to the exterior facing face of the first exterior wall member. The second exterior wall member may be a stucco containing an expanded perlite. The first exterior wall member may be a gypsum and fiberglass mat sheathing, foam board, oriented strand board (OSB), or plywood. 
     At least one exterior wall portion of the at least one exterior wall may further include at least one interior wall member on an interior of the building; and a plurality of studs coupling the interior wall member to the first exterior wall member. The studs may be steel, wood, or alternatively the wall construction may be some other material such as concrete, concrete masonry unit (CMU) or other building material. 
     At least one exterior wall portion of the at least one exterior wall may further include fiberglass batting received between the interior wall member and the first exterior wall member between the studs. 
     A method n environmental control system for a building having at least one exterior wall may be summarized as including at a first time, closing at least one upper vent positioned proximate a top of at least one exterior wall portion of the at least one exterior wall of the building to trap air in at least one space of the at least one exterior wall portion, and which at least one top vent selectively provides fluid communication from the at least one space in the at least one exterior wall portion, the at least one space formed between at least a first exterior wall member and at least a second exterior wall member, where the first and the second exterior wall members form at least a portion of the at least one exterior wall portion of the exterior wall of the building with the first exterior wall member being spaced interiorly of the second exterior wall member; and at a second time, opening the at least one upper vent to allow air to exhaust out of the upper vent from the at least one space of the at least one exterior wall portion into the exterior environment. 
     The method may further include allowing air to continually pass through at least one lower vent positioned proximate a bottom portion of the at least one exterior wall portion of the at least one exterior wall of the building and which at least one lower vent provides fluid communication between the exterior environment outside of the building and the at least one space in the at least one exterior wall. Closing at least one upper vent may include operating at least one of an electric motor or a solenoid. At least one of the opening or the inclosing at least one upper vent may be responsive to a temperature. At least one of the opening or the closing at least one upper vent may be responsive to a timer or a user input. 
     The method may further include actively moving air through the at least one space when the at least one upper vent is open. The at least one upper vent in at least one exterior wall portion of the at least one exterior wall of the building may include opening the at least one upper vent in a first one of the at least one exterior wall portion of the at least one exterior wall of the building while maintaining the at least one upper vent closed in a second one of the at least one exterior wall of the building. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a top plan view of a floor of a building, including exterior walls and interior walls, the exterior walls forming spaces therein and an environmental control system including upper and lower vents to selectively retain and exhaust air from the spaces and a control subsystem to control such, according to one non-limiting illustrated embodiment. 
         FIG. 2  is a schematic diagram of an environmental control system including vents actuators, a control subsystem and various sensors or input devices to selectively control the vents according to one non-limiting illustrated embodiment. 
         FIG. 3  is a cross-sectional view of an upper portion of a wall showing an upper vent with a damper and actuator according to another non-limiting illustrated embodiment. 
         FIG. 4  is a cross-sectional view of the upper portion of the wall of  FIG. 3  showing a rough in kit before installation of a hood of the vent, damper and actuator to the vent according to another non-limiting illustrated embodiment. 
         FIG. 5A  is a cross-sectional view of a lower portion of the wall showing a lower vent with a perforated drip screen and optional drainage matting according to another non-limiting illustrated embodiment. 
         FIG. 5B  is an isometric view of the perforated drip screen of the lower vent according to another non-limiting illustrated embodiment. 
         FIG. 6  is a cross-sectional view of the lower portion of the wall of  FIG. 5  showing an additional weep screed according to another non-limiting illustrated embodiment. 
     
    
    
     In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings. 
     DETAILED DESCRIPTION 
     In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one skilled in the relevant art will recognize that embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures associated with building materials, ducts, fans or blowers, control systems and communications have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments. 
     Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.” 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Further more, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The headings and Abstract of the Disclosure provided herein are for convenience only and do not interpret the scope or meaning of the embodiments. 
       FIG. 1  shows a building  100  including an environmental control system, according to one illustrated embodiment. 
     The building  100  includes a number of exterior walls  102   a - 102   d  (four shown, collectively  102 ), a number of interior walls  104   a - 104   f  (collectively  104 ), doors  106   a - 106   c  (collectively  106 ) and windows (not shown). The exterior walls  102  separate an interior  108  of the building  100  from an exterior  110  thereof. 
     The building  100  may be constructed according to any variety of construction techniques and/or materials. As is common in many parts of North America, the exterior walls  102  may include a plurality of spaced apart studs,  112   a - 112   n  (only three called out in  FIG. 1 , collectively  112 ) typically extending vertically between a top plate (not shown in  FIG. 1 ) and a sill or bottom plate (not shown in  FIG. 1 ). The top plate and/or sill or bottom plate may separate different floors or stories of the building  100 . While described in more detail below particularly with later reference to  FIGS. 3-6 , the exterior wall  102  typically includes at least one layer of interior sheathing or material  114  (e.g., plaster board or sheet rock) and at least one layer of an exterior sheathing or material  116 ,  118  (e.g., oriented strand board, stucco or stucco with expanded perlite) spaced from the interior sheathing or material  114  by the studs  112 . Such structure may form or constitute an exterior wall portion  120  of the exterior wall  102 . The exterior wall portion  120  may, for example, constitute one floor of the building  100 , or a portion of one floor of the building  100 . Alternatively, the exterior wall portion  120  may constitute two or more floors of the building  100 . 
     The exterior wall portion  120  may include at least one space  122  between the interior and the exterior sheathing or material  114 ,  116 ,  118 , including between two or more layers of the exterior sheathing or material  116 ,  118 . In some instances, these spaces  122  may be filled or partially filled with a thermally insulative material (not shown in  FIG. 1 ) such as fiberglass batting or closed cell foam. In other instances these spaces  122  may contain only air. 
     The exterior wall portion  120  of the exterior wall  102  includes a number of vents  124  positioned or located proximate a bottom of the exterior wall portion  120 , and hence denominated herein as lower vents. The lower vents  124  provide fluid communication between the space  122  in the exterior wall  102  and the external environment  110 . The lower vents  124  may be positioned and configured to allow fluid, for instance a liquid such as water, to drip out of the space  122 . The lower vents  124  may also be configured to allow circulation of a fluid, such as air, into the space  122  from the external environment  110 . The lower vents  124  may be configured to prevent the intrusion of insets, vermin or other pests into the space  122 , for example by appropriately sized apertures. 
     The exterior wall portion  120  of the exterior wall  102  includes a number of vents  126  positioned or located proximate a bottom of the exterior wall portion, and hence denominated herein as upper vents. The upper vents  126  may be opened and closed to selectively provide fluid communication between the space  122  in the exterior wall  102  and the external environment  110 . The upper  126  may be positioned and configured to allow exhausting of a fluid, such as air, out of the space  122  into the external environment  110 . The upper vents  126  may be configured to prevent the intrusion of insets, vermin or other pests into the space  122 , for example by appropriately sized apertures or a screen. 
     A control subsystem  128  may be communicatively coupled to control an opening and closing of at least some of at least the upper vents  126 . In some embodiments, at least some of the lower vents  124  may also be selectively opened and closed under control of the control subsystem  128 . While explained in more detail below with particularly with later reference to  FIG. 2 , the control subsystem  128  may be communicatively coupled to an input device such as keypad  130  by which a user may provide user input to control operation of the upper vents  126 , and optionally the lower vents  124 . Additionally, one or more external temperature sensors  132   a - 132   d  (four shown, collectively  132 ) may be communicatively coupled to the control subsystem  128  to provide signals indicative of an outdoor temperature. Additionally, or alternatively, the control subsystem  128  may be communicatively coupled to one or more indoor temperature sensors, for instance a thermostat  134  associated with an independent heating and/or cooling system (e.g., furnace, air conditioner, swamp cooler, not illustrated in  FIG. 1 ). 
     Optionally, one or more fans or blowers  136   a - 136   n  (only two called out in  FIG. 1 , collectively  136 ) may be positioned and selectively operable to cause or assist circulation in the space  122 . The fans or blowers  136  are communicatively coupled to be controlled by the control subsystem  128 . While illustrated as projecting into the interior  108  of the building  100 , the fans or blowers  136  may be positioned in the exterior walls, in a basement or cellar or in an attic or other space that is not commonly used or occupied, or even in the vent itself. 
       FIG. 2  shows an environmental control system  200  for a building, according to one illustrated embodiment. 
     The environmental control system  200  includes a number of vent actuators  202   a - 202   d  (only four illustrated, collectively  202 ) and a control subsystem  204  communicatively coupled to control the vent actuators  202  based on certain conditions. The vent actuators  202  may take the form of electric motors, solenoids, electromagnets or other actuators that can be selectively operated to open and close the vents. For example, the electric motors, solenoids, electromagnets or other actuators may be physically or magnetically coupled to a damper or door (not illustrated in  FIG. 2 ) that is selectively movable between an open position providing fluid communication between the space  122  ( FIG. 1 ) and the external environment  110  ( FIG. 1 ), and a closed positioned in which the damper or door blocks fluid communication between the space  122  and the external environment  110 . As explained above, at least the upper vents  126  ( FIG. 1 ) may be selectively closed to retain air in spaces  122  in the exterior walls  102  ( FIG. 1 ) and selectively opened to exhaust the air to the external environment  110 , based on various sensed conditions, thresholds and/or other control signals or parameters. 
     The environmental control system  200  optionally includes a number of fans or blowers  206   a - 206   b  (only four illustrated, collectively  206 ). As explained above, the fans or blowers  206  may be positioned and selectively cause air to circulate in the space  122  ( FIG. 1 ), for example to assist in exhausting air from the space  122  to the external environment  110  via the upper vents  124 . 
     The control subsystem  204  may include one or more controllers  208 , for instance a microcontroller, microprocessor, programmable gate array or application specific integrated circuit. The control subsystem  202  may also include one or more computer- or processor-readable non-transitory storage mediums that store instructions executable by the controller that cause the controller to control the vent actuators and/or fans or blowers based on at least one condition. The computer- or processor-readable non-transitory storage mediums may, for example, take the form of one or more read-only memories (ROMs)  210  and/or random access memories (RAMs)  212 . The controller  208 , computer- or processor-readable storage mediums  210 ,  212  and/or other components such as ports  214   a - 214   c  (only three called out, collectively  214 ) may be coupled by one or more buses  215 . The buses  215  may take a variety of forms including power buses, communications buses, instruction buses, and/or data buses. 
     The ports  214  may provide communications to and/or from the vent actuators  202 , fans or blowers  206  and/or other components such as user input devices and sensors. For example, one or more external or exterior temperature sensors  216  (only one illustrated in  FIG. 2 ) may provide signals indicative of an external or outdoor temperature to the control subsystem  204  via the ports  214 . Also for example, one or more internal temperature sensors  218 ,  220  may provide signals indicative of an external or outdoor temperature to the control subsystem via the ports. One or more of the internal temperature sensors  218  may be dedicated to operation of the environment control system  200 . Alternatively, one or more of the internal temperature sensors may be independent of the environment control system, for instance, a thermostat  220  of an independent heating and/or cooling system  222  of the building  100  ( FIG. 1 ) may provide the signals. Optionally, signals may come directly from the independent heating and/or cooling system  222  of the building  100 , as illustrated by the broken line arrow in  FIG. 2 . The signals may encode a measured or sensed temperature or may simply indicate whether a threshold temperature has been met. Thus, for example, a signal that turns a furnace ON or an air conditioner OFF may indicate that the upper vents  126  ( FIG. 1 ) should be closed to retain warm air in the space  122  in the exterior walls  102 . Alternatively, a signal that turns a furnace OFF or turns an air conditioner ON may indicate that the upper vents  126  ( FIG. 1 ) should be opened to exhaust warm air from the space  122  in the exterior walls  102 . Also for example, one or more photosensors  223  (only one illustrated in  FIG. 2 ) may provide signals indicative of an amount of light in the external environment  110  ( FIG. 1 ) to the control subsystem  204  via the ports  214 . The level or amount of measured or sensed light may indicate an amount of solar insolation and hence a temperature, time of day or even season. For example, a variation in the level of solar insolation over a 24 hour period may indicate time or day or the yearly current season (e.g., summer, winter, fall, spring). Such may be used to determine which of a number of defined patterns of opening and closing of the vents should be employed when under automatic control. As described herein, the vent(s) may additionally or alternatively be manually controlled by the user. 
     Additionally, or alternatively various user input devices may be employed. For example, a user may employ a keypad with or without a display, for instance a wall mounted keypad  224  to interact with the control subsystem  204 . Also for example, the user may employ a computer or computer system  226  to interact with the control subsystem  204 . The user may employ a mobile communications device, for instance a cellular phone or smart or wireless personal digital assistant (PDA)  228  to interact with the control subsystem  204 . The user may employ a timer  230  to interact with the control subsystem  204 . The user may use the various user input devices to program the control subsystem  204  or to manually control or even override the programming of the control subsystem  204 . Thus, a user may set various temperature thresholds for opening or closing the vents, or may cause the vents to open and close independent of, measured or sensed temperatures. 
     The ports may take the form of wired connectors or couplers, for instance Universal Serial Bus ports (USB) or Firewire® ports. The ports may take the form of wireless connectors or couplers for instance infrared transceivers or radio transceivers and antennas such as those compatible with 802.11 wireless communications standards or other protocols. Communications may be via any of a variety of protocols including power line communications protocols for communications over standard electrical wiring or Ethernet protocols for communications over twisted pair wiring. 
     In use, at a first time the control system  204  closes at least one upper vent positioned proximate a top of at least one exterior wall portion of the at least one exterior wall of the building to trap air in at least one space of the at least one exterior wall portion. The control system  204  may close the at least one upper vent in response to a variety of conditions. For example, the control system  204  may close the at least one upper vent in response to a temperature sensed or measured in the external environment or in the interior of the building falling below some threshold temperature. The control system  204  may close the at least one upper vent in response to occurrence of a time of day or a season. The control system  204  may close the at least one upper vent in response to a level or magnitude of light exceeding or falling below a defined threshold magnitude, or in response to a duration of a level or magnitude of light exceeding or falling below a defined threshold duration. The control system  204  may close the at least one upper vent in response to a signal from any of the various sensors or input devices previously described. 
     At a second time, the control system  204  may open the at least one upper vent to allow air to exhaust out of the upper vent from the at least one space of the at least one exterior wall portion into the exterior environment. The control system  204  may open the at least one upper vent in response to a variety of conditions. For example, the control system  204  may open the at least one upper vent in response to a temperature sensed or measured in the external environment or in the interior of the building raising above some threshold temperature, which may be the same as or different form a threshold temperature at which the upper vent is closed. The control system  204  may open the at least one upper vent in response to occurrence of a time of day or a season. The control system  204  may open the at least one upper vent in response to a level or magnitude of light exceeding or falling below a defined threshold magnitude, or in response to a duration of a level or magnitude of light exceeding or falling below a defined threshold duration. The control system  204  may open the at least one upper vent in response to a signal from any of the various sensors or input devices previously described. 
     The control system  204  may open and or close vents, for instance upper vents, in one exterior wall separately from the vents in other ones of the exterior walls. For example, the upper vents in an exterior wall with a southern exposure may be open and/or closed at different times than upper vents in an exterior wall with a northern exposure to adjust for different levels of solar insolation experienced by the respective exterior walls. 
     As explained above the lower vents may not be closeable, thus allowing air to continually pass through at least one lower vent positioned proximate a bottom portion of the at least one exterior wall portion of the at least one exterior wall of the building. In other embodiments, the lower vents may include dampers, doors or other mechanisms that allow the control system  204  to selectively open and close the lower vents. If closeable, the control system  204  should periodically open the lower vents to ensure that moisture or collected water may be exhausted. Some embodiments may include a moisture sensor to detect the buildup or collection of water at the bottom of the spaces. The control system  204  may then open the lower vents from time-to-time when the sensed or measured moisture exceeds a defined threshold. 
     The control system  204  may close or open selective vents by communicating signals or closing a switch or relay to provide power to at least one of an electric motor, a solenoid or other actuator coupled to move the damper, door or other device of the vent. For example, the control system  204  may open at least one upper vent in a first one of the exterior walls of the building while maintaining at least one upper vent closed in a second one of the exterior walls of the building. 
     Further, the control system  204  may selectively operate one or more fans or blowers to assist in circulating the air in the spaces in the walls. The control system may operate the fans or blowers by transmitting signals or closing a switch or relay to provide power to the fans or blowers. For example, the control system  204  may turn ON selected blowers to exhaust one exterior wall while maintaining other fans or blowers in an OFF state. Also for example, the control system  204  may operate selected fans or blowers to circulate trapped air from one or more exterior walls to other exterior walls. For instance, the control system  204  may selectively operate the fans or blowers to circulate warm air entrapped in an exterior wall with a southern exposure to an exterior wall with a northern exposure and/or exterior walls with an eastern or western exposure. Additionally or alternatively, passive options for enhancing circulation may be employed, for example including vents with a portion forming a Venturi tube or wind driven fans (e.g., similar to chef&#39;s hat turbine vent, roof ventilator). 
       FIG. 3  shows an upper portion of an exterior wall portion  300  proximate a roof  302 , the exterior wall portion  300  including at least one upper vent  304  with a hood  306 , damper  308   a ,  308   b  and actuator  310  according to another non-limiting illustrated embodiment. 
     The cross-sectional view of the illustrated exterior wall portion  300  is located between studs  112  ( FIG. 1 ) taken as a vertical section perpendicular to the major faces of the exterior wall  102  ( FIG. 1 ). An upper plate or sill  313  is visible in  FIG. 3 . 
     The exterior wall portion  300  includes one or more layers of an interior sheathing or material  312 , for example wall board or plaster board. One or more layers of plaster and/or paint  314  may be carried on an interiorly facing surface of the interior sheathing or material  312 . 
     The exterior wall portion  300  includes a number of layers of an exterior sheathing and/or material. In particular, the exterior wall portion  300  is illustrated as a stucco installation. From an interior toward an exterior of the exterior wall portion  300 , the layers may include a sheathing  316 , a weather resistant barrier for example a building wrap or paper  318 , a lath  320 , a Kraft paper  322  or other web material, and a cladding  324  in the form of stucco. The lath  320 , for instance a truss lath, provides a frame for keying the stucco cladding  324  as well as supporting the Kraft paper  322  and forming a space  326  in the exterior wall portion  300 , sometimes denominated herein as an air gap. The laths described in U.S. Pat. No. 6,820,387 and U.S. Patent Application Publication Number 2007-0175145 A1 may be suitable. The air gap  326  is in addition to a space  328  defined between the interior sheathing  312  and the exterior sheathing and/or material layers  316 - 326 , which space  328  may be filled with an insulating material  330 , for instance fiberglass batting or closed cell foam. The sheathing  316  is intermediate the interior sheathing  312  and the cladding  324 , so may in certain instances be denominated as intermediate sheathing or layer. The sheathing  316  may take any of a variety of forms, for example fiberglass mat sheathing (e.g., DENSGLASS® sheathing) or other suitable sheathing material (e.g., foam board, oriented strand board, plywood). The building wrap  318  may take the form of TYVEK® building wrap or some other building paper which forms a weather resistant barrier. The building wrap  318  may take the form of a corrugated building wrap, for example Tyvek® StuccoWrap® commercially available DuPont™. The building wrap  318  may be mechanically attached to the sheathing  316 . Alternatively, a trowel on membrane may be employed as a weather resistant barrier, which may be applied by spraying, brushing and/or rolling. As discussed in more detail below, the stucco cladding  324  may take any of variety of forms, for example the forms described in U.S. patent application Ser. No. 12/508,384 filed Jul. 23, 2009. Such may advantageously reduce the weight of and/or enhance the thermal insulation provided by the stucco cladding  324 . Optionally, the exterior wall portion  300  may include a strip of drainage matting  332  positioned between the sheathing  316  and the stucco cladding  324 . 
     The lath  320  may be attached to the sheathing  316  via fasteners, for instance screws  334 . A frame  336  may be provided in an opening  338  ( FIG. 4 ) in the stucco cladding  324  to allow mating of a vent assembly  340 . As best illustrated in  FIG. 4 , the exterior wall portion  300  may be prepared and the vent assembly  340  installed after completion of the remainder of the exterior wall portion  300 . The vent assembly  340  may be fastened to the frame  336  via fasteners, for instance push in snap fasteners  342  (only one called out in  FIG. 3 ). The frame  336  may advantageously include stucco stops  336   a ,  336   b  (only two called out in  FIGS. 3 and 4 ). Likewise, stucco stops  336   b  may be provided at a terminus of the exterior wall portion  300 . The frame  336  and/or vent assembly  340  has one or more passages that provide fluid communication into the space  326 . 
     The vent assembly  340  may include the hood  306 , damper or door  308  and a vent actuator  310 . As previously explained the vent actuator  310  may take the form of an electric motor, solenoid, electromagnet or other actuator. An electrical connector  344   a  is located in the opening to physically and electrically mate with an electrical connector  344   b  of the vent assembly  340  to provide power and control of the vent actuator  310 . The damper or door is illustrated in the closed position in solid line as  308   a , and in the open position in broken line as  308   b . The vent assembly  340  may include an insect screen  346 . While not illustrated as such, the vent assembly  340  may have a fan or blower including an electric motor, blades and electrical connector. 
       FIG. 4  shows the upper portion of the exterior wall portion  300  of  FIG. 3 , with a rough in kit, before installation of the vent assembly  340  including the hood  306 , damper  308 , vent actuator  310  and electrical connector  344   b  to the vent according to another non-limiting illustrated embodiment. 
     As explained above, an electrical connector  344   b  of the vent assembly  340  may be physically and electrically coupled to a complimentary connector  344   a  in the exterior wall portion  300 . Electrical wiring  348  may run through the exterior walls  102  ( FIG. 1 ). The vent assembly  340  may be physically coupled to the frame  336  via fasteners, for instance via the push in snap fasteners  342 . 
     The illustrated exterior wall portion  300  may represent the upper portion of one floor or story of a building  100  ( FIG. 1 ). Thus, while the upper vent  304  is illustrated proximate the top of the exterior wall portion  300 , in some installations there may be additional floors or stories above the illustrated exterior wall portion  300 . Each such floor or story may be treated as a separate exterior wall portion, particularly where plates or sills are employed to function as firebreaks in the exterior wall construction. Thus, while denominated as an upper vent  304  positioned proximate a top of an exterior wall portion  300 , there may in fact be a lower vent of another exterior wall portion spaced relatively above the upper vent or additional exterior wall portions above the upper vent  304 . 
       FIG. 5A  shows a lower portion of an exterior wall portion  500  proximate a floor plate or sill  513 , the exterior wall portion  500  including a lower vent  404  according to another non-limiting illustrated embodiment. 
     Similar to the upper exterior wall portion  300 , the lower exterior wall portion  500  includes one or more layers of an interior sheathing or material  512 , for example wall board or plaster board. One or more layers of plaster and/or paint  514  may be carried on an interiorly facing surface of the interior sheathing or material  512 . 
     The exterior wall portion  400  includes a number of layers of an exterior sheathing and/or material. In particular, the exterior wall portion  500  is illustrated as a stucco installation. From an interior toward an exterior of the exterior wall portion  500 , the layers may include a sheathing  516 , a weather resistant barrier for example a building wrap or paper  518 , a lath  520 , a Kraft paper  522  or other web material, and a cladding  524  in the form of stucco. The lath  520  provides a frame for keying the stucco cladding  524  as well as supporting the Kraft paper  522  and forming a space  526  in the exterior wall portion  500 , sometimes denominated herein as an air gap. The laths described in U.S. Pat. No. 6,820,387 and U.S. Patent Application Publication Number 2007-0175145 A1 may be suitable. The air gap  526  may be in addition to a space (not called out in  FIG. 5A ) defined between the interior sheathing  512  and the exterior sheathing and/or material layers  516 - 526 , which space may be filled with an insulating material (not called out in  FIG. 5A ), for instance fiberglass batting or closed cell foam. The sheathing  516  is intermediate the interior sheathing  512  and the cladding  524 , so may in certain instances be denominated as intermediate sheathing or layer. The sheathing  516  may take any of a variety of forms, for example fiberglass mat sheathing (e.g., DENSGLASS® sheathing) or other suitable sheathing material (e.g., foam board, oriented strand board, plywood). The building wrap  518  may take the form of TYVEK® building wrap or some other building paper which forms a weather resistant barrier. Alternatively, a trowel on membrane may be employed as a weather resistant barrier, which may be applied by spraying, brushing and/or rolling. The stucco cladding  524  may take any of variety of forms, for example the forms described in U.S. patent application Ser. No. 12/508,384 filed Jul. 23, 2009 which may advantageously reduce weight and/or enhance the thermal insulation provided by the stucco cladding  524 . Optionally, the lower exterior wall portion  500  may include a strip of drainage matting  532  positioned between the sheathing  516  and the stucco cladding  524 . 
     The lower vent  504  includes a perforated drip screen  550  which provides fluid communication to exterior or external environment  110  ( FIG. 1 ) to allows fluids, for example liquids such as water to drain from the space  526 , and allow fluids such as air to circulate into the space  526 . The perforated drip screen  550  prevents insects, vermin or other undesirable pests to enter the space  526 . 
     The perforations  552  (only one called out in  FIG. 5B ) of the perforated drip screen  550  are best illustrated in  FIG. 5B . The perforations  552  should be sized sufficiently small as to preclude passage of insects, vermin and other undesirable pests, yet be sufficiently large as to allow water to drain therethrough. 
     The perforated drip screen  550  may be secured to the sheathing  516  via fasteners (e.g., screws, nails, tacks) and/or adhesives. The perforated drip screen  550  may function as a frame. In particular, the perforated drip screen  550  may include a stucco stop  554  and a bottom edge  556  that protects a bottom edge of the stucco cladding  524 . The perforations  552  are spaced rearwardly from the stucco stop  554  to prevent the stucco cladding  524  from blocking or otherwise interfering with the perforations  552 . The perforated drip screen  550  may have a generally L-shape profile, with a relatively longer leg extending generally vertically when in use and a relatively shorter leg through which the perforations  552  extend through extending generally horizontally when in use. 
       FIG. 6  shows a lower portion of an exterior wall portion  600  proximate a floor plate or sill  613 , the exterior wall portion  600  including a lower vent  604  according to another non-limiting illustrated embodiment. 
     The construction of the lower exterior wall portion  600  is similar or identical to the lower exterior wall portion  500  ( FIG. 5A ) so will the description of such will not be repeated in the interest of brevity. Only significant differences will are described. 
     In contrast to the embodiment of  FIGS. 5A and 5B , the embodiment of  FIG. 6  employs a weep screed  650  in place of the perforated drip screen  550  ( FIGS. 5A and 5B ). The weep screed  650  may be secured to the intermediate sheathing  516  ( FIG. 5A ) and foundation  656  via fasteners (e.g., screws, nails, tacks) and/or adhesives. Drain matting  632 , for example with a support paper edge, may prevent intrusion of insects, vermin or other pests via the vent  604  while allowing fluid communication of liquids (e.g., water) and gases (e.g., air). 
     EXAMPLES 
     In a first example, an exterior wall may include steel studs having a depth of 3½ inches, and spaced 16 inches on center. The interior sheathing may be drywall of ½ inch thick with an associated thermal resistance or R value of approximately 0.45. The intermediate sheathing may be DensGlass® sheathing with an R value of approximately 0.56. The exterior wall may include fiberglass batting between the interior sheathing and the intermediate sheathing, having an associated R value of approximately 13. The wall wire lath may provide an air gap of approximately ⅜ inches with an R value of approximately 1.7 for heating and an estimated R value of from approximately 3 to approximately 4 for cooling. The exterior most sheathing may take the form of an approximately 1 inches layer of stucco containing an expanded perlite and having an associated R value of approximately 1. When determining thermal resistance, there is an air film associated with each surface/air interface which air films have an R value of approximately 0.68. In the described exterior wall structure there is an air film associated with the interior facing surface or face of the interior sheathing material and an air film associated with the exterior facing surface or face of the stucco. There are also two air films associated with the materials forming the air gap. The total R value for the described structure is 18.92, less steel framing loss estimated at 1.7, for a total effective R value of 17.22 for the exterior wall. 
     In a second example, an exterior wall may include steel studs having a depth of 5½ inches, and spaced 24 inches on center. The interior sheathing may be drywall of ½ inch thick with an associated thermal resistance or R value of approximately 0.45. The intermediate sheathing may be DensGlass® sheathing with an R value of approximately 0.56. The exterior wall may include fiberglass batting between the interior sheathing and the intermediate sheathing, having an associated R value of approximately 19. The wall wire lath may provide an air gap of approximately ⅜ inches with an R value of approximately 1.7 for heating and an estimated R value of from approximately 3 to approximately 4 for cooling. The exterior most sheathing may take the form of an approximately 1 inches layer of stucco containing an expanded perlite and having an associated R value of approximately 1. When determining thermal resistance, there is an air film associated with each surface/air interface which air films have an R value of approximately 0.68. In the described exterior wall structure there is an air film associated with the interior facing surface or face of the interior sheathing material and an air film associated with the exterior facing surface or face of the stucco. There are also two air films associated with the materials forming the air gap. The total R value for the described structure is 24.92, less steel framing loss estimated at 1.7, for a total effective R value of 23.22 for the exterior wall. 
     While the above examples employ certain dimensions, other dimensions may be suitable. For example, the exterior wall may include a space or air gap of a different size. For instance, a large space of air gap may provide a higher total R value. A space or air gap of ¾ inch to 1½ inches may easily achieved using conventional building materials or the lath discussed above. 
     Additionally, or alternatively, the exterior wall may include one or more additional layers of material, which may increase the total R value. For example, the exterior wall may advantageously include a radiant barrier positioned between the intermediate sheathing and the cladding. For instance, a radiant barrier of a material bearing a reflective coating (e.g., aluminum) may be adhered or otherwise attached to an interior facing surface of the Kraft paper. Suitable radiant barriers may be commercially available from various sources, including the Fi-Foil Company of Auburndale Fla. Use of a corrugated building wrap may also increase the total R value. 
     CONCLUSION 
     Various embodiments are directed to venting a space or air gap in at least a portion of an exterior wall, the space formed between at least a first and second exterior wall members. In the illustrated embodiments, the second exterior wall member may be a cladding or Kraft paper and the first exterior wall member is may be the intermediate layer of sheathing positioned between the cladding and an interior sheathing or material (e.g., plaster board) and/or the building wrap carried thereon. In other embodiments, the space may be formed between different structural elements of the exterior wall. Walls employing an open frame construction may omit the intermediate sheathing and place the building wrap or paper directly over the studs. In open frame construction, the space or air gap may be formed between the building wrap and either the cladding and/or the Kraft paper. Where an EIFS installation is employed, the space or air gap may be formed between the insulation board and some other element of the EIFS installation or the framing. The concepts described herein are also applicable to other construction techniques, including those which do not employ studs, for example concrete, tilt up panels, concrete masonry units, insulated concrete forms, etc. For instance, any of the above construction materials may form the first exterior wall member in conjunction with a cladding material as the second exterior wall member and a standoff structure (e.g., lath, hat track, Z-grits) to form a space or air gap therebetween, with vents positioned in the cladding operable to selectively vent the space or air gap. Yet even further embodiments my employ continuous insulation such as rigid insulation sheets, which may or may not have tongues and grooves. In such construction, the rigid insulation sheets may form the first exterior wall member, a cladding or some other material may form the second exterior wall member, and a standoff structure may form the space or air gap between the rigid insulation sheets and the cladding or other material. 
     The illustrated embodiments include vents located proximate a bottom of the portion of the wall and vents proximate a top of the wall portion, which may be selectively closed or opened to respectively retain air in the space or exhaust air from the space. The wall portion may, for example, be a floor or story of a house. Thus, the terms lower and upper are used to indicate a relative position with respect to each other in a given wall portion. As previously explained, it is possible, for example, to have the upper vents in a first or lower story to be spaced relatively above the lower vents in a second or upper story. 
     While illustrated as having a roughly square perimeter, the vent assembly  340  ( FIG. 3 ) may take a more elongated form. For instance, the vent assembly  340  may extend along all or a substantial portion of the exterior wall  102 . Thus, the vent assembly  340  may resemble the perforated drip screen  550  ( FIG. 5 ), but would include a damper or door  308   a ,  308   b  and vent actuator  310  operable to open and close the damper or door  308   a ,  308   b.    
     While illustrated as exhausting to the external environment, in some embodiments air in the space may be exhausted from the space or air gap in the exterior wall into some other space, for instance into a room in the house which is typically inhabited or into an attic or other typically uninhabited space. Advantageously, the exterior wall may include another space, positioned between the intermediate layer of sheathing and the interior sheathing, which may include a thermally insulative material other than air. 
     While the illustrated embodiments show cladding in the form of stucco, other cladding materials may be employed. For example, various substantially air tight claddings may be advantageously used, for instance stucco, brick, manufactured stone, exterior insulation finishing system (EIFS) installations, etc. EIFS installations typically include an insulation board which is attached to the substrate or sheathing, a reinforcing mesh and a base or brown coat (e.g., polymer and cement) overlying the insulation board, and a textured finish coat of material overlying the base or brown coat. Less advantageously, various non-air tight claddings may be employed, for instance cement board, wood siding, vinyl siding, aluminum siding. It may be advantageous to employ an air barrier (e.g., another layer of building wrap) outwardly toward the exterior of the space or air gap where the exterior wall employs a non-air tight cladding. 
     While the illustrated embodiments show a lath that forms the space or air gap, numerous other structures or elements may be employed to form the space or air gap between the intermediate sheathing and cladding. For example, the external wall may include wood strapping, drainage mats or metal (e.g., steel) spacers such as hat track, corrugated sheets or channels, Z girts or other spacer or standoff structures. 
     The above description of illustrated embodiments, including what is described in the Abstract, is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Although specific embodiments of and examples are described herein for illustrative purposes, various equivalent modifications can be made without departing from the spirit and scope of the disclosure, as will be recognized by those skilled in the relevant art. The teachings provided herein of the various embodiments can be applied to other context, not necessarily the exemplary vented space building construction generally described above. To the extent they are not inconsistent, the teachings of U.S. Pat. No. 6,820,387; U.S. patent application Ser. No. 10/935,821 filed Sep. 8, 2004; U.S. patent application Ser. No. 11/679,526 filed Feb. 27, 2007; and U.S. patent application Ser. No. 12/508,384 filed Jul. 23, 2009; and are incorporated herein by reference in their entirety. 
     In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.