Patent Publication Number: US-2015079896-A1

Title: Two-Piece Ventilation Units, Apparatus, Systems, and Related Methods

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. patent application No. 29/422,087 titled EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPRIETARY DESIGN, METHOD AND VISUAL ORNAMENTAL CHARACTERISTICS IS CLAIMED, THE ORNAMENTAL DESIGN FOR A VENTILATION SYSTEM (FAN/EXHAUST) UTILIZING SOLAR AND/OR ELECTRIC POWER, filed by Stocker et al. on May 16, 2012 the entirety of which is incorporated herein as if set forth in full. This application also claims priority to and is a non provisional application of U.S. provisional patent application No. 61/879,439 titled INTER-CHANGEABLE ATTIC FANS AND RELATED APPARATUS, SYSTEMS, AND METHODS, filed by Stocker on Sep. 18, 2013 the entirety of which is incorporated herein as if set forth in full. 
    
    
     BACKGROUND 
     Many workers are injured every year while installing ventilation fans on residential, commercial, industrial, agricultural, and other types of buildings, utility applications, etc. Take for instance the situation of installing a fan on a typical residential roof. These roofs, of course, are elevated necessitating the use of ladders, scaffolding, etc. to reach the worksite. Thus, frequently, the worker must stand on a ladder while installing the fan. These fans (and associated hardware such as housings, flashing, etc.) often weigh quite a bit and are bulky and awkward to work with. Maneuvering them while perched on a ladder, necessarily, increases the strain on the worker and the risk of falling (and other injuries) to which they are exposed. Angled roofs of various pitches aggravate these risks. 
     Moreover, to install a fan on a typical roof, the worker must carry the fan aloft on the ladder, position the fan with its flashing under the shingles, felt paper, tar paper, slate, metal sheeting, etc. on the roof and then fasten the fan to the roof. Of course, some roofing materials cannot so easily be “lifted.” For instance, some roofs include a layer of tar applied directly to the roof deck. While installing the fan, the worker often finds it difficult (if not impossible) to see around the fan and verify its positioning and that the flashing is underneath the roofing materials. As a result, these fans are often installed incorrectly resulting in an un-professional appearance fan and leaks of water (for instance, rain) in the proximity of the fan. 
     Additionally, fans require power to operate and power might/might not be available in close proximity to the location for particular roof mounted fan. Thus, wires, cables, conduits, etc. must be run to the fan and connected thereto. These activities complicate the installation, increase the cost thereof, and increase the number of technicians, workmen, crafts, etc. involved. In such situations, it might be desirable to use solar power to drive these fans. However, solar panels can be eye soars, take up space on the roof, etc. 
     Yet, building owners (and/or other interested parties) still desire the benefits associated with such fans (such as improved ventilation). For instance, if functional, these fans can ventilate the attics and/or other crawl ways underneath the roof. In turn, the ventilation decreases the temperature of these spaces thereby reducing air conditioning loads of the buildings. 
     SUMMARY 
     The following presents a simplified summary in order to provide an understanding of some aspects of the disclosed subject matter. This summary is not an extensive overview of the disclosed subject matter, and is not intended to identify key/critical elements or to delineate the scope of such subject matter. A purpose of the summary is to present some concepts in a simplified form as a prelude to the more detailed disclosure that is presented herein. The current disclosure provides systems, apparatus, methods, etc. for ventilating attics (and/or other spaces) and, more a particularly, two-piece ventilations units with adjustable (and flush fitting) solar panels and/or quick attachment fittings whereby fan assemblies of the ventilation units can be quickly attached to/detached from bases of the ventilation units. 
     Embodiments provide two-piece fans for use in ventilating spaces such as attics, crawlways, etc. These fans can require relatively low power and can possess high reliability. Moreover, fans of the current embodiment can be powered via solar panels, solar systems, etc. and/or power systems available in the buildings in/on which they might be installed. Fans of embodiments can be used in residential, commercial and/or utility applications, can be thermostat controlled, and can be windstorm certified per ASTM-E330 (and/or in accordance with other techniques). 
     Fans of embodiments are technologically, functionally and aesthetically superior to heretofore-available fans. Such fans can are rugged, durable, practical, windstorm certified and relatively inexpensive to manufacture, install, operate, maintain, modify, etc. Fans of embodiments possess elegant low profiles, blend nicely into their environments, and can be painted to match/complement their surroundings. In addition, or in the alternative, fans of embodiments possess adjustable solar panels. Such fans can include adjustable brackets with multiple locking states which support the solar panels and allow their positions to be adjusted. 
     Fans of embodiments can be used to provide proper ventilation for many spaces. In some situations these fans ventilate spaces to reduce temperatures inside enclosed spaces throughout the year such as attics, crawl spaces, warehouses, storage areas, sheds, barns, etc. In the summer, in particular, solar powered attic fans of embodiments help make such areas more comfortable by converting passive ventilation to active ventilation. 
     Fans of embodiments can reduce HVAC (heating, ventilation, and air conditioning) costs and reduce cooling cycles thereby saving energy and money. Furthermore, by reducing interior temperatures these fans can reduce premature deterioration of shingles, roof boards, sheathing, siding, insulation, stored valuables, etc. Proper ventilation can also prevent/reduce moisture (from relatively warm air) condensing on the under sides of relatively cool roofs, beams, rafters, etc. Moreover, because fans of some embodiments are solar powered, they can cost the owner/operator little or nothing to operate. Various embodiments provide fans with solar panels (and their adjustable brackets) which appear to be embedded in the fan housings rather than appearing as add-ons or appearing as if they have been glued onto the fans. 
     Some embodiments provide two-piece ventilation units comprising bottom bases, top housings, solar panels, locks, and biasing members. The bottom bases of the current embodiment define flashing which is shaped and dimensioned to divert runoff around the fans. They also define riser portions extending from the flashing and further define first halves of twist-on, quick attachment couplings. The top housings of the current embodiment contain fans and define second halves of the twist-on, quick attachment couplings. The top housings are releasably coupled to the bottom bases via the twist-on/off quick attachment couplings. Furthermore, the solar panels couple to the top housings and are pivotable between stowed positions in which they lie flush with the top housings and extended positions in which they extend at an angle from the top housings. Moreover, the solar panels are in electrical communication with the fans. The locks operatively couple with the bottom bases and the top housings and, when in their locked positions, lock the twist-on, quick attachment couplings in their coupled positions. The biasing members operatively couple with the locks and urge the locks toward their coupled positions. 
     Various embodiments provide ventilation units comprising bases (defining flashing portions) and housings which define, respectively, first and second halves of quick attachment couplings. The quick attachment couplings allow the housings to be releasably coupled to the bases. In some embodiments, the ventilation units further comprise solar panels coupled to the housings which are pivotable between stowed positions in which they lay flush with the housings and elevated positions in which they extend from the top housings. 
     If desired, the quick attachment couplings of the current embodiment can be twist-on (twist-off) quick attachment couplings. The ventilation units can further comprise locks operatively coupled to the bases and, which when in locked positions, can lock the twist-on, quick attachment couplings in coupled positions. Furthermore, biasing members can operatively couple with the locks and urge the locks toward their locked positions. Risers of some embodiments can be adapted to releasable couple between the bases and the housings. In some embodiments, the flashing portions can be adapted to be mounted on pitched roofs and the ventilation units can comprise fans contained in the housings. In addition, or in the alternative, the ventilation units of the current embodiment further comprise electrical connections adapted to receive 120 VAC (volts alternating current). 
     Embodiments provide ventilation units comprising bases, housings (coupled to the bases), and solar panels. The solar panels couple with the housings and pivot between stowed positions in which they lie flush with the housings and extended positions in which they extend from the housings at angles. In some cases, the ventilation units further comprise fans and electrical connections adapted to receive 120 VAC. 
     Ventilation units of various embodiments possess bases and housings which define quick attachment couplings by which the housings are releasably coupled to the bases. In the alternative, or in addition, the bases define riser portions extending from the flashings and further defining the quick attachment couplings. The quick attachment couplings can be twist-on quick attachment couplings. Moreover, the quick attachment couplings can be locked and can be biased toward their locked positions. 
     To the accomplishment of the foregoing and related ends, certain illustrative aspects are described herein in connection with the annexed figures. These aspects are indicative of various non-limiting ways in which the disclosed subject matter may be practiced, all of which are intended to be within the scope of the disclosed subject matter. Other novel and/or nonobvious features will become apparent from the following detailed disclosure when considered in conjunction with the figures and are also within the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number usually corresponds to the figure in which the reference number first appears. The use of the same reference numbers in different figures usually indicates similar or identical items. 
         FIG. 1  illustrates a building. 
         FIG. 2  illustrates a user installing a roof-mounted fan. 
         FIG. 3  further illustrates a user installing a roof-mounted fan. 
         FIG. 4  still further illustrates a user installing a roof-mounted fan. 
         FIG. 5  illustrates a two-piece fan with a solar panel in an extended position. 
         FIG. 6  further illustrates a two-piece fan with a solar panel in a stowed position. 
         FIG. 7  illustrates aspects of a two-piece fan. 
         FIG. 8  illustrates a fan assembly of a two-piece fan. 
         FIG. 9  illustrates a top plan view of a housing of a two-piece fan. 
         FIG. 10  further illustrates an exploded view of a fan assembly for a two-piece fan. 
         FIG. 11  illustrates a cross-sectional view of a two-piece fan. 
         FIG. 12  illustrates a top plan view of a pair of closures for two-piece fans. 
         FIG. 13  illustrates an exploded view of a two-piece fan. 
         FIG. 14  illustrates a two-piece fan installed on a roof. 
         FIG. 15  illustrates an exploded view of a two-piece fan and a riser. 
         FIG. 16  illustrates a two-piece fan and a riser installed on a roof. 
         FIG. 17  illustrates a corrugated roof and bases for two-piece fans. 
         FIG. 18  illustrates one half of a quick attachment coupling for two-piece fans. 
         FIG. 18A  illustrates a cross-sectional view as seen along line AA in  FIG. 18 . 
         FIG. 19  illustrates another two-piece fan and a roof curb. 
         FIG. 19A  illustrates a cross-sectional view of the base of  FIG. 19 . 
         FIG. 20  illustrates a schematic of a circuit associated with a two-piece fan. 
         FIG. 21  illustrates a flowchart of a method related to two-piece fans. 
         FIG. 22  illustrates a quick attachment coupling for multi-piece fans. 
     
    
    
     DETAILED DESCRIPTION 
     The current disclosure provides systems, apparatus, methods, etc. for ventilating attics (and/or similar spaces) and, more a particularly, two-piece ventilations units with adjustable (and flush fitting) solar panels and/or quick attachment fittings whereby fan assemblies of the ventilation units can be quickly attached to/detached from bases of the ventilation units. 
       FIG. 1  illustrates a building. More particularly,  FIG. 1  illustrates a building  100 , walls  101 , a ceiling  102 , air-conditioned spaces  103 , a roof  104 , a crawl way  105 , HVAC (heating, ventilation, and air-conditioning) equipment  106 , ducts  108 , an air conditioner (evaporator)  110 , a roof vent  112 , and an roof-mounted fan  114 . The building  100  could be a residential building (as shown), a commercial building, an industrial building, etc. The building  100  exists in a region in which the sun and other heat sources create a heat load on the building  100 . It also exists in an area where neighboring property owners might wish to maintain the aesthetic appearance of the neighborhood. Thus, the owner of the building  100  might wish to manage the heat load of the building  100  while not adversely affecting the aesthetic qualities of the building  100 , the neighborhood, etc. 
     The building  100  also includes a number of walls  101  as well as or, in the alternative to, other structures. Typically, these structures define one or more of the “air-conditioned” spaces  103  and one or more of the crawlways  105 . The air-conditioned spaces  103  are said to be “air-conditioned” in the sense that the condition of the air therein might be maintained more or less at some given state and, more specifically, at some desired temperature. Yet the external heat load (from the sun and/or other sources) and, potentially, internal heat loads (for instance, from lighting, electrical/mechanical equipment, occupants, etc.) can affect the temperature of those air-conditioned spaces  103 . In many cases, the crawl way  105  (or attic) is included in the design of the building  100  to provide a degree of separation between the air-conditioned spaces  103  and the external environment (and its heat loads). Yet, that crawlway  105  itself can become warm thereby exposing the air-conditioned spaces  103  to heat flux from the crawl way  105  itself and/or reduce the amount of heat which would otherwise escape from the air-conditioned spaces  103  through that space. 
     Moreover, many building designers, owners, maintenance personnel, etc. are known to place various pieces of equipment in these crawl ways  105 . For instance, building designers frequently locate HVAC equipment  106  and associated ducts  108  in these crawl ways  105 . Some HVAC equipment  106 , of course, represent sources of heat themselves. The ducts  108  often convey air-conditioned air and, even if insulated, allow that air-conditioned air to absorb heat from the air in the crawl way  105 . Thus, heat from the HVAC equipment  106  and other heat sources can be conveyed into the air-conditioned spaces  103  via the ducts  108 . 
     The roof  104  along with the ceiling  102  defines the crawl way  105  and tends to trap heat in that crawl way  105 . Indeed, warm (or even hot) air in the crawl way  105  can rise to the crown or apex of the roof  104  where it becomes trapped unless vented. As a result, a temperature gradient can exist as sensed at various heights in the crawl way  105  with the hottest air frequently being found near the apex of the roof  104 . 
     In many situations, users might place a roof vent  112  on the roof  104  to vent the crawl way  105 . If placed near the apex of the roof  104 , the roof vent  112  therefore allows the warmer air in the crawlway  105  to rise through itself and therefore escape from the crawl way  105 . However, such passive roof vents  112  rely on natural convection to drive the flow of the warm air and might not therefore be that effective in managing the heat load(s) affecting the crawl way  105  (and/or the air-conditioned spaces  103 ). Indeed, natural convection typically does not happen in a substantial manner until the crawl way  105  temperature reaches about 136 degrees F. Thus, some users include a roof-mounted fan  114  on the roof  104  to actively ventilate the crawl way  105 . 
     Such active ventilation equipment such as a roof-mounted fan  214 , though comes with certain drawbacks. For one thing, heretofore-available roof-mounted fans  114  are bulky, awkward, and heavy and therefore difficult to install as  FIGS. 2-4  illustrate. More particularly,  FIG. 2  illustrates a user installing a roof-mounted fan  214  on a building  200 .  FIG. 2  also illustrates a roof  204 , a user  216 , and a ladder  218 . As illustrated, the user  216  is installing the roof-mounted fan  214  near the apex of an angled roof  204 . Indeed, the user  216  has managed to carry the bulky roof-mounted fan  214  up the ladder  218  at something of a risk of dropping the fan and/or falling off the ladder  218  (or otherwise damaging the fan and/or injuring him/her self). Moreover, having managed to carry the roof-mounted fan  214  aloft, the user  216  must now perch at the top of the ladder  218 , maneuver it into place, and mount it to the roof.  204 . To do so, the user  216  must often reach around the roof-mounted fan  214  to its opposite side which the user  216  cannot see, much less reach conveniently. 
     Further still, the user  216  must then access the under side of the roof-mounted fan  214  from the attic of the building  200  to provide power to the roof-mounted fan  214 . That power might or might not be available at the location of the roof-mounted fan  214 . Thus, the user  216  might need to run wires, a conduit, etc. to the roof-mounted fan  214  as well as wire it to a thermostat if thermostatic control of the roof-mounted fan  214  is desired. In the alternative, the user  216  might have purchased a roof-mounted fan  214  with an add-ons solar panel. However, solar panels are often considered eyesores and add-on solar panels typically aggravate this condition. Indeed, some homeowners associations (HOA), municipalities, etc. place restrictions on the use of solar panels on roofs  204  (and/or other locations). 
     Further still, with heretofore-available roof-mounted fans, the solar panels are simply added to the fans with little or no attempt to incorporate the solar panels into the aesthetic design of these fans. Thus, these solar panels detract from the aesthetic features of these heretofore-available roof-mounted fans  214 . Moreover, the solar panels (on installed roof-mounted fans  214 ) might/might not point toward the sun thereby reducing their efficiency to a point at which they might not be able to adequately drive the fans. 
       FIG. 3  further illustrates a user installing a roof-mounted fan  214 . More particularly,  FIG. 3  illustrates a flashing  320 , a penetration  322 , rafters  324 , a roof deck  326 , roofing materials  328 , and tools  330 . The user, of course, could be a worker, home (or building) owner, a maintenance technician (electrician or mechanic perhaps), or other user. Nonetheless, the roof-mounted fan  214  is often so bulky that the user  216  can barely get their arms around it and must carry it in a position whereat its center of gravity is relatively distant from the user  216 . Heretofore-available roof-mounted fans  214  also happen to be heavy making carrying and maneuvering these roof-mounted fans  214  that much more difficult difficult. More specifically, the user  216  must (despite these challenges) maneuver the roof-mounted fan  214  over the penetration  322 , center it, and secure it to the roof deck  326 . 
     As those skilled in the art will appreciate, roof deck  326  rests on numerous rafters  324 . Typically, the rafters  324  are long 2″×4″ boards which (laid in an appropriate manner) can support the weight of the roof deck  326 , material (for instance, snow, water, etc.) on it, users  216 , wind loads (with appropriate bracing), etc. Typically, the rafters  324  are spaced apart by 24 inches and/or correspond (in spacing) to the typical 4×8 foot size of the plywood panels that make up the roof deck  326 . Other rafter  324  spacing dimensions are possible though. Moreover, the rafters  324  and/or roof deck  326  are typically pitched at angles corresponding to a rise/fall of 3 inches per foot although buildings having different roof pitches (for instance, 7 and 10 roof pitches) are certainly in existence and within the scope of the current disclosure. Indeed, some roofs  304  are flat (or have pitches much less than 3 inches per foot) and might have rafters  324  with increased dimensions to better bear the loads associated with such roof pitches. 
     The roof deck  326  itself is typically made of 4×8 foot sheets of plywood on which the roofing materials  328  are secured. In many cases, those roofing materials  328  include an underlying layer(s) of tarpaper and one or more layers of shingles. The tarpaper serves to waterproof the roof  304  so that rain, snowmelt, and/or other forms of water cannot penetrate the roof  304  and/or seep into the building. The tarpaper typically rests on the plywood of the roof deck  326  with the shingles overlying it. The shingles are thicker and more durable than the tarpaper and primarily serve to protect the tarpaper from damage by the elements, workers, objects falling (or being blown) onto the roof  304 , etc. Shingles are typically applied to the roof  304  in overlapping rows with the lower ends of shingles in higher rows resting on the upper ends of the shingles in lower rows. Moreover, shingles in adjacent rows are positioned such that the gaps between shingles of a given row do not align with gaps in adjacent rows. Thus, these features tend to waterproof the roof  304  when taken together so long as no penetration through the roofing materials  328  occurs. Note that roofs with ceramic tiles, concrete tiles, sheet metal (corrugated or otherwise), wooden shakes, etc. are within the scope of the current disclosure. 
     With continuing reference to  FIG. 3 , installing a roof-mounted fan  214  on a roof  204  typically requires that a relatively large penetration  322  be made in the roof  204  and roofing materials  328 . Indeed, to install a roof-mounted fan  214  most users  216  would enter the crawl way  105  beneath the roof  204  and select a location (usually near the roof apex) for the fan. They would then find a space between two rafters  324  for the fan. If the space is large enough to accommodate the fan, the user  216  often drills a hole (hammers a nail, etc.) through the roof deck  326  at the desired location for the center of the fan. They then climb down out of the crawl way  105 , exit the building, and climb to the top of the roof  204  where they would locate the previously drilled hole. Using a compass of sorts, the user  216  then typically marks the location of the intended periphery of the penetration  322  in accordance with the diameter of the fan. Then, using an appropriate saw or other tool(s), the user  214  cuts through the shingles, tarpaper, other roofing materials  328 , and the roof deck  326  to form the penetration  322 . 
       FIG. 4  still further illustrates a user installing a roof-mounted fan. Once the penetration  322  is prepared, the user  216  then maneuvers the bulky roof-mounted fan  214  into position roughly over the penetration  322 . But, provision must usually be made to prevent water from entering the building  200  through the penetration  322 . For such reasons, the roof-mounted fan  214  includes the flashing  220  around its lower end that, if properly installed (each time a roof-mounted fan  214  is installed, replaced, etc.), will exclude such water. Accordingly, the user  214  must lift the roofing material  328  near one of the sides of the penetration  322  and apply caulk (or some other sealant) to the roof deck  326  before sliding the flashing  320  underneath the temporarily lifted roofing material  328 . The user  216  must repeat these actions for every side of the penetration  322 /fan. 
     Moreover, the user  214  must do so without damaging the remaining roofing material  328 ; while not being able to see around the fan; and by maneuvering that bulky, awkward, roof-mounted fan  214  to make even small positional adjustments. With roof-mounted fans  214  heretofore-available, it is quite likely that the installation will fail in at least some of these regards thereby allowing water to penetrate the building  200  (not to mention perhaps leading to an installation with an un workman-like appearance). The user  214  can then tamp the roofing material  328  down over the flashing  320  of the fan and hope that wind does not “get under it” and remove it from the roof  204  thereby leading to yet more damage to the building. Of course, the user  216  typically also has to reenter the crawl way  105  (from the other side of the roof  204 ) and connect power to the roof-mounted fan  214 . Accordingly, the installation of each heretofore-available fans  214  tends to be time-consuming, expensive, and prone to failures, errors, omissions, etc. 
       FIGS. 5-8  illustrate a two-piece fan with a solar panel in various positions. The two-piece fan  500  of the current embodiment comprises at least two-pieces: a fan housing  502  and a base  504 . The two-piece fan  500  of the current embodiment also includes a solar panel  506  and adjustable bracket  508  as well as flashing  510 . The fan housing  502  contains a fan, motor, and associated bearings, races, etc. and airflow guides, vanes, etc. It therefore contains the active mechanical components of the two-piece fan  500  of the current embodiment. Moreover, the solar panel  506  and adjustable bracket  508  operationally couple with the fan housing  502 . The fan housing  502 , additionally, can include wiring to electrically connect the solar panel  506  to the fan and perhaps some controls (for instance, thermostats, thermal cut-off switches, remote control circuitry, etc.) for the fan motor. 
     Mechanically, the adjustable bracket  508  operatively couples the solar panel  506  to the fan housing  502 . In some embodiments, the adjustable bracket  508  includes one or more “stops,” at which it can be locked, to position the solar panel  506  in a corresponding number of positions relative to the fan housing  502 . Thus, the solar panel  506  pivots about the fan housing  502  through an angle a1 between its stowed position (see  FIG. 6 ) and its extended position ( FIG. 5 ) and through the various intermediate stop-related positions. These positions allow a user  214  to more accurately point the solar panel  506  at the sun or other light source as might be desired. Indeed, by orienting the fan housing  502  and using the adjustable stops, users  214  can orient the solar panel  506  to point generally toward the sun in many if not all locations including many north-facing roofs. A range of angle a1 from 0 degrees in the stowed position to about 45 degrees has been found to be satisfactory for such purposes. 
     In the stowed position, though, the solar panel  506  rests in the fan housing  502  with its surface flush with the nominally upper surface of the fan housing  502 . In this position, the adjustable brackets fold into the housing thereby allowing the solar panel  506  to appear to be embedded in the housing and/or flush with its surface. 
     The fan housing  502  also defines one or more vents/drains  512 . These vents/drains  512  provide a flow path around the solar panel  506  when the solar panel  506  is in its stowed position, flush with (or embedded in) the fan housing  502 . In this way, even when the solar panel  506  is stowed some air can flow beneath it and cool it. These vents/drains  512  can also serve as finger holds for users  214  to reach underneath the solar panel  506  and lift it to one of its non-stowed positions. They also allow for water to drain from under the solar panel  506 . 
     Furthermore, the fan housing  502  of the current embodiment defines a low profile and has an overall oblong, rounded shape. The vents/drains contribute to this low profile (a height less than about 7″ in some embodiments and less than about 3″ in the current embodiment), rounded appearance in that they are formed integrally with the (nominally) upper portions of the sides of the fan housing  502 . The vents/drains  512  are also rounded at least in part for aesthetic considerations. Note that the fan housing can be made of some paintable material such as ABS (Acrylonitrile butadiene styrene) plastic so that the two-piece fan  214  can be painted in accordance with user desires, local aesthetic rules, deed restrictions, ordinances, etc. 
     Note that  FIGS. 5-7  illustrate the two pieces (the fan housing  502  and the base  504 ) of the two-piece fan  500  of the current embodiment being coupled together.  FIG. 8 , in contrast, illustrates the fan housing  502  separate and apart from any base  504 . Indeed, the bases  504  can be installed on various roofs  204  with the fan housings  502  being installed at some different time and/or interchanged with one another. In accordance with the current embodiment, therefore, the fan housings  502  can be interchanged with one another, removed, replaced, etc. without disturbing the roof  204 , the roof deck  326 , the roofing materials  328 , etc. and without tools  330  and the like. Furthermore, once a base  504  of suitable size is installed on a roof  204 , the user can “install” a “fan” by merely carrying a fan housing  502  to the already installed base  504 , placing it on the base  504 , and removably coupling that fan housing  502  to the base  502 . In the current scenario, the user  214  need not carry or maneuver the (bulk of the) base  504 , flashing  510 , etc. Thus, the current embodiment facilitates the installation (and/or replacement, maintenance, etc.) of fans while eliminating much of the work, expense, and inconvenience associated therewith. 
       FIG. 9  illustrates a top plan view of a housing of a two-piece fan. More particularly,  FIG. 9  illustrates a fan housing  900 , vents/drains  912 , a body  918 , sides  919 , a recess  920 , and ribs  922 . As alluded to elsewhere herein, the body  918  of the fan housing  900  contains a fan, its blades, etc. and defines the vent/drains  912 . Additionally, in the current embodiment, the body  918  also defines the recess  920  into which the solar panel  506  fits and/or appears to be embedded (when stowed) in the housing. Those solar panels  506  can be polycrystalline, multicrystaline, monocrystaline, etc. without departing from the scope of the current disclosure. In some embodiments, the body  918  also defines one or more of the ribs  922  on its nominally upper surface in the recess  920 . These ribs  922  can provide a degree of rigidity to that surface and can allow some space between it and the solar panel  506  (when stowed). This space can allow the solar panel  506  to breath and thus remain relatively cool during operation (and during non-operation). This space also allows the area under/behind the solar panel  506  to drain should moisture be present. 
       FIG. 10  further illustrates an exploded view of a housing for a two-piece fan. More particularly,  FIG. 10  illustrates the fan  1000  and its housing  1002 , solar panel  1006 , adjustable brackets  1008 , cowling  1030 , closure  1032 , fan motor  1034 , fan blades  1036 , bosses  1038 , fastener holes  1039 , and rails/locks  1040 . Generally, the fan motor and blades  1034  and  1036  (as a unit) respectively fit inside the cowling  1030  which fits inside the housing  1002 . The closure  1032  along with the housing  1002  (and appropriate fasteners) closes the fan  1000  as an assembly and clamps it together. As is disclosed further with regard to  FIG. 11 , the closure  1032  defines at least one aperture that allows the fan to draw air into itself while the cowling  1030  is shaped and dimensioned to smoothly turn that flowing air with relatively low head loss back toward the closure  1032  in a relatively small axial distance (less than 4-7″ in many embodiments). In some embodiments, the cowling  1030  eliminates air pockets and associated energy wasting eddy currents therein. The cowling  1030  can also include guide vanes for the air if desired. The closure  1032  also defines at least one aperture which allows the (turned) airflow to exit the fan  1000 . Thus, the air flows upward through the closure  1032 , through the fan blades  1036  (which drive the airflow at least in part), through the turn guided by the cowling  1030 , and then back out through the closure  1032 . 
     As further illustrated by  FIG. 10 , the closure  1032  defines one or more bosses  1038  with holes adapted to receive closure fasteners. Those holes align with the fastener holes  1039  on the housing  1002 . Thus, with the cowling  1032  and fan blades  1036  and fan motor  1034  in the housing  1002 , fasteners can be used to assemble the fan  1000  into a separate, stand-alone unit. 
       FIG. 10  also shows that the solar panel  1006  can include or be operationally coupled to the adjustable brackets  1008 . The adjustable bracket  1008  can cooperate with the corresponding rails/locks  1040  to allow users to adjust the position of the solar panel  1006  with respect to the housing  1002 . The rail/locks  1040  can also, or in the alternative, cooperate with the adjustable brackets  1008  to lock the solar panel  1006  in one or more of those positions. 
     In the current embodiment, a frame  1041  surrounds, holds, and/or supports the solar panel  1006 . While the frame  1041  of the current embodiment can provide structural support to the solar panel, another function it provides is to shield the solar panel  1006  from the environment, physical damage/abuse, and form being seen. Thus, the frame  1041  aids in preserving the aesthetic appearance of the fan and/or its housings. Furthermore, the frame  1041  can be (spray) painted in accordance with user desires, homeowner association rules, ordinances, etc. A backing  1042  can also be applied to the side of the solar panel  1006  closest to the body of the two-piece fan  1000 . It too can be painted and/or it can be black so as to shield the backside of the solar panel from view and to aid in the aesthetic features of the fan. 
       FIG. 11  illustrates a cross-sectional view of a two-piece fan. More particularly it shows the fan motor  1034  and fan blades  1036  assembled within the cowling  1030  which is itself within the housing  1002 . Further,  FIG. 11  illustrates the closure  1032  fastened to the housing (via fasteners in the fastener holes  1039  and bosses  1038 ) and clamping the fan assembly  1102  together.  FIG. 11  also shows the two-piece fan  1100  with the solar panel  1006  operationally coupled to the housing assembly  1102  via the adjustable bracket  1008 . Moreover,  FIG. 11  illustrates the base  1104  including the flashing  1110  releasably attached to the fan assembly  1102 . Note that the fan assembly  1102  and base  1104  can be separated from one another with, if desired, the base  1104  being coupled to and/or being installed on a roof or other structure. In the embodiment illustrated by  FIG. 11 , furthermore, the various components of the two-piece fan  1100  are coaxial with one another although they need not be for the practice of the current embodiment. 
     Moreover,  FIG. 11  illustrates a motor bracket  1120 . In the current embodiment, the motor bracket  1120  defines various attachment points corresponding to various motors. Thus, it can allow for the interchange of motors as might be desired. The motor bracket  1120  can also provide physical protection to the motor and/or its coupling to the fan blades against mechanical damage from, for instance, animals that might intrude into the fan housing. This feature helps keep the fan blades in balance, running smoothly, and without undue noise. 
       FIG. 12  illustrates a top plan view of a pair of closures for two-piece fans. Both closures  1200 A and B include a generally planar body  1202 A and B shaped and dimensioned to fit into the open end of various housings  1002 . The closures  1200 A and B also define, respectively, central apertures  1204 A and B through which the various fans (or fan blades  1136 ) can draw air. The closures  1200 A and B also defined a plurality of apertures  1206 A and B through which air, driven by the fan blades  1136 , can flow from the fans. In some embodiments, the closures  1200  can include a screen over one or more of the apertures to, for instance, keep insects, birds, rodents, other animals, debris, water, etc. out of the fans. 
       FIG. 13  illustrates an exploded view of a two-piece fan. More particularly,  FIG. 13  illustrates a two-piece fan  1300  including a fan assembly  1302 , a riser  1303 , and a base  1304 . The fan assembly  1302 , of the current embodiment, includes a fan (a motor and a set of blades in this embodiment), a housing, and a closure. In  FIG. 13  a solar panel is not shown although the two-piece fan  1300  could include a solar panel with or without adjustable brackets. The base  1304  includes a flashing and is shaped and dimensioned to be attached to a roof, roof curb, or other structure and to lend the two-piece fan  1300  stability when installed. 
     In the current embodiment, the two-piece fan  1300  also includes the riser  1303  which could be considered as a part of the base  1304  or the fan assembly  1302  or even a third component/assembly of the “two-piece” fan  1300 . The riser  1303  is shaped and dimensioned to reside between the fan assembly  1302  and the base  1304 . While it can be coaxial with the other pieces of the two-piece fan  1300 , it does add height to the two-piece fan  1300 . In other words, the riser  1303  (or extender) spaces the fan assembly  1302  apart from the roof or other structure to which the two-piece fan  1300  might be mounted. Thus, should water, snow, ice, debris, etc. accumulate around the base  1304 , the operation of the fan can remain relatively un-affected. But, the extension need not be in a vertical direction to practice the current embodiment. 
     Moreover, because the open end of the riser  1303  (when installed on a base  1304 ) might be clear of such debris, a two-piece fan  1300  (or rather a fan assembly  1302  of a two-piece fan  1300 ) can be installed even in the presence of that debris in many cases. Indeed, since 5-6″ of snow is often considered to be good insulation, users can install fan assemblies on risers with lengths of about 6″ without disturbing that snow. For roofs covered with sod, dirt, grass, sand, gravel, etc. two-piece fans (with risers and/or riser portions) of embodiments provide similar features. 
       FIG. 13  also illustrates that risers  1303  of the current embodiment can include two sets of quick attachment coupling halves  1310  and  1312 . These coupling halves  1310  and  1312  can be shaped and dimensioned to mate with corresponding coupling halves  1314  on the bases  1304  and fan assemblies  1302 . Also, if desired, one set of the coupling halves  1310  or  1312  can be adapted to mate with corresponding coupling halves on the fan assemblies  1302  while the other set (on the riser  1303 ) can be adapted to mate with the coupling halves on the bases  1304 . In such manners, risers  1303  can be stacked one atop another to extend the fan assemblies  1302  to lengths determined by the dimensions of the selected risers  1303  and/or their numbers. If desired, the various coupling halves  1310 ,  1312 , and/or  1314  can be adapted to pull the various components/assemblies  1302 ,  1303 , and/or  1304  into close fitting and/or weather proof alignment with one another. Additionally, or in the alternative, these components  1302 ,  1303 , and/or  1304  can be adapted to be used with gaskets, O-rings, sealants, and/or other weatherproofing techniques to prevent water intrusion, air infiltration, etc. through the joints there between. 
       FIG. 14  illustrates such a two-piece fan installed on a roof with a riser  1303  installed between the fan assembly  1302  and the base  1304 .  FIG. 15  illustrates an exploded view of a two-piece fan and multiple risers  1503 A and  1503 B installed therewith.  FIG. 15  also shows that such multi-riser two-piece fans  1500  can include a solar panel and adjustable brackets) coupled thereto.  FIG. 16  illustrates a two-piece fan and a riser installed on a roof. In the embodiment illustrated in  FIG. 16 , the riser  1603  is configured to turn through an angle a2. That angle a2 could correspond to one of the common angles at which roofs are pitched although it need not do so. In such cases though, the use of the angled riser  1603  can serve to turn the orientation of the two-piece fan (or fan assembly  1602 ) to some desired direction such as vertical (as shown). Moreover, in some embodiments, one or more risers can be used in combination/conjunction with other risers whether straight, angled, or otherwise.  FIG. 16  also illustrates, in at least some sense, that the base  1604  can be considered an assembly. For instance, the base  1604  could define or comprise a flashing portion  1610  coupled to a riser portion  1630 . The riser portion  1630  could further define, comprise, be coupled to, etc. quick attachment couplings. 
       FIG. 17  illustrates a corrugated roof and bases for two-piece fans. More particularly, the corrugated roof  1700  of the current embodiment includes a portion  1702  which appears trapezoidal when viewed in cross-section and a portion  1704  which appears sinusoidal in cross-section. The corrugated roof  1700  also includes two bases  1706  and  1708  which, respectively define flashings with corresponding corrugated trapezoidal and sinusoidal cross-sections. Thus, embodiments allow two-piece fans to be installed on, mounted on, attached to, etc. corrugated roofs without altering the corresponding risers and/or fan assemblies. 
       FIG. 18  illustrates one half of a quick attachment coupling for a two-piece fan and  FIG. 18A  illustrates a cross-sectional view as seen along line AA in  FIG. 18 . More particularly,  FIGS. 18 and 18A  illustrate that the quick attachment coupling  1800  of the current embodiment defines a male half  1802  and a female half  1804  with the two halves being designed to releasably engage each other and to releasably couple assemblies of two-piece fans together. Thus, these male and female halves  1802  and  1804 , respectively, can be shaped and dimensioned to withstand wind (and/or other) loads likely to be imposed on various two-piece fans with and/or without risers. Additionally, these coupling halves  1802  and  1804  can be shaped and dimensioned to draw the fan assemblies together with sufficient force to form a seal there between in the presence and/or absence of gaskets, O-rings, and/or other sealing structures/devices. 
     With continuing reference to  FIG. 18 , the female half  1804  of the current embodiment can define a relatively large aperture  1806  which can accept a corresponding and/or relatively large portion  1810  of the male half  1802 . These structures allow the halves  1802  and  1804  to engage each other and disengage from each other. The female half  1802  can also defines a narrow aperture  1812  which can accept a corresponding small portion  1814  of the male half  1802 . Thus, once the halves  1802  and  1804  are engaged with each other, the narrow portion  1814  of the male half  1802  can be slid along the narrow aperture  1812  of the female half  1804  so that the halves  1802  and  1804  can remain engaged with each other despite axial forces imposed on their corresponding fan assemblies. The halves  1802  and  1804  can also remain in sliding engagement with one another (at least for some distance) in such circumstances even if some torsional forces attempt to rotate one fan assembly relative to the other in the current embodiment. Nonetheless, such features allow assemblies of embodiments to be releasably coupled to one another with a twist of one assembly relative to another. 
       FIGS. 18 and 18A  also illustrate that the female and male halves  1802  and  1804 , respectively, define guide surfaces  1815  and  1816 . These guide surfaces  1815  and  1816  can be shaped and dimensioned such that, as the coupling halves  1802  and  1804  slide relative to one another, the guide surfaces  1815  and  1816  urge the halves  1802  and  1804  toward one another (axially) thereby drawing the respective assemblies into abutting relationship. Moreover, the guide surfaces  1815  and  1816  can be configured to impart enough force on the respective fan assemblies to form a seal there between. That seal can be made, enhanced, etc. with a gasket, O-ring, etc. which might/might not be positioned in a groove  1820  in the surface of one fan assembly or another. 
     Further still, in some embodiments, the quick attachment coupling  1800  includes a latch  1822 . The latch  1822  can be positioned on the fan assembly with the female half  1804  to releasably capture the male half  1802  as the halves engage each other. In some embodiments, the latch  1822  (and the coupling halves  1802  and  1804 ) is configured and positioned to be released manually. In addition, or in the alternative, the latch  1822  can be biased into a position (for instance a locked/latched position) by a biasing members such as a spring  1824 . 
       FIG. 19  illustrates a base for a two-piece fan and  FIG. 19A  illustrates a cross-sectional of the base of  FIG. 19 . The base  1904  of the current embodiment mates with rectangular roof curbs  1906  so that two-piece fans can be mounted thereon in accordance with embodiments. Instead of a flashing, the base  1904  defines an adaptor  1910  shaped and dimensioned to mate with the roof curb  1906  and to seal thereto. Quick attachment couplings, fasteners, etc. can be used to secure the adaptor  1910  (and base  1904 ) to the roof curb  1906 . Moreover, the adaptor  1910  can further define a lip  1912  which can aid in registering the base  1904  with the roof curb  1906 . The lip  1912  can also assist in sealing the joint between the base  1904  and the roof curb  1906  and can be used as a location for quick attachment couplings, fasteners, etc. for securing the base  1904  to the roof curb  1906 . 
       FIG. 20  illustrates a schematic of a circuit associated with a two-piece fan. More particularly,  FIG. 20  illustrates a circuit  2000  which includes a fan motor  2002 , a solar panel (or cell)  2004 , a source of (120 VAC) line power  2006 , an inverter  2008 , an on/off switch And/or breaker)  2010 , a thermostat  2012 , a thermal cutoff switch  2014 , an isolator  2016 , and two pairs of contacts  2020  and  2022 , quick disconnects, etc. Generally, the solar panel  2004  and line power  2006  are wired in parallel across the fan motor  2002  in the current embodiment. Moreover, the contacts  2020  allow those components on the fan assembly to be connected to (and disconnected from) line power  2006  while the contacts  2022  allow the solar panel to be electrically (dis) connected to the fan motor  2002 . 
     Of course, fans of embodiments could operate on only one of the solar panel  2004  or line power  2006 . In such embodiments, the circuit  2000  can be simplified accordingly. Indeed, where power is only available from the solar panel  2004 , the fan motor  2002  will slow down/stop as the light fades thereby allowing natural convection/breezes to ventilate the crawl way  105  during dark periods. 
     Nonetheless, the inverter  2008  illustrated by  FIG. 20  converts the line power  2006  to DC (direct current) power compatible with the fan motor  2002  which can be selected to be driven by DC power from either/both of the solar panel  2004  and/or the inverter  2008  (and, thus, line power  2006 ). The isolator  2016  can be included in the circuit  2000  so as to protect the solar panel  2004  from being back-driven by that DC power. Moreover, the thermostat  2012  can determine when the fan motor  2002  runs responsive to the temperature sensed by the thermostat  2012  while on/off switch  2010  allows users to control the fan motor  2002  at least as far as line power  2006  might be involved. Of course, if desired, the fan motor  2002  can be instrumented with the thermal cutoff switch  2013  to shut it off if it should over-heat. 
       FIG. 20  also schematically illustrates that the on/off switch  2010  and the source of line power  2006  can be located in/on the building on which the fan is to be mounted. Meanwhile, the remaining components illustrated by  FIG. 20  can be located on the fan assembly (or if desired the base or riser) associated with the circuit  2000 . A pair of wires  2024  can run through the fan assembly from the components there on toward the riser/base. These wires  1024  can be routed through the riser/base and thence to some connection point and can terminate in the contacts  2020 . In some embodiments, the wires  1024  run external to the fan assembly and can be routed through the building/environment outside of the fan, fan assembly, riser, base, etc. although they need not be so routed to practice embodiments. Another pair of wires  1026  can be routed through the fan assembly/riser/base so that the thermostat  2012  can be removably (re) located in or near the inlet of the base, riser, fan assembly. 
     In some embodiments, though, the those wires  1026  further comprise a  36 ″ (or other length) cable allowing the thermostat  2012  to be located at a location with temperatures representative of the crawl way  105 . For instance, the area/strata of air near the roof apex is often warmer than the overall crawl way  105 . Placing the thermostat  2012  elsewhere (for instance lower) in the crawl way  105  by using the wires  2026  can allow for control of the fan motor  2002  responsive to temperatures more representative of overall conditions in the crawl way  105 . 
       FIG. 21  illustrates a flowchart of a method related to two-piece fans. The method  2100  includes numerous activities such as identifying a desire for improved ventilation. See reference  2102 . That desire might arise from a user noticing that one or more air-conditioned spaces  103  in a building  100  has been and/or has become warmer than desired. In some cases that desire might arise from a user noticing that a crawl way  105  has become susceptible to mold, mildew, etc. Of course, many circumstances could prompt a user to desire improved ventilation and, indeed, these circumstances might occur in various combinations. 
     With continuing reference to  FIG. 21 , one response to such situations is to install (or change) a fan that ventilates the crawl way  105  of the building  100 . Doing so would probably remove warm air from the crawl way  105  and allow warm air from elsewhere to rise to the crawl way  105  where it would also be removed. Such airflow would tend to cool the crawl way  105 , the HVAC equipment  106  and/or ducts  108  therein as well as likely reducing the heat load(s) on the air-conditioned spaces  103  of  FIG. 1 . 
     Therefore, given the size of the building  100 , its air-conditioned spaces  103 , the solar insolation in the building&#39;s environment, likely weather/climate conditions, the likely occupancy/use of the building, etc. a user can select a fan assembly by size and/or type for use in ventilating the crawl way  105 . With heretofore available fans, once a user installs the selected fan, a change or modification to that fan (or selection thereof) might necessitate a re-engineering/re-design of the installation-site as well as, perhaps, performing again most (if not all) of the installation procedures for the (newly) selected heretofore available fan. Thus, with such fans, changing a selection and/or replacing an existing fan could be comparatively expensive. In contrast, many of these adverse consequences can be avoided with two-piece fans of embodiments although doing so is not necessary for the practice of embodiments. 
     With reference again to  FIG. 21 , method  2100  can continue with a user selecting various assemblies with which to build/install a two-piece fan  1300  of embodiments. For instance, a user can select a base  1304  by its diameter (or size as pertinent to HVAC considerations), the type of roof  104  it is to be installed on, its shape (for instance, round or rectangular), etc. Moreover, the user can select the base  1304  independently of their selection of the fan assembly  1302 . See reference  2104 . If desired, the user can select one or more risers  1303  for use with the base  1304 . These risers  1303  can be straight, angled, etc. and the user can select more than one riser  1303  if desired. Thus, the user can design a two-piece fan  1300  while accommodating local concerns such as the possibility that rain, snow, ice, debris, etc. might accumulate on the roof  104  near the fan  1300 . 
     Method  2100  can continue with the user selecting a fan assembly  1302 . The user can base this selection on the size of the fan desired (for instance, desired flow rate, head/pressure, energy consumption, etc.), its type (axial, centrifugal, mixed, etc.), etc. See reference  2106 . Again, the user can make the selection of the fan assembly  1302  and base  1304  (and riser) more or less independently of one another provided that they are generally the same size and shape at the joint where they are to be coupled to one another. 
     At some point, a user can install the base  1304 . Installing the base  1304  can be performed at a different time, by different users, with different tools, etc. than the installation of the fan assembly  1302  (and/or riser  1303 ). Thus, for instance, the installation of the base  1304  could be performed by a user(s) with mechanical/carpentry skills while installation of the fan assembly  1302  could be performed by a user with enough electronic skill to make the electrical connections and/or mechanical skills to install the fan assembly  1302  and/or the solar panel. 
     The installation of the base  1304  can include various activities. For instance, a user can enter the crawl way  105  (or other space opposite the intended location of the fan) and mark an appropriate location for the center of the fan. Often, the user will identify a location between two rafters  324  and mark that location with any convenient writing, marking, etc. tool. The user can then drill a hole through the roof  104  so that the desired location of the fan becomes apparent from the other side of the roof. The user, moreover, can then access the other side of the roof and use a compass or other tool to mark the outline of the duct-space defined by the base  1304 . Using that marking as a guide, the user can then cut through the roof to define the penetration  322  through which air will flow as induced by the fan. Thus, the user can locate the position of the to-be-installed fan as indicated at reference  2108 . 
     Further still, the user can lift the roofing material  328  of the roof  102  adjacent to the penetration  322  in preparation for installing the base  1302  and, if desired, apply caulking (or some other sealant) to the roof deck  326  in preparation for sealing the base  1304  to the roof. The user can then, if desired, slide one side of the flashing  1310  under an appropriate portion of the roofing material  328  and then maneuver the base  1302  alone (sans the fan assembly  1302 , riser  1303 , etc.) into its final place on the roof  104  and/or over the penetration  322 . Thus, much of the inconvenience, difficulty, awkwardness, etc. of working with these bulky, heretofore available fans can be eliminated. This condition can facilitate the work, reduce associated expenses, and/or reduce the likelihood/severity of mistakes, oversights, etc. Furthermore, the user can use fasteners to fasten the base  1304  to the roof deck  326 . See reference  2110 . 
       FIG. 21  also illustrates (at reference  2116 ) the user coupling a riser  1303  to the base  1304 . More particularly, in accordance with embodiments, the user can maneuver the riser  1303  to the vicinity of the base  1304  (after it is installed if desired) and roughly align the coupling halves  1802  and  1804  with one another. Once the halves  1802  and  1804  are roughly aligned, the user can engage the male half  1802  and the female half  1804  and then (by maneuvering/twisting the riser  1303 ) translate one relative to the other thereby causing the latch  1820  to latch/lock the halves together. Thus, the user can mount the riser  1303  to the base  1304  and do so without tools. Note that at this point that much of the overall two-piece fan (in terms of physical envelope size) is installed. 
     In many situations, the fan assembly  1302  (including the fan motor) might be the heavier of the two (or three or more) pieces of the fan. Thus, at reference  2118 ,  FIG. 21  illustrates the user installing the fan assembly  1302  as a separate piece on the base  1304  and/or riser  1303 . Since the user is doing so with only the fan assembly  1302  (and not the base  1304  or riser  1303 ) in their hands, such activities might be easier, more convenient, less awkward, etc. than would otherwise be the case. Thus, the user can maneuver the fan assembly  1302  into the proximity of the base/riser  1304 / 1303  and roughly align the corresponding coupling halves  1802  and  1804 . Moreover, the user can then latch the coupling in place with a twist. In the alternative, or in addition, types of couplings other than twist-on/off couplings can be used to couple the various assemblies together. For instance, bayonet fittings could be used. Of course, the user could install the fan assembly  1302  with a riser  1303  attached thereto if desired. 
     In some embodiments, the user can attend to certain electrical portions of the installation. For instance, the user can place the thermostat  2012  at a location where it can sense temperatures in (or associated with) the crawl way  105 . See reference  2120 . If the thermostat is a component of the fan assembly  1302 , the user might not need to do so though since it could be pre-located in the fan assembly  1302  (or attached thereto) during manufacture. In accordance with embodiments though, the user can connect the connectors  2020  to line power if desired. See reference  2121 . 
     Method  2100  also shows that the user can mount a solar panel to the fan assembly as at reference  2122 . If the solar panel  1306  is a separate component of the fan assembly  1302 , the user can also connect the connections  2022 . Additionally, in accordance with embodiments, the user can point the solar panel  1306  toward the sun by adjusting the adjustable brackets  1308  and, perhaps, locking them it in a selected position. Note also that with angled risers, the installation of the angled riser (disclosed elsewhere herein) can include adjusting the orientation of that angled riser to be compatible with obtaining a satisfactory “sun angle” for the solar panel  1306 . See reference  2124 .  FIG. 21  also shows that the user can turn the fan on as indicated at reference  2128  and/or verify its operation. 
     At some point, though, it might become desirable to change the fan. For instance, use of the building, occupancy of the building, heat loads, etc. could change or the user might desire a different fan. See reference  2130 . Thus, the user could select another fan assembly  1302  and/or riser(s)  1303 . Since the base  1304  is already installed, the user need not select another base  1304  although they could. See reference  2132 . Such features allow suppliers of these fans to reduce their stocks of fans since they can mix and match fan assemblies, risers, bases, etc. as desired by end users. Moreover, here, the user could then repeat all or portions of method  2100  as indicated at reference  2134 . Note that if the inter-change of a fan assembly is interrupted for some time, covering the aperture of the riser is generally easier, more convenient than trying to cover a raw penetration through the roof. For instance, a plastic bag can be stretched over the riser to close the aperture as opposed to having to place a tarp over a penetration and some how securing the tarp and excluding runoff from entering the penetration anyway. Of course, if the user is satisfied with the fan as installed or for other reasons, method  2100  can end. 
       FIG. 22  illustrates a quick attachment coupling for multi-piece fans. The multi-piece fan  200  of the current embodiment comprises two assemblies  2202  and  2204  which can be bases, risers, fan assemblies etc. As  FIG. 22  illustrates the multi-piece fan  2200  includes a quick attachment coupling  2240 . In the current embodiment, the quick attachment coupling  2240  includes a flexible detent  2250 , catch, dog, pawl, ratchet, etc. and a post  2256  or other protrusion which the flexible detent  2250  can engage. When the two assemblies  2202  and  2204  are mated, the post  2256  (on one assembly  2202 ) extends through an aperture  2252  defined by the other assembly  2204 . The flexible detent  2250  operationally couples with the assembly  2204  which defines the aperture in the current embodiment. The flexible detent  2250  can be made of metal, plastic, etc. 
     Moreover, the flexible detent  2250  is positioned relative to the aperture  2252  (and/or the post  2254 ) such that when the assemblies rotate and/or twist relative to one another, the flexible detent  2250  engages the post and flexes allowing the post  2250  to pass relative to itself. A hook  2260  defined by the flexible detent  2250  can then catch on the post  2254  thereby securing the assemblies  2202  and  2204  to each other. Note that the flexibility of the flexible detent  2250  (and/or shape of the hook  2260 ) can be selected so that some select amount of torque must be applied (in the opposite direction of rotation) to overcome the detent and free the flexible detent  2250  from the post  2252 . In the alternative, or in addition, the quick attachment coupling  2240  can be disengaged, manually, with a tool, etc. by pressing on, pulling, etc. the flexible detent  2250  and/or post  2252 . 
     While certain terms have been used herein which might imply certain directions or orientations, these terms are used merely for the sake of convenience and are non-limiting. For instance, the term “height” is a dimensional term as used herein but does not imply that that dimension necessarily lies along a vertical or even approximately vertical direction. Thus, fans, fan assemblies, risers, bases, etc. of embodiments disclosed herein are not limited to any particular orientation. 
     Embodiments provide two-piece fans with highly efficient solar panels. These solar panels can be monocrystaline and can produce 22 watts at 17.6 VDC/1.22 amps. Fan motors of embodiments can be brushless, high reliability, high efficiency motors capable of operating at 6-100 VDC and in some embodiments (more specifically 12-36 VDC). Moreover, fans of embodiments can include sets of five nylon/polymeric blades. Fans comprising such motors and blades can ventilate areas of 1800 square feet and can induce  1300  CFM (cubic feet per minute) and/or more or less airflow. In some embodiments, the fan assemblies include one AC motor wired to interconnects at which it can receive AC power (for instance 120 VAC) from the building power system and one DC motor wired to interconnects at which it can receive DC power from a solar panel and/or other source. 
     Housings of embodiments can be made from aluminum, galvanized steel, various plastics such as automotive grade ABS, high-impact resistant plastic, etc. Housings of the current embodiment can also be UV (ultraviolet) stabilized and can include embedded fire retardant resin(s). These housings can also be configured to double lock with their respective (and separate) bases. In embodiments, the double locking can be via keyhole standoffs which guide the two connecting pieces together. A flexible metal pin on one or the other of the mating pieces/assemblies can be configured to snap in place to secure the assemblies together. Because the bases and housings/fan assemblies of embodiments are separate components, installation, support, maintenance, etc. can be easier than with heretofore-available fans. In some embodiments, fan assemblies can be about 24″ by about 24″ by about 7″ in size and can weigh about 26 pounds. Bases of the current embodiment can be about 28″ by about 28″ by about 11.″ Furthermore, fans of embodiments comprise thermal switches and thermoballs (and/or other devices capable of measuring temperature which can regulate the various fans disclosed here) on (for instance) 36″ cables. 
     Two-piece fans of embodiments convert passive ventilation to active ventilation and can extend the life of roofs, AC units, stored valuables, etc. and can reduce moisture and mildew. Two-piece fans of embodiments are resistant to even extreme weather and windstorm rated and certified. Such fans reduce HVAC costs and cooling cycles. They also increase air exchanges so that even if solar heat causes temperatures to soar in attics, crawl spaces, and the like, properly balanced fans of embodiments increase air exchanges to as many as ten times per hour. The increased air exchange in accordance with embodiments keeps living spaces cooler and saves building owners money. 
     CONCLUSION 
     Although the subject matter has been disclosed in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts disclosed above. Rather, the specific features and acts described herein are disclosed as illustrative implementations of the claims.