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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of application Ser. No. 11/116,081, filed Apr. 27, 2005 now abandoned, which claims the benefit of Provisional Application Ser. No. 60/566,673, filed Apr. 30, 2004, the entire disclosures of each hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an enclosed structure that may be attached to the exterior wall of an existing or new building, such structure typically being referred to as a patio enclosure, sunroom, or solarium. More particularly, the invention relates to a patio enclosure having a high proportion of windows and a roof and constructed from a framework of composite members and insulating wall panels. Even more particularly, this invention relates to composite plastic members extruded from material having improved thermal characteristics and stability. Yet even more particularly, the invention is related to beam members used in forming a wall assembly of the enclosure that enables wire services to be concealed, accessed, and routed from the connections at the house to, and for use in, remote areas of the enclosure. 
     2. Description of Prior Art 
     Patio enclosures and sunrooms are not new to the building industry. When adding onto or remodeling an existing home or other structure, many people turn to the patio enclosure or sunroom. Such rooms are relatively easy for trained technicians to construct and are inexpensive when compared to other improvements that can be made to a home, such as remodeled bathrooms or kitchens. These enclosures have traditionally been constructed of an aluminum frame with windows or glass sections. Aluminum sunrooms are shaped with vertical walls that have a curved transition to the roof, although most may have a marquee roof or gable type roof. 
     The following United States patents and patent Publication illustrate various enclosures, non-metallic structural elements used in constructing these enclosures, and the materials used in forming the non-metallic structural elements: U.S. Pat. No. 5,497,594 to Guiseppe et al.; U.S. Pat. No. 5,848,512 to Conn; U.S. Pat. No. 6,003,279 to Schneider; U.S. Pat. No. 6,015,611 to Deaner et al.; U.S. Pat. No. 6,117,924 to Brandt; U.S. Pat. No. 6,248,813 to Zehner; U.S. Pat. No. 6,412,227 to DeZen; U.S. Pat. No. 6,337,138 and U.S. Pat. No. 6,344,504 to Zehner et al.; U.S. Pat. No. 6,460,309 to Schneider; and 2002/0066248 to Buhrts et al. 
     As discussed in Schneider U.S. Pat. No. 6,003,279 and U.S. Pat. No. 6,460,309, aluminum framed enclosures have several disadvantages. The main problem is poor thermal efficiency. Due to the high rate at which aluminum conducts heat, a room constructed from aluminum cannot stay comfortably cool in the summer, without air conditioning, or warm in the winter, without supplemental heating. This drawback results in dramatically increased cooling and heating costs. Further, a high rate of heat transfer can lead to condensation on the interior surfaces of the aluminum structures. Moreover, many of the windows in aluminum frame type sunrooms are generally installed in such a way that the windows cannot be opened and no screens are present. 
     Another disadvantage is high maintenance. Aluminum must be painted if chipped and is easily dented. Construction of aluminum rooms is a major disadvantage as well. Because of the nature of the metal, the aluminum pieces must be assembled with external fasteners. External fasteners increase the time of assembly and degrade the overall aesthetics of the room. 
     In light of these various deficiencies, Schneider U.S. Pat. No. 6,003,279 discloses various structural members, which include reinforced and non-reinforced polyvinyl chloride extrusions, which are joined together at joints using hardware which cannot be seen from inside or outside the enclosure, thereby enhancing the aesthetic appeal of the enclosure. Further, Conn U.S. Pat. No. 5,848,512 and Schneider U.S. Pat. No. 6,460,309 disclose an I-beam that is extruded from plastic and configured such that the vertical spacer wall defines a central passageway that extends between the opposite ends of the beam. Schneider U.S. Pat. No. 6,460,309 is directed to a vinyl roofing system utilizing the channel beam to interconnect roof panels with a roof cap. 
     In obviating certain of the problems associated with unwanted condensation and thermal conductivity, many framing enclosure designs have used a “sleeve” approach wherein the aluminum elements and sections are enclosed within PVC frames. A drawback to this approach is that the aluminum reinforcing still has to be properly insulated from the rest of the vinyl profile. This approach results in massive, bulky sections with high material costs. 
     A need continues for a low maintenance sunroom/patio enclosure that is economical, has improved thermal efficiency and minimizes thermal condensation arising from thermal transmittance, provides sliding or double hung windows and/or doorway, has an aesthetic appearance, conceals connecting fasteners, and employs fastening components that are easy to use when erecting the enclosure. 
     Accordingly, a primary object of this invention is the provision of a sunroom/patio enclosure that obtains the benefits of framing elements and sections of polymeric and like material, and achieves the above noted needs. 
     Another object of this invention is the provision of a sunroom/patio enclosure using frame elements formed of composite PVC to allow parts to have smaller cross-sections without a great degree of internal reinforcing. 
     As is known, steel has much lower conductivity to thermal loss than aluminum, and has higher strength properties with lower cost. 
     Accordingly, another object of this invention is the elimination of most if not all aluminum components from the enclosure product, such as by replacing some frame connecting elements with galvanized steel. 
     Another object of this invention is the provision of an enclosure structure that shows no screw heads on the inside or the outside of the enclosure room. 
     A further object of this invention is the provision of an enclosure structure comprised of composite PVC to combine the properties of wood with the maintenance free advantages of vinyl. 
     A further object of this invention is the provision of an enclosed patio structure and the like, that is built onto an existing building, such as a residential house having connectivity to a source of electricity, cable, phone and like services, and enables wiring from these services to be routed from the house and used in areas of the enclosure remote to the house. 
     A significant object of this invention is the provision of a wire raceway that enables wires to be routed, in a concealed but accessible manner, from a source operably associated with the house, to a remote area of the patio room. 
     An aspect of this invention is the modification of beam structure wherein horizontally and vertically disposed header and post beams may be configured to enable a snap-fit interconnection and also a means by which a bundle of like or different wires may be concealed in the beam structure and routed through the header beam and distributed into one or more of the post beams, laterally spaced from one another and in different wall assemblies, and thus provide various services at different locations of the room but remote from the house. 
     To enable access to the wires, such as for routing, repair, and/or connection to terminal boxes, a removable cover plate is snap-fitted to the header beam to permit easy access to the wires therein and routing the wires therethrough and into and through various of the post beams and one or more removable outlet plates snap-fitted about outlet openings in the post beams. 
     SUMMARY OF THE INVENTION 
     Briefly described the objects of the present invention are achieved, in a room structure for attachment to the exterior wall of a building mounted on a foundation adjacent to said exterior wall, said room structure comprising an upright frame assembly having an upper end and formed by at least one enclosure wall and a roof structure extending between said exterior wall and the upper end of said frame assembly, said frame assembly including at least one vertically disposed support member. In particular, an improved room structure according to this invention integrates a wire service raceway into horizontal and vertical header and post beams, the raceway being closable for aesthetic purposes but accessible for appropriately routing one or wires to one or more post beams disposed at different room location. 
     In a first preferred embodiment according to this invention, there is provided a room structure attached to a building, comprising 
     a wall assembly including at least one horizontally disposed header beam and at least one vertically disposed post beam for supporting the header beam, said header beam and post beam being configured to pass an electrical service wire from the building to the post beam, in an accessible but concealed manner, wherein to provide electrical services to the room structure at a location remote to the building, wherein 
     said post beam includes opposite end portions and closed chamber extending between the ends thereof, 
     said header beam includes opposite and portions and outwardly open first and second channels at right angles to one another, said first channel including an outlet, 
     means for connecting one end portion of the post beam to the second channel to form a right-angled structure with the outlet registered with the chamber, 
     a cover plate for removably covering said second channel to form an closed yet accessible raceway for receiving, concealing and passing said wire, at least in part, through said first channel and into said chamber, and 
     an outlet plate for accessing the chamber, said outlet plate being distal to the one end portion of said post beam to access said electrical wire in the post beam. 
     In a second embodiment according to this invention, there is provided an improvement in a room structure for attachment to the exterior wall of a building mounted on a foundation adjacent to said wall, said room structure comprising a wall assembly including at least one horizontally disposed header beam and at least one vertically disposed post beam for supporting the header beam, the improvement wherein 
     said header beam and post beam are configured to pass an electrical service wire from the building to the post beam, in an accessible but concealed manner, wherein to provide electrical services to the room at a location remote to the building, wherein 
     said header beam includes a downwardly open first channel and an outwardly open second channel, said channels at right angles to one another, 
     said post beam is generally H-shaped and includes a pair of first wall elements at right angles to a pair of second wall elements, the wall elements forming outwardly open third and forth channels and a central box chamber that extend between upper and lower end portions of the beam, wherein one of said third and fourth channels is adapted to receive the edge of a wall panel of said wall assembly and one of said end portions is received in the downwardly open first channel of said header beam, 
     first means for covering said second channel to form a concealed raceway for receiving and passing said wire, at least in part, 
     second means for removably connecting said one end portion of said post beam to said header beam, and 
     third means for passing electrical services from the header to the other end portion of the post beam. 
     According to the improved room structure, said second channel is formed, at least in part, by upper and lower wall elements, and said first means for covering comprises a cover plate, said cover plate being coextensive with the outwardly open second channel and including a pair of resilient fingers, each finger having a free end that is spaced from the plate and interfittable within said second channel, and one and the other of said pairs of fingers and said pair of wall elements having a locking hook and locking recess that interlocks with a locking hook when the fingers are interfitted within the second channel. 
     The first means comprises said cover plate being removably connected to the header, said cover being generally planar and vertically disposed in parallel spaced relation to the wall assembly when connected to the header and including an upper closure portion, from which the fingers extend, and a lower skirt portion, juxtaposed with the wall assembly, removal of the cover plate being effectuated by insertion of a tool in the space between the skirt portion and the wall and urging the skirt portion away from the wall assembly and the fingers from latched engagement with the lock recesses. 
     The third means comprises the second channel including an opening, wherein connection of the header beam and the post beam registers the opening with the box chamber to enable a service wire to pass through the header and downwardly through the box chamber of the post beam. 
     The second means for removably connecting comprises a pair of locking grooves provided in the downwardly open first channel of the header beam, and a locking rib formed on each said first wall element, insertion of the end portion of the post beam into the first channel causing the locking grooves and locking ribs to snap fit into engagement with one another. 
     In a third embodiment according to this invention there is disclosed an improvement in a room structure for attachment to the exterior wall of a building and adapted for use with a power source associated with said building, said room structure comprising a frame assembly including a horizontally disposed header beam, a vertically disposed post beam having upper and lower end portions, a wall panel connected to the header and post beams to form, at least in part, a room closure, the improvement comprising 
     means for concealing and routing a service wire from said building to an area of the room structure remote to the building, said wire having rearward and forward ends with the rearward end thereof connected to the source, said means for concealing and routing comprising 
     said post beam including a closed chamber for receiving a portion of said wire and positioning the forward end of said wire proximate to the lower end portion of said post beam, 
     said header beam including an outwardly open first channel for receiving and passing a portion of said wire proximate to the rearward end of said wire, a downwardly open second channel for receiving and fitting atop the upper end portion of said post beam, and an outlet for passing a medial portion of said wire between the second channel and into the closed chamber of said post beam, 
     first means for removably connecting the upper end portion of said post beam to said header beam, 
     a cover plate, 
     second means for removably connecting said cover plate in covering relation with said outwardly open first channel to form a closed raceway for passing and concealing a portion of said wire, removal of said cover plate exposing and providing access to the wire portion therein, and 
     third means for accessing the forward end portion of said wire in said box chamber. 
     According to this improvement, 
     said first channel includes a pair of wall elements that form an outwardly open U-shape, and 
     said second means comprises said cover plate including a pair of resiliently deflectable latch fingers adapted to be received in said first channel, wherein one and the other of each of said wall elements and each of said latch fingers, respectively, includes a latch hook and a lock recess adapted to engage in a respective lock recess. 
     Further and according to this improvement, 
     said post beam includes respective pairs of spaced apart first and second wall elements that combine to form an H-shape and the box chamber, 
     said second channel is formed by a pair of laterally spaced third wall elements that form a downwardly open U-shape sized to fit about and receive the upper end portion of the post beam with the third wall elements of said header beam in juxtaposed relation with the first wall elements of said post beam, and 
     said first means comprises one and the other of each of said third wall elements and said first wall elements, respectively, includes a groove and a rib, wherein the ribs are adapted to interlock with the grooves when the post beam is fitted into the second channel. 
     Further and according to this embodiment, 
     one of said third wall elements that forms the second channel of said header beam includes an interior face that is juxtaposed against one said first wall element of said post beam and an exterior face, and 
     said cover plate includes an upper first portion and a lower second portion, wherein the upper first portion is disposed in covering relation with the outwardly open second channel and the lower second portion is disposed in covering relation with the exterior face of the header beam when the cover is connected thereto. 
     Additionally, said third means includes an opening in one or the other of said first wall elements proximate to the lower end portion of the box beam and in communication with the chamber thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects, advantages and features of the invention will become apparent from the following description taken in conjunction with the accompanying drawings, which illustrate specific embodiments of the invention. In the drawings: 
         FIG. 1  is an exploded perspective view of a patio enclosure positioned for assembly using a variety of frame members and structural elements according to this invention; 
         FIGS. 1A-1E  are cross-sectional views of structural elements used in assembling the enclosure of  FIG. 1 ; 
         FIG. 2  is an elevation view showing the front side of the patio enclosure of  FIG. 1 , following assembly to an exterior wall of a house; 
         FIG. 3  is an elevation view showing the left side of the patio enclosure of  FIG. 2 ; 
         FIG. 4  is an elevation view showing the right side of the patio enclosure of  FIG. 2 ; 
         FIG. 5  is a section view of the front wall taken along line  5 - 5  of  FIG. 2  showing an H-beam disposed vertically, C-shaped upper and lower track members disposed horizontally, L-shaped flanges securing the opposite ends of the beam to the track members, and connections that extend along the top and bottom ends of the front wall of the enclosure and connect the upper track member to the lower front end of the roof structure and the lower track member to the ground structure; 
         FIG. 6  is a section view of the front wall taken along line  6 - 6  of  FIG. 2  showing a C-shaped channel member disposed horizontally, the bottom edge of a window channel supported on the channel member, the upper and lower edges of a front wall panel received in the channel member and lower track member, and a connection, which extends along and connects the front wall of the enclosure to the ground structure; 
         FIG. 7  is a section view of the front wall taken along line  7 - 7  of  FIG. 2  showing the upper track member, the top edge of the window channel supporting a channel member, the upper and lower edges of a the front wall panel received in the upper track member and the channel member, and a the connection between the upper track member and the roof structure; 
         FIG. 8  is a section view of the right side wall taken along line  8 - 8  of  FIG. 4  showing a channel member, the top edge of a window channel supporting the channel member, the upper and lower edges of a right side wall panel received in the upper and channel members, and a connection between the upper track member and the roof structure, which extends along and between the lower front and upper rearward end of the roof structure of the enclosure; 
         FIG. 9  is a section view of the front wall taken along line  9 - 9  of  FIG. 2  showing two window channels separated by an H-beam, and a pair of L-shaped flanges and a pair of E-shaped filler channels interfitted into oppositely facing outwardly open channels of the H-beam, the flanges for connecting the H-beam to the a track member, and thus to the ground structure; 
         FIG. 10  is a section view of the front wall taken along line  10 - 10  of  FIG. 2  showing opposite edges of front wall panels and an L-shaped flange for connecting the beam to the ground structure interfitted into oppositely facing outwardly open channels of the H-beam; 
         FIG. 11  is a section view of the right side wall taken along line  11 - 11  of  FIG. 4  showing a C-shaped track member connected to the exterior wall, a window channel, and an E-shaped filler and an L-shaped flange interfitted into an outwardly open channel of the track member; 
         FIG. 12  is a section view of the right side wall taken along line  12 - 12  of  FIG. 4  showing a track member disposed vertically and connected to the exterior wall and a vertical edge portion of an enclosure panel interfitted into the track member; 
         FIG. 13  is a section view of the left side wall taken along line  13 - 13  of  FIG. 3  showing a C-shaped track member disposed vertically and connected to the exterior wall, a C-shaped track disposed vertically and connected by an L-shaped flange to the lower track, and thus to the ground structure, and a wall panel having opposite vertical edges interfitted into opposed channels of the track members; 
         FIG. 14  is a section view taken along line  14 - 14  of  FIG. 3  showing a box-shaped corner post having opposed channels for connecting the left and front wall panels to one another, and L-shaped flanges for connecting the corner post to a track member of the enclosure, 
         FIG. 15  is an exploded perspective assembly view of another preferred embodiment according to this invention wherein the header and post beams of the enclosure of  FIG. 1  are modified and cooperate with a removable closure cover and cover plate to provide an accessible raceway and electrical services to the enclosure, 
         FIG. 16  is an end view of the header beam, 
         FIG. 17  is an end view of the post beam, 
         FIG. 18  is an end view of the closure cover, 
         FIG. 19  is an enlarged view of a portion of a spring finger of the closure cover of  FIG. 18 , 
         FIG. 20  is a section view taken along line  20 - 20  of  FIG. 15  showing spaced apertures formed in a wall element of the header beam for routing electrical wiring services extending along and through the header beam into a post beam; and 
         FIG. 21  is an elevation view, partially in section, showing the horizontal header beam assembled atop a vertical post beam and electrical wires routed horizontally through a passageway in the header and vertically downwardly through the center of the post beam for connection to a service outlet in the lower end portion of the post beam. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS.  1  and  2 - 4  there is shown an exemplary patio enclosure, generally indicated at  10 , constructed according to the present invention. The enclosure  10  is supported from below by a load-bearing substrate  12  and laterally by the exterior wall  14  of an existing structure, such as a house (not shown). The load bearing substrate  12  may be a concrete slab, wood decking, or the like. 
     As shown in  FIG. 1 , the enclosure  10  comprises a front wall  16 , a pair of lateral side walls  18  and  20 , and a sloping roof  22 . The walls  16 ,  18  and  20  project upwardly from the substrate  12  where they are joined to the roof  22 . The sidewalls  18  and  20  have opposite lateral ends connected, respectively, to the house and a respective lateral end of the front wall  16 . 
     The walls and roof of the enclosure  10  are formed by a framework of joined horizontal and vertical structural members, such as structural filler wall panels  24  and roof panels  26 , multiple pairs of sliding glass windows  28 , framed screens  30  for each pair of windows (one shown), and an optional conventional door assembly  32 . 
     Each wall panel  24  is generally rectangularly shaped and has a central body  24   a  of polymeric material, such as foam, and outer layers  24   b  and  24   c  wherein to provide a wall panel element of generally uniform thickness. The thickness of the wall panel  24  is such that the lateral edges thereof may be interfitted into the squared-C channel of a structural element according to this invention (described in detail below). Preferably, both of the layers  24   b  and  24   c  are clad with vinyl. 
     Preferably and according to this invention, certain of the structural elements used in this assembly are shown and identified on  FIGS. 1A-1E . These structural elements include a corner post  34 , a post or H-beam  36 , a base track  38 , a cross-beam channel  40 , and a filler  44 . As will be discussed below, nails, screws and like threaded fasteners, flanges and like connecting elements are used to connect the structural elements together and form modular wall portions and the patio enclosure  10 . 
     Preferably and according to this invention, each of these structural elements are comprised of a composite PVC material and extruded into the desired cross-section and length. Subsequent to extrusion, a vinyl surface is clad to the exterior surfaces of the structural elements. The resulting element is sometimes referred to a composite PVC element. The structural elements made from the composite PVC material are generally stronger than wood, metal, or vinyl, has no adverse heat conduction, and has the durability of vinyl. Although extrusion is a preferable method, these elements may be injection molded. 
     According to one aspect, the composite material is comprised of a bound together mixture of cellulosic material (esp. sawdust or like finely pulverized dried wood, such as wood flour) and baking flour (e.g., the fine powdery foodstuff obtained by grinding and sifting the meal of a grain, especially wheat, used chiefly in baking). Suitable woods for sawdust are resin-free softwoods such as pine, fir and spruce, and to a lesser extent, hardwoods. The percentage of sawdust to baking flour, measured by weight or volume, and a binder and/or mixer ingredient used to hold the composition together is determined, in part, on a cross-section property of the structural element that is desired (i.e., thickness and area moment of inertia of the cross-section). 
     Referring to  FIG. 1A , the corner post  34  is box-like, in cross-section, axially elongated, and formed by walls  46 ,  48 ,  50  and  52 . The walls intersect with one another to form a square central opening  54  and outwardly open squared-C shaped channels  56  and  58  for receiving the lateral edge of a wall panel  24 . The walls  46  and  52  form an exterior corner with the outwardly facing surfaces  46   a  and  52   a  thereof clad with vinyl. 
     Referring to  FIG. 1B , the post or H-beam  36  is axially elongated and includes a central body  60  and a pair of transverse flanges  62  and  64 , which define oppositely facing squared-C shaped channels  63  and  65 . The exterior surfaces  62   a  and  64   a  of the flanges  62  and  64  are clad with vinyl and the central body  60  is hollow and defines a central rectangular-shaped passageway  66 . 
     Referring to  FIG. 1C , the base track  38  is axially extending and includes a flat base member  68  having opposite lateral edges  68   a  and  68   b  and a pair of opposed L-shaped arms  70  and  72 , the arms being spaced apart and defining a track  73  therebetween. The L-shaped arms  70  and  72  are generally perpendicular to the plane of the base member  68  and define opposed squared-C shaped channels  70   a  and  72   a  that are in faced relation and communicate with the central track  73 . The arm  70  extends along and upstands from the lateral edge  68   a  of the base member  68 . The arm  72  extends along and upstands from the base member  68  at a location inwardly of the lateral edge  68   b  of the base member  68  wherein to define an offset base portion  69 . The exterior surfaces  70   b ,  72   b , and  69   a , respectively, of the upstanding arms  70  and  72  and the offset base portion  69  are clad with vinyl. 
     Referring to  FIG. 1D , the cross-beam channel  40  is axially extending and forms a generally squared-C shape in cross-section. The channel  40  includes a base member  76  and a pair of opposed upstanding legs  78  wherein to define a squared-C shaped channel  80  having a width adapted to receive the lateral edge of a wall panel  24  interfitted therewithin. The base member  76  is hollow and defines a central rectangular shaped passageway  77 . The exterior surface  76   a  and  78   a , respectively, of the base member  76  and the legs  78  are clad with vinyl. 
     Referring to  FIG. 1E , the filler  44  is axially extending and generally E-shaped in cross-section. The filler  44  includes a flat base  82  and three upstanding legs  84 ,  86 , and  88 , the legs  84  and  88  being outer legs and upstanding from the opposite respective lateral edges of the filler, and the leg  86  being a central leg upstanding from a central location of the base  82 . The legs  84  and  86 , and the legs  86  and  88 , respectively, cooperate to form two squared-C shaped channels  85  and  87 . The exterior surface  82   a  of the central base member  80  is clad with vinyl. 
     As shown in FIGS.  1  and  2 - 4 , the front, left, and right walls  16 ,  18  and  20  of the enclosure  10  are assembled by the formed by various of the structural elements  36 ,  38 ,  40 ,  42 , and  44  and wall panels  24 . As shown in  FIG. 2 , the front wall  16  is defined by and extends between two box-beams  34  and includes two H-beams  36  wherein to define three modular wall portions, each portion including a window framing  28  and wall panels  16 . As shown in  FIGS. 3 and 4 , the left and right side walls  18  and  20  are defined by and extend between a box beam  34  and a base track  38 . The right side wall  20  includes an H-beam  36  and defines two modular wall portions and the left side wall  18  includes optional door framing  32 . 
     As shown in  FIG. 5 , the modular wall portion of the front wall  16  includes elongated lower and upper base tracks  38 , denoted as  38   a  and  38   b  and disposed horizontally, and an H-beam  36  disposed vertically. L-shaped flanges  90  are secured at predetermined locations along the lower and upper base tracks  38   a  and  38   b  and serve to properly space and position the H-beams  36  and the corner box-beams  34  in a manner to receive wall panels  24 , or door or window framing  28  and  32 . 
     The lower base track  38   a  is positioned atop the substrate  12  and secured thereto by an L-shaped flange  90  and at least one threaded fastener  92 . The flange  90  has opposite legs  90   a  and  90   b  and is nested in the track  73  formed between the opposed L-shaped arms  70  and  72  of the base member  68  with the flange leg  90   a  seated atop the base member  68  of the base track  38   a  and the flange leg  90   b  extending vertically upwardly from the base track. Fasteners  92  extend through the flange leg  90   a , the base member  68 , and into the substrate  12 . 
     The upper track  38   b  forms the upward vertical extension of the front wall  24  and is secured, at least in part, to the upward vertical extension of the H-beam  36 . As with the track  38   a , the upper track  38   b  is provided with positioning flanges  90 . 
     The lower and upper ends  36   a  and  36   b  of the H-beam  36  are nested into a respective track  73  formed between the opposed L-shaped arms of each respective track  38   a  and  38   b . So positioned by the flanges  90  secured to the lower and upper tracks  38   a  and  38   b , the flange leg  90   b  extending upwardly from the lower track  38   a  is threadably secured to the lower end portion of the H-beam, and the flange leg  90   b  extending downwardly from the upper track  38   b  is threadably secured to the upper end portion of the H-beam. 
     A wall panel  24  is inserted downwardly into the opposed squared-C channels of successive H-beams  36  or corner post  34  and H-beam  36 . As can be seen in  FIG. 5 , the protective outer layers  24   b  and  24   c  of the panel  24  are generally coextensive (i.e., flush) with the outward extension of the flanges  62  and  64  of the H-beam  36 . 
     The upper track  38   b  forms a closure cap and support for a forward lower front end of the roof structure  22 . To provide support and sealing, an axially elongated, generally cylindrical strand  94  of elastomeric material is supported atop the upper track  38   b , on the extended base portion  74  thereof, and supports and moisture seals the roof structure  22  of the enclosure  10 . 
     As shown in  FIG. 6 , a cross-beam channel  40  is interfitted onto and supported atop the upper lateral horizontally extending edge of the wall panel  24 . Further, window framing  28  is thereafter supported atop the cross-beam channel  40 . 
     As shown in  FIG. 7 , a cross-beam channel  40  is interfitted onto the lower lateral horizontally extending edge of the wall panel  24 . Further, window framing  28  is thereafter abutted against the cross-beam channel  40 . In a manner described in connection with  FIG. 5 , the upper track  38   b  and strand  94  are shown in relation to the roof structure  22 . 
     As shown in  FIG. 8 , the upper track  38   b  of the right wall  20  is shown supporting the roof structure  22 . The right wall  22  includes an upper track  38   b , a wall panel  24 , and window framing  28 . Because the upper end of the right wall  20  angles upwardly and is supporting relation with the bottom surface of the roof structure  22 , the support strand  94  is not needed. Further, the base portion  74  extends in a direction outwardly of the enclosure  10 . 
     As shown in  FIG. 9 , an H-beam  36  is shown separating two window framing sections  28 , and L-shaped flanges  90  are connected to opposite sides of the central body  60  extending between the flanges  62  and  64  of the H-beam. Importantly, an E-shaped filler  44  is inserted into each of the two opposed squared-C channels  63  and  65  of the H-beam. 
     According to this invention, the cross-sections of the filler  44  and the squared-C channels  63  and  65  of the H-beam are such that the filler  44  forms, with the flanges and channels of the H-beam, a closure that makes the beam and filler elements appear as one unitary structure. That is, the base surface  82   a  of the filler  44  and the surfaces formed by the lateral edges of the respective flanges  62  and  64  are substantially coextensive with one another. The interfitment between the outer legs  84  and  88  of the filler  44  and the interior facing walls of the flanges  62  and  64  results in a snug frictional snap-fit interengegement. 
     As shown in  FIG. 10 , the opposed squared-C channels  63  and  65  of an H-beam  36  are shown receiving opposite respective lateral vertical edges of a respective pair of panels  24 , and a flange  90  positioning the H-beam  36 . 
     As shown in  FIG. 11 , a track  38  is disposed vertically and connected to the existing structure  14 , and window framing  28  of the left side wall  18  is shown relative to the track. 
     Further and according to this invention, the cross-sections of a filler  44  and the central track  73  of a base track  38  are such that the filler  44  forms, with the central track  73 , a closure that makes the two elements appear as one unitary structure. The interfitment between the outer legs  84  and  88  of the filler  44  and the interior facing ends of the L-shaped arms  70  and  72  of the base track  38  results in a snug snap-fit frictional interengagement. 
     As shown in  FIG. 12 , a base track  38  is threadably fastened to the exterior wall  14  and the vertical lateral edge of a wall panel  24  is interfitted within the track  73  formed between the opposed L-shaped arms  70  and  72  of the base track  38 . 
     As shown in  FIG. 13 , a base track  38 , a wall panel  24 , and a cross-beam channel  40  extend vertically upwardly from their connection to a horizontally extending lower base track (not shown). The opposite lateral vertically disposed edges of the wall panel  24  are interfitted within the central track  73  and squared-C channel  80  formed by the vertically disposed base track  38  and cross-beam channel  40 . A flange  90  positions and secures the lower end of the cross-beam channel  40  relative to the lower base track. Further, the cross-beam channel  40  positions associated window framing  28 . 
     As shown in  FIG. 14 , a corner post  34  connects the vertical edges of the left and front walls  18  and  20 . The corner post  34  extends vertically upwardly from the substrate  12  and is connected to two base tracks  38   a , the base tracks extending horizontally along the substrate and at right angles to one another. The two base tracks  38   a  are connected to the substrate  12  by L-shaped flanges  90  in a manner described above. One L-shaped flange  90  is disposed in one base track  38   a  and has a vertical leg  90   a  received in the squared-C channel  56  and threadably fastened to the wall  48  of the corner post beam. The other L-shaped flange  90  is disposed in the other base track  38   a  and has a vertical leg  90   a  received in the squared-C channel  58  and threadably fastened to the wall  50  of the corner post beam. 
     An E-shaped filler beam  44  is snugly interfitted within the squared-C channels  56  and  58  wherein to provide the corner post  34  with a clean aesthetic appearance. 
     As shown in  FIG. 1 , the roof  22  is generally rectangularly shaped, angles downwardly from the exterior wall  14 , and is generally coextensive with the front and side walls  16 ,  18  and  20  of the enclosure  10 . The roof structure includes severally generally rectangularly shaped roof panels  26 , a rearward channel bracket  98 , a forward channel bracket  100 , left and right end brackets  102  and  104 , and a plurality of H-beams  36 . The roof panels  26  are as described for the wall panels  24 . Further, the channels  98  and  100  and end brackets  102  and  104  are comprised of a composite PVC, as described herein above. 
     The rearward channel bracket  98  is mounted to the exterior wall  14  and has an outwardly open channel  98   a  adapted to receive rearward lateral edges of the roof panels  26  and rearward end portions of the H-beams  36 . 
     The forward channel bracket  100  has an outwardly open channel  100   a  adapted to receive forward lateral edges of the roof panels  26  and forward end portions of the H-beams  36 . Further, the channel bracket  100  includes an upwardly open channel  100   b , which forms a gutter or trough for directing water from the roof. 
     The left and right end brackets  102  ands  104  have outwardly open channels  102   a  and  104   a , respectively, for receiving the lateral edge of a roof panel  26 . 
     As assembled, the rear channel  98  is connected to the exterior wall  14 . The rectangular roof panels  26  have their opposite longitudinal edge portions interfitted within the channel  63  and  65  of a respective H-beam  36 , or left and right end bracket  100  and  102 , and their opposite lateral edges ends interfitted within a channel  98   a  and  100   a  in the rearward and forward channel brackets  98  and  100 . The opposite ends of the channel brackets  98  and  100  are connected to the opposite ends of the left and right end brackets  102  and  104 . 
     As contemplated herein, the patio enclosure  10  may be advantageously supplied to the user in kit form, ready to go and for assembly to an existing structure. The kit for constructing an enclosure to the exterior wall of an existing structure would generally comprise the various structural elements as described in detail herein above. 
     In particular, the kit would comprise a plurality of wall panels  24  of predetermined height, width, and thickness, framing structure  28  and  32  for at least one window or door, a plurality of elongated track beams  38 , the track beams forming upper and lower end caps of front and side walls  16 ,  18  and  20  formed by the kit, a plurality of vertical uprights  36  of H-shaped cross section, a plurality of corner posts  34 , a plurality of C-shaped cross-beams  40 , a plurality of closure members  44  of squared-C cross-section, the closure members being snap-fittable into a respective C-shaped channel provided in the H-beam and corner post, and fasteners  90  and  92  for positioning and securing the wall panels, framing structure, track beams, H-beams, corner posts, C-shaped cross-beams, and closure members to one another and the support structure. 
     Preferably, and according to this embodiment of the invention, the track beams, H-beam, corner-post, C-shaped cross-beam, and closure members of the kit are extruded or injection molded of a composite PVC, with predetermined exterior surfaces clad with a vinyl. 
     According to an alternate preferred embodiment of a room structure, as shown in  FIGS. 15-21 , various of the horizontal and vertical header and post beams of the patio enclosure  10  of  FIG. 1  are modified and configured to define passageways through which electrical service wires may be passed. One end of each wire, respectively, is connected to a supply source, such as a terminal or fuse box of the building to which the room structure is attached as a build on, the wire passed through a modified header beam extending horizontally, vertically downwardly and through a modified post beam, and the other end connected to an outlet at the lower end of the post beam. The connection of the wire ends to the fuse box and outlet are not shown herein as being conventional and known to those skilled in the art. 
     The outlet may take different forms, such as for completing electrical connection with a standard electrical connector for passing electricity, or phone and/or cable interconnection, and/or a switch. Also, the outlet may be available inside or coverable with a plate and accessible for use both within and outside of the enclosure. 
     Several wires may be passed through the header and post beam structures. These wires may be separated or branched off and directed through one or more of the vertical post beams to supply electrical service to all parts of the room structure. 
     While described in the context of supplying electricity to the enclosure, the wire could also be for providing electrical connection with a television and/or cable service, comprise a telephone line, or a switch for completing an interconnection to turn on yet another service. The electrical outlet and/or switch may be protectively covered from the elements or accidental touching by children and accessible for use both interiorly or exteriorly of the enclosure. 
     Turning to the drawings,  FIG. 15  is an enlarged view of a portion of the enclosure  10  wherein the horizontally extending lower and upper header beams  38   a  and  38   b  are modified, and identified by the reference numbers  138   a  and  138   b , and at least one of the vertically extending post beams  36  is modified, and identified by the reference number  136 . The post and header beams  136  and  138   b  are similar to the beams  36  and  38   b  shown in  FIG. 1  in that each is longitudinally elongated and of uniform cross-section between the opposite ends thereof. As will be described herein below, one or more wires “W” pass from the house, horizontally and through the upper header beam  138   b , and vertically downwardly and through the upper end portion of a vertical post beam  136 . 
     The horizontally extending lower header beam  138   a  may be modified in a manner like the upper header beam  138   b  and connect in like manner to the lower end of the post beam  136 . 
       FIG. 15  illustrates a medial portion of the header beam  138   b  positioned for assembly atop the top vertical end portion of the post beam  136 , a cover plate  106  positioned for removable connection to the header beam  138   b , and an outlet plate  108  positioned for removable connection to a lower end portion of the post beam  136  and access to the lower end portion of a wire “W”. The medial portion of the header beam  138   b  is shown partially in section and disposed generally horizontally with the dashed lines representing the longitudinally extending portions thereof. The post beam  136  is shown interfitted with rectangular wall or panel sections “P” (shown by the dashed lines). 
     Referring to  FIGS. 15 and 16 , the header beam  138   b  comprises an array of generally planar rectangular shaped wall elements  110 ,  112 ,  114 ,  116 , and  118 . The wall elements are generally at right angles to one another. The wall elements  110  and  112  are at right angles to one another with the wall element  110  being disposed horizontally and the wall element  112  being disposed vertically. The wall elements  110  and  114  extend generally at right angles from the wall element  112  and are in generally parallel relation to one another. The wall element  116  is at right angles to and extends vertically between the wall elements  110  and  114 . The wall elements  118  and  112  extend generally at right angles to the wall element  110 . 
     Further, the wall elements  110 - 118  cooperate to form a closed box chamber  120 , the wall elements  110 ,  116  and  114 , in part, form a U-shaped channel  122 , and the wall elements  112 ,  114  and  118 , in part, form a U-shaped channel  124 . The box chamber  120  extends between the opposite longitudinal ends of the header and preferably is filled with thermal insulation material  126 . The channel  122  is positioned to open interiorly of the enclosure and adapted to form, with the removable cover plate  106 , a closed raceway  128  for passing wires. The channel  124  is adapted receive and seat atop the post beam. 
     Referring to  FIGS. 15 and 17 , the vertically extending post beam  136  is generally “H” shaped, longitudinally extending, and comprises a pair of generally planar, parallel, rectangular shaped wall elements  130  and  132  and a pair of wall elements  134  that are at right angles to and extend between the wall elements  130  and  132 . The wall elements  130 ,  132 , and  134  form, in part, a closed central box chamber  140  and a pair of outwardly opening U-shaped channels  142  and  144 . The channels  142  and  144  are sized to receive a vertical edge of a rectangular wall or panel section “P” (shown by the dashed lines in  FIG. 15 ). 
     Further, according to this invention, the connection between the post and header beams  136  and  138   a  and/or  138   b  is by a snap fit interconnection. In this regard the outer surfaces of the wall elements  130  and  132  of the post beam(s)  136  are provided with a respective transversely extending groove  146  and the inner surfaces of the wall elements  112  and  118 , which form the channel  124  of the header, are provided with a respective rib  148 . 
     In use, the post beams  136  are vertically disposed and the upper and lower end portions thereof, respectively, connected to the horizontally disposed upper and lower header beams  138   b  and  138   a . The panels “P” are interfitted such that their opposite vertical edges are interfitted within opposed channels  142  and  144  and their upper and lower horizontal edges interfitted within the headers. 
     The end portion of the post beam  136  is fitted into the channel  124  of the header beam  138   b  at a sufficient distance to cause the end of the post beam to seat against the wall element  114 . Thereupon, the ribs  148  on the post beam  136  snap fit within a respective of the grooves  146  in the header beam and form an interlocked connection therewith. 
     Further and according to this preferred embodiment of the invention, an accessible concealed passageway is defined for passing wires, as described, through a header beam  138   a  and/or  138   b , and routed through, at least in part, one or more of the vertical post beams  136 . 
     According to this aspect of the invention, and referring to  FIGS. 15 ,  16 ,  18  and  21 , the cover plate  106  is adapted to be releasably connected to the wall elements  110  and  114  of the header beam  138   b  whereby to close the channel  122  and form therewith the accessible wire passageway  128 . The wall elements  110  and  114  are generally parallel to one another and each includes a shaped lock recess  150 . The lock recesses  150  are in juxtaposed mirror image relation with one another and extend in generally parallel relation between the opposite ends of the header. 
     Referring to  FIGS. 18 and 19 , the cover plate  106  comprises a generally planar longitudinally extending rectangular shaped plate  152  having exterior and outer surfaces  152   a  and  152   b  and a pair of resilient latch or locking fingers  154  and  156 . The latch fingers  154 , 156  project outwardly from the upper half of the interior surface  152   b  and at a right angle thereto and terminate in a respective hook  155  and  157 . The latch fingers  154 , 156  are in the form of a cantilever beam and adapted to flex relative to the plate  152 . Preferably, the latch fingers  154 , 156  are generally flat and planar and extend in generally parallel relation to one another between opposite ends of the cover plate  106 . Depending on the application, the latch fingers  154  and  156  may be other than integral and in one piece and be segmented and in sections. 
       FIG. 19  shows detail of the hook  155 , with the hook  157  being a mirror image thereof. The hook  155  is disposed at an angle of about 26° to the latch finger  154  and defines a rearward angled abutment shoulder  159  disposed at about 80° to the finger  154 . The lock recess  150  is complementary to engage with the hook  155  and the abutment shoulder  159  of the locking finger. 
     In use, the cover plate  106  is positioned against the inwardly facing side of the header beam  138   b  and the latch fingers  154  and  156  inserted into the channel  122 , whereupon the hooks  155  and  157  engage the wall elements  110  and  114 , causing the latch fingers  154  and  156  to deflect towards one another. Further insertion results in the hooks  155  and  157  being brought into register and engagement with the lock recesses  150 . So fitted, the cover plate  106  is connected to the header, closes the channel  122  and forms the closed wire raceway  128 . 
     The cover plate  106  is substantially coextensive with and forms an aesthetic cover for the header and the exterior surface of the wall element  118 . 
     Further, the lower half of the cover plate  106  forms a resilient release mechanism or skirt  152   c  for assisting in removal of the cover plate. The skirt  152   c  is adapted to be pried upwardly, such as by the insertion of a tool “T” between the wall element  118  skirt  152   c  formed by the lower half of the plate  152 , whereby to pop the cover plate  106  free from engagement and allow access to the passageway  128  for accessing, routing, repairing and passing wiring through the header  138   b  and respective of the vertical post beams  136 . 
     Referring to  FIG. 21 , the tool “T” is shown as a screwdriver having a flat-headed end. The end of the screwdriver is inserted between the plate  152  and wall element  118  of the header  138   b . As shown by the dashed lines, the skirt portion is flexed outwardly and away from the header, thus urging the hook  157  of the latch finger  156  from connection with the lock recess  150 . in the wall element  114  Further force causes the cover plate  106  to pop out from the channel  122  and be removed from connection to the header. 
     The hooks  155  and  157  and lock recesses  150  could be reversed, wherein the hooks are on the wall elements  110  and  114  and the lock recesses are in the latch fingers  154  and  156 . Similarly, the ribs and grooves could be reversed, wherein the ribs  148  extend outwardly from the wall elements  130  and  132  of the post beam  136  and the grooves  146  are in the wall elements  118  and  112  of the header beam. 
     Further, an appropriate opening or cutout  160  is provided through the wall element  114  of the header beam  138   b , the cutout being proximate to the inlet into the channel  122  and in that portion of the wall element  114  that is defined between the wall elements  118  and  116 . The cutout  160  allows one or more wires W of a wiring bundle to be turned 90° relative to the passageway  128  and directed vertically downwardly and into and through the box chamber  140  of a post beam  136 . 
     As shown in  FIG. 20 , two laterally spaced post beams (shown in dashed lines) are connected to the header beam and the wall element  114  of the header is provided with two laterally spaced cutouts  160   a  and  160   b . Each cutout  160   a  and  160   b  is positioned for directing one or more wires into the box chamber  140  of a respective of the laterally spaced first and second post beams. As shown in phantom lines, a bundle of five wires passes through the channel  122 , with three wires W 2  of the bundle being routed through the outlet  160   a  and into the first post beam and two wires W 1  of the bundle being routed through the opening  160   b  and into the second post beam. 
     Referring back to  FIG. 15 , one or more of the post beams  136  of the enclosure is provided with at least one opening  162  to provide access to the interior passage or box chamber  140  of the respective post beam  136  and access to the free ends of the wiring services routed thereto. Typically, the free end of the wiring terminates at an electrical apparatus, such as to provide connection to a plug-in electrical outlet, jacks for connection to music, cable and phone systems, or a switch, to name a few. The electrical apparatus is in an appropriate wiring box, which box is disposed in the interior chamber  140  of the post beam  136  and fixedly mounted to the inner surface thereof. The wire termination is not shown as being known. 
     The opening  162  is typically covered by an appropriate outlet plate  108  to protectively cover the electrical connections as well as improve the appearance of the outlet. As shown, the outlet plate  108  includes a “squared” access port  108   a  for connection to electrical wiring (such as conventional wire plug outlets) and a “round” access port  108   b  for connection to computer or cable type connections. 
     Preferably, the outlet plate  108  is connected to the post beam  136  in an aesthetic manner. According to this invention, the backside of the outlet plate  108  is provided with ribs  108   c , which conform to and frictionally engage with edge surfaces  162   a  that define the shape of the outlet opening  162 . The outlet plate  108  is releasably connected in a snap fit to the post beam  136  and avoids the use of unsightly screws that would be seen on the front side. 
     Preferably and according to this invention, each of these structural beams  136  and  138  are as described above. Briefly, each is comprised of a composite PVC material and extruded into the desired cross-section and length. Subsequent to extrusion, a vinyl surface is clad to the exterior surfaces of the structural elements. The composite material is comprised of a bound together mixture of cellulosic material, as described herein above. The cover plate  106  is entirely of a suitable polymeric material, and either integrally molded or formed by a suitable extrusion process. 
     While there have been illustrated and described particular embodiments of patio enclosure structure and arrangements according to this invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall within the true spirit and scope of the present invention.

Summary:
An enclosed structure, such as a patio enclosure, sunroom, or solarium, is attachable to the exterior wall of a building, has a high proportion of windows and a roof, and constructed from a framework of composite members and insulating wall panels, wherein header and post beams of the room wall assemblies are extruded from material having improved thermal characteristics and stability. Importantly, the beams enable wire services to be routed in concealed fashion from a power source associated with the building to accessible locations in the room and remote to the building. The header and post beams are configured to enable the wire services to be concealed but yet accessible for repair and routing through the header beams and into one or more post beams, as desired.