referring to fig1 the complete assembly comprises a head assembly 200 , a sill assembly 300 , a mullion assembly 400 and two mirror image jamb assemblies 500 . referring to fig2 the mullion assembly 400 near the head assembly 200 comprises mullion plastic covers 10 that house slotted tubing 18 ( shown in fig4 , 9 and 12 ), self - leveling one - way pressure valves 22 ( shown in fig1 ) and strip nozzles 30 ( shown in fig4 , 8 , 10 and 12 ). a mullion synthetic rubber sealing cap 14 closes off a mullion mounting bracket 26 ( shown in fig4 ) from the elements and is necessary for the aesthetics of the assembly . the head assembly 200 near the mullion assembly 400 comprises a head plastic cover 42 , that houses air supply tubing 38 ( shown in fig6 ) and polystyrene insulation 34 ( shown in fig4 , 6 , and 12 ). a head synthetic rubber sealing cap 46 closes off a head mounting bracket 50 , shown in fig6 from the elements and is necessary for the aesthetics of the assembly . it is slightly different in shape from the mullion synthetic rubber sealing cap 14 but serves the same purpose and function . fig3 shows the head assembly 200 near the jamb assembly 500 . the head assembly 200 comprises a plastic head cap 54 , that closes off the end of the head assembly 200 . the jamb assembly 500 comprises a plastic cover 10 , that houses slotted tubing 18 , a self - leveling one - way pressure valve 22 , polystyrene insulation 34 , and a strip nozzle 30 ( all as shown in fig5 ). fig4 shows half of the mullion assembly 400 , in cross - section along the line 4 -- 4 of fig1 . it consists of a mullion mounting bracket 28 , that is attached to a window mullion with screws through holes 27 . the plastic cover 10 , locks in place at a groove 13 in the mounting bracket 28 , and is held in place with fastening screws 29 . a strip nozzle 30 , fits into the plastic cover 10 through grooves 32 , in the strip nozzle 30 . this allows for a variety of jet arrangements and sizes in the assembly . the slotted tubing 18 is bonded to the strip nozzle 30 with adhesive prior to installation . this arrangement allows for a variety of slotted tubing sizes to be used . the slotted tubing and strip nozzle assembly is protected from exterior elements by the polystyrene insulation 34 . the plastic cover 10 , is angled to provide a deflecting surface 11 , to recirculate the vented air over the window area . only one side of the mullion assembly 400 , is illustrated here for simplicity . with both sides in place , the mullion synthetic rubber sealing cap 14 is snapped onto the mounting bracket center ridge 25 . the weather grooves 15 prevent moisture and air from penetrating the assembly , and make a firm seal to the plastic covers 10 . fig5 illustrates the jamb assembly 500 in cross - section along the line 5 -- 5 of fig1 . the slotted tube 18 , strip nozzle 30 , insulation 34 , and plastic cover 10 are similar in form and assembly to those illustrated in fig4 . the jamb mounting bracket 58 , is designed differently for a single strip nozzle assembly , as is the jamb synthetic rubber sealing cap 46 . function and installation of the assembly is identical to the mullion assembly 400 , illustrated in fig4 . fig6 is a cross - section of the head assembly 200 along the line 6 -- 6 if fig1 . it comprises a mounting bracket 50 having an edge lip 51 and a center ridge 53 attached to the window head with screws through holes 52 . a head plastic cover 42 hooks onto the edge lip 51 at one end . the other end of the head plastic cover 42 is fastened to the mounting bracket 50 with fasteners 29 . the head plastic cover 42 houses air supply tubes 38 , that are protected from the exterior elements by polystyrene insulation 34 . a synthetic rubber sealing cap 46 snaps onto the center ridge 53 , and weather grooves 15 in the sealing cap 46 prevent moisture and air from penetrating the assembly . the air supply tubes 38 , penetrate through the assembly mounting brackets at the jambs and mullions , as shown in fig2 and 6 . the other end of the air supply tubes 38 , penetrate the wall or window jamb assembly , and are connected to a centrifugal fan of conventional design ( not shown ) located at the structure &# 39 ; s interior , or are part of the exhaust air ducts ( or grill assembly ) in the h . v . a . c . system . ventilated air is drawn into the centrifugal fan , through the air supply tubes 38 to the slotted tubing 18 , and is exhausted through the jets 31 , shown in fig4 , 8 and 10 , across the exterior of the window surface . generally , the head assembly 200 would not include strip nozzles or slotted tubing , unless a specific application demands it . fig7 is a cross - section of the sill assembly 300 along the line 7 -- 7 of fig1 . parts 50 , 42 , 46 , and 29 are identical to those parts illustrated in fig8 of the head assembly 200 . the air supply tubing 38 , and polystyrene insulation 34 , are generally omitted from the sill assembly 300 , unless a specific application dictates the need . this is true for the strip nozzle 30 , and slotted tubing 18 , in the assembly also . unique to the sill assembly 300 , is the sill camber 68 . it is a separate piece with a 5 degree slant , installed to prevent water from accumulating on the sill . fig8 illustrates the strip nozzle 30 in elevation view as part of a jamb assembly 500 or a mullion assembly 400 . only one of the jets 31 , through which the vented air is passed , is illustrated for simplicity . obviously , it is preferred that each strip nozzle 30 be provided with a plurality of jets 31 . expansion grooves 33 , allow for the expansion or contraction of the assembly cover 10 , and strip nozzle 30 . the air supply tubes 38 , are shown where they enter the assembly at the self - leveling one way pressure valve 22 , shown in fig1 . fig9 a and 9b show side and end views of the slotted tubing 18 . a variety of sizes will accommodate a variety of applications and demands . plastic is suitable for low pressure applications , but other materials can be substituted depending on the design conditions . the slotted tubing 18 , is capped off on one end with a tubing cap 19 ( shown in fig9 c and 9d ), which is bonded to the slotted tubing 18 , with adhesive prior to installation . fig1 a , 10b and 10c show the strip nozzle 30 , again with only one jet 31 shown for simplicity . fig1 a is a front elevational view showing the jet 31 , fig1 b is a cross sectional view showing the strip grooves 32 that lock into the plastic cover 10 , and fig1 c is an interior view along the line 10c -- 10c of fig1 b . the interior edges 37 of the strip nozzle 30 are to be bonded to the exterior edges of slot in the slotted tubing 18 , preferably with adhesive , in order to create an airtight unit before assembly . separately manufacturing the strip nozzles and slotted tubing and then bonding them together allows for a variety of nozzle designs to be used for different applications . of course , the strip nozzles and slotted tubing also could be integrally formed , resulting in a nozzle tube having a plurality of spaced transverse air jets . fig1 a , 11b and 11c show the self - leveling one - way pressure valve 22 , which allows vented air to enter the slotted tubing 18 from the air supply tubes 38 , but prevents a reversal of this air flow . fig1 a is an end view of the valve 22 showing the inlet port cap 24 and the extended levelers 25 . the levelers 25 are configured to close the inlet port cap 24 when there is no air flowing out of the air supply tubes 38 or when the pressure in the slotted tubing 18 is greater than the pressure in the air supply tubes 38 , which could be caused by , for example , gusts of air . fig1 b illustrates the valve in the closed position and fig1 c illustrates the valve 22 in the open position . of course , other valves of conventional design could be employed instead . it is preferred to provide a transition duct ( not shown ) between the fan and the air supply tubes because the diameter of the tube probably will be smaller than the diameter of the fan and because one fan can be used in conjunction with a plurality of air supply tubes . the size and configuration of the transition duct would vary depending on the size and configuration ( round , square , oval , etc .) of the air supply tubes and the number of air supply tubes serviced by the fan . it is further preferred to provide a damper in the transition duct connected to the control unit to control pressure / flow characteristics , so that if the one way pressure valve 22 is closed , the air will be ventilated through the normal outflow channels . fig1 illustrates an alternative embodiment , in which the strip nozzle 30 , slotted tubing 18 and polystyrene insulation 34 are integrally formed into an entire window jamb assembly 62 or mullion assembly 61 , instead of being retrofitted . in this embodiment , the glass 65 also has seals 64 and stops 63 . the invention has been disclosed with respect to particular preferred embodiments . it will be apparent to those in the art that many modifications and alterations can be made to the disclosed embodiments without departing from the spirit or scope of the invention . for example , the air supply tubing and slotted tubing can be of any cross section , not just round . for a further example , the strip nozzle and the slotted tubing can be integrally formed into a tube having air jet apertures . for a still further example , the control unit could be merely a switch . for a still further example , the air jet apertures could be located at the corners of the windows and could direct air diagonally across the window . for an even further example , the air jets need not be aligned and transverse and the air supply tubes and nozzle tubes could be integrally formed . moreover , the air jet apertures could be located in or on any part or parts of the window frame , including the head and the sill . accordingly , no limitations are to be inferred or implied except as specifically set forth in the appended claims .