the connector of the solar energy unit in panel 11 e 6 from the building exterior roll down the slab edge membrane 36 and install the slab edge cover 14 a 7 from the building interior snap on the interior base cover 37 and install the head glazing bead 38 the above wiring procedures may be easily completed in open spaces before steps 6 and 7 even though the wiring penetrations in steps 1 and 2 are between the pressure equalized airloop space 41 or 31 and the interior air space 33 they are within the dry segment of the outer airloop therefore the wiring penetrations will not cause water leakage the wiring penetrations in steps 3 and 4 are between pressure equalized airloop spaces therefore they will not cause water leakage fig5 shows a fragmental cross section taken along line 5 5 of fig1 showing the vertical joint between adjacent window wall panels 11 d 11 e the vertical joint between side by side window wall panels 11 d 11 e is formed with a vertical joint member 45 in between and engaged with wall panel 11 d and wall panel 11 e the vertical joint is formed during installation of the wall panels 11 d 11 e and vertical joint member 45 in the manner described in u s pat no 8 001 738 to summarize a preferred installation procedure after installation of base and ceiling positioning tracks and anchoring tracks as shown in fig4 a window wall panel is erected from.