shelf 146 a sponge gasket 184 is disposed between panel member 120c and pressure plate 138 and a sponge gasket 186 is disposed between panel member 120c and surface 180 of body 178 similarly a sponge gasket 188 is disposed between panel member 120d and pressure plate 138 and a sponge gasket 190 is disposed between panel member 120d and surface 180 of body 178 sponge gaskets 184 186 188 and 190 are preferably substantially identical to sponge gaskets 154 and 156 of fig4 by tightening screws 151 panel members 120c and 120d are secured to and form a weather seal with mullion 110 cover 140 may then be fastened to pressure plate 138 as described hereinabove in connection with sill member 102 mullions 106 108 and 112 are preferably substantially identical to mullion 110 intermediate horizontal members 113 114 and 116 preferably have a substantially identical structure and are preferably made from the same materials as mullion 110 therefore by way of example using a pressure plate 138 and sponge gaskets intermediate horizontal member 114 may be secured to and form a weather seal with panel members 120b and 120c intermediate horizonal members 113 114 and 116 are preferably secured to mullions on each end using conventional shear blocks attached to each mullion and by screwing each end of the horizontal members into a shear block the following technique is preferred to install curtain wall 100 within a building due to the design of the sill members head members mullions and intermediate horizontal members of the present invention curtain.