(a) Equation NA6-3 - VT of Center of Glass (COG) calculation
VTT = VTF x VTC
Where:
VTT = Is the Total Performance of the fenestration including glass and frame
VTF = 0.53 for projecting windows, such as casement and awning windows
VTF = 0.67 for operable or sliding windows
VTF = 0.77 for fixed or non operable windows
VTF= 0.88 for curtain wall/storefront, Site-built and manufactured non-curb mounted skylights
VTF = 1.0 for Curb Mounted manufactured Skylights
VTC = Center of glass VT is calculated in accordance with NFRC 200 Section 4.5.1.1 or NFRC 202 for Translucent Products or NFRC 203 for Tubular Daylighting Devices and Hybrid Tubular Daylighting Devices or ASTM E972 http://www.nfrc.org/software.aspx