
Wind CalculatorThe wind design calculator is used to calculate the roof edge design pressure required to meet the ANSI/SPRI ES1 Wind Design Standard and the 2003 International Building Code Section 1504.5 "Edge Securement for Low Slope Roof."Why calculator results do not exactly match results using charts in ES1 document Differences between values for the Design Pressure (P) listed on this site and those computed using the ANSI/SPRI ES1 documentation are the result of generalizations of structure heights in producing the ANSI/SPRI ES1 velocity pressure charts. Both the ANSI/SPRI ES1 charts and the Wind Calculator use the same formulas in the SEI/ACSE 702 standard to produce velocity pressure values (q_{z}). However, the ANSI/SPRI ES1 charts show velocity pressure values for a single, generalized height within a range of heights supplied. This method is less exact then by using the true height with the formulas in the SEI/ACSE 702 standard for calculating velocity pressure, as the Wind Calculator does. The most dramatic difference in these two approaches is in exposures B & C since the ANSI/SPRI ES1 charts use a broad range of 060 ft. for its lowest values while using 10 to 20 ft. jumps for the rest of the charts. Less dramatic are the generalities in the charts for exposure D since it uses 015 initially then ranges 5 to 20 ft. there after. The smaller the range used, the more similar the Wind Calculator and ANSI/SPRI ES1 final Design Pressure values will be. Since ANSI/SPRI ES1 is a guide to the SEI/ACSE 702 standard, and as such does not reflect the standard in whole, every effort was made to be more exact to the SEI/ACSE 702 standard in calculating out values using the Wind Calculator. For this reason, the results provided by the Wind Calculator should supersede those provided by the ANSI/SPRI ES1 documentation. 
