Step 1: For each window/door add the length + width and multiply by 2, then add 24"
Step 2: Add all opening sizes together to find the total linear feet
Step 3: Multiply by 1.15 for waste
Step 4: Divide this total number by 94.5" for the overall number of flanges needed
Step 5: Take the total linear feet from step 3, remove 30%, then divide by 22 for the total number of tubes needed
Step 6: There are 12 tubes in each case. Use this to find the necessary number of cases and single tubes
Step 7: For each opening apply this formular (length + 1') x (width +1')
Step 8: Add together the totals from step 7 for the overall square footage needed, then mulitply by 1.20 for waste
Step 9: Divide the overall total from step 8 by 1000' to find the quantity of rolls needed.
Poly sheet is only sold by the full roll so always round up, i.e 1.2 = 2 rolls.