If dialog below is to unclear I think I can figure it out using 45 degree distance if I knew the following: 1. What is the distance to subtract from the 45 degree distance for the two 45 elbows on each end? Is 3.54" per 45 degree elbow correct? 2. What does using a 90 elbow add to the length? Is 7.3" on each end correct? 3. Is 1 1/2 subtracted from each pipe and elbow for joint overlap? Venting for Kozy Heat Slayton using 5x8 double wall Selkirk venting. I need verification this routing will work.(see attachment) It appears to meet the requirements in the Slayton install manual. I could eliminate the second 90 elbow after the FP and replace it with two 45's if I could figure out the math. I plan on using Selkirk as it fits with out an appliance adapter. I would like to use standard pipe if possible, there is a 4-10" adjustable vent if necessary. 1" clearance from combustibles. Here are the numbers necessary to do the math. horizontal from FP Vent connection O.C. through wall =18 3/4". Horizontal from garage wall to center of 24" O.C. garage rafter is 43". Total horizontal run would be from FP vent connection O.C. 18 3/4" +43"=61 3/4". Vertical from FP vent connection to bottom of top sill on interior wall is 42 1/2". Add 3" for a double sill to 45 1/2" from FP to bottom of Garage rafter. The garage rafters are 24" o.c. and run parallel to the FP.