Have HVAC Questions? Ask an HVAC Expert for Answers
Let me ask a couple of questions? What size vent are you using and is it straight up or how many elbows will be in vent?
You can determine total allowable length including any elbows by the charts on pages 51 to 54 in this manual.
Sorry, got called away from my desk. Can you tell me what the altitude is where you live ? Or I may can determine if you tell me where. Then I will calculate for you.