GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

HVAC pressure design

jberks | Posted in Mechanicals on

More of a mechanical design question:

My reno presents some interesting challenges regarding the duct work where I’m avoiding vertical chases and bulkheads for ductwork.

I’m doing a 4 zone, low velocity forced air system.

Doing the pressure calcs, specifically the 3rd floor zone I’m getting around 0.7″w.c. Based on the Lennox unit I want, the specs say the max is 1″w.c.

Where I’m afraid is I’ve never installed a furnace on a system like this. So I was wondering if anyone as any experience in this regard of pressure drop of a duct system and unit performance (or issues)

Is 0.3″w.c. a good buffer for pressure?
Can I go right up to 1″w.c. without any issues?
Is there a standard practice pressure value I should be going by?



GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. GBA Editor
    Martin Holladay | | #1

    Assuming that your calculations are correct, then everything should be OK, since 0.7 is less than 1.0.

    At a recent conference, I heard Dean Gamble give a presentation on static pressure. Good stuff. Here is a link to the presentation -- there might be some info in there that helps you:

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |