What Size Humidifier or Dehumidifier Do I Need for my Home? Humidity Calculations Demo

This is mathy, but it’s not anything too difficult for anyone to understand I think. There are lots of nuances and caveats, which I think make the whole thing more interesting! Ideal absolute humidity range is ~35-65 grains per pound.

∆Gr/lb = Inside gr/lb - Outside gr/lb

Gr/hr = ∆Gr/lb x CFM x 4.5

Lb/hr = Gr/hr / 7000

Lb/day = Lb/hr x 24

Gal/day = Lb/day x 0.12

Pints/day = Gal/day x 8

Manual J Default Air Leakage Inputs vs. Blower Door Test ACH50

I'm pretty sure the awesome folks who created Manual J (like Hank Rutkowski- hear my interview with him here), and the softwares we use to run the calculations (Elite RHVAC, used here, and Wrightsoft) do not have a lot of personal experience with the test dynamics of home enclosures, and may never have actually used a blower door before. Here's a demonstration of why it's so important to respect the blower door if you're doing HVAC design for residential construction or home improvement.

Learn to perform and analyze Blower Door and Duct Tightness Tests in my 1 Day Training at: https://buildingperformanceworkshop.com/det-verifier

There are two blower door brands, both available at: https://www.trutechtools.com/system-blower-doors-and-duct-testers.html

See a tour of a full Manual J report below: