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

Understanding blower door numbers. Air seal to 62.5 cfm 50

Will R | Posted in General Questions on

I’m trying to understand a number that I was given by mass save. I convinced them to reconsider air sealing and they’ve agreed. They’ve proposed to air-seal to “62.5 cfm50.” How do I convert that to ach50? I had a blower door test done already which found “20,980 cubic ft.; 2600 cu ft/min = 156,000 cu ft/hr. hence 7.4 air changes/hour.” which included our basement. 5.7 ach50 with basement door closed. Zone 5, outside of Boston, 1915, 1.5 level bungalow, 1620sqft which does not include the basement. 

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.

Replies

  1. Trevor Lambert | | #1

    You've got the formula right there. 62.5*60/20980= 0.18 ACH50.

  2. Will R | | #2

    Thank you. I didn’t think this was correct though. Mass Save is not air sealing to less passive house standards.

  3. Trevor Lambert | | #3

    Maybe they've got an errant decimal point.

  4. Jon R | | #4

    I suspect they meant 62.5 cfm ACHnat. Which is around 3 ACH50.

  5. Will R | | #5

    Jon, I believe that makes the most sense. Not a decimal error because I’ve seen others with similar quotes. Thanks!

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |