Bought mine in 1994.
We have a total of 8, with the oldest being just over 10 years old, and the newest is 1 week old. We have equal numbers of Retrotec, and Minneapolis.
My oldest blower door was a metal fan and wood frame. Mid 1980s, when we used to pressurize houses to push the smoke out the cracks and crevices around windows and doors...... I'd love to share a photo of it if ya'll want to see it!
I got mine 1st blower door used in 1993 made in 1992. Before that we used a attic fan on a plywood sheet with 20 pulleys to change speeds. It was +- 30% and took 3-4 hours to set up a "test" I did rent a battery setup with a DC motor in 1988, had 4 lead battery that filled a one ton truck.
My blower door is so old that I keep finding salt on it when it was inundated in Noah's flood.
I have two or 3 from 2010 and 12. Actually I have a full business ( search So cal Craigs weatherization) for sale. Ran over 3000 tests and we never guessed on the reports to CAP, but maybe at the door setup we might say what we thought And yes with enough homes and tests we might get within 2 or 300 points. The Location of your business is the KEY for success in this business. David Starrett
I have done thousands of BD tests over 36 years - we have about 22 BD ranging in age from last year to 1984 (still works fine with modern manometers). We train our auditors to make driveway guesses at BD numbers, and locations of major issues before they go in a house. I can tell you you must have an analytic mind to begin with, and a lot of experience before you can get about half the houses within a 1000+ CFM50 range. I would stress that my guess is in fact a guess and would council my customers to do what the Energy Score website says to do:
"You are encouraged to follow up with a more extensive whole house energy assessment. A whole house assessment often includes the use of diagnostic tools such as a blower door test, and factors in the behavior of your home’s occupants and includes more specific and prioritized energy improvements."
The DOE Home Energy Score may start to see these dwindle. Our assessor claims he can guesstimate the tightness option (they give you a list of good choices) of the home and hit it pretty close with the same impact as entering actual CFM. Certainly not for a novice!
Got it when i was Board Pres. of VHERO, part of an early effort by DOE/EPA to establish HERO,'s in the early 90's.