Ventilation, Diagnostics, and DET Verifier Training Break Down

Done with our first 4-day training at our Atlanta home- save a spot in the next one! This time we had people travel all the way from New York and Texas- remember, we’re 5 minutes from the busiest airport in the world, and this is a state-of-the-art training center. You’ll be happy you made the time for the trip!
https://BuildingPerformanceWorkshop.com/training

First Blower Door and Duct Testing Certification Trainings

Our first 8 newly certified DET Verifiers came through our brand new training center at our home in Atlanta! It was a thrill, honestly, since I haven’t given any in-person trainings in over a year (like most trainers). Everyone passed their certification exams, which doesn’t always happen- they have to earn 80% on both written and hands-on exams with the equipment, and do a bunch of geometry calculations that we all forgot since high school.

They all totally rocked the use of the blower door and duct tightness tester, and are ready to rock the houses in Georgia, South Carolina, Tennessee, Kentucky, Indiana, and Alabama (no joke, that’s where all these folks work). Super happy also that we didn’t have a bunch of last minute registrations, which used to be the bane of my existence. Sold out weeks ahead of time- very grateful!

A few class stats:

Furthest Traveled: Nashville, TN (thanks DocAir for sending 3 of your crew!)

Funniest Pandemic Hobby: breeding fish

Funniest Place to Keep a Calculator: chest pocket of bib overalls

Number of 100% scores on exam: 2 (25%)

Newest DET Verifier Certified in Georgia!

Never taught a DET Verifier training for one before- this should be interesting!

In a customized 1-on-1 COVID-adapted class, Corbett Lunsford trained, examined and certified Treondras Manning, HVAC technician and Georgia’s newest certified Duct and Envelope Testing (DET) Verifier. As a DET Verifier, Treondras is certified to perform blower door tests and duct tightness testing on new construction and renovations in the state of Georgia. He is also one of Corbett’s Mastermind students, and is helping homeowners in the Atlanta area tune the air quality, comfort, durability and energy efficiency of their homes with his building science and diagnostics expertise.

DET Verifier Trainees are taught the accepted blower door and duct leakage test protocols from the book ‘Home Performance Diagnostics: the Guide to Advanced Testing’ written by trainer Corbett Lunsford

Treondras Manning, right before he received his well-deserved certification as a Georgia certified DET Verifier

Watch DET Verifier Treondras Manning test Corbett’s heat pump cabinet for duct leakage in the high performance house his family is building.

DEAR CORBETT: HVAC Equipment Airflow Frustration

Dear Corbett,

I was going thru the videos in the training portal. Overall, I like your videos. However, every now and then, a portion of one leaves me less than satisfied with the answer. Usually, my disatisfaction is because you are rushing through and just skimming the details and explainations. I realize that your trying to limit the video's length and accept it.

However, I found one video that had something that you brought up, but didn't explain that frustrated me enough to write. The video is in the training portal, 'Mastermind Series Jan 2015' at 30:01 minutes in. Your talking about system airflows and you bring up NCI. You go to say how they add up supply airflows, return airflows, and compare it to what the airflow should be to get leakage. You say that that is wrong but don't explain. You finish by saying that system airflow needs to be measured at the blower. 

So, the question I have is: Are you objecting to comparing either the supply or return airflows to what the system airflow SHOULD be (i.e. not measured) or something else?

Would you agree with the following? 
(Equipment airflow) - (sum of supply register airflow) = (supply side leakage)
(Equipment airflow) - (sum of return register airflow) = (return side leakage)

Equipment airflow to be measured at or near the blower by one of the several methods. I am calling it equipment airflow and not system airflow just to be clear that it is what the fan actually produces.

Finally, are you doing full manual J's or just block load calculations to get ballpark numbers?

Thanks,
TJ

-_-_-

Dear TJ-

Great question, and I'm happy to clarify what I meant! Thanks for letting me know when my broad strokes don't actually answer your question and leave you frustrated- I always want to give a full picture of what home performance testing actually means.

My issue with measuring the supply airflows and return airflows, and inferring duct leakage from that is:

1. How do you know what airflow the equipment is producing unless you measure the actual airflow at the equipment? You can use a calculation like 400cfm x tons of A/C, but what if it's heating season, 20 degrees outside, and the NEST thermostat won't let you disable the compressor's service disconnect and still run the air handler? Also, what if the installer targeted 350cfm per ton, or 450cfm?
2. Even if you measure the equipment airflow, you won't be measuring the equipment cabinet air leakage, which is almost always there. In fact, the IECC duct leakage test assumes that 25% of all the duct leakage will be in the cabinet in new construction.
3. The only way to measure duct leakage is to perform a duct tightness test, or for a quicker and more localized look, perform a pressure pan test during blower door testing.
4. Measuring airflow is notoriously difficult. What tool and technique are we using? Pitot tube has high user error, passive flow hood (balometer) is not accurate for residential grilles and low flows, and anemometers need to be corrected for net free area of the grilles. Lots to scratch your head about, and it turns out the best way to measure airflow in the 21st century is still a plastic garbage bag.

To answer your final question, if all you need is a ballpark number, a block load is fine, but I always do a full room-by-room load calculation if I'm being paid to do an actual Manual J.

Hope that helps, and keep the questions coming!
Looking Forward,
Corbett