After 18+ years of interviewing and working for literally 1000’s of metro Atllanta homeowners,
there is one ‘absolute’ that all economic & socio-economic levels of homeowners have in
Their HVAC Air-Ducts are a mess, and they have no idea to what extent.
Newer homes, older homes, starter homes and multi-million dollar homes, it doesn’t matter. It
seems that few professionals care about air-ducts ...
- The plumber & electrician lay on them, step on them, and abuse them.
- The air-duct cleaner tears them up, and leaves them full of holes.
- The exterminator crushes them, or curses them.
- The HVAC tech, during his seasonal “maintenance inspection”, ignores them!
- The installer leaves them twisted, kinked, torn, zig-zagged, tangled in a mess, or cut too
- The careless installer straps them so tight they are squeezed in half, or left lying in the
- dirt and mud under the house with a tight crawlspace.
- The cable guy cuts holes in them to run cables from room to room, floor to floor. (Don’t doubt me, I’ve seen it many times!)
Here is a bit of trivia for you: Who is the lowest paid man on a residential HVAC install crew in
new construction? Answer: The guy installing the air-ducts!
It can’t be that difficult. “ Hook this flexible pipe up to the furnace, run it over to that vent, and
hook it up over there.” (And do it as fast as you can, because we have 3 houses to get done
A Flowhood test will tell you two very important things:
1. If your air-ducts are properly sized to match your equipment.
2. If your air-ducts are balanced. The air-flow through the Supply air-ducts should match or be at least within 10% of the air-flow through the Return air-ducts.
Now I will say that, recently, air-duct design has improved. Conscientious “green” builders and
tougher codes mean that flexible air-ducts in new homes are supposed to be more efficient, and
But I’m not talking strictly about leaky ducts… I’m talking about the airflow moving through your
So, what is a Flowhood test, and why do you need one?
A Flowhood, by it’s proper name, is a Balometer. It measures the volume of air moving
through an object. In this case, it’s used to measure how much air is moving through your HVAC
A Flowhood test will tell you two very important things:
1. If your air-ducts are properly sized to match your equipment.
2. If your air-ducts are balanced. The air-flow through the Supply air-ducts should match or
be at least within 10% of the air-flow through the Return air-ducts.
You see, you can spend $9,000+ on a super-bang, high-tech, latest
wham-bam furnace and air conditioning change-out, but when you hook it
up to those 20+ year old air-ducts, you’re very likely getting the
performance of 10-year-old technology. You don’t have to waste your
My Flowhood at work today … Case Study # 1
I was in a beautiful, large, Atlanta 10 year old house today, where the homeowners just spent a
BUNCH of money completely replacing two HVAC systems. Five months ago they hired us to
install spray foam attic insulation. This is a two-story house on slab. With both furnaces in the
attic. One furnace handles the downstairs, and one handles the upstairs. They are complaining
that three upstairs bedrooms and a bath are not getting enough airflow from the vents.
Chris (my son) and I took our Flowhood and measured the airflow through both sets of air-ducts.
● Only one central Return-Air Vent for the entire upstairs system.
● For the downstairs system, an equally huge central Return-Air vent was in the upstairs
hall ceiling! (POOR DESIGN! System Return vents should serve the same area as the
● With the HVAC running, room & zone pressures were so wacky that the interior doors
would open and close by themselves. The Master Suite door would actually close and
● Install a Return air vent in each bedroom upstairs. I’d love to add Return air vents
downstairs, but it would require extensive sheetrock and demo work.
● Improve the sizes of selected Supply air-ducts, to improve airflow to each room.
● Re-arrange two ducts, that are kinked & twisted.
BTW, I quoted the solution, and he’s on our schedule. We will take 3 men, one need a full day.
Is there a Standard we should be going by?
HVAC equipment manufacturers build their equipment to exacting standards. The whole
purpose of a forced-air furnace and ac cabinet is to raise and lower the temperature of air, and
blow that air into your home. Modern residential equipment is designed to move 400 cfm of air,
per ton of AC, through the cabinet. At minimum, as I am told, they should have 300 cfm per ton.
CFM stands for “cubic feet per minute”. It is a measurement of airflow… the quantity of air
moving through an object.
In my experience, the most popular sized (residential) AC systems I find are:
● 2 ton
● 2.5 ton
● 3 ton
● 3.5 ton
Multiply the manufacturer’s recommended and allowed CFM by the size of your equipment. This
will tell you how much total airflow should be traveling through your cabinet.
● 2 tons = 600 - 800 CFM Airflow
● 2.5 tons = 750 - 1000 CFM Airflow
● 3 tons = 900 - 1,200 CFM Airflow
● 3.5 tons = 1,050 - 1,400 CFM Airflow
Not Enough Airflow … Case Study # 2
Manufacturers have built-in safety relays to limit risk and damage to equipment from too little
airflow. I’ve been in homes where the furnace would come on, start warming up the house, and
suddenly shut off… only to come back on again in 5 minutes, only to repeat the cycle…
over-and-over. We call this “short-cycling”. Using an infra-red thermometer, I’ve watched the air
flow temperature climb into the mid 130 degree range, and suddenly the heat-limit switch (that
is preventing the furnace from overheating), shut the furnace off, due to not enough airflow
through the furnace.
In one occasion, because of short-cycling, I actually climbed under the house, pulled the filter
out, and left the filter-tray door open on the furnace. The additional fresh air allowed enough
extra air to be drawn into the furnace, to allow it to operate properly to heat the home for this
family with small children… until we added return air vents in the house, (it was Christmas eve,
and we installed the added Return Air vents a couple days later).
Flowhood reveals Criminal Activity! … Case Study # 3
In another million-dollar custom home, after performing our Flowhood test, I couldn’t figure out
why this huge 4 ton system wasn’t short cycling due to not enough airflow through the air-ducts.
After climbing into the far reaches of this huge attic, unbelievably, I found a 12” diameter
Supply-Air duct blowing into the attic. Taped to the duct was a note: “Leave this duct alone”.
Some HVAC “hack” had sold Ms Homeowner an oversized system, and attached it to the
existing 3-ton set of air-ducts. Clearly, when he hooked it all up, it wouldn’t run properly, so he
simply blew the extra ton (400 CFM) of air into the atmosphere! She had no idea of the money
she was wasting, until her Flowhood test revealed the truth.
Recent home purchases, homes with bonus rooms, or added rooms, or recent additions and
remodels should definitely have a Flowhood test performed.
$300,000 Remodel got Careless … Case Study # 4
About three months ago we were using the Flowhood, and found a vent in the master suite
closet that wasn’t connected to anything! When we removed the vent cover, it was a hole in the
sheetrock, where wires went back and forth from downstairs. The contractor simply used an air
vent to cover the hole. But it was a huge source of cold drafts, dust, and bugs that was easily
sealed, after the client knew it wasn’t an air vent.
In that same house, the Supply-air vent (in the ceiling) of the master bath showed no airflow
reading on our Flowhood. It took some work, but we climbed out over the ceiling, in the attic -
and found the air-duct just lying there in the attic insulation. The air-duct wasn’t long enough to
reach the vent, so the remodeler left it lying there, blowing into the attic.
Looks Are Deceiving … Case Study # 5
When bonus rooms or small additions are completed, it’s not unusual to find pitiful air-duct
modifications, that leave the room painfully uncomfortable due to a lack of airflow. Just because
it’s a nice big vent in the wall or ceiling (or floor) doesn’t mean that air is moving through it.
Earlier this year, I received a phone call … “ Bob, we sold our house and just moved. We need
you to come fix this one, like you did our last house! ” I arrived, before any furniture had been
moved, and began taking my Flowhood readings. In one upstairs room I found a very large wall
vent, but it had zero airflow, according to my Flowhood.
When I inspected the vent more closely, I saw that it was actually hiding a wall safe! The new
homeowners had no idea it was there! Actually, I’ve discovered quite a few wall air vent grills
that weren't HVAC related. We installed an actual Return-air vent in that room, because there
was no return airflow.
What about Those Air-Vent Grills? Does Design Matter?
About 3 years ago I was called to a home in an upscale senior living community. Mr
Homeowner’s office was always too hot (summer) and too cold (winter). What I found was that
the air flow of the Supply Air vent was sufficient for his office, but the grill was the wrong design.
His desk was against the far opposite wall from the Supply air vent, which was located in a
kneewall directly over a set of french doors that sayed open.
My remedy was to replace the 3-way grill with a high velocity grill. The three-way grill throws
(deflects) the conditioned air to each side, and downward. The high velocity grill allows the air to
pass straight through, with little obstruction.
In the attic, we redesigned the flex air duct for improved airflow, and those two measures
rewarded our homeowner with dramatically more airflow into his office.
There are videos on this subject, that may help you: https://www.birdinsulation.com/videos/
Scroll through the Home Performance Minute library, and read my titles.
Airflow Trivia that makes Common Sense
One of the quickest ways to improve airflow through an air-duct system is by redesigning the air
ducts. Installers pull the duct straps so tight, it constricts & limits the air movement. We fix this
all-the-time! And homeowners love us for the improved comfort in their homes!
Got a noisy vent, right by your favorite chair, that annoys you during TV time, or book-reading
time, and quiet-times? That noise is probably due to poor air-duct design and/or vent grill
Do you have those fancy wood vent covers in your floor air-vents? Our Flowhood tests reveal
that those wood vent grills cut down on airflow by as much as 30%! That’s a THIRD of your
airflow! In a 3-ton air conditioning system, that loss of airflow equals one third of your equipment
It’s Sad but True, some contractors are dishonest… Case Study # 6
Last year I received a request to come to an exotic, custom Atlanta home, because the baby’s
upstairs room wasn’t getting enough heat. I began testing with the Flowhood. Unbelievably I
found that the ceiling Supply air vent was sealed with sheetrock, with the vent cover attached to
the sheetrock to hide the omission! When I explained my findings to Mr Homeowner, I was told
of a recent remodel. The sheetrock guy had covered the vent, and (apparently) forgot to cut the
opening and attach the HVAC duct boot. Our guess is, when he was finished and realized what
he’d done, he simply screwed the vent cover onto the sheetrock ceiling to hide his
Damage from Cleaning the Ducts … Case Study # 7
In that same house, downstairs, my Flowhood revealed another vent with no airflow. Climbing
into the crawlspace, I found the disconnected air-duct, lying in the dirt, directly under a broken
splice (wye connection). Because it took some work crawIing back there, I took a picture on my
phone, and when shown to Mr Homeowner, he said, “We had the air-ducts cleaned a couple
The stories never end … Those Poor Ducts!
More than once I’ve found where the tile guys have tiled right over a floor vent with tile. And
Supply air ducts shoved into holes under kitchen cabinets or kitchen islands, and the air just has
to find a way into the room!
Imagine the excitement homeowners experience, after living in their house for years, putting up
with too hot, or too cold rooms. They hire BIRD to perform a Flowhood test, and we discover
manual dampers in their air duct system! Dampers that were positioned to restrict airflow. After
a simple twist of the lever, they have magical airflow!
Don’t Expect what you Don’t Inspect. Nobody wants to “Hug a Duct”.
Why doesn’t the HVAC community perform Flowhood tests? My guess is, they don't like dealing
with air-ducts. The average HVAC tech is paid to run diagnostic calls, or to install equipment.
The last thing they want to do is lose a sale, because of waiting on scheduling a test or
confusing a homeowner.
And, homeowners with suddenly no Heat or AC, won’t wait on tests… they want comfort NOW!
That’s why it’s important to Test Your Airflow While your Equipment is in Good Shape,
before the emergency!
Don’t Fool Yourself. Are you thinking you’re protected with that Maintenance Agreement from
your HVAC guy? HAHAHAHA! That’s a stretch. Are there amazing HVAC techs that evaluate
air-ducts with their annual inspections, you betcha. But my 18 years of experience tells me, after
being in 1000’s of Atlanta homes, that even though a furnace has a sticker proclaiming that it’s
annually inspected … the air flow through the air-ducts is likely less than ideal.
At Bird Family Insulation, WE LOVE AIR-DUCTS! Here’s a promise for you : We’ll
love your air-ducts like our very own.
Stop wasting your money. Your home can be more comfortable, more healthy, and with smaller
Schedule your Flowhood test today. Call the office and tell Savannah you’re needing a
FLOWHOOD Test. She’ll ask you a few questions, quote the rate, and schedule your
appointment. Call her now… 404-538-9168 . If you are a previous client of Bird Family
Insulation, your test-rate is REDUCED!