A while back I wrote a blog on the occurrence of air stratification in homes. This is when warm and cold air layer in a room. Recently I came across a classic example of this during an energy audit. The infrared image at the right very distinctly shows how the air has layered in this room. The temperature difference between the ceiling and the floor, over 15 º F.
The second infrared image shows the same occurrence in a connected room.
The reasons for this happening are for one physics and the other poor installation of the heating ducts.
In Connecticut we heat our homes most of the year. Consequently the heating registers should be located when at all possible in or near the floor.
In the two rooms pictured the heating registers were placed in or near the ceiling. The bright spot in the second image is the heating register.
With the idea to evenly heat the room the installers placed return air ducts near the floor thinking the warm air will be drawn down by the ducts. Not surprisingly that theory did not pan out. What's more if return ducts could be installed near the floor, they just as easily could have been made heating ducts. This was true in the second room as well. A storage room behind the wall affords ample space to install the registers 
down low.
This is a standard case of physics winning out over mechanics, but by applying a little more mechanics the problem can be resolved. In the room with the high ceiling putting in a ceiling fan will almost assuredly resolve the issue. Ceiling fans are a good energy efficient way to "homogenize" the room air. Running the fan will evenly warm the space causing the heating system to run less often.
The second half of the solution would be to relocate the registers. Doing this will be more costly and labor intense than putting in the fan, but will further achieve the desired benefit of a more evenly heated space.
Identifying a problem such as this one would be difficult without the aid of an infrared camera. However an HVAC installer should be cognizant of this effect when placing duct work. In the instances when ducts are unable to be ideally placed suggesting a ceiling fan be installed would be good advice.
Layer cake is tasty, but not on a wall.
James Quarello
JRV Home Inspection Services, LLC
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thanks for this...I have reBlogged this post as part of the Eco-All-Stars February LINK LOVE Challenge!
James,
I see the registers in the ceiling all the time and always think to my self that they are not in the optimal location. Often it is in houses where, for one reason or another, it is the only way they could get heat in the room, other than baseboards or something like that.
James awesome----I think they need to move the floor up----way up:)
janeAnne, Thanks for the reblog and I will definitely participate in your February challenge.
Steven, That is often times the compromise. The registers have to be located in an less than ideal location due to the homes construction.
Charlie, I heard of raisin' the roof, but the floor. You are an innovator:)
James, this seems like a "no-brainer", and clearly that just how this system was installed. (with no brain)
Alan, I have to agree. There would seem to have been little thought applied to this installation.
James, I see this in new 2 story homes more often than not. The HVAC contractor will run his duct to the first floor ceiling and branch to the first and second floor from there. The 2nd story will have registers low and the first will have registers in or near the ceiling. Save money on material and labor, but the homeowner suffers in the long run.
Jack, That's odd beause here they run the ducts in the basement and then a trunk to the attic. The way they do it out your way would easily allow placing the registers at the floor on both levels.
How do they hide the trunk between floors? Do they box it out?
James, here we see all kinds of set ups. Lots of times the lower level is hit from the basement or crawl space to the floor registers with a trunk run to the attic to ceiling registers for the upper level. Otherwise it gets boxed out in the ceiling of the first level to distribute to the second floor. Sometimes they will run up partitions and branch out to the floor registers to avoid the boxing out mess. The ones I find interesting are the ones where the system is essentially "backwards" from what we consider "conventional wisdom" today, where the cold air returns are at the windows and the hot air registers are on the inside walls. Regardless of where the registers are the key to stratification is relative to the amount of air circulation and the amount of insulation in the walls/ceiling. In a "super-insulated" structure with above R-30 in the side walls and Above R-40 in the attic----there will be very little stratification. Unless of course the windows and doors are open:)
That's funny because I can not recall ever seeing duct work here run any other way than I described.
I once inspected a newer home (3 years) where they hooked up the ducts backwards. I felt heat blow on my face walking through the bedroom door with two heating registers over the windows in a corner bedroom. Starting checking things out, whole second floor was backwards, two zones! The guy that bought the house originally, I heard, felt inspections were a waste of money. He was "wasting" his money to have the duct work fixed.
Where did you come across the info on the super insulated structure not stratifying. Please do tell.
James, I knew that would peak your interest:) Well of course there will always be some amount of stratification, but the kinds of stratification we are accustomed to in 2x4 construction would not exist in the Super Insulated home. You will not likely find much published info on it because it is information from my own super-insulated structures built in the late 70's. Those structures utilized truss-type studs (2x10 width) for an R-40 plus wall----with ceiling insulation of R-60. Once you insulate to those standards, air movement within the structure has enough convective movement on its own---powered by cooler windows---to result in very little stratification---less than 5 degrees. So, while heat rises---it also can be circulated naturally if it can't escape. This is sort of the simplistic discription:)
The windows would be the heat loss areas, as they are now, so would the impetus of convective movement be driven by the cooler windows? In other words would the cold windows drive heat movment from the warmer center and thus evenly heat the room.
I think that is what I said---but what you said sounds better:) Other things that have to be factored in is ceiling height and thermal mass. The houses I am talking about had double 5/8" drywall to help moderate temperatures as well as other thermal mass components such as solar heated slabs and Trombe walls.
VERY interesting. What type of heating system did the house have, forced air, hydronic baseboard or radiant.
All different types. Some had passive solar with wood backup (one that didn't require any bank financing that would have required some mechanical type of system). Others were hydronic baseboard (no nice hydronic in-floor back then) Some were all electric baseboard. The biggest problem was finding furnaces small enough even for 2500 sq ft houses so they were usually heated with either dedicated gas or electric 30 gallon water heaters. These houses would have a lot more options today. Typically the the savings of not installing a normal furnace more than offset the extra cost of insulation. The costs of the house were no more expensive that a normal 2x4 house of the time as there was typically less lumber in them than a normal 2x4 house. The heating load for a 1600 sq ft house was typically calculated at 4000BTUH at 0 degrees ambient---which as you know is about equivalent to a toaster. Lighting, appliances and personal activities all played into the heating calculations of the houses. I have been accused of lying about these numbers and falsifying electric company bills:) Here is a picture of what the framing looks like. Everything possible was done to minimize solid wood all the way through the wall---note even the hollow headers that could be blown full of insulation.
Charlie, You were waaay ahead of your time man. That is truly amazing. I have never heard of or seen framing like that. It makes absolute complete sense.
It's funny how you had trouble finding heating systems small enough. The thinking was and for a large part still is bigger is better.
I would guess those walls were not filled with fiberglass. I am fervent disciple of cellulose as I believe are you.
What were you playing on the radio?
Each bay would have had five 2-1/8" holes drilled in it (from the inside prior to installing the drywall----so that you would know that you were hitting everywhere) and then cellulose was pumped. I used to buy cellulose fiber by the tractor trailor load----a friend of mine owned one of the first celluose insulation plants in the NE and was instrumental in some of the early fire testing and best-installation practices-----this was in the early 70's.
On the radio would have been Pink Floyd:)
The plant I know of in NE is National Fiber. I have had their technical director give us a seminar which was exceptional.
Believe it or not I was listening to Floyd in the 70s myself.
Back in those days it was C&M Fiber in Weedsport NY----long since lost track of the owner and what happened to the business. Long after many other groups are long forgotten---Floyd will endure.
Mr James,
It looks like your only friend is Mr Charles. Relax, I still like you and my cousin Wheat is so pleased that you agreed to send us money.
Great post James! What a great demonstration that physics trumps mechanics. Physics trumps Markanichs too, by the way. I recommend ceiling fans to my clients too - a cheap way to help even things out with real high ceilings. My understanding is that they cost about 3 cents a day.
As to the layer cake, I think I saw one of those on the Food Network cake competition. What's the flavor, tutti-fruiti?
Yes, Charles is waaaay ahead of his time. For a while now... Trombe walls? Isn't he that sports announcer? Sorry, that's Bob Trumpe, silly me...
P.s. My name is pronounced like mechanic with an "r."
Mr. Nutsy, The checks in the mail.
Jay, Thanks. You're right, ceiling fans are a very cheap way to move air and lower those heating cooling bills. The problem I find is almost no one turns them on in the winter.
Mr Q,
Wheat and I will check the mailbox every day. Thank you for your vote of confidence. We will send you a copy of the first pressing in vinyl.
Nutsy and Wheatloaf
Nutsy, Don't get worried if you don't see the check right away. It's a looooooong way from CT to WA.
Plus, James----isn't the check from that old account you closed when you were still in high school?:)
Yeah, I wouldn't drop that sucker, it's liable to end up on the moon.