Do you know what this is? It's an HVAC register!
This is a high-velocity forced air system, sometimes called a "mini-duct" system.
And the ducts are really small! About 2" wide. And the covers are very attractive!
Larger rooms can need more than one register! Very large rooms as many as 4 or 6.
These systems blow a lot of air. These registers are blowing a little over 1200 cubic feet per minute.
A register on a traditional system would be 400-600cfm.
Depending on where the unit is located, like in the attic, the registers can be put into the ceiling.
When do you typically see these systems?
This house was built in 1928. When conventional ducts will not fit through or around older construction, these mini-duct systems are exceptionally useful when renovating and upgrading.
And don't worry about things falling into the ducts. They are screened to prevent that.
It is recommended that you remove the screen periodically and vacuum out the duct below.
This is what the duct looks like from below.
It is truly a mini duct! That is insulated, sealed very well, and aluminum tape holds the connection tightly and forever if done properly.
This is what the air handler looks like. This is one of three in this house! It's a big house.
In this house, two units like this are in the basement and one in the attic. They are strictly for air conditioning, with conventional compressors outside.
These systems require that the air flows constantly. So the blower is always running.
This is necessary to stir enough air in the room so the temperature between floor and ceiling rarely exceeds more than a couple of degrees. With a conventional system the difference between floor and ceiling can be as much as 30 or 40 degrees in a loose house!
The constant air flow also reduces the amount of dust that can settle into the duct work.
According to my research, when used for air conditioning, there is a greater reduction of humidity with these high-velocity systems. This is because the pressure in the air system is greater, thereby allowing a smaller volume of air to transfer the same number of BTUs to the cooling system. The same number of molecules of air are flowing, but they are packed together more tightly! The volume of air flowing over the coils is reduced, so the air flows over the coils for more time, and more humidity is condensed out of the air.
There has to be room underneath the main level for these systems to be installed. And you can see that in this house it works very well.
They are used often on historical properties. I see them a lot in Virginia, but don't know about the rest of the country. And why not? The ducts can fit into tight spaces, so in older properties they work very well.
My recommendation: the next time you see something like this, you can tell your clients what great systems they are!
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560