Round ceiling diffusers

[fan-of-fans]

One thing I've always liked about houses from around the mid-century were the round ceiling hvac diffusers. A lot of houses here built in the 1950s-early 70s had them and the they went away. I was always fascinated by them and the pull-chain dampers they had. You can still get them and the dampers at the home centers.

I miss seeing the really big one in the stores too, but they seem to be making a bit of a comeback at least there.

 

[stricklybojack]

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Yes, the big ones in the department stores!

 

[gusherb]

Two of the oldest department store buildings around here, now housing a Kmart and a Menards and dating back to the mid 70s have those round diffusers. The duct diameter has got to be at least 30" on those things and the entire diffuser is like 60" wide. I still see quite a few big round diffusers used on spiral duct installs these days.

Another thing that fascinates me are the big square diffusers that Target uses in all of its stores. I tried to figure out who makes them one time, but none of the manufacturers that make that stuff listed anything like those in the 48x48 dimension that they are. Best I can come up with is that they're custom made for target. Never seen them anywhere else.

 

[tomturbomatic]

Do you think the round ones went away when the construction went to the big self-contained HVAC units on the roof of the building so the return is in the center and the discharge is around the perimeter?

 

[cuffs054]

Fan, I with you man! 57 FLA house had them. I liked the look and the way they spread air.

 

[gusherb]

Tom

I think it was more a matter of availability and preference. The 24x24 diffusers we see all over now that just lay into the T-bar system didn't seem to be around until the 1980s, and of course those are very easy to install as they don't need to be supported by anything but the already existing ceiling system. I'm not sure how the old round diffusers are supported but I can only assume that they're tethered to the rafters or to the ductwork itself, instead of laying into the T-bar system.

 

[gredmondson]

   The house my folks built in 1959 had them.  I was tall and could reach them to adjust the airflow.  I remember being told that they were on the ceiling because cold air fell (though it is probably more that hot air rises).  

   I liked their looks too. The house was lath and plaster.  I can see that straight line registers are probably more cost efficient now.

  In Bakersfield,  California, people paid more to keep cool in the summer than they paid to stay warm in the winter.  Also, my folks lived in an oil area, and they received free natural gas for decades, but there was no free electricity.

 

[circlew]

I've seen lots of houses in Mississippi with the round diffusers in the ceilings, but they are very rare around here. This being due to cooling being more important in the South, while heating is in the North. The registers are placed near the floor in most homes here.

In commercial buildings, I've noticed round ones used in drywall ceilings, while square are used in the suspended ceiling areas. I also see the round used when no finish ceiling is used, with the ductwork exposed.

 

[arbilab]

In latter-day institutional installations, rectangular registers integrated better with drop ceilings.

 

[washer111]

We've got a single square-type diffuser in the kitchen. The ceiling is lowered in the hallway to accommodate the large ductwork, and thus there is a "shoot-off" visible in one of the bedrooms leading to the ceiling. That part of the ceiling usually gets quite cool

 

Several other houses built later near me have the big round diffusers. They basically look like the oval fluorescent lights that were popular about 15-20 years ago, with a little slit for air just near the diameter.

It appears as though they could be rotated to control airflow(?)

 

New round diffusers I've seen were in a hospital: It was a round shape, but basically looked like a white fan-blade for a jet engine, or maybe a centrifugal pump. 

 

Best thing about these diffusers (particularly) is they offer very consistent airflow in ALL directions.

Square-ceiling diffusers seem to blow most round the corners, and only from the outermost point - the inner parts don't do anything aside from "decoration."

Large through-the-wall diffusers are one-directional and create more "breeze." 

 

Personally, round-diffusers would be my choice as they offer breeze-free (or draft-less) heating and cooling, although cooling is when you notice the "breeze" more. Having a draft when cooling makes it feel colder until the system kicks off, which then means you feel hot; cooling you rather than the room, as I put it. 

 

[davey7]

A friend of mine had ducted AC installed maybe 10-15 years ago and the upstairs registers (in the ceiling) are circular diffusers.

I'm a fan of eyeball/nozzle registers but you rarely see them in the US.

 

[gusherb]

Those eyeball diffusers are usually used in high static systems and are mostly for directing air down from very high placements.

If I had a very high ceiling placement that needed to get heat all the way down to the floor those would be a good use for that. I believe the reason we don't see them much is because they're very expensive. The prices are well over $100 per diffuser. So they usually wind up in high profile commercial applications.

 

[davey7]

I've seen them used in residential settings in Japan in "residential" sizes - I worked for a Japanese client who used them out in Schaumberg for a huge industrial showroom.