HVAC Efficiency

[elwin]

In a building with high ceiling, is there an advantage in operating efficiency or cost of operation to dropping the supply and return ducts of roof mounted HVAC units. Does this really create a "dead air" zone with some insulating effect?
If there are benefits, are there reasonable limits, ie 6 feet of "dead space" as a minimum?

 

[235zzzo]

Hello Elwin

To get the main aspect from your question, if you say that the building has a high ceiling and you want to treat it efficiently and low cost operation, try to be caucious with diffusion system, you will choose. I call your attention to analyse diffusion systems, such as the so-called "displacement diffusion systems", which means a diffusion (supply) with slow motion at the occupied zones, according with the layout and architecture possibilities/limtations and the returns at the half-high and/or at the top, close to the ceiling. At this high, you should have always the extraction grids to extract the used and polluted air. Of course you need to use air ducts. Hoping this can help. zzzo

 

[ChasBean1]

I've been tossing your question around in my mind and to a coworker and it's very interesting. My guess would be yes, there would be some energy savings (and his was no!). This sounds like one of those things that only a before and after evaluation would really tell. Exhaust capture location, room dynamics, and diffuser air throw would make each analysis unique and providing definitive answer a little too difficult as a quick answer in a forum... Chas