Which one is better? Hi-Velocity vs traditional Forced Air sol'ns for the home

I am guessing this topic has come up before however I am hoping some HVAC folks out there would help me understand the advantages and dis-advantages of traditional forced air distribution systems as compared to Hi Velocity forced air systems. Specifically with respect to IAQ (indoor air quality), efficiency, comfort and ease of installation. Also does one type of system work better at a lower design heat temperature? Thank you for your time and willingness to share your expertise!

Tags: Air, Forced, Furnace, HVAC, Hi, IAQ, Velocity

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Great question!

I've never had the opportunity to install these systems, but I am a little familiar with them. 


Could save money on installation if there are access issues

Zoning capabilities are good with zoning controls and variable speed fans


Higher velocity is going to equal a higher static pressure drop, which means that your blower motor is going to be working overtime. Unfortunately, I couldn't find the engineering data behind their duct sizing - they do list maximum duct lengths, but not pressure drop data. I suspect they use larger motors on their blowers than a standard system. This penalty will double if you follow their indoor air quality recommendations and run the fan continuously to filter air.

I also couldn't find the "manual T" performance characteristics of their supply registers. But, if the air is moving fast, I suspect you'll be able to hear it coming out of the register. You'll want to verify the throw distances and noise criterion of their supply registers.

For me, I would think these systems work best when you can't use a standard system because of space restrictions. You could do a cost savings analysis and compare ease of installation versus operations cost (pretty sure these are going to use extra electricity to operate). I'd check with manufacturer to get blower information and register information. Also, try comparing the fan motor horsepower to an equivalent standard unit.

Other units I'd recommend: Carrier makes the infinity system that can be zoned without a bypass. Lifebreath makes nice units that have built in HRVs, FirstCo makes nice hydronic air handlers. You can always install a little fantech HRV with a MERV 6 filter, or use an AprilAire or similar media filter instead of a paper filter on a standard system.

For the ultimate in air quality, comfort, and control, modulating communicating equipment.  Period.  

Carrier Infinity or American Standard/Trane.  I'm not familiar with the other's Brady mentions, but if you want zone control, communicating equipment understands air flow.  This is particularly important when zoning, as he is suggesting.  

I have a Unico in my house, but I was space restricted.  I'm happy with it, but it doesn't hold a candle to Communicating equipment. 

I'm happy with my Fantec ERV.  

Unico systems operate the evaporator close to freezing, lower CFM. If you can keep the air handler/ductwork in conditioned space, you may be able to offset much of the efficiency loss caused by the low CFM system.


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