What is High-Velocity Air Conditioning?

There’s nothing quite like relaxing on the top floor of your three-story Victorian. During summer, there’s also no better recipe for heatstroke.

Of course, I get it, you don’t want to chop up your historic plaster ceilings and ruin the historical essence of your home by installing a central air conditioning system, even if it does mean every July is a fight for your life, right?

What if I told you there was another way? A way to install air conditioning in a historic house, or any house for that matter, that doesn’t require huge holes in the ceiling and big messes on the floor. It’s called High-Velocity Air Conditioning.

What is High-Velocity Air Conditioning?

Energy Star estimates that in traditional residential ductwork About 20% to 30% of the air is lost through “leaks, holes, and poorly connected ducts.” That’s terribly wasteful.

Unlike conventional air conditioning systems, Small-Duct High-Velocity Air Conditioning (SDHV) systems utilize high pressure to achieve thoroughly mixed air, creating maximum cooling, or heating since they aren’t just for AC, from floor to ceiling.

This different design creates much less opportunity for loss with High-Velocity Air Conditioning systems losing 5% or less to air leakage. There is less surface area for energy loss, mini-ducts are better insulated, and joints are better sealed through he used of gaskets.

This is made possible by the small size of the vents and ducts, which means less complexity to install as well as less invasive methods to get you there.

Without getting too bogged down with the technicalities, the biggest difference between this and conventional air conditioning systems is in how they cycle. Traditional AC systems cycle on and off as dictated by the thermostat. High-Velocity Air Conditioning systems also cycle on and off as needed, but the air handler runs continuously in order to keep the pressure up within the system. The result is less drastic power fluctuations, as well as the eradication of warm and cool spots.

Traditional HVAC systems have square vents around 6″x12″ whereas a high-velocity vent is usually round and only 3-5 inches in diameter. That small size means less damage to your ceilings or floors and and less visual distraction too.

What Are The Costs?

You may think that this type of system is expensive, but that’s not necessarily the case. Try out this calculator, which will give you a ballpark estimate for parts and labor in your area.

The cost, as compared to traditional HVAC systems, is nearly identical. So, for roughly the same amount as you’d spend on a system that would devalue the worth and aesthetic of your historic home, you could install a barely-noticeable High-Velocity Air Conditioning system instead.

Further, that’s assuming that you would even shell out the cash to pay for installation. If you do it yourself, it’s an even cheaper prospect. While you may be thinking there is no way you can install a HVAC system yourself keep reading because unlike traditional HVAC systems an SDHV system is so much easier to install that is may actually be within the reach of a serious DIYer.

How Difficult Is It?

The key to its ease is in the design, which is fairly standard across all brands. Unlike conventional ducting, the ductwork here is composed of insulated and flexible ducts that branch off of the plenum like branches off a tree.

These ducts are also so small that they’re able to fit within nearly any framing tolerance, so you won’t need to worry about performing any pesky framing modifications. Similarly, the discrete plenum can be installed anywhere from the basement to an attic crawlspace, given its small and uniform size.

Additionally, since the high velocity of the system is not created at the plenum but at the outlet vents, bends or elbows in the ductwork have little to no impact on airflow, which is a huge improvement over traditional HVAC systems.

Since these systems don’t require opening up whole walls you may run into issues in old houses where there is fire-blocking in your framing or other obstructions in your walls which will require some rerouting, but the location of SDHV vents is more flexible than traditional vents. That means these obstacles are more annoyance than performance problems.

And in historic homes with ballon framing you usually don’t have any problems installing a SDHV system. This is one of the few benefits of balloon framing.

Are They Loud?

Not at all, actually. Given that SDHV systems are generally powered by 1/4-hp to 3/4-hp motors, they create very little noise directly. Add to this that all air is blown through a high-grade HEPA filter, and the High-Velocity Air Conditioning system makes for not only quiet cooling, but also some of the cleanest conditioned air on the market.

While the noise from the system is quieter than a traditional system the sound from the high-velocity air flow may be something that bothers some people. Newer systems have “mufflers” on them to keep things as quiet as possible, but the sound of fast moving air is still there so you may want to see a system in action before you fully commit.

Where to Get One

There are several reputable brands that offer SDHV parts and systems. I’ll name a few to give you a leg up on your research:

• UNICO – One of the more well-known manufacturers with a great track record. They’ve even been endorsed by the National Trust for Historic Preservation
• High-Velocity AC – As their name suggests, specialists in SDHV systems
• SpacePak – They specialize in retaining aesthetic and architectural integrity

There are plenty of other options out there, but these three will be a good jumping-off point so you can gauge what works best for your needs and your budget.

Not Just AC

I’ve been talking about these SDHV systems as though they are only for air conditioning, but in actuality these operate just like traditional HVAC systems to both heat and cool your home.

Just like any system they have a thermostat that controls everything and a central AC unit and boiler, heat pump, or furnace. The flexibility is there to work with other types of systems you’re more familiar with.

It’s mainly the plenum, air handler, and ductwork that makes this systems function so differently.

Final Thoughts

There you have it: just about everything you need to know to get started on the path towards blessedly cool, future summers. Let’s do a quick recap. Compared to traditional HVAC systems, High-Velocity Air Conditioning systems are:

• More compact
• Easier to install
• Comparable in price
• Cleaner
• Less invasive

All that combined, it seems crazy not to at least give it a look, right? As an old home owner I’m kind of kicking myself that I didn’t know about them when I purchased my old bungalow.

Wen my HVAC system comes due for replacement I can assure you that I will be looking at installing a High-Velocity Air Conditioning System in my house and maybe you should too.