Allow me to make the case as to why ductless air conditioners aka mini split ac’s, make more sense in most homes than old school central air conditioning systems that utilize ducts to distribute the air. Although this applies in most climates, I can make the case as to why these systems are best in the desert especially.
In an extremely hot place like Mesa, AZ (a suburb of Phoenix, Arizona) where the Magic Touch Mechanical offices are located, we rely on our AC units from late March to late October. According to our two largest power companies, SRP (Salt River Project) and APS (Arizona Public Service), our air conditioners account for approximately half of our power consumption – and according to the Department of Energy, and our own findings from conducting thousands of home energy audits, that number is possibly even slightly understated.
In recent years, we’ve seen some of the hottest summers on record here in Arizona, and they are growing longer. As I write this article in mid-January, it is 75 degrees Fahrenheit! With utility costs rising year after year, not using the most energy efficient technology that exists today seems not only short-sighted, but fiscally and environmentally irresponsible. (Yes, this HVAC Contractor owns this technology himself).
In almost every other part of the world, ductless mini-split air conditioners and heat pumps are the standard, and ducted central air is the rarity. While the US is catching on, and ductless units are the fastest growing segment of the HVAC industry – it sure took us a long time to catch on!
So, what is it about ductless mini-splits that make more sense than ducted central air conditioners? Let’s compare a few of the key features and break them down a little.
Mini-Split Ductless Air Conditioners & Heat Pumps are More Efficient Out of the Box
Ductless Mini Split’s Use VRF (Variable Refrigerant Flow) and Inverter Compressors
Excluding many of the cheap knock-offs coming out of China and Mexico that are being sold online (that’s another article I’ve already written about), ductless mini splits utilize VRF (Variable Refrigerant Flow) technology via an Inverter Compressor. In laymen terms this basically means the compressor is only using the amount of energy needed to match the cooling or heating load.
As an example, let’s say the unit is capable of producing a total of 3-tons of air conditioning (36,000 BTUH), and that is what is required to cool the home to 75 degrees on a 108-degree day. On a 95-degree day, let’s pretend the total load on the home only requires 2-tons of air conditioning to achieve the 75-degree setting. The ductless mini split AC unit is capable of “throttling down” to 2-tons, which is 66.66% of its total capacity or capability.
A conventional central air conditioner in the same scenario would produce the full 3-tons of energy no matter what, so on that same 95-degree day it used 33.33% more energy that was needed.
There is no Air Duct Load / Duct Loss with a Ductless Mini Split
When determining the total cooling and heating load on a home or commercial building, the proper method is to perform what’s known as a “ACCA Manual J” or “load calculation”. This method accounts for all of the ways heat enters or leaves a structure. To break that down in its simplest terms, consider this; if you put two of the exact homes side by side and one home has six more inches of attic insulation than the other, the home with more insulation will resist heat entering through the attic than the one with less.
One of the large considerations when performing a load calculation are the air ducts themselves. The more air ducts involved, the greater the energy loss – known as duct loss. In other words, we know there will be energy lost because that energy has to travel long distances through air ducts which are inherently inefficient.
In Phoenix, where we notoriously build homes with ductwork located in the attic (which is 30 degrees hotter than the outside temperature), the duct loss can be enormous (even with brand new, well-sealed ducts). So, a home that might have only required 3-tons of air conditioning to maintain 75-degrees on a 108-degree day, may now require 4-tons due to duct loss.
Since mini-splits are as their name implies “duct-less” there is no energy lost through air ducts. In other words, the ductless unit can now be three tons to do the same job the 4-ton central air conditioner can do – 25% less energy produced means a 25% lower power bill.
Ductless Mini Splits Can be Used for Perfect Heating and AC Zoning
Unlike our brothers and sisters across the pond, we Americans have a tendency to live in homes that are way larger than we probably actually need. These large homes are often affectionately known as McMansions (because like McDonalds they are everywhere). We don’t use all the conditioned space in our homes all the time.
While my own home is considerably smaller than many of my friends and clients’ homes, I’m guilty of this myself now that I’m an empty nester. I have a whole floor with a den (aka 2nd living room), bedroom (aka guest room), and full bath (aka guest bathroom) that I seldom go into. This floor accounts for almost 1/3 of my homes total square footage.
With a central air and heating system, this seldom used space is being maintained at the same temperatures as the used space. With a ductless mini-split system, these areas or “zones” can be sectioned off because each room or zone can be heated and cooled independently of each other. While it would probably not be advisable to completely shut these systems off on a hot summer day, consider the energy savings if 1/3 of your home that was not being used could be set to cool to 84 or 85 degrees, while the portions being used are set to 74 or 75.
Ductless Mini Splits Provide Better Indoor Air Quality
An often-overlooked benefit of not having to rely on air ducts is the vastly improved air quality thanks to ductless technology. Go climb in your attic and stir up some insulation if you want to see what I mean. Your attic is undoubtedly the dustiest, dirtiest part of your home – and where are your ducts? Think about your duct system like a giant vacuum. When you hear your air conditioning technician talking about “return” air ducts (where your air filter is located), he’s referring to the half of the duct system that is sucking in air from your home which is then heated or cooled and blown back into your home through the “supply” air ducts.
Air ducts leak! Even well sealed air ducts are never 100% air tight. Most people think leaky ducts mean they are blowing cool air into the attic and don’t consider the hot air that’s being sucked out of the attic into the ducts – and then blown into your home! What’s in that air that’s being sucked into your duct system? If you said dust, you are correct!
Eliminate the ducts, eliminate the dust. Less dust in your home means less dust being inhaled into your lungs.
More Reasons Ductless Mini Split Heat Pumps & AC’s Make More Sense
- Ductless mini splits are quieter than central air conditioners and heat pumps.
- Ductless mini splits last longer than central air conditioners and heat pumps.
- Ductless mini splits are more reliable than central air conditioners and heat pumps.
- Ductless mini splits are better for the environment than central air conditioners and heat pumps.
Giving Central Air Conditioners the Thanks They Deserve
To be fair to central air conditioning which has provided me a career and paycheck for the last thirty years, let me play devil’s advocate to close.
- The upfront cost to replace an existing central air system with another is considerably less money than removing it and replacing it with a whole-home ductless system.
- Less contractor options. Ductless equipment is high-tech and requires well trained service technicians, installers, and estimators many air conditioning companies don’t have…there’s an easier way to make a buck unfortunately.
- That’s all I have for this section – we should all own this technology!