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Common HVAC Myths Busted

Heating, air conditioning, indoor air quality and other HVAC topics are ones that are commonly misunderstood due to several persistent myths.

Common HVAC Myths Busted

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Bryan Carnahan


August 13th, 2020

You don’t know what you don’t know. This tautological statement may seem like nonsense, but it certainly applies to several areas in our lives.

We work with whatever knowledge we think is correct, but there’s a lot of potential knowledge in the world, and no one can learn all of it.

HVAC is a deeper rabbit hole of complex equipment and processes than many people realize. As a result, a lot of misconceptions crop up around it.

While this isn’t normally an issue, it can be at the cost of your comfort, wallet, or even safety if you don’t know the in’s and out’s of HVAC in a way that allows you to make good decisions.

So let’s start making some better decisions, starting with those based on common HVAC myths.

We’ve already detailed some common myths surrounding heating and cooling, respectively, and this article takes a look at some misconceptions that cross the lines of heating and cooling to cover ALL HVAC processes.

RELATED: The Definitive List of Air Conditioning Myths

RELATED: The Definitive List of Home Heating Myths

Ready to complete your training and debunk the last of our most common HVAC misconceptions? Good. We’re happy to help.

A man and a woman sitting on a couch together under an HVAC unit.

Common HVAC Myths

Myth: Bigger is better

Fact: Bigger can actually be worse sometimes. The size, or power, of a system is carefully measured to properly heat and cool your home. A more powerful system will be ok at times, but other times will end up short-cycling (shutting on and off prematurely), which can cause long-term damage to the system. There’s also the fact that you’re paying upfront for power that you don’t need.

With variable-speed air conditioners or heaters, which only come in full tons (a unit of measurement for a system’s power), it can sometimes be advantageous to round up to the nearest tonnage. For example, if your home measures out at 2.5 tons, a 3-ton unit is fine. But variable-speed equipment is also designed to only provide the heating or cooling capacity that is needed, so you’re rarely, if ever, going to use that full 3 tons.

Myth: If it ain’t broke, don’t fix it

Fact: If you’re not scheduling regular maintenance of your entire HVAC system, you’re losing out on a lot of efficiency and comfort, and potentially damaging your system. Good maintenance should be proactive, which means it’s taking place before anything breaks down entirely. But a running system isn’t necessarily a healthy system, and this is particularly true with neglected maintenance.

Myth: Duct tape is good for duct leaks

Fact: Duct tape is unfortunately named, because it should never be used to fix a leaking or damaged duct. Certain types of foil tape can be used for this purpose, but this is generally not a type of tape that homeowners commonly have on-hand.

Even worse is when duct tape is used to repair chimney flues, which can get very hot. The duct tape will melt, becoming a potential hazard in addition to doing nothing beneficial.

A diagram explaining all the vectors that a house loses heat from.

Myth: If you know the square footage of a home, you can give an accurate estimate

Fact: Square footage is one part of the equation, but far from the only element involved in accurately estimating the heating and cooling needs of a home.

For some common examples: how many windows are there? What direction(s) do they face? Are they single-pane or triple-pane? What about insulation? Ceiling height? The make of your doors and how drafty they get? Each of these can and often will change the heating and cooling needs of your home.

This myth persists because some contractors don’t properly calculate a home’s needs and only use square footage. This is lazy and disingenuous to the customer. Nationally-approved standards exist (from the Air Conditioning Contractors of America), so there’s no excuse for taking the easy way out.

Myth: A new HVAC system will increase the value of my home as I’m getting ready to sell

Fact: Well, potentially, but not usually. The issue here is that a home inspector who isn’t an HVAC person won’t be looking for the overall sophistication of the equipment. They’ll generally be looking for two things only: whether or not the brand is recognizable, and whether or not it’s very old and in need of replacement.

So what a new A/C or furnace can do is take that off the negotiation table when you’re settling on a price for the home. If either is in imminent need of replacement, it may be used against you. However, the difference between one that’s, say, eight years old vs. brand new, or single-stage vs. variable-speed, is far less likely to matter.

Myth: HVAC equipment matters less than insulation and windows

Fact: All of them matter, and delinquency in one is going to hurt the other two. Ideally, you want an efficient HVAC system paired with a “tight” house that leaks as little energy as possible. Beyond that, it’s impossible to say which is more important to the long-term comfort of your home, and anyone telling you otherwise is probably just looking to sell something.

Myth: A denser air filter is always better

Fact: Here’s another case where it can actually make things worse. Take a standard one-inch air filter. To replace it with a denser HEPA filter might seem like a good idea, and it will catch more particles. But it’s also reducing airflow significantly, which hurts your system in numerous ways.

The best air filters can catch a lot of particles, but also allow for healthy airflow in your system. That’s why it’s often best to upgrade to a four-inch filter or similar option.

The other danger is that that same one-inch HEPA filter will clog up faster, which makes the problem of airflow even worse. Unless you’re very regimented about changing your filter, you’re going to lose years off of the life of your system due to the extra work it’s putting in to overcome the loss of proper airflow.

Myth: A high-efficiency HVAC system will always lower my energy bills

Fact: This is technically true as written, but the reason we can’t always promise cost savings is that your savings depends largely on how much you use your A/C or furnace.

Let’s say you don’t mind colder temperatures in the winter and your thermostat is set at 67. The cost savings in the winter for that home is going to be far less than in a home that prefers 78 degree winters, in which the furnace will be running constantly.

Another reason savings can be illusory is due to climate. Yes, minute to minute, a brand new, energy-efficient furnace will cost less than a 20-year-old furnace with a lower efficiency rating. But if you live in the southern United States and have mild winters, your actual savings will be minimal each year. The same is true on the cooling side.

The good news is, savings can be significant when you are using your system regularly. However, it’s a myth that this will always be the case.

Myth: Thermostat placement doesn’t make much of a difference

Fact: It can make a lot of difference. Ideally, the following is true:

  1. The thermostat is on an interior wall.
  2. It is not adjacent to any windows
  3. It is never in direct sunlight
  4. It isn’t near the major appliances in the kitchen

All of this is because the temperature will dip or spike in some areas of the home, even if those temperatures aren’t indicative of the entire home’s temperature. Avoiding them is key to steady, even comfort.

Myth: The less time my air conditioner or furnace has to run, the less energy it’s using

Fact: This is true between extreme and temperate days, where the extreme temperatures will require longer-running equipment and more energy usage.

Where this isn’t true, though, is where it comes to the equipment itself. A variable-speed A/C or furnace will often run for a longer period of time than a single-stage or two-stage piece of equipment. However, some variable-speed systems can operate at as low as 25% capacity, meaning you’re only using a fraction of the cost during the increased uptime. By contrast, the frequent on/off of systems that only operate at 100% capacity may have slightly less uptime, but will be using more overall energy.

Myth: An air handler is the same thing as a furnace

Fact: An air handler is exactly what it sounds like: equipment that manages the airflow in a home’s HVAC system. The primary component in the air handler is the blower motor and fan, which circulates air - both heating and cooling - throughout your ductwork.

Often, you’ll hear a unit called a furnace, when it’s actually an air handler with separate electric heating components installed with it. In practice, it’s not always important that you know the difference, but it can matter when it comes time to replace your equipment.

RELATED: Air Conditioner, Heat Pump, Furnace & Air Handler: What’s the Difference?

Myth: I don’t have to know about my HVAC equipment; that’s what my technician is for

Fact: I suppose this could be true if you have a really patient HVAC partner who takes a lot of time to walk through all aspects of your system. Those types of contractors do exist. Even the best of them, though, won’t know your specific situation better than you will. So the more you educate yourself, the better your questions will be when it comes time to repair or replace your system, and the better your decisions will be about any major HVAC investment.

Don’t Be Myth-taken

Puns aside, that last myth is perhaps the most important of the whole bunch. We’ve devoted our entire, comprehensive Learning Center to customer education, because we see value in having an informed customer base that expects consistent best practices from HVAC contractors.

Once you’re done absorbing any information that you need, it will be time to take the next step, which means reaching out to a trusted HVAC partner. If you’re in Columbus, Ohio, or the surrounding area, we hope that means reaching out to us. Wherever you are, though, we hope you have a better idea of what to do (and avoid) to get the most out of your HVAC system.


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