Top 10 HVAC Myths You Might Believe

What is a Myth?

  • Traditionally a story explaining some unusual event or concerning the early history of an ethnic group.
  • A widely held, but (absolutely) false idea or belief.

We have a lot of myths, fairy tales, and urban legends that keep getting repeated and believed by the unsuspecting. Ever hear the one about the girl who had spider eggs growing in her cheek and didn’t know it? Never happened. What about how swallowed gum stays in your stomach for seven years? Not even close to true. Eating carrots improves night vision? The British made it up in World War 2 to distract from how they used radar in nighttime aerial combat. Seriously, look it up.

Point is, we could go on and on forever. Unfortunately, we could also spend quite a lot of time on HVAC myths, because there are way too many of those. Unlike a fun urban legend, believing in HVAC myths might cost you a bundle.

Before you do that, let’s drop some knowledge.

10. Closing a vent saves heat.

airflow problemsMany people close off certain rooms of their house in winter in order to save money and energy. They shut the vents, close the door, and forget about it while thinking they’re improving their home efficiency. Unfortunately, they are not, because this is one of the more common HVAC myths.

A modern forced air heating system is designed to distribute the heat load throughout a building. When the flow is blocked, the system can be thrown out of balance. This may cause it to break down over the long term. In the short term, it means the system has to work harder to do its job.

“Work smarter not harder,” as the old saying goes. A harder working furnace wastes energy, costs you more money, and can cause excess wear and tear on the unit.

The ideal way to save money during winter heating is to allow your central heating system to do its job as efficiently as possible. That means heating evenly throughout your home regardless of whether or not you regularly use certain areas. Not only will this prevent unnecessary energy consumption, but it will also make the house feel warmer overall since cold rooms aren’t dragging heat from elsewhere in the house

9. Ceiling fans reduce room air temperature.

Many people consider ceiling fans an excellent way to make their house cooler without having to turn up the air conditioning. Ceiling fan operation can improve your interior air comfort, but it does not actually reduce air temperature. Any fan works by circulating air throughout an interior space. Cool air moving across your skin disturbs heat, and makes you feel more comfortable.

Now, that being said, ceiling fans are a good way to save money via turning the air down a few degrees. On the other hand, if you leave a ceiling fan going in a room no one is using, you’re wasting energy. The comfort created by a ceiling fan is only effective if there’s someone there to feel it.

In short, don’t leave the ceiling fan on if you’re in the room, but you can use them to make your house seem cooler. That will allow you to turn the AC down, save a little money, and still enjoy the comfort level you’re used to.

8. The furnace heats faster if you turn the thermostat way up.

When you arrive home to a cold house after a long trip, everyone knows you turn the thermostat way up to get the house warm as quickly as possible. After all, the higher the temperature is set, the harder the furnace works, and, obviously, the faster it works too.

This is 100% a member of the HVAC myths club.

Whether you’re using a furnace, boiler, energy efficient heat pump, or some other heating element, pretty much all of them deliver heat at a constant rate. Your thermostat does not determine how hard they work, only how long they run to ensure there is sufficient heat inside your house to reach the desired temperature.

Okay, so what does that mean?

Turning the thermostat way up to warm your house faster doesn’t work. If you let the system get to that higher temperature, you’re wasting money, since you’ll just turn it back down to the ‘normal’ level anyway.

In the same vein, turning the thermometer way down in the summer doesn’t mean your air conditioner goes faster. It doesn’t. Like your furnace or boiler, the air conditioner cools at a constant rate, and turning it way down to ‘work faster’ just wastes energy and money.

7. Lowering the thermostat when you’re not going to be home doesn’t do any good.

Everybody knows that lowering the thermostat in winter when you leave the house doesn’t save any money or energy. After all, your furnace will just have to work even harder when you get home to catch back up. This has gotta be true. This isn’t one of those HVAC myths, right?


The less your furnace operates, the less energy it uses. The less energy it uses, the more money you save. When you’re gone for long periods of time, your furnace doesn’t have to put in the same level of work as if you were at home, so it’s not using as much energy. The ‘extra work’ it does when heating the house back up after you get home is nothing compared to the hours it spent working heating an empty house.

Some math would be nice to back this up wouldn’t it? Fortunately, there has been plenty of research down in this area. Reducing the interior temperature by 10 degrees or more when you’re at work can save you as much as 15% on your monthly bill. If you think you won’t remember to do this, invest a little money in a programmable thermostat and have it do the adjusting for you.

6. Energy efficiency doesn’t make a home more valuable.

air conditioner sizingAn energy efficient home might allow you to save a little money here and there, but it won’t increase the resale value of your home, or, at least, that’s how the myth goes.

Yes, obviously, this myth is false. Whether for pragmatic fiscal reasons or due to increasing environmental-awareness, many Americans are interested in reducing their energy consumption. High efficiency homes can sell for more money, and homes with poor efficiency sit on the market longer.

How do we know this? A 2008 NAHB study of homebuyers in the United States provides the data. If a home reduces annual energy expenses by only $1000, more than 50% of buyers were willing to pay over $10,000 more to purchase the house. Since many energy efficiency improvements can cost far less than $10,000, the incentives for someone looking to sell a home on the open market are obvious.

5. The thermostat can go wherever you want.

programmable thermostats save energySome people would have you believe you can put a thermostat on any wall in the house, and you’re done. This could not be further from the truth. If you want to ensure you get good air comfort, where you place the thermostat is very important.

Here are some basic guidelines:

  • Never install a thermostat on an exterior wall.
  • Always install the thermostat in an area of the house that will have be representative of how you want the house to feel. In other words, a bathroom you rarely use is not an option.
  • Make sure there aren’t any hot pipes in the wall where you aim to place the thermostat. This can throw off the operation.
  • Stay out of direct sunlight. This will artificially increase the reading in winter, and make you a whole lot more uncomfortable.

Follow those basic steps and you should be fine. Ignore them, and you will have air comfort problems.

4. If it ain’t broke, don’t fix it. Routine checks are a waste of money.

So long as your air conditioner or furnace is running fine, there’s no need to have it checked by an HVAC professional, right?

Wrong. Chances are your system is perfectly normal, and, in fact, will be for the foreseeable future. After all, modern HVAC technology is a lot more reliable than it used to be. That does not make it perfect. A mechanical problem can always arise even as the system functions normally, and you’ve done everything you’re supposed to do.

To ensure long term operating reliability and energy economy, your best move is to schedule an annual maintenance check with a local contractor. They will inspect your system to make sure it is actually fine and running smooth. They’ll identify the beginning of long term mechanical problems, nip them in the bud, and ensure you get a lot of years from your system. Even better, their maintenance checks will prevent efficiency decreases due to wear, tear, and particulate build up.

3. You don’t have to change your air filters once a month. Once every three months or so is fine.

The absolute, no joke, number one thing you can do to keep you air conditioner and furnace running effectively is to keep your air filter clean. Whether your clean a permanent air filter or replace a disposable one, a dirty filter is the #1 HVAC problem in America. Dirty filters can cause efficiency loss, mechanical breakdown, and, if left too long, total system failure.

You need to check and change your HVAC system air filter, at minimum, once a month. If you have a lot of interior pollution due to local factors, shedding, pets, or even a house full of relatives during the holiday season, the filter might need to be changed more regularly.

Keep an eye on your air filter, and you’ll reap the rewards long term. If you don’t, all you’ll reap are expensive repair bills and annoying breakdowns. Plus, your interior air will be a whole lot dirtier.

2. Bigger is always better! Too hot for you? Get a bigger air conditioner.

air-source heat pumpIf there is one thing American’s believe, it’s that bigger is always better. Want a drink? Get the 20 ounce instead of the 10. Need a new car? Get the Hummer! Want reliable air comfort? Get the biggest air conditioner and furnace you can afford!

Actually, that last one is 100% wrong. A bigger air conditioner than you need will not give you better air comfort. In fact, it will deliver inferior air comfort, waste energy, and be more prone to mechanical breakdown.

What you need for your home is a properly sized system. You want the Goldilocks Solution: not too big, not too small, just right. Anything else, and you’ll have problems.

1. The longer my air conditioner runs, the more it costs.

geothermal tax creditsNot true, not true at all. Yes, if your air conditioner runs 24 hours a day, that’s a problem you need to get checked out. Either your unit is too small to adequately cool your house, or something has gone wrong. However, an AC unit that runs a long time is not necessarily a problem.

Look at it this way: air conditioners typically use more energy in the first 5 minutes of running than they do in the next half hour. A unit that starts and stops 4 or 5 times every hour is actually using more energy than if it ran the whole hour uninterrupted.

Rapid start-stop operation is also bad on the compressor. Activation and deactivation puts more stress on the compressor than continuous running, so a unit switching on and off frequently is more likely to have a fouled compressor than not. Plus, you’ll get worse interior humidity and overall air comfort.

So, what’s the solution?

First, ensure your air conditioner is properly sized for your home. That should eliminate a lot of the problem. Second, if you can, invest in a two-stage compressor. These are both more energy efficient, and they last longer since one compressor operates at a lower operational cycle for a longer period of time. This actually saves energy and increases reliability.

Finally, if you notice your air conditioner or furnace kicking on and off a lot, get in touch with your HVAC contractor and get the system checked. Something, somewhere is wrong.

HVAC Truths are Better than HVAC Myths

Those are the top 10 HVAC myths we hear most often. Hopefully, we’ve successfully shown why you shouldn’t pay much attention. The truth, as they say, will set you free. In the case of HVAC myths, the truth will give you better air comfort and help you save money without sacrificing home comfort.

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