cold drink with condensation on glass

In the late 1980s and into the early 2000s, our technicians would often be laughed at if they said a Denver home needed air conditioning! Many people living in the Denver area didn’t used to have air conditioning in their homes. How things have since changed! If you have lived in Colorado for a while you know that the summers have gotten hotter here. Additionally, the technology keeps getting better and the standard for comfort changes along with that.

Now that more homes in our area have air conditioning, we hear many homeowners ask: why is one level of my house a completely different temperature from another? And then they ask: can I fix this by closing off vents on the cooler level?

Actually, no. That’s not what you want to do!

Read on to discover why large, multi-level homes can have different temperatures between levels, and the easy trick to addressing it.

Denver’s Air Conditioning Past Affects Current Homes

Because most houses in the Denver area didn’t used to have air conditioning, the ductwork found in most older homes is geared more towards heating. It wasn’t until about 2010 that houses were built with air conditioning ductwork as a priority.

The key thing to acknowledge with cooling a home is the return ducts. If you have a cold basement, that’s usually because there’s no return air vent down there. And if your upstairs is too hot this is almost always because there’s deficient return ductwork on the top floor. This is very common in Denver because older homes weren’t built with air conditioning in mind.

You see, most homes only have one thermostat on the main level. But the thermostat doesn’t know how hot it is upstairs, and it will only order as many air changes as the main level needs.

Does Closing Vents Help Even Out Temperatures in a Home?

Everyone wants what we like to call The Goldilocks Zone. Not too cold, not too hot, but just right! We understand why closing air vents seems like you get something from it. It gives people the idea of relief, like when you close vents in a car. But that small, contained space is not comparable to a home and very different equipment is involved. However, it’s good to understand when it’s ok to do this, and when it’s not.

It’s ok to close the vents in your basement during the summer when you’re running air conditioning. Cool basements don’t need that extra cool air and closing off vents won’t affect the air conditioning unit the way it does a furnance. But don’t confuse the blowing air vents with the cold air return vents. The return vents (located on the side of the walls) need to remain unblocked.

In the winter, you may be tempted to close vents to put more heat into certain rooms. But in furnaces you have to be a lot more careful about causing air restrictions than you do with air conditioners. What you’re doing when you’re closing vents is preventing the air from moving. Which is actually like simulating a dirty filter, because closing the vents slows the air way down.

Furnaces are engineered to move very specific Cubic Feet Per Minute (CFM) of air, across a heat exchanger, that’s firing at a very specific BTU level. Once you cause that air restriction, it’s not moving enough air and it can overheat. This is referred to as ‘going out on a limit’. You just don’t want to do this.

The bottom line is: the more air circulating through the house, the better. It’s best to keep all your vents open, but if you want to close them in the summer that’s ok, just remember to reopen them when you start using the furnace.  

Here’s a better tactic . . .

Tweaking the Fan Setting on the Thermostat

The way that most thermostats are set up for air conditioning is that the fan only turns on when there’s a call for cooling. Then the unit runs for a bit, moves the air around, and turns off. That setting is seen as ‘FAN AUTO’ on your thermostat. But you can change that to ‘FAN ON’. By turning the fan to the on position, even if your air conditioner is not turning on, the fan alone is going to pull hot air down from upstairs. Since a basement is naturally cool and doesn’t need much air conditioning, the fan will pull cold air up from the basement and you will homogenize the air temperature. This greatly reduces that air imbalance from downstairs to upstairs.

Will turning the fan to ON increase the cost of running your air conditioning unit? That depends on the age and type of the unit. If you have an older model, with a powerful blower, and a large house to cool, the fan running more often will consume more energy. That’s where the newer and more energy efficient air conditioner models come into play.

Permanent Duct Modification or Air Conditioning Replacement

In some cases, you are only going to achieve temperature balance with either equipment modification, or a full replacement. For instance, you can have a return air duct installed in your lower level if needed, and that’s a fairly easy addition.

Or, it’s always worth it to invest in newer, energy efficient equipment that works best for your home. A modulating air conditioner, or ‘two-stage’ air conditioner, will have longer run cycles. The unit has to be strong enough to cool a home when it’s a 90-degree day, which Denver has plenty of, but it doesn’t need to be as strong on an 80-degree day. On cooler days, the unit runs at a lower power so it’s running longer, pulling more humidity out of the air, and homogenizing the air.

So, the next time you are tempted to close that vent to get more cool air into a hot room, go to your thermostat instead! Or better yet, consider the long-term benefits of a new air conditioner model for your home.

Learn About Air Conditioning Replacement and Installation