Should I Close My AC Vents
I’m a member of a few community Facebook groups where the discussion revolves around neighborhood activities & recommendations. One of these groups is for Chandler, AZ residents – a city Magic Touch Mechanical has thousands of clients in. In a recent post, a member asked: Should I close my AC vents? She had hot rooms which she was hoping to get more air into by closing vents in unoccupied rooms.
The Question: Should I Close My AC Vents?
The answers came in by the hundreds and ranged from accurate to absurd! Unfortunately, most of the “advice” she received was simply incorrect. I know what you’re thinking, how could anything on the internet be wrong, right? I frequently wonder why people seek medical, legal or technical advice from strangers as opposed to asking a pro. However, I digress, let’s answer the question – should I close my AC vents?
NO! You Should Not Close Your AC Vents.
I’ll explain exactly why in greater detail, but first let’s answer the main question: Should I close my AC vents?
There is no middle-ground here – you should not close your AC vents!
Closing AC vents can have costly, damaging results to your utility bill, air conditioner, even your home itself. If that sounds a little too stern, consider the following.
Closing your air conditioning vents can:
- Reduce the efficiency of your HVAC equipment.
- Increase your utility bills.
- Damage or permanently ruin expensive motors, circuit boards, and the compressor in your AC unit.
- Raise the humidity (moisture) levels in your home damaging structural elements of your home and furnishings.
- Decrease your overall comfort throughout your home.
Why You Shouldn’t Close Your AC Vents
Closing air vents puts back-pressure on your entire HVAC system. We refer to this as external static pressure. Too much static pressure is a leading cause of air conditioner and component failures. In essence, you’re making the problem worse.
Think about static pressure like heart disease and plaque buildup in your veins. Too much plaque buildup and you strain your heart to the point of a heart attack. Your ducts are the veins of your HVAC system, and the compressor is the heart.
The Difference Between a Vent and a Register
For the remainder of the article, I’ll continue to use the word ‘vent’, however technically the correct word is ‘register’. Although we all grew up calling them vents, air registers are the name of the device connected to air supply ducts. Vents are most often used for ventilation (exhaust) and the return air side of a duct system and are permanently open. They cannot be closed because they have fixed veins or bars. Vents are also known as return grills, exhaust grills, or just grills and are most often “stamped” out of metal. Since most people call them vents, for the purpose of this article, we’ll all be wrong together!
Why Can You Close Some Vents if You’re Not Supposed To?
That’s a great question, I’m glad I asked! Why do vents come with an apparatus to open and close them if I shouldn’t close my vents? The answer is quite technical so I’m going to answer it in the simplest terms possible.
Technically, your duct system should be “balanced” twice a year, before the cooling season and again before heating season. Here’s why I say ‘technically’:
ACCA – Air Conditioning Contractors of America is the group that writes the standards for the HVAC Industry in North America. ACCA’s Standards & Practices are adopted by most manufacturers, cities, municipalities, and other code officials. One such Standard is known as ACCA – Manual D, which covers the standards for designing and installing residential ductwork.
ACCA Standards recommend semi-annual air balancing which includes adjusting (not closing!) dampers and registers (vents). You’ve probably never heard that but don’t worry, you’re not alone. I’m willing to bet most air conditioning contractors, technicians, and installers don’t know that either. I’m just an HVAC geek and I teach technicians and estimators how to perform things like ACCA Manual D, Manual J, etc.
When balancing a homes ductwork, we use tools like flow-hoods and velometers to measure the exact CFM of air being delivered. We then make adjustments to dampers and registers accordingly. Sometimes, we (Magic Touch Mechanical) take it one step further and use pressure pans to test the room pressure. Frankly, this is not a “regular” service we offer – I explain why in the next few paragraphs.
Why Does ACCA Recommend Air Balancing So Often?
Airflow requirements differ for heating systems and cooling systems. In most cases, heating air travels at a lower CFM (Cubic Feet per Minute) than cooling air. Even units that use the same blower for both heating and cooling will operate at different speeds in heating & cooling. These fans run at a lower speed in the heating season, and a higher speed in the cooling season. If they share one common duct system (most homes do), technically they need to be re-balanced each season as a result.
If you’re thinking: I’ve never had my air balanced, do I have to think about this now every year too? Don’t worry, quite frankly you don’t.
Sure, in a perfect world your home builder would have hired the best HVAC Install Company. They would’ve designed and installed your HVAC system including ductwork to the exact standards. The city inspector would be intimately familiar with these standards and all the proper testing would’ve been completed.
Let’s all laugh together now!
Sadly, the reality is most duct systems (even in brand new homes) are far from perfect. In fact, studies have found that most duct systems tested in homes have semi-severe to very-severe design & install flaws. Sad but true. How can you balance (fine-tune) something that’s far out of tune to begin with? You know the saying; you can’t fix a knife-wound with a Band-Aid?
Magic Touch takes a more “permanent solution” approach which I discuss in my recommendations at the end of this article.
My AC Unit Has a Variable Speed Blower Motor
Should I close my AC vents if my AC unit has a variable speed blower motor? Variable speed blower motors have their advantages in the right application. Unfortunately, if you find yourself wanting to close your AC vents and have a VS motor it makes things worse.
Variable speed motors are designed to slow themselves down to match the external static pressure. Rather than increase the speed to “power through” the restriction they do the opposite. The answer you seek is the same for anyone who’s unit has a constant torque or multi-speed motor.
If I Shouldn’t Close My Vents, What Should I Do?
If the comfort issues you’re experiencing in your home are a minor inconvenience, try the following to see if it’s enough:
- Leave all bedroom doors open to allow for better airflow throughout the home.
- Use ceiling fans or a box fan to help circulate the air. Just know that fans cool people, not spaces.
- Reduce the amount of sunlight entering the room, especially during the hottest part of the day.
If the comfort issues are more serious you likely have larger problems with your HVAC system (equipment, ductwork, or both). If that’s the case:
Fix your ductwork! This is a permanent solution as opposed to a workaround or band-aid.
Back to the heart analogy: When you have plaque buildup the doctor doesn’t just ignore blocked veins, they perform surgery!
Comfort issues caused by ductwork deficiencies are almost always repairable, it just requires hiring the right air conditioning company to do it. Even in homes where ductwork is inaccessible there are other options such as ductless heat pumps and zoning systems.
Of course, a 20-year-old Buick Skylark will never perform like a brand-new Corvette. And putting a Corvette motor in that Skylark will not perform the same either. The air conditioner, furnace, ducting, and registers all work together as one “system.” So, if you really want to solve your homes comfort issues now and forever – call a pro. There are companies around the nation like Magic Touch that specialize in not just air conditioning but duct systems and whole-home solutions. When we’re done, you won’t ever think about closing your vents again.
Until then – don’t close your AC vents! Leave your vents open or you may be calling a pro for an emergency quote as opposed to a pre-planned one.