Closed Vents in Rooms

Issues Caused by Closing the Vents in Unused Rooms

Every year, nearly half of your home’s energy bills can be directly attributed to heating and cooling your living space. So when you are looking to save money each month, cutting heating and air conditioning is a good place to start. But what about air vents?

Whether it is a guest room or formal dining room, most homes have rooms that are not used every day or at least not all day. Yet if your system is running, you are paying to heat and cool these rooms even when they are not in use. Logic might tell you to minimize the waste and close the vents in those unused rooms, right?

Well, not exactly! If your system was installed properly, your ductwork was sized so that the amount of air going into your air conditioning system equals the volume of air going out of your system. By closing the air vents in unused rooms, you are essentially disturbing the balance and placing undue stress on the air conditioning system. This could cause the system to work harder, lessening its efficiency and potentially shortening its natural lifespan.

The Problem with Blocked Vents

The purpose of the shutters inside your vents is to allow you to direct where the air goes when it first enters the room. They are not intended to be completely closed. If you test the louvers, you will notice that they do not form a firm seal over the vent. However, it is enough of a seal to create a problem.

The blower fan that is responsible for sending air through the ventilation system likely utilizes a single-speed motor that is designed to push air against a maximum pressure difference. By restricting the airflow, the blower must push against higher pressure. When this happens, the motor will continue to work, but its speed will drop as the pressure increases, causing a drop in airflow.

8 Unintended Consequences of Closing Vents

  1. Increased duct leakage
  2. Lower air flow throughout the house
  3. Increased energy use
  4. Comfort problems because of low air flow
  5. Frozen air conditioner coil
  6. Dead compressor
  7. Cracked heat exchanger, with the potential for getting carbon monoxide in your home
  8. Condensation and mold growth in winter due to lower surface temperatures in rooms with closed vents

The Dangers of Closing Air Vents in Unused Rooms

System Damage
Restricting airflow to your system by closing off vents can cause your air handler to overheat and your evaporator coils to freeze over. In addition, because your system has to work harder when pressure builds up inside your ducts, closing vents in unused rooms increases the chances of overstressing major components like the compressor and causing those parts to break down.

Burst Ducts
As if a damaged system is not bad enough, closed air vents can cause ductwork to leak or burst. When you close vents, pressure builds up in your ducts. And, rather than direct that air into your home, the pressure can cause small leaks in your ducts to become larger. This could result in you paying to cool your attic or crawlspace instead of your home!

The average home already loses about 20 to 30 percent of air through minuscule leaks and poor connections in the ductwork. When you close the registers in unused rooms, the pressure builds and turns those small leaks into big problems.

Lost Efficiency
You probably purchased your air conditioner or heater after comparing all the options and chose the most efficient model for your budget, so why risk its efficiency? The buildup of pressure means your air conditioner must work harder to distribute air throughout your home and your air conditioner will run longer to cool the same amount of space with less volume of cooled air.

Add that to the increased leaky ductwork, and your air conditioner’s efficiency can decrease dramatically simply by closing a few vents. When your system works overtime, you are not saving any money. In fact, you are probably paying more monthly and will pay more in repair or replacement costs sooner than you need to.

Carbon Monoxide
All of the above issues are nuisances both to your family’s comfort level and your pocketbook, but the risk of carbon monoxide is no joke. When you close the air vents in unused rooms, it is much easier for the heat exchanger to crack, which can release deadly carbon monoxide into the home.

Carbon monoxide is a tasteless, colorless and odorless gas that is undetectable to humans. When inhaled, it displaces the oxygen in the blood and deprives the brain, heart and other organs of much-needed oxygen. The gas can overcome you in moments without warning. Make sure you have a carbon monoxide detector installed in your home and keep those air vents open.

Mold Growth
When cold air and warm air meet, condensation and mold forms. For example in the summer, if there are leaks in your ductwork, the hot humid attic air mixed with the cool air conditioner air will form condensation and create mold.

While mold is a nuisance, it is typically easy to control in the home. However, when it is lurking behind air vents inside the ductwork, your only option is to call in the professionals. Keeping those air vents open will help things stay nice and dry. As a result, you will prevent moisture build-up and unhealthy mold spores from plaguing your family.

How closing air vents can make you less comfortable

If closing air vents forces more air out of supply side air duct leaks, then that means less conditioned air is being delivered to certain rooms in your home. You may notice a room that is hard to heat or cool because there is very little air coming out the supply air vents. That could be partially due to air duct leaks. The reduced airflow may also be due to the blower slowing down because it cannot work against the extra pressure caused by the closed air ducts.

How Can I Control Which Rooms Receive Comfort?

If you want to cut off heating and cooling to certain parts of the house, the most efficient way to do so is by installing a zoned HVAC system. This will effectively cut off this portion of your ductwork from the rest of your home so you can manage it with a completely separate set of thermostat settings.

You can also consider having a ductless mini split system installed. Each of the mini air handlers in the system can be operated independently of the others. You only need to have the air handlers working in the rooms that require it. And since there’s no ductwork, there’s no pressure increase!

Final Thoughts

While it may sound counter-intuitive, leave your air vents open. If you are attempting to save money, try increasing the temperature when you are at work and while you sleep. Research shows that the longer your house stays at an increased temperature when cooling, or a reduced temperature when heating, the more energy you will save. Setting your temperature back 10 or more degrees for 8 hours while you sleep or go to work can reduce your energy bill by 5-15 percent.

If your system needs repair or if you would like to upgrade to a more energy efficient system, call us on 951-926-1002. You can also visit our Contact page and complete the contact form.