Damage to Your Ductwork
When multiple vents are closed, that airflow must be redirected to other areas of your home where vents are open and the air can be released. This causes pressure to build up within your ductwork, which can lead to serious and expensive damage down the road.
If you have a top/bottom return vent setup, close the top vents in the winter months. Closing the top vents will make your system draw in air from the bottom vents that are at the low point in the room where cold air settles.
It is a common myth amongst homeowners that closing air vents saves energy and makes the home more comfortable. Many think that by closing cold air returns, the conditioned air is redirected to other areas that the homeowners want, but closing air vents in vacant rooms is far from helpful.
Many homeowners have been led to believe that closing air vents saves energy and makes the home more comfortable. Unfortunately, this “tip” is anything but — closing air vents does not save energy and actually does more harm than good.
Key Points. Does closing vents in unused rooms help? The answer is no: In reality, it may hurt your HVAC system, lead to costly repairs, and cause other problems.
That said, closing your vents is best for saving energy but not for redirecting cool air throughout your home. Some homeowners believe that by closing the vents in their basements, cool air will automatically be redirected toward the upper levels of a house. Unfortunately, that's not how your furnace fan works.
Since cold air sinks and hot air rises, in the summer you should set the bottom floor's thermostat about 2°F higher than the thermostat upstairs. The cold air from upstairs will help keep the downstairs more comfortable and reduce wear on the equipment. The same offset temperatures can be used in the winter too.
Close some, but not all, supply vents on the first floor for better circulation to the second floor. Also, make sure nothing blocks your vents upstairs, and that your air-return vents are open. Seal all cracks, holes, and gaps around windows to prevent seepage.
Winter Thermostat Settings
Set the first floor's thermostat to your desired temperature, and then decrease the temperature setting on your thermostats by two degrees as you go up. Warm air on the first floor will rise and make the upper floors more comfortable.
When vents are closed, that pressure builds up, potentially causing damage to the HVAC system. Increased air pressure can create cracks and holes in the ductwork. It can also cause your furnace's heat exchanger to crack. Leave all air vents open to prevent extensive damage to your home's heating system this winter.
You most likely thought covering your air vents would certainly save you energy, but it does the opposite. Considering that this could damage your cooling and heating system, fractures and other damage could allow air to leave your air ducts and cost you much more in energy bills.
This is the last thing you expect to happen when you close off too many vents. Unfortunately, there isn't the correct amount of airflow and this can cause the coils to freeze and cause damage to the unit's compressor. This typically results in repairing or replacing it before the unit can run efficiently once again.
However, closing the intake vents will cause problems for the ventilation system of your house. It is better to keep intake vents open even in winter times.
Adjust the dampers.
If the second floor of your home is warmer in the summer months, keep the dampers on the second-floor vents fully open and only partially open the vents on the first floor to force more of the cool air to enter the second-floor areas.
Other solutions to the problem include adding a secondary system to the home or using a ductless split system. These are commonly used to supply supplementary heating or cooling. You also can also add insulation in the attic space, where much of the heat is lost during colder months.
Cold air is denser than warm air, so it stays on the bottom while warm air rises. That's why the downstairs can feel so chilly while the upstairs is toasty in the winter. The temperature differential between the upstairs and downstairs in an average two-story home is between 8 to 10 degrees.
Need to adjust heat vents.
Sometimes more heat vents are needed. But, often a solution is to partially close downstairs heat vents and make sure upstairs heat vents are fully open.
That hot air seeps into your attic before settling onto your top floor. If you don't have attic space to buffer the heat or your roof isn't well-insulated, you'll automatically feel hotter upstairs.
Poor insulation and/or ventilation
The number one reason why it is hot upstairs, cold downstairs is that the attic is poorly insulated or ventilated. It might seem counterproductive to add insulation for warmth and then circulate cold air through it, but the combination actually works together in a very important way.
In general, it is usually OK to close vents in a basement. It is on the main floor that you probably do not want to close any vents. Your furnace fan is moving cool air in the summer months. If you reduce the number of exit points for the cool air, your furnace fan can no longer move as much air.
When To Close the Vents. If summer is the right time to open your crawl space vents, winter is the perfect time to close them. Colder weather results in drier air. Dry air and freezing temperatures are the biggest risks for crawl spaces due to the likelihood of freezing pipes.
Contrary to popular belief, closing your bedroom doors does not improve the efficiency of your HVAC system and may actually increase your utility bills. When you close a bedroom door, you effectively block the air's pathway, and that blockage can lead to issues with airflow.