Why You Should Leave Vents and Registers Open

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Air Conditioner Is Not WorkingWhen it comes to saving money on heating every year, we hear the same things.  But, while “put on a sweater and lower the thermostat” is good, “close vents in unused rooms” is more damaging than it’s worth.  Sadly, it seems like common sense so we find people closing vents and registers in the hope of saving a few dollars every month.  With heating and cooling making up roughly half of our energy bill every month, you’d think that every bit helps.  But what if the dollars you save just get put towards future repairs caused by the attempted savings?

Basic Ventilation Principles

First, how does ventilation actually work in your home?  Houses are mostly closed systems, with controlled filtration that keeps the air clean and clear.  As a closed system, this means that nothing is moving the air internally.  A blower fan works to circulate the air throughout your home.  The moving air redistributes heat by either dumping it into condenser coils or picking it up from the furnace.

There are two basic types of motors used in these fans.  One is a variable motor that can adjust itself based on the amount of pressure it’s seeing, while the other runs at the same rate regardless of external conditions.  Because the second one is less complicated and slightly cheaper, it’s more common in homes.  Unfortunately, this means that your home, more than likely, is going to be working harder to move air through a smaller space.

Air moves in a cycle, as it leaves a space, more air replaces it.  This is why your home uses a system of vents and registers to move air through the building.  When you close an air vent, you reduce the number of avenues available to moving air, restricting flow.

Pressure Problems

This moves us to the major problem with closing air vents: pressure.  From the ducts to the climate control unit, whether it’s heating or air conditioning, your system has been sized to suit the needs of your home.  The amount of air that your blower fan can move is suited to the flow rate of your ventilation system and the size of your home.

The reduction in airflow is a problem for effective heating.  On the standard motor used in most household blower fans, that increased pressure means that air flows at a lower rate, leading to problems with heat transfer.  Additionally, the increased pressure means a higher chance for hot air to escape through existing leaks or to cause new leaks in your ducting.

Of course, if you have a variable motor, the reduced airflow is not a problem.  The fan motor will ramp up, increasing airflow against the additional pressure.  But this comes at the cost of the energy you might have saved otherwise.  Variable motors work themselves harder to make up for the decrease in airflow, decreasing lifespan, and costing you more in energy to operate the fan.

Heat Backup

We mentioned that one drawback to closing vents is a problem with heat exchange.  When airflow is reduced, the air is not refreshed quickly enough for proper heat exchange to take place.  Hot air moves into the room at a lower rate, leading to colder rooms or longer furnaces on-cycles.  In a heating system, the reduced flow rate means that the temperature of the heat exchanger will increase as the air around it stays hotter for longer.  That increase in heat can lead to a cracked heating coil or exchanger, as it isn’t able to give off the heat quickly enough to prevent damaging itself.

During the summer, you’ll find a similar issue with air conditioners.  Less heat will be deposited into the condenser coil.  It will cool down, leading to a formation of ice.  Since ice is an insulator, it makes it more difficult for the condenser to release heat.  It will freeze over, eventually leading to compressor damage and home with high heat and humidity.

Alternatives for Saving Money

While it’s not guaranteed that closing vents will lead to permanent damage, it will cause your system to work harder than it needs to.  Often, the rooms you try to keep climate-controlled will stay at the temperature you want, but you won’t save more than one or two dollars, and that’s only if your climate control system is improperly sized, to begin with.

So what can you do to reduce costs during the winter (or any season really)?

  • Adjust the thermostat so your system operates less
  • Leave doors to extreme temperature rooms open to help distribute heat evenly
  • Use a ceiling fan to circulate existing air
  • Use a thermally reflective film on your windows to reduce heat transfer
  • Test your system to see if upgrading to a more energy-efficient unit will help

If you still have any questions or want to upgrade to a more efficient system, give us a call at (302) 368-3848 for any of your Delaware, Maryland, and Pennsylvania home service needs — plumbing, electrical, HVAC, propane, and more!

Call us 24 hours a day, 7 days a week to answer any questions you might have.

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