4 Reasons to Open Interior Doors When Using Your HVAC System

When using your HVAC system effectively, some seemingly innocuous things can have a significant impact on its performance.

One example of this is closing interior doors.

You may think that closing doors can help to concentrate heated and cooled air where it is needed, but, in fact, there are several downsides to
this approach.

Discover four reasons to leave interior doors open when using your HVAC system.


1. Increase Energy Efficiency

The energy efficiency of your furnace and air conditioner is extremely sensitive to changes in the air pressure balance in your home. When you close one of
your doors, that room becomes pressurized as your HVAC system continues to pump air into it. This pressure can force conditioned air out of any small gaps it
can find.

Conditioned air forced out of a room this way typically finds its way outside or into areas of your home where it isn’t useful, such as crawlspaces. All of
the energy that went to heating or cooling this air goes to waste, and your system will have to work harder to replace it. Furthermore, working against higher
air pressure in rooms with closed doors puts extra strain on your blower motor and causes it to use more energy.

2. Preserve Indoor Air Quality

Closing an interior door when you use your furnace or air conditioner doesn’t just create high pressure in that room. The pressure differential results in
slightly negative pressure throughout the rest of your home. This negative pressure can draw air in through any available points of entry in your home just as
high pressure forces air out.

Air that enters your home from unintended sources doesn’t pass through the furnace filter or other filtration devices in your HVAC system until it cycles
back through the return duct. This means that air that enters your home constantly due to negative pressure often contains contaminants like dust or pet dander.
Leaving doors open to maintain the correct air balance prevents reduced indoor air quality.

3. Reduce Risk of Mold Growth

Moisture from virtually any source can fuel mold infestations, including moisture in the air. Most often, mold from humid air occurs in places where this
humidity has condensed on windows, walls, and other surfaces in your home. This effect is especially pronounced in the winter as a result of the temperature
differential between your home’s interior and the outside air.

Ventilation is essential to prevent condensation from causing mold. Condensation proves more difficult to form if humid air is moving. Closing the door to a
room essentially causes all the air in the room to remain stagnant, and mold growth is more likely to occur.

4. Prevent Furnace Back Drafting

The most concerning problem that can happen due to negative air pressure is a furnace back draft. Your furnace flue plays an essential role in removing
carbon monoxide and other harmful combustion byproducts from your home. Because the furnace flue is essentially a straight path to the outdoors, negative
pressure can draw outdoor air down through it and cause fumes to back draft in your home.

Fortunately, it usually requires significant negative air pressure in your home for a backdraft to occur. It often requires several points of blocked air in
your home, such as would be present with several closed doors, blocked vents, and potential other problems such as duct blockages. Furthermore, if your furnace
flue has a flue cap, it isn’t susceptible to back drafting.

Maintaining adequate airflow throughout your home is essential for efficient furnace operation, and leaving your doors open will help. For more HVAC tips and
professional service, Chrismon Heating & Cooling is here to help!

Call us today.