Will Closing Bedroom Doors Save Heating & Cooling Cost

Closed Bedroom Doors May Cost You

It’s March 20th and 2 degrees outside; this has many Minnesota home owners looking for ways to save money when heating their home.  A common question our customers ask is will they save on their heating and cooling cost by closing bedroom doors.  This is a good question seeing the #1 utility expense in your home is heating and cooling.

What is the theory on this

If I close doors will I reduce how much space I need to heat?  Say I have a 2500 square foot home and I close the bedroom doors, I may now only have 1900 square feet to control?  While it sounds good in theory it isn’t true. 

What is the result

According to information by Home Energy, a non-profit publication this is not true.  Today’s heating and cooling system fans move a lot of air around the home.  A typical home furnace moves between 1000-2000 cubic feet of air per minute.  This is equivalent to moving 1000-2000 14-inch balloons every minute in your home.  When you close a doorway you block the path for air to efficiently move through your house.  If you put your mouth over a Coke bottle and blow into it there is no place for the air to go.  Same thing happens with your home.  Your furnace has so much air it has to move, if it gets forced into a place it will find somewhere to leak the air out.   

When air is forced into a closed room an equal amount of air is drawn into the main part of the home to replace the lost air.  Depending on the number of doors closed it could increase the warm or cold air drawn in from outside by 300-900%.  One common spot it may get air from is drawing air down your existing chimney.  The reverse flow of hundreds of cubic feet of air can bring carbon monoxide into the home.  This is a whole different story on the safety effect caused by closing bedroom doors.   Carbon Monoxide (CO) is an odorless gas that is the number one accidental poising in America.  In a test done by Home Energy they closed all the doors in a home and found they had 1000 CFM of outside air being drawn into the home.  It doesn’t take an expert to figure out that bringing in the frigid 2 degree air this morning in the Twin Cities is not good.  So the money it cost to heat up this cold outdoor air or in summer cool off that hot humid air will cost you more.

What can I do

Having properly sized return air ducts in a bedroom so the air can properly get back to the furnace is a great solution.  With the hundreds of homes I visit every year this seems to be the number one problem, undersized return air ductwork.  New construction building is a competitive market.  This tends to lead to lower cost and less experienced labor installing HVAC to save money upfront.  Unfortunately it cost homeowners much more over time living there.  One theory says if you don’t have enough return air in a room you can undercut the door so air gets under it.  The sad truth is in order to effectively do this you need to cut 14” off the bottom of the door and I don’t know many people who want that.  The best is to consult a professional heating and cooling company that specializes in existing homes and is certified in air balancing by organizations like National Comfort Institute (NCI) for example.  They can test your current ductwork pressure and add return air where needed or add transfer grilles.  It is suggested to hire a qualified company because if improperly installed they won’t circulate airflow as it should.

Another easy way to save on your utility cost is change your furnace filter regularly, which typically is every 30 days.  A great way to save on your air conditioning is have it cleaned annually by a professional.  According to a study conducted by Pacific Gas and Electric (PG&E), a dirty outside unit (that may not look dirty), can increase your electric bill as much as 30%.

Summer or winter closing your bedroom doors will not save you any money and may actually cost you more and compromise the comfort of your home.