We have probably all done it from time to time — closed the door to one or two rooms that aren’t in use in order to increase energy efficiency.
After all, why heat or cool a room if no one will use it regularly? Yet, is it really a good idea?
The answer is no, but not for the reasons you think.
Closing a door reduces air flow into the room along with air flow in your entire house. Air becomes trapped behind the closed door and pressurizes the room, which, in turn, forces cooled air out of the house through any opening the air finds. Each cubic yard of air forced out of a building requires an equal amount to be drawn in to replace it. The number of doors closed off in a house increases the exchange rate of outside air entering the home by a rate of 300 to 900 percent. The more interior doors are closed, the higher the percentage.
What does this mean for the average homeowner? Very simply, utility bills increase while comfort decreases and the potential for health problems suddenly appears.
Why does all that happen? Air follows the path of least resistance. In your home, the biggest and straightest holes are usually the chimney or flues for your water heater and furnace. These openings have smooth surfaces that make it easy for air to slide down in the same way that it slid outside. Reverse air flow from these openings is called a backdraft and can bring in carbon monoxide (CO) and other combustible gases, outdoor pollutants and humidity. Negative effects of reverse airflow can include cold drafts, high humidity, increased mold or even carbon monoxide poisoning.
Another factor is the presence of new windows and doors that provide tighter seals to the outside and hold warmed or cooled air inside more efficiently. Measures such as these and making sure that HVAC ducts are airtight also further seal the building, but sometimes can exacerbate interior air quality problems.
If you need to close off rooms, try to do so for only a portion of the day so that air flow is adequate.
To learn more about optimum HVAC use and indoor air quality, continue following our blog for new posts.