No matter what season your HVAC system’s purpose is to maintain a constant, comfortable temperature in your home. During the extremes of the year (summer and winter) running your system can get expensive. You’ll find a lot of tips out there relating to home energy efficiency, one very common one is keeping bedroom doors closed.
The idea is that limiting air movement and space that needs to be heated or cooled will make the system run more efficiently. It seems to make sense. There is no need for unused rooms to be cooled or heated all day so closing them off should save you money. That’s not how it works though.
The reverse is actually true. The door blocks airflow so when the door is shut it creates pressure in the room. The trapped air will not stay put, it escapes through any crevice it can and is then replaced in equal amount. This process actually increases the amount of air being drawn into closed rooms, thus significantly increasing utility bills.
This air isn’t coming from your heating and cooling system either. It’s coming in from your water heater, chimney, leaks in windows, etc. Since it’s not passing through your system it is unfiltered. So you’re not only pulling in air, you’re also pulling in contaminants. The result can be damage to your home or danger to the occupants in the form of high CO levels or possible mold or mildew growth.
There are some solutions to this issue that will help cut your costs. The most obvious is to simply leave your doors open. If you have pets you need kept out of certain rooms using gates can be a better solution than closing the door. That doesn’t always work and sometimes those living in the house need privacy and closed doors are the only option.
You can also consider installing returns in all your rooms. You have to run ducts into each room which means cutting holes and possible hiring a pro to do the work so it might not be cheap but it is a simple solution overall. Another, similar, option is installing transfer grills. They are placed in a door, above the frame, or somewhere beside a door and they allow increased air flow between closed rooms and the hallway. If you choose to install a transfer grill, it’s always a good idea to hire a qualified contractor. Improperly installed, they won’t circulate airflow as they should and may not solve your HVAC issues. In addition, not all doors are suited for a grill — professionals will be able to tell you if what you have works or if you will need to replace your door.
No matter what the weather extreme closing interior doors will actually lower your HVAC system efficiency. It’s far better to leave your doors open or installing returns or grills to keep the air circulating properly.