Closing doors to keep the warmed or cooled air in is a common mistake homeowners make when attempting to follow questionable temperature control tips. The best way to keep your heating or cooling costs down is to keep your doors open. That may seem contrary to popular belief, but confining the air flow by closing doors actually fails miserably at confining cooled air or warm air in a room. All air in a room eventually escapes through small vents under doors around windows, etc. When the air escapes, it must be replaced by new air which is pulled into the room by the vacuum pressure created by the closed doors.
This vacuum pressure causes the HVAC system to go into overload attempting to warm or cool the neglected spaces behind closed doors. So instead of saving money, you would actually be increasing your energy usage and therefore your energy bills. More and more warm air is drawn into the spaces behind closed doors making your heater work harder.
Not all the replacement air is coming from your HVAC system, much of it is being pulled in from your chimney, from leaks in your windows and from other areas allowing in outside air. This air unlike the air from your furnace or air conditioner which is filtered is completely without filter. You are then allowing in contaminants, allergens, pollen, mold and mildew.
The most effective things to do are to install systems that allow air to flow freely from room to room. If open doors are not the best option due to privacy issues, try installing transfer grills above the doors to allow the free flow of air. Installing returns in each room is an expensive option, I is an effective one. Leaving doors open or establishing air flow with returns or transfer grills keeps the air moving and reduces the amount of work your HVAC must do.
Temperature control tips all begin with unhindered air flow. When the air moves freely, no vacuum is present to force the production of large amounts of warmed or cooled air to replace escaping air from a closed room. The simple answer to the question, ‘Should I close my doors to keep warm air in?’, is ‘No’. Never hinder the free flow of air for the sake of energy conservation.