I have heard a couple of theories on using AC or heat when there’s a space in a home not being used. Some people have said keeping the door shut will decrease the usage, and others have said keeping the doorway open will allow the temperature of the house to be more even and an HVAC unit to be more cost-effective. Since I now have two bedrooms at my home that are empty, I decided that it was time to consult an experienced HVAC technician. I am really only using about a third of my home and not in any position to move to a smaller place, but would love to lower the cost of heating and cooling. I called an HVAC service number to provide some maintenance on my system and to suggest some cost saving measures too. The HVAC tech checked both the indoor and outdoor units, ductwork in addition to vents. Everything was in sound condition, except my air filter, which unfortunately needed replacing. He had a filter with him, and suggested I change mine no less than every two months, perhaps a few extra times in the coolest and warmest months. When I asked him about the empty room theories, he suggested closing the door. He said closing off both rooms might lead to problems because the air flow in the ducts remains the same whether it’s being used or not. Since some of the air is not flowing through the rooms, the excess may cause holes in ducts, the coils to freeze and even major damage. The HVAC unit was meant to work for the complete house, so restricting it too much can cause more damage compared to the little savings each month, and that would be more than it’s worth. I followed his recommendations and saw a drop in the cost of my monthly energy bill.