In air conditioning, energy efficiency can be defined, as the percentage of energy consumed that goes into the system, compared with the absorbed energy overall. Most of us already understand, that opening exterior doors and windows reduces the efficiency of our HVAC systems since we are introducing hotter or colder air. What many people don’t know, is that leaving interior doors open can actually boost the efficiency and improve the Indoor Air Quality (IAQ) in their homes.
HVAC System Basics
An air conditioning system works by drawing in external air, cooling it down and then dissipating it throughout the home. Most HVAC systems don’t have return air vents; they rely on expelling excess air into larger indoor spaces and out of exterior building openings. When we close internal doors, we reduce the free flow of the air, and this inhibits the expulsion of any excess air. This causes pressure to build up, the air is forced out of the enclosed room via any openings. In an airtight pressurized space, the space that is created by ejecting air will be replaced by an equal amount of air from the external environment. As the air is forced out, outdoor air will rush in through fire ducts and water heater flues. This will cause the system to work harder, in order to replace the escaped cool air and the process will repeat itself.
The Outdoor Air
The HVAC system in your home may have already heated, cooled and purified your indoor air to your satisfaction. The new outdoor air that has been forced in has not been treated in any way. This will adversely affect your IAQ; the HVAC system must work harder for longer, and it will become less efficient. Not only will this make the system more expensive to run, but it will also be less effective at conditioning your indoor air.
Leaving Interior Doors Open
When you leave your interior doors open, the HVAC system in your home will work more efficiently. There will be little to no trapped air to cause a build of pressure in the rooms of your home. All of the energy that is consumed by the system will be directed towards conditioning the IAQ to your requirements. In essence, the system will not be fighting against itself. Additionally, since the IAQ is improved, you can avoid the stuffy feeling experienced when a smaller room has been heated without any ventilation.
Maximum HVAC System Effectiveness
Any HVAC equipment will only be as effective if a number of other factors are addressed. There should be an adequate space so that air circulation is possible. Any small rooms or rooms that have tight fitting doors can trap the air and cause a build up in air pressure. Leaving interior doors open or having looser fitting door can be very beneficial. The air will not become more pressurised, and you can avoid having a rush of hot or cold outdoor air being pulled into the room through the flue.
While leaving exterior doors open can compromise efficiency before you go around the home shutting all your internal doors, you may want to consider how you will be affecting the comfort level and performance of your system. You may be pleasantly surprised at the difference leaving your internal doors open can create.