If you’re like most homeowners, you’re concerned about energy costs and environmental costs of your HVAC system. It’s true that your air conditioner unit, heat pump, and furnace use a fair bit of energy between the three of them.
You also may have had the idea to close the vents in your unused rooms while you’re out for the day. It sounds like a good idea, right?
However, this HVAC contractor does not recommend closing your vents in unused rooms. But why?
Why HVAC Contractors Say: Don’t Close The Vents!
When you close the vents in your room, you restrict airflow in the entire HVAC system. Due to this restriction, the blower in your system has to push air against more pressure.
Depending on the type of blower you have, it will compensate for this additional pressure in one of two ways. If you have an ECM blower (electronically commutated motor; present in newer homes or HVAC installations), it starts to ramp up the energy usage. This makes it overall less efficient to close the vents!
If you have a PSC motor (permanent split capacitor; present in the majority of homes overall), it continues to spin but at a lower speed. This lowers airflow from the blower.
Lower airflow could freeze the coil while air conditioning is on. This happens because the airflow is what keeps the coil from getting too cold and freezing the condensation from the air. This causes a frozen coil. It could also cause liquid refrigerant to pass back through the compressor because the low airflow is preventing the refrigerant from evaporating.
Lower airflow could cause cracks in the heat exchanger, which could potentially cause a carbon monoxide leak. These leaks can be fatal.
How The System Works
The HVAC system’s blower is the machine that pulls and pushes air, from return ducts back through supply ducts. This is how airflow is controlled throughout the house through the vents.
When the HVAC system is built and installed, it’s designed so that the blower pushes against some maximum pressure. Typically, it’s 0.5 IWC,
The problem here is that closed vents increase pressure. When the pressure goes past 0.5 IWC, bad things can happen.
What’s The Answer?
Don’t close the vents, control the temperature.
Most importantly, make sure you have a quality HVAC unit installed in your home, by a professional HVAC contractor who knows what they’re doing. No pro worth their salt will tell you that you should be messing with the vents all the time!