The vents in your home are there to supply air from your HVAC unit to that room. These vents typically have levers so that you can adjust the direction of airflow. They can also be used to seal off the vents all together, preventing warm or cold air from entering the room.
Logic would dictate that by sealing off these vents, your heater or AC won’t have to deal with controlling the climate of that room, potentially saving you money on your utility bill from increased efficiency, but as it turns out, this isn’t the case at all.
Surprisingly, closing the vents in your home typically has the opposite effect of making your HVAC unit less efficient. This causes your bill to go up. So take it from the expert technicians at Hanna that if you want to save some money on your utility bills, there are better alternatives than to close your vents.
Why is this?
It all comes down to the amount of pressure in your ducts. The ductwork and your HVAC system are both designed to provide just the perfect amount of airflow, against just the right amount of pressure. By closing vents, you’re increasing this pressure. At the very least, this can cause your HVAC unit to run less efficiently. At worse, it can damage your equipment and pose a potentially lethal health risk.
ECM vs PSC
The specific issues you’ll run into by closing vents depends primarily on the type of blower in your HVAC system, either permanent split capacitor (PSC) or electronically commutated motor (ECM). This basically means that either your blower is PSC and has a fixed speed, or it is ECM, and its electronics can adjust the blower speed depending on the needs of your home.
Consider the added pressure of closing vents. For a PSC system, which won’t be able to speed up to overcome that increased pressure, you will have less airflow, which may eventually damage your equipment as it feeds back into the heater itself. This won’t happen instantly, and you’d have to close off most of the vents in your home for the pressure to become that great, but it’s still a concern.
For air conditioners, this may cause less airflow over the evaporator coil, which is the part that cools the air. If there’s less air picking up that “coldness,” then it’s building up on your coil, causing it to freeze and turn into a block of ice. This may eventually ruin your compressor.
Reduced airflow for a heater causes it to simply become to hot and perhaps crack, a potentially deadly problem. A cracked heat exchange can leak poisonous carbon monoxide into your home. This gas is odorless and deadly.
As stated earlier, these issues won’t happen quickly, and you’d have to close off most of the vents in your home before permanently damaging your hardware. But the increased pressure of closed vents will restrict the airflow from a PSC blower and cause comfort issues.
The issues with a ECM blower aren’t nearly as dangerous or damaging, but they exist nonetheless. These blowers are designed to modulate their speed depending on your needs, anywhere between 0 to 100%. If you close too many vents, the increased pressure will cause your ECM blower to climb in speed to overcome it. You can imagine how much more expensive your bill will be – and how much more quickly your equipment will wear down – if your HVAC unit is running at 80% when it should be running at 40.
It’s quite similar to having a dirty filter. In order for your unit to push the air through dirty filters, it must work harder. It’s much the same for a duct system with closed vents. There are also fewer places for that air to go, so it will end up leaking out, or be forced back down into your basement or floor cavities.
So, the next time you’re thinking about closing off the vents to your home, take it from the Hanna’s expert technicians, and don’t. Contact us if you have any questions about your home’s HVAC unit, and how to potentially save money.