Dangers of Blocked Cold Air Registers If your HVAC system is designed this way, blocking off a single return vent can wreak havoc on the system and lead to: Pressure imbalances that let allergens and pollutants get pulled into your air supply from unconditioned areas.
Insufficient return air can lead to higher energy bills. When your HVAC system doesn't receive enough return air, it must work harder to maintain the desired temperature, increasing energy consumption. Homeowners might notice a spike in utility costs without a corresponding increase in usage.
The engine's combustion relies heavily on air, which mixes with fuel to generate energy. In the absence of a sufficient quantity of oxygen, an engine will not be able to generate power, and it may not even start. Whenever the air filter in your car's engine becomes too clogged, it may start to misfire.
If there's no way for air to circulate from the outflow vent to the intake vent, then air will not flow at all. A common source of the problem is the room's door doesn't have an air gap underneath or an air vent going through it.
Their purpose is to allow air to return to the furnace to be heated or cooled. It is an air inlet. If your home has returns in most rooms this is the best setup, allowing for the best circulation and air flow. But sometimes we see that people cover/close them up because they don't realize their importance.
Reduced efficiency: Your HVAC system will work less efficiently if you block a return air vent. This will make the units use more energy and will raise your utility costs.
Inconsistent air temperatures throughout your home could be a sign of not enough return air. You may also notice poor indoor air quality that feels stuffy. You also may notice an increase in your utility bill since your HVAC system might be working harder due to the lack of return air.
Because the return air vent works to suck air from a room and back into the ducts, you can try this simple test to see if it is working: take a tissue or thin paper and hold it in front of the return air vent, about 6” away. If the paper is being pulled toward the vent, you know it is doing its main duty.
Not enough return air in summer can cause rooms close to the central unit to be cooler and those farther from it to be warmer. In winter, rooms farther from the furnace can be too cool. An improperly sized return duct is one of the most common reasons for this (another being an AC or furnace issue).
Dirty filters, leaky ducts, and poor insulation can cause cold return vents. Leaky ducts often cause cold air to blow even after cranking the heat up. 20-30% of air, especially hot air, is lost because of leaky ducts. Cracked, holey ductwork needs sealing or replacement.
Decreased Acceleration and Power
One of the first signs of a clogged intake air filter is a noticeable decrease in acceleration and power. If your car feels sluggish or struggles to pick up speed, it could be due to restricted airflow caused by a dirty filter.
By installing more return vents throughout your home, they can trap the air and remove it, improving air circulation. A drawback with this method is that your ductwork needs enough space to support additional vents. Smaller homes that can't add more vents need to pursue other options.
Instead, there should be at least one return vent in every room, with two or three being ideal. If your house has only one return vent, this is not a problem — make sure to keep the doors open in every room so the air can circulate properly. Make sure there are no furniture, draperies, rugs, etc. blocking return vents.
While return vents don't always require filters, adding them provides additional filtration, improving indoor air quality and keeping dirt and debris out of your system.
While furnaces can stop operating for complicated reasons, home owners should check a few usual suspects first behind a lack of hot blowing air: Electrical problems causing a loss of power. Blocked air vents and ducts restricting airflow. Improperly configured thermostat settings.
Having a number of return vents (preferably one in every room, but also 2 or three is far better than just one) creates regular air pressure. If you have one return vent, your house is great. Maintain the doors to every room open so air can properly flow.
Check the Furnace Filter.
A dirty furnace filter is one of the most common reasons furnaces don't produce enough heat. Luckily, this is an easy and inexpensive fix. While you're at it, buy one or two extras and make a note in your calendar to check it again in a month.
In the heating cycle, blocked cold air returns can cause the heat exchanger inside the blower compartment to store too much heat and eventually crack. If the cracks are too large, the furnace can emit carbon monoxide into your home's air. Such a condition normally requires a complete system replacement.
Signs of an air duct clog include: One room in your house is hotter than all the others. Dirty air coming from vents. Unusual spikes in electric bills.
Return vents should be located in centralized rooms, such as larger living spaces or family rooms. These central locations allow return vents to efficiently pull air from the house and into the system. In most cases, you'll find return air vents located on a wall instead of the floor or ceiling.
The best fix for return-air problems is to install a return-air grille from each conditioned room in your home back to the furnace, A/C or heat pump. Air coming into the room is balanced with the amount returning, regardless of whether room doors are closed.
Due in large part to the short cycling issues mentioned above, components on an oversized heating and/or air conditioning systems are more likely to fail sooner than those on a properly sized system. As a result, you may end up having to replace your HVAC system sooner than expected.