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.
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.
You should never close your HVAC return vents, but supply vents can be adjusted to improve home comfort. In this blog, the trained professionals at Damiani's Comfort Design explain the strategy behind opening your supply vents and the dangers of keeping your return vents closed.
Blocked vents can pose a severe danger to your home and family. Carbon monoxide poisoning, fire hazards, and increased humidity levels are all potential risks and hazards of blocked vents. Regularly inspect and maintain your vents to ensure they function correctly and unobstructed.
Closing supply vents throws your heating and cooling system off balance, creates airflow problems, and makes the system work harder. That's why it's better to keep all the vents open for optimized airflow and energy efficiency.
So how much space does an air return vent need to work properly? Home Inspection Insider explains that an air return vent needs 6-12 inches of space in front of it, and recommends that you do not put large, bulky furniture like couches and bookshelves in front of an air return vent.
Closing air vents can lead to several different issues in your home: It can cause leaks in the HVAC system or make existing leaks worse. It can make your HVAC system less efficient rather than saving energy. Pressure can damage your heat exchanger, resulting in dangerous carbon monoxide leaks.
Obstructed ventilation areas are a serious hazard. Whether through dust or other larger objects, when airflow to equipment like fans or vents is blocked, this can cause heat to build. In this instance, the dry fibrous make-up of dust can act like fuel to a spark or flame.
Block Off the Vent: You can block the vent by placing a piece of furniture at the opening or purchasing a magnetic damper that's strong enough to stick to the steel on the wall or ceiling. Plastic sheeting can be placed over the opening as well. You can also install a vent grille filter.
If they are too small, airflow will be restricted and there will not be enough air circulation to heat or cool the inside of your home. Return air ducts must be sealed and unobstructed — Sealing return air ducts is just as important as sealing supply ducts.
Undersized return ducts can cause up to 20% of the conditioned air in your home to escape. This occurs due to air pressure and not a hole in a duct. The excess pressure is caused by exhaust air staying in a room longer. The room may become uncomfortable and stuffy.
Hot air rises and cool air sinks. Therefore, opening the right return vents in the summer and winter significantly improves the distribution of air by your forced-air system. You'll also enjoy more even heating and cooling throughout your home. In the summer, open your high returns and close the low ones.
While blocking air bricks may seem like a good way to keep the cold out, it can cause more harm than good. Covering these vital vents stops fresh air from flowing into your home. This lack of airflow leads to damp and moisture buildup. Damp conditions are perfect for wood rot and mould growth.
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.
Guess where that air goes, that's being sucked into the Return Air vent. It goes back to the air handler, into a large plenum (box), mixed and joined with the Return Air from the other rooms. Blending the air together helps eliminate the hot/cold rooms and zones in your house.
If furniture or drapes are blocking your heating vents, you're making your furnace work harder than it should. Blocked vents increase air pressure in your ductwork, which can create cracks and leaks.
EXPERT RECOMMENDATION: If you want to try to balance the airflow throughout your home, you should not close vents completely; HOWEVER, you can close them slightly (not more than 75% closed) to help distribute air better to the areas that need it most.
Avoid blocking air vents with pillows, furniture, plants, or pictures. When the air vents are blocked it means that heated or cooled air needs to squeeze by what is blocking it to reach the rest of the room.
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.
“If the return air vent is blocked, the furnace is going to try and pull air from anywhere that it can,” Ryan says. If you have any sort of gap in your ductwork, the system will pull from these places instead, carrying contaminants into your home and reducing air quality.
Closing the vents doesn't do it any favors. In fact, instead of helping the air conditioner cool less, closed registers force the same amount of air through other ducts. This builds pressure in the system and makes your HVAC system work harder to distribute the air where you need it.
As conditioned air is pushed in, the air already in the home needs a place to escape. Return air vents serve this purpose by helping to pull in the air and putting it back into the system. This is what maintains proper air pressure in a home.
Even one blocked vent in the home can cause an inefficiency in air flow, which means your HVAC system will likely have to work harder to achieve the desired temperature. The result may be a home that is riddled with uneven temperatures from room to room.
All objects should be at least 6 to 12 inches away from the vent. However, when it comes to big bulky items, such as your sofa, recliner or bookcase, it's best to never place them in front of your return air vent.