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.
The first thing to check is the filters in the return air duct(s). This might be at the furnace or they could be at the return air grilles. Next thing to check is to see if the evaporator (cooling) coil in the furnace ductwork is frozen. These are the two primary causes of no airflow from the registers.
Symptoms include weak airflow and uneven cooling or heating throughout your home, with some rooms feeling much cooler or warmer than others. Homeowners should regularly check vents for consistent airflow. If you notice a significant drop in air pressure or uneven temperatures, it could indicate return air issues.
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.
Reports of funny smells
Musty odours and smells of damp around the building can result from poor ventilation. You should check the HVAC system to ensure that it's distributing clean air correctly and that waste air is leaving the building properly.
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.
The easiest way to check if the fan is ventilating properly is to take a Kleenex or single square of toilet paper and place it along the fan while it's running. If the fan holds up the paper and keeps it attached, then it's working properly.
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.
Return vents tend to be bigger than supply vents, and you won't feel any air coming from them. When an HVAC system delivers air to a room, it increases that room's air pressure. Return vents exist to remove the extra air.
Maintenance Needs
Return vent filters, if used, also need regular replacement to avoid airflow issues. By properly maintaining both types of filters, you can get great airflow, reduce strain on your HVAC system, and rest easy knowing you have cleaner air.
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.
Parts of Your Home Are Hotter or Colder
If there's not enough return air, your living room can be 10℉+ warmer or cooler than, for example, the bedrooms.
We've seen how it can create safety hazards, mess with your home's heating and cooling, and even damage your bed. Blocked vents can cause fire risks, poor air quality, uneven temperatures, and moisture buildup. Instead of covering vents, try rearranging your furniture or using vent deflectors to direct airflow.
Low airflow can make your ears hurt in one room compared to another. Use a barometer to measure the pressure in the kitchen, living room, bedroom, and other rooms in the house. If you notice different pressure measurements throughout the house, this is a sign there's not enough return air.
1. Openings shall not be located less than 10 feet (3048 mm) measured in any direction from an open combustion chamber or draft hood of another appliance located in the same room or space. 2. Return air shall not be taken from a hazardous or insanitary location or a refrigeration room as defined in this code.
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.
Conversely, in the Winter heating season, you will want to pull the coldest air back to the furnace to be warmed and create circulation. In these months, you'll want the lower air return open and the upper air return closed.
Lots of things can cause your blower to have trouble, especially if it gets too dirty. A fan clogged by dirt, a stuck wheel, broken motor, or a loose fan belt are all common problems that reduce the amount of airflow you feel coming from your vents. How to fix: Call an AC tech to examine and fix the blower.
If your AC is running but not cooling, it could be due to a dirty air filter, incorrect thermostat settings, a malfunctioning thermostat, a refrigerant leak, dirty condenser coils, blocked vents or ducts, a faulty compressor, frozen evaporator coils, or electrical issues.
To identify a return vent, take a piece of paper and hold it up to the vent. If the paper is drawn towards the vent, then it's a return vent. Return vents are usually larger than supply vents, and they usually don't have adjustable slats to direct airflow since the air is going into the ducts instead of out.
Return vents are usually larger than supply vents and are in large rooms in the home. The return vents in your home help equalize the pressure that changes as your HVAC system heats or cools your home. These vents should never be fully closed because closing them off restricts airflow and strains the system.
An anemometer, a test instrument that measures air velocity is used to determine the average airspeed in the duct. Then the average feet per minute is multiplied by the area of the duct in square feet to determine the airflow moving through the duct.
Persistent Odors: Homes should refresh and clear out odors naturally through proper ventilation. If cooking smells, smoke, or other odors last longer than they should, it's likely your home isn't circulating air properly.
In summary, a ventilation test makes sure you correctly configure the ventilation systems in your building and that the air flow is of a good standard. This is in order to maintain a high standard of indoor air quality. Furthermore, ventilations tests make sure designers follow The Building Regulations.