While it can be tempting to block the cold air returns for rooms you're not using to save energy or place furniture against them to arrange a room, blocking these registers is one of the most common ways to undermine your cooling and heating system.
Doing that may have the following detrimental effects: It will impede, and therefore reduce, the total system air flow. 1. Air may not reach places in the system that you want air conditioned. 2. The air temperature of air coming out of your registers will likely be too cold in the summer and too warm in the winter. 3.
If these air return systems are obstructed, not only will you block the proper airflow and create stuffiness in the rooms of your house, but you will have uneven cooling or heating, lack of proper filtration, and potentially higher energy bills.
Return air ducts must be sealed and unobstructed — Sealing return air ducts is just as important as sealing supply ducts. Sealing all duct section connections with mastic, a specialized rubbery sealant, or with metal tape prevents air leaks.
Use cardboard. Paper won't hold against the air pressure. Those vents just screw on and off. You could unscrew it, pull it down, cut a piece of cardboard to fit the opening, then screw it back up there. That would look a lot cleaner than taping cardboard over the outside.
A build up of pressure can be caused by covered vents. This could lead to a cracked heat exchanger which in turn can lead to leaking carbon monoxide. Covering your vents can damage your HVAC system and cause cracks that could allow air to escape your ducts.
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.
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.
All supply- and return-duct connections should be sealed with mastic or approved tape. Because ductwork in cavity spaces is likely to be inaccessible, the duct system for airtightness should be tested with a duct-blaster test before installing the drywall.
Common Issues with Return Ducts: Clogs and Leaks
You can generally identify a blocked air duct by a distinct drop in heating and cooling efficiency, increased energy costs, and occasionally a musty, dusty smell throughout the home.
If you prioritize heating, put the HVAC and vents in (or below) the floor. This principle works for return heating vents as well. Place returns for cooling in the ceiling where the warm air congregates and heating returns in or near the floor where the cold air congregates.
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.
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.
You should never block your air return vents. Period. However, if you're looking to keep your home cooler in the summer, you can try closing lower supply vents and keeping upper ones open, allowing cooler air temperatures to come in from above and sink throughout your house.
The filter belongs on the return side of your HVAC's furnace and AC system. It's a “must” to have one there. And if you have a return air filter of the right size that is properly installed, then there is no need for a supply vent filter.
Except for factory-installed ducts, plenums, and casings or exhaust air ducts where the temperature difference between the inside and outside of the duct is less than 15℉, the IECC calls for insulation to be installed in supply and return ducts: In attics vented to the outside.
While it can be tempting to block the cold air returns for rooms you're not using to save energy or place furniture against them to arrange a room, blocking these registers is one of the most common ways to undermine your cooling and heating system.
“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.
In most applications, the door undercut would need to be 1.5 inches or greater to allow enough air to pass. There are some through-the-door alternatives that can be effective.
Any gaps you see in or around the cold air return should be spray foamed, caulked or mastic in order to create an energy efficient HVAC system.
Piping shall not be installed in or through a ducted supply, return or exhaust, or a clothes chute, chimney or gas vent, dumbwaiter or elevator shaft.
In winter, enable the bottom cold air to return and in the summer, enable the upper return. It's that simple.
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.
A blocked air vent can permit mold or mildew to develop in and around your vents and ductwork if you reside in a humid location. You can be wasting money on utility costs. You most likely thought covering your air vents would certainly save you energy, but it does the opposite.
In warmer months, do the opposite — open the supply vents in higher locations and close the ones placed lower. This will direct more cold air to the ceiling, which will sink to cool the whole space.