The problem with one large central return air vent

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There are three major reasons why we love to have a well-insulated and airtight homes that have well-designed HVAC systems; air quality, efficiency, and comfort. When a contractor or builders fails to make your home airtight by skimping on hacks in an HVAC system, then the building ends up with dirtier air, less comfort, and you spend more on your heating and cooling.

Know what the source of these problems are?

Having a single central air return.

Central returns are not the ideal HVAC design and they also increase the intensity of air leakage and create issues with indoor air quality. This is why we don’t like them.

The ideal HVAC design is where there is an air return in every bedroom of your home. However, when the home is two-stories – and in some instances the contractor or builder wanted to minimize the costs – there is a single return in the upstairs hallway. This is not a good idea because there are two problems with this setup:

When the bedroom doors have been closed, the return does not get air. Instead of the return bringing in air, it ends up creating a negative pressure environment, and the clean and conditioned air and replaced by outdoor air that has not been filtered or attic air. This means the setup leaves a lot of air infiltration.

Bedroom are going to get supply air, and this leaves them with a lot of positive air when the doors are closed. The conditioned air is going to leak from the bedroom to the outdoors instead of returning to the HVAC system of your home.

  • Dirtier air.
  • More energy is lost.
  • Higher utility bills.
  • More HVAC wear and tear.
  • Less comfort.

Your central air return could be the cause of your heating and cooling problems.

While it is rare, negative pressure can be so bad that it starts to pull CO from your gas appliances. When the house does not have an equal pressure balance – and there are combustion appliances in your home that isn’t conditioned or vented – then it becomes a possibility.

The central return could be bringing outdoor air (and the humidity of summer) inside your home, the same way a vacuum cleaner can make the basket dirty. This could be the cause of energy loss in the upstairs bedrooms – or any rooms upstairs that have not been connected with the air return.

Having a door undercut is not going to offer enough return air pathways. The door undercut might work for a closet or small bathroom, but not for a bedroom. If you want to know if the undercut will be effective in allowing enough air movement is by performing a pressure tests on that room.

The good thing is the problem is easy to fix.

There are different ways of improving airflow, reducing infiltration, and curbing energy loss when you have a single central return. Some of them include;

Start by adding a return for bedrooms that don’t have one.

This is the best option, but when possible. If the return is on the other side of the bedroom wall or you can add ductwork, then this becomes the best option for you.

Installing a transfer grille.

This is a wall cut out above the door and has a grille on both sides. It helps by opening up the air pathway from the room, and this allows more air in your central return. Adding a transfer grille to the bottom of the bedroom door can help expand the door.

Installing a jumper duct.

This is a little like the transfer grille, but the difference is it involves ductwork. The ceiling near the door is cut, a duct installed above the room, then runs through the attic. At the other end of the hallway close to your central return, another one is installed. It is referred to as the jumper duct because the air is going to “jump” from the room to the hall.

Jumper ducts are quieter than transfer grillers. You will spend less installing transfer grilles though. If you are worried about noise, then have jumper ducts installed. If you are looking for the option that costs less, then choose a transfer grille.

If you install one of the above fixes, then you will have a better pressure balance in your home. You will feel more comfortable and the air quality inside your home will improve. You will also see a difference in energy consumption. You are going to get all of these benefits by just helping air move around your home.

What is my next move if a have a single central return?

This depends. If you don’t close the doors or you are okay leaving them open all the time, then you don’t have to do anything. Central returns become a problem when the doors are closed, and not when they are open.

If you like closing your door, then you need to be a little more concerned. It is a good idea to get a home performance professional who is going to do a test on pressure balance in your home and advise you on whether you need adjustments. You should request a combustion safety test if you have gas appliances in your home.

If you have this problem, don’t worry because there is an easy soliton. The problems will most times be solved by installing more returns, jumper ducts, or transfer grills.

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