How To Add Return Air Duct? (A Step By Step Guide)

The duct channels are an important part of any HVAC system that is responsible for carrying warm or cool air into the living space from the furnace and carrying the same amount of air back to the furnace or air handler, from where the air will be circulated out through the supply vents. 

Without return ducts, the air will not be able to undergo its full circulation thus impacting the efficiency of heating and cooling of the whole system. On top of that, if the air is not circulated back to the air handler or the furnace, it will make the HVAC work twice as hard to keep the space at the desired temperature and this will show up in increased energy bills.

The only way out of this is to add return air ducts. The question is how to do it because you might have heard or read that adding return ducts is a hectic process. Although that cannot be denied, it is still not complicated to the extent of being impossible. The process has been broken down for you in detail below. Read on to find out.

How To Add Return Air Duct
Bombaert Patrick /

How To Add Return Air Duct?

It is not always necessary to take professional help to add return air ducts when you can accomplish it by a DIY project. It can be done easily in a couple of days. No matter how long it takes, the point it you can do it by yourself and all you have to do to follow the steps given below.

Determine where the ducts are needed

The first thing you have to do before you can actually get to the installation process of the return ducts is to determine where you need them. Deciding on the return air duct location is a crucial executive decision and choosing the right spot can make all the difference. The best location can be decided by choosing the route for the air to travel between the vents and the air handler.

In most cases, these ductwork channels are already decided and made ready when the house is being constructed so you can call the company who undertook the construction project of your house and ask them for the ductwork configuration.

You might also need to reconfigure the vents if you are adding ducts. While deciding the spot for fitting the vent grilles you need to be careful about not cutting into pipes that run above the drywall. Once you figure out the ductwork configuration and know which ductwork leads to the furnace and which does not, you will see if additional return ducts are necessary or if you can do with the existing ductwork. 

Add vent holes for airflow

Now you have to create holes in the vent for the air to flow through it. This is a relatively simple process, but just make sure to not make the holes for the return vents too big. It is best that you take measurements before cutting the return air duct holes.

It is still okay if you cut them too small because then you can just shave off the sides but if you accidentally cut them too big, then it is going to cost you additional time and money to fix the mistake.

Connecting Round Air Ducts

Ducts can be of two types – round ones and rectangular ones. For the round ducts, select the required size and type of duct and see if one end is crimped or not. If both ends are uncrimped then you have to crimp one of them. You can ask the shop to give you ducts that are already crimped or you can just do it yourself with a crimping tool.

Now you have to connect two pieces of the duct by inserting the crimped end of one duct into the uncrimped end of the other. It might not go right in because of the friction of the two surfaces acting against each other so use a flathead screw to guide the crimped end in. When this is done you have to tape the seams together with foil tape to hold the joint in place.

To secure the seam further, insert a ½ inch of self-tapping sheet metal screw right where the ends of the two duct pieces overlap. In a similar manner add two more screws around the round seam and make sure the screws are at equal distances from each other. This will make the joint solid and prevent the ducts from moving about.

Connecting Rectangular Air Ducts

If you get ducts that are rectangular in shape then the process to connect them will be very different than connecting round ones.

First off get some s-cleats and start by attaching two to the two opposite raw metal edges of the air ducts. Make sure the length of the s-cleats is longer than the length of the side that is being connected. Now take another duct of the same dimensions and slowly fit the two opposite raw metal edges onto the s-cleats attached to the adjoining duct.

Now press the two ducts towards each other so that there is no gap between the two.

After this is done, slip the drives on the two other sides of the ducts and as with the s-cleats, the drives must be slightly longer than the sides being attached to. The exceeding part of the drives on the four side corners has to be hammered down over the sides to ensure complete solidity of the joint. Use foil tape to further ensure that the ducts are tightly joined and airtight.

Installing the Ducts

So far it was just preparation for adding a return air duct as this is the final and the most important step of an HVAC return air duct installation. Fair advice- you might need a hand from someone else. It does not have to be a professional but just someone who can help you carry the duct and supply you with the necessary tool when you are installing the duct.

First of all, remove any insulation materials and any other ceiling installations in the spaces between the ceiling studs which are in the route of the duct. Then position the newly connected ducts to the ductwork.

The tools that you will need are – a metal bender tool, drive cleats, duct connectors, and metal clamps. Tighten the newly installed ducts at the bottom of the ceiling joists. To secure the air duct to the ceiling or to the wall, use a hanger strap or saddle support.

Finally, use aluminum duct collars to attach the duct to the outlet vent of the plenum box.

Install the Air filter

Consider this as the final step of the process to install return air ducts to your HVAC. All you have to do is attach the HVAC filter to the outlet grill of the duct you just added.

It is recommended that you do not skip adding the air filters because then the ducts you just painstakingly built will be filled with debris and get blocked in no time.

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Wrapping Up

Most HVACs these days have a forced air system and that is why adding the return air ducts is important so that air inside the living space can be siphoned back to the furnace or the air handler.

Moreover adding return ducts also make the HVAC unit more energy efficient, not to mention the bettering of the air quality that is brought about.

In essence, this is an installation that you will not regret spending time and energy on.

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