Your home's central air conditioning and heating system will operate with a higher level of efficiency and effectiveness if the air pressure is equalized throughout the house. Uneven air pressure causes the system to work harder, and it can also lead to stagnant air which makes the space less comfortable for occupants. Below is how you can install return air grilles in your home's wood doors to preserve proper airflow and equalize pressure:
Tools and materials needed
Two return air grilles measuring 10 inches by 10 inches for each door - return air grilles are sold for floor, ceiling and wall use, so be sure to select one that is designed for vertical surfaces. Also, avoid grilles with movable louvers; these are likely to rattle or be accidentally closed. Grilles are typically sold according to "rough in" sizes, the dimensions you need to cut in the door itself in order to fit the grille.
Multipurpose tool with wood cutting blade
Electric drill with ⅛-inch drill bit
Large sheet of paper
1. Determine which doors need return air grilles - Not all doors need return air grilles; for example, if a door is only infrequently closed, then you don't need to install grilles. Also, for doors with more than a one and one-half-inch opening between the bottom of the door and the floor, installing grilles will not add much value. Finally, remember that grilles do reduce privacy, so don't install grilles in doors where privacy is of utmost importance.
2. Create a door grille template - For a 10-inch by 10-inch return air grille, you will need to create a template for laying out the location and size of the cuts in the door. Draw a 10-inch square on a piece of paper and cut the square out with a pair of scissors. Fold the square in half and unfold it again to locate its midpoint along the top and bottom.
3. Locate and place the template - Once you have created the template, locate the middle of the door from side-to-side by using a tape measure. Then, measure up from the bottom of the door 6 inches and place a mark at the intersection with the horizontal midpoint. This is where the bottom of your template will be located, so line up the midpoint of the paper square with the mark you just made on the door. Tape the square to the door with a few small pieces of masking tape; be sure to measure the square's distance to the bottom of the door to determine if it is level. If it isn't, remove the tape and reposition the square to make it even.
4. Cut around the template - After the template is in position and you are satisfied it is aligned evenly, then you will need to cut around its edges. A multipurpose tool with a fine-tooth wood cutting blade will provide you with excellent results, but you can also use a jig saw. When cutting, be careful not to penetrate through to the other side since you will want to measure and cut that side separately. Once you are finished cutting, remove the template and save it for use on the other side of the door. Pull the piece of wood out of the door and discard it.
5. Repeat the placement and cutting on the opposite side of the door - After cutting out the first opening on one side, repeat steps 3 and 4 on the other side of the door. Be careful when cutting on the opposite side of the door so your cuts are aligned with one another.
6. Install the return air grilles - Hold one of the grilles up to an opening you just cut in the door, and align it until you determine where it should go. Mark the screw locations on the door by using a pencil through the grille holes, and drill ⅛-inch pilot holes in each of the four spots. Next, install the grille by using the included screws; be careful not to overtighten the screws or you may strip the holes in the door. Repeat the same installation process on the opposite side of the door.
If you have specific questions about how your HVAC system is functioning, check out the site of an HVAC contractor in your area.