What’s behind your return air grille?

What’s behind your return air grille? Most would say, the return air duct.


If you live in Australia and have a ducted heating system, have a look behind the wall mounted return air grille. First of all, you will find a filter, (which needs to be cleaned or replaced regularly…….we’ll get to that later).

Behind the filter where you would expect to find a duct, you will actually find the inside of the wall. (Check out the photos below).

The problem here is that the air inside this part of the wall is connected to the air inside all of the other walls, as well as the air inside the roof space, and the air under the floor if you have a suspended floor system. THIS IS THE RETURN AIR PATH. The return air path goes directly to the air handling unit, then to the supply air path. You don’t want to be breathing contaminated air from the roof, walls and floor, and you don’t want unconditioned air from these areas mixing with your conditioned air.

I inspected the return air at a recently completed house on the weekend. Inside the cavity I found general rubbish including plastic wrappers, building construction waste, dirt, and plaster dust. Unfortunately, this is normal construction practice. You will have to make a special request to get anything different.

If you are building a new house and intend to have central heating, request that the return air void is sealed. At least get the plasterer to line the space like a small cupboard. Seal the intersections and seal the return air spigot connection.

A sealed air path will provide greater air quality, better energy efficiency and a healthier home. There is no need to put up with poor practice. Breathing is pretty important, make sure that the air you’re breathing is clean.

By the way don’t forget to clean your filter on a regular basis. If it’s beyond cleaning, replace it.