Cold Air Return In Attic

For the system to work you have to re circulate the air back to the furnace.

Cold air return in attic.

In other words there s a lot of air infiltration. That would then reduce the flow of conditioned air to that space. If you had no return air in your room you would create a positive pressure. When bedroom doors are closed the return is starved for air.

The return air vent openings need to be on the opposite side of the room so the conditioned air is pulled across the room. This pulls the air across your body. First building codes in many areas require that the cold air return line gets external insulation and therefore you will need to leave a gap for the insulation around the duct return line. Cavities or interstitial spaces within walls are also sometimes used as supply or return air pathways.

It is very difficult to make such cavity spaces airtight. I live in a 3 story townhouse and my return air ducts for the 3rd floor run through the attic space. These cavities often create a connection of inside air with outside air from an attic or crawlspace. I was up in the attic yesterday and noticed something about my return air duct that is strange.

If the supply ducts are in the floor then the return air should be located up high. If the supply ducts are high or in the ceiling then the return air ducts or grills should be low on a wall. Those are valid reasons to do it so the real answer is to make the attic at least semi conditioned space. Unlike supply vents return vents do not need to be cased in metal.

Instead of bringing in air from the home it creates a negative pressure environment where clean conditioned air is replaced by unfiltered outdoor air. That is why you need a cold air return image 1. These vents are seen in many types of furnace systems although there are alternatives such as drawing air from the outside or from the area around the furnace. The return vent pulls cold air from the bottom of the room and returns it to the furnace to be reheated and returned as warm air.

Running a metal cold air return duct between studs requires knowledge of both hvac systems and the components involved in framing.