Attic Furnace No Return Plenum

Cabling is not rated for plenum use.

Attic furnace no return plenum.

My mother has had me going up into her attic to seal the leaky ducts and parts of the plenum air handler that join up to the furnace and coil units. Building cavities used as return air plenums is one of the leading causes of duct leakage in homes today. I think a cmp cable cost twice a non rated cable so my guess is all your communication fire alarm and misc. The sealed attic is great with return and supply duct inside of the thermal envelope of the building.

The return is on top and the supply is on the bottom. An attic is a space not a structural component the space cannot support anything but air. Everything would need to be plenum rated including the low voltage cabling. If there is no return duct the concept is that the attic space becomes a return air plenum and this is not uncommon in commercial plenums.

The major drawback is what material can go in your plenum. If the space is conditioned it no longer is an attic and needs to be called conditioned space wiring within an area used as a plenum has to be in conduit. No return air plenum. If you have a door at the top or bottom of the stairs you can replace with a louvered door.

No radios or storage. Not to mention that the air handler itself is in its own plenum. You ll also need to provide a return path from a basement air handler or main level return to the second floor. A 14 trunk too small emerges from the foundation wall in the basement in a roughly 2 2 notch at the top of the foundation wall.

How can and attic be held to the same standard as a plenum when its used for storage and water heaters and such. Ceiling space as a return air plenum. Anyhow the return box and the other box that has the ducts coming out of it are made of sheet metal. Otherwise this is a code violation.

The rating plate will state the max. Static pressure but it is usually 0 5 wci. I have a huge concern about fire safety. Inspectors can learn how air leakage from ductwork may cause home energy loss increase utility bills lower comfort levels and make the hvac system less efficient.

As noted by one previous poster all materials in the attic must be plenum rated. The return air plenum was a room with doors and banks of filters. When i was removing the trunk i found that they simply used a 14 elbow under the furnace not a proper plenum box. Reality returns should be ducted with a small supply and return connected to the attic space.