I ve replaced the supply ducts and have insulated and encapsulated my crawlspace according to the best methods presented on this site.
Return air duct in attic.
If the supply ducts are in the floor then the return air should be located up high.
While none of these spaces makes an acceptable air pathway on its own some building cavities such as floor joists can make acceptable duct chases to contain an insulated air sealed metal or flex supply or return duct.
If that return duct is pulling in any outside air then the opposite has to be happening somewhere else in the system ie it is pushing out an equal amount of heated air.
I have a couple questions.
An attic over a garage that doesn t have room for an actual entrance is usually treated like an unheated attic and totally sealed off from the house.
At 21c i d guess you have a lot of leaks on the return side.
If the supply ducts are high or in the ceiling then the return air ducts or grills should be low on a wall.
A return air temp b outside air temp c airflow across evaporator coil d return air leaks from attic if you measure supply and return temperatures at the grille and at the air handler you can get an good idea of where your biggest losses are occurring.
I ve read a bunch of articles here and on bsc s site concerning ducts in the attic.
Transfer ducts may achieve this by increasing the return transfer 1 1 2 times the cross sectional area square inches of the supply duct entering the room or space it is serving and the door having at least an unrestricted 1 inch undercut to achieve proper return air balance.
The passive vents probably reduced that negative effect by allowing more air to flow from the the outdoors but it s still almost always better from an energy use point of view to not use turbine vents or powered attic vents of any significant size.
This pulls the air across your body.
The return air vent openings need to be on the opposite side of the room so the conditioned air is pulled across the room.
6 tips for good ductwork design.
That s right your heating and air system is nothing more than a big circulation unit.
To maintain balanced air pressure and air movement your duct system needs return vents for air in the room to be pulled back into the hvac system.
My 1948 ranch house has supply ducts in the crawlspace return ducts in the attic.
The ducts through which the air travels are part of a sealed system that usually is located in the attic for structures with slabs or under the floors on structures that are raised off the ground.
Not providing enough returns is a common ductwork design flaw that leads to comfort complaints.
In the summer the return duct removes warm air from inside and transports it to the outside to be conditioned.
A return duct is the part of the system that carries the air back to the furnace or air handler where it will then be circulated back out through the supply vents.
Air handler platforms used as return air plenums can draw air from vented attics and crawlspaces through other connected framing cavities.
