For the system to work you have to re circulate the air back to the furnace.
Air return from finished attic.
This isolates the attic from the rest of the home which means the attic isn t part of the conditioned envelope.
To meet all three goals insulating your finished attic ventilating the roof and maximizing headroom use a combination of dense batt insulation rigid foam sheeting and air chutes.
Air handler platforms used as return air plenums can draw air from vented attics and crawlspaces through other connected framing cavities.
That is why you need a cold air return image 1.
That s measured after you finish the ceiling if you don t have enough height you ll have to raise the roof line and that adds a lot to your construction costs.
One of the most effective ways to convert your attic space into a spare bedroom is to remove the insulation from the floor and add insulation to the attic ceiling.
What is different in the basement is that most of the ductwork is on the ceiling.
Essentially that allows the warm air to circulate better.
If you leave a cold air return opening on the ceiling.
It s much better to place it low to suck out the cold stratified air.
Building codes vary by location but most require at least a 7 foot clearance for attic expansions.
The basement is no exception to the rule.
If you had no return air in your room you would create a positive pressure.
If the supply ducts are in the floor then the return air should be located up high.
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.
The return air vent openings need to be on the opposite side of the room so the conditioned air is pulled across the room.
Hot air heating systems function best if there is at least one cold air return on each floor of the house.
That would then reduce the flow of conditioned air to that space.
I finished our basement with a cold air return located near the floor.
Supply air from furnaces and air conditioners should be on outside walls.
Most codes require a specified minimum amount of headroom and it s tough to meet this requirement when insulating a finished attic especially since most.
At 21c i d guess you have a lot of leaks on the return side.
Essentially you re bringing the attic into the rest of the house.
Nail a piece of sheet metal onto the back of a stud cavity.
First check for head clearance.
I also included a fresh air return with motorized damper to bring in outside air.