The total drop in efficiency can be up to 35.
Attic furnace requirements.
Upright furnaces shall be permitted to be installed in an attic furred or under floor space exceeding 5 feet 1524 mm in height provided the required listings and furnace and duct.
That means you have higher energy costs and less efficiency since you re blowing the air down instead of allowing it to rise naturally.
The passage must not be smaller than 30 high x 22 wide and no longer than 20 unless it s at least 6 tall and then no more than 50 passageways must have a solid floor no less than 24 wide.
An attic furnace is closer to the upper stories of a multi level home.
Attic furnace passageway minimum dimensions requirements.
The opening passageway must allow for unobstructed access.
So why put an hvac system up in the attic at all.
Well mainly it s a way to save space.
Air ducts lose a fair amount of heat through leakage so shorter lengths are more efficient.
Most updated central air conditioned homes have a new air conditioner split system meaning the ac is broken up into parts.
30 inches high 762 mm 22 inches wide 559 mm 20 feet max length 6096 mm.
An outdoor unit which houses the fan condenser and compressor and an indoor unit which holds the evaporator and fan.
If you place the furnace in the attic then you must install the infrastructure in the building to force the warm air to the bottom floor.