Greetings All,
It’s been a few years since I’ve posted a question on this forum. Have always received outstanding insight and solutions to this homeowner’s problems.
I am thinking of building a new home in southern Michigan in 2006. I have always wondered why the AC evaporator coils are located on top of the furnace which is in the basements of most homes.
1. Is it a viable option to place the fan/evaporator coil in the attic, and then design the ductwork to enter from the ceilings of rooms in the house?
2. I suspect this would be a more expensive option than having the traditional furnace/AC combo unit in the basement. But I suspect it would be alot more efficient than trying to force cold air from the basement AC all the way to the second floor of a house.
Am I way off base in thinking of doing this?
Replies
I would suggest that if you do something like this you put the air handler in a closet, so that all the ductwork is in "conditioned space". Ductwork is rarely airtight, and losses in attics and crawlspaces cause a lot of lost efficiency.
In many climates where houses are built slab on grade the mechanical system is located in the attic. These are more arrid climates and cooling is more imporatnt thena heating.
Owen Roberts Group
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(Of course, it's not generally wise to locate the compressor/condenser in the attic, as this doesn't provide ideal airflow through the condenser and dumps even more heat into the attic.)
He said the evaporator coil, not the condensing unit.
So?
I would look into making the attic space a part of your conditioned space. That way, if you locate your AC system there, you don't have to worry about it freezing up in the winter time or losing most of its capacity to cooling the attic in the summertime.
The way to do it is either to insulate with spray-in foam between the rafter bays (which is what I did, for the same reasons as you, AC), or to apply the requisite inches of insulation to the exterior of the rafters (which makes for a thick roof). Either construction technique will work and not require any ventilation of the attic space.
As for which way is more expensive, I have no idea. However, I suspect that an AC system that works from the ceilings of rooms will, all things being equal, perform better than an AC system whose inlets are in the floor. IIRC, I read the same in the Manual-D... In climates where the ductwork is also used for heating, and where heating pre-dominates, the ductwork outlets may perform better when in the floor.
It depends also on the size of the house. You might find that you can really minimize the amount of ductwork taking up room in your home by splitting the load between two AC systems instead of trying to accomodate it all with just one. Properly installed and insulated ductwork will cost lots for the labor, so where do the total costs intersect?