undecided

[russholden]

I want to replace the furnace and duct work in my house. The house was built in 1957. One contractor suggested that I put the unit in the attic. It is currently under the house in the crawl space. Can anyone tell me which would be more efficient, in the attic or under the house? I live in Mississippi. I will replace the A/C unit as well.

[REP]

Furnaces and a/c s need to be worked on every so often.Install the equipment where it is easier to get to and to work on.
The only things that you must be aware of are the venting and the condensate line both heating and a/c.

[skippedover]

First you need to find the right company. That's the one that does a proper load analysis, designs the duct system using the ACCA Manual 'D' and selects the equipment based on the load calc and your budget. If you've already got a duct system in the crawl space, it might be the better way to go. On the other hand, if the existing system is falling apart, then a new system might be the way to go. Here's the skinny on that.

Warm air rises. Cold air falls. If you live in a 1-story home, then it makes little difference to the air whether it's coming out of the ceiling or the floor. If the system is properly designed, it should be equally as comfortable in either location. The key is proper load analysis and proper duct design. I've attached a more lengthy method of finding the right contractor. I hope it helps. Nothing like an educated consumer.

[amd]

I would have it put in the crawl space - even if the ductwork is well insulated, the supply air will pick up a fair bit of heat during the cooling season, resulting in higher operating costs.

Another disadvantage -> Water damage may occur if the condensate line gets blocked. (Ya, I know there are secondary drain pans, float switches which can shut the system off before overflowing occurs, etc - however, nothing's foolproof.)