its best to ues the 80+...it will save you service calls..in the winter...the condensate will will only cause you problems.....nip it in the bud.....

I have put many 90+ furnace in a attic. Under normal heating use it will not freeze inside the furnace. I put the trap and drain in the insulation down close to the ceiling, and make sure you have insulation above the drain and none below the drain and trap. If you want to turn it off for the winter months, just poor a quart of rv antifreeze down the stack.If its done right you should not have any trouble . I think it is well worth it to go from 80+ to 93 to 95%.

Is your current furnace in the attic? If the current system is not there, I would never install a new one in the attic.

In general the attic is a bad location for a furnace because of difficult access (for filter changes)and the huge possibility of duct leakage.

Paulbm... Why would someone turn off the furnace in their house for the winter??!!

location of the heating system and amount of duct leakage are not related to each other.
attic installs are fairly common, not the best locatin IMO..but ITRW and all that.
I agree that the 90+ is the way to go.
make sure that mastic is used to seal all connections
to plenums and to seal ducts, even if not replacing ducts..
seal existing ductwork if applicable.
if you foam insulate the roofline then the attic becomes
semi-conditioned which improves the performance of the system, and makes ductleakage and attic to house leakage
(air infiltration) less of an issue.
best of luck.

You can always enclose the area around the furnace with a couple inches of foam board and then pick up the ceiling insulation in the enclosed area to make it partly conditioned space.

* Posted by dallasbill (My Page) on
Wed, Apr 22, 09 at 12:04

Paulbm... Why would someone turn off the furnace in their house for the winter??!!

People are stupid & cheap. I knew of a case where someone had an air handler with hot water coil in an uninsulated attic and went away for the weekend. Turned off the heat altogether for 2 days came back and when he turned it on the HW coil cracked and soaked his hole ceiling and he had to replace the coil and ceiling.

Why would someone turn off the furnace in their house for the winter??!!
I live in a resort area. and i lot of my customers go south for a couple of months in the winter. They have there homes set up to drain down so the can turn off the heat for a time. It is a very common thing in my area. I live on a very large lake so we have very few basements and a lot of slabs floors. That is why we do a lot of over head heating system. A lot of the existing homes
were built for cabins around here, they been added on to a few times and there is no place to put a furnace except in the attic. I do a lot more existing
homes then i do new homes. I have never had a furnace freeze up in a attic.
In my area it can get down to 20 below.

Would you guys go with a two stage 97% with gas valve throttling from York for the furnace or with a variable speed 80% from lennox or trane?

Thank you for the help with this.

To me that would be easy pick. The different in price between a 80 and 97 is not that great. so when you buy a $1.00 worth of gas, do you want 97 cents of heat or 80 cents of heat. It starts paying back quite fast. later paulbm