I assume you also have an AC condenser and coil as part of this furnace installation. If that is the case then proper drainage is a concern. You want a properly pitched drain with a trap that you can easily clean. The EZ-Trap see through drain would be nice to have. You want a secondary drain pan in case there is ever a problem.

Get a 4 inch media filter installed where the return meets the furnace. You will have to go into the attic once a year to replace it. The duct work should be a minimum of R8. Any hard ducts should be sealed with mastic and covered with insulation.

I would like to see the gas line be black pipe all the way to the furnace with a drip leg.

This post was edited by mike_home on Tue, May 21, 13 at 8:09

Drain pan with automatic cut off switch...

Very good suggestion on the cut off switch.

There is no AC unit just furnace - thank you all!

so, how did it go?
did they mastic seal furnace to supply/return plenums?

check & see if your ductwork is mastic sealed where
ducts leave plenum?

mastic dries to either a gray or white finish.
it should be a thick application with no gaps or
voids.

most homes have duct leakage, 30% seems
to be average. so over 1/4 of the air you
pay to condition...doesn't make it into the house.

mastic sealing ducts, plenums, returns & supply
boxes has a fast payback and immediate effect
on flow of air into the house.

best of luck.