Don't get too upset about having the air handler and duct work installed in the attic. Many builders will do this in new homes in order to save money. It is always better to install the equipment inside the conditioned space whenever possible. The 3 mini splits would have cost more than $13K, but probably not much more.

You could condition the attic space but that is expensive. A compromise would be to build an insulated room around the equipment. You could cover the duct work with additional insulation as best you can.

Attic powered exhaust fans have a bad reputation because most are installed incorrectly. I have had one in my attic for many years and I think it helps in keeping the second floor cool. If you install one, you must have adequate air intakes. If you don't then you will create negative air pressure and conditioned air from the house can be pulled into the attic. I recommend installing a cut off switch so the fan does not come on during warm days in the spring and fall.

I read through your post a few times and I guess I am missing exactly what your problem is. Is the A/C not keeping the upstairs cool? Have you found it to be expensive to run? As for the attic fan, if you haven't installed it yet, why not try it a while without it and see what happens?

@Dovetonsils: I am concerned with energy efficiency, cost, and wear-n-tear on equipment. Basically, am I going to be paying x amount of more dollars per month be cause of the heating or cooling of the air through the ducts. I heard the temp loss can be as much as -15 to -25 degrees.

pav's do cool off attics, for the reasons you list.

they also exacerbate duct leakage.

but it is what it is at this point.

foam insulating the attic would take care of

extreme heat gain from attic kneewalls,

and put both ductwork & equipment inside

an insulated semi conditioned space.

while you don't give your location... in mine putting

additional insulation over ductwork will cause condensation

issues. not so in dry climates. so your location plays

into the decision.

you can insulate & use a foil faced foam board to

air seal & add insulation value to the kneewalls.

done effectively it will address some of the heat

gain through the walls.

southface inst had excellent detail in this pdf:

http://www.southface.org/default-interior/Documents/airsealingkeypoints.pdf

best of luck

@energy_rater_la: Thanks for the advice/pdf. I live in Maryland. My ducts are flex ducts with an R-6 rating. Can I add additional foil-face insulation duct wrap to help?

not sure for your climate. talk to some local hvac folks

& see if the two vapor barriers will cause the insulation

to condensate. wrapping over flex, you have a reflective

vapor barrier, then adding more insulation & another

reflective surface adds another vapor barrier.

personally, I'd concentrate on mastic sealing each

duct at the take off collar at the supply plenum.

then mastic seal each plenum where it connects

to the equipment. and the return where it sits

on the attic floor. (open the return and caulk

from inside...each 2x to each other & corners of 2x's)

average duct leakage is 30% nationwide, so duct

sealing is a fast return of the sweat to get it done.

then you'd remove the supply grills from inside the house

and use Hardcast brand #1402 mastic tape to seal supply

boxes at ceiling. see attached pic.

we have lots of duct systems in attics here. not the best

way to go...but like I said...it is what it is.

best of luck...

Well, I've been reading A LOT about his subject. I have scheduled an energy audit to see how to tackle the problem. I may just make the attic a conditioned space. I feel confident I could do this on my own without much issue, but I do have and English/French Cottage style house... i.e. tons of knee walls and varying roof lines, which makes the process that much more difficult. I'll keep everyone posted. Thanks for the help!

I'm in FL and just went through this exercise. Had the HVAC contractor re-insulate and seal all the ductwork, but he botched the job badly, so I re-did it myself. Properly sealing and wrapping metal ductwork and sealing all the joints, eliminating kinks in flex return ducts, and replacing old and rotting 1" ductboard transitions and boxes solved most of the problems, but I think there remain problems related to the ductwork design. I'm really interested in seeing the results of your energy audit.