Flat roof, rooftop AC Ducting question

[jweddylv]

looking at an older house in Las Vegas (built in the 70's). the house has a flat roof and 2 rooftop ac units. It appears that the house originally had only one unit, with the second unit added later. The issue is that when they installed the second unit they installed the ductwork in the ceiling of the kitchen. the house has no attic so they create a drop ceiling for the duct work. The end result is the kitchen now has a 7' ceiling. My question is would it be feasible (and advisable) to remove the ductwork from the drop ceiling and relocate it to the roof (adequately insulated if possible)? I know no prices here but wonder the ballpark cost of such a project?

[energy_rater_La]

they could have furred down just portions of the ceiling rather than dropping
the whole ceiling...but it depends on configuration of your house.

I would NEVER put ductwork where it is exposed to direct
sun. IMO there isn't enough insulation to compensate for the
heat.
again..not knowing the config of your house it is difficult
to know.

don't know exsimated costs as it varies from area to area.

and would you really want to cut several holes into the flat roof?
I'd run away from that..or have you hire a professional roofer
and require a disclaimer releasing me from water leaks when
they happen. and the will..just a matter of time.

best of luck.

[hcong]

You are going to have a lot of heat transfer to and from the desert environment... You might have to upsize your unit to meet the losses in cooling and heating. It is do able but it won't be cheap, then again re-ducting the inside might cost around the same. I would recommend relocating your ducts into soffits and walls. Also see if the ducts at rectangular... you can reduce the height and increase the width of the ducts.

[catmanacman]

Put a gable roof on it and move the units,wont be cheap but will increase the value of your home

[jweddylv]

thanks for the replys, it seems like the best solution my be to put a gable roof over the existing roof and running the ductwork as needed. not a cheap option but probably the best solution. the weird thing is that the problem is only with one of the 2 rooftop units that created the drop ceiling in the kitchen, the other is run in the walls.

if we were to do a gable roof would we keep the one part rooftop units we have and just leave them under the roof?

[catmanacman]

You would have to move the unit to the outside of the new roof

[hcong]

thanks for the replys, it seems like the best solution my be to put a gable roof over the existing roof and running the ductwork as needed. not a cheap option but probably the best solution. the weird thing is that the problem is only with one of the 2 rooftop units that created the drop ceiling in the kitchen, the other is run in the walls.

if we were to do a gable roof would we keep the one part rooftop units we have and just leave them under the roof?

If the zone doesn't need more than 4-5 tons, maybe a ductless split would be cheaper than a new roof. I don't know what your house looks like but many architects are designing flat roofs to look more modern.

[duckman06]

looking at an older house in Las Vegas (built in the 70's). the house has a flat roof and 2 rooftop ac units. It appears that the house originally had only one unit, with the second unit added later. The issue is that when they installed the second unit they installed the ductwork in the ceiling of the kitchen. the house has no attic so they create a drop ceiling for the duct work. The end result is the kitchen now has a 7' ceiling. My question is would it be feasible (and advisable) to remove the ductwork from the drop ceiling and relocate it to the roof (adequately insulated if possible)? I know no prices here but wonder the ballpark cost of such a project?

I would look at another route as all the pros are stating. Metal ductwork on your roof will not look good and will lead to problems. I have seen 1st hand and never looks or works well for long periods. Mini split might be the way to go due to the flat roof.