I love the single unit HVACs. I hate the unit in the attic - it has leaked so many times. Now that I am ready to replace the attic unit, I was wondering if I could have the same setup as my 1st floor DualFuel Heat Pump (single unit)

Houses are so badly designed when the downstairs unit has more power than the upstairs one, which gets hotter.

I understand there will be hell with duct replacements, but isnt there an easy way, instead of replacing all ducts and registers to just have a duct going to the place where the upstairs duct starts ? I really want a single unit and one which I dont have to bother with in the stupid attic.

I came across the reverse in this post: Should I move the furnace upstairs to help cool the 2nd story?


No, not really. The work you're describing doesn't sound remotely cost-effective, or effective at all for that matter. Running a huge duct from the basement to the attic will choke off the airflow. Not to mention that if you're going to to that, you're already doing half the work necessary to redo the ductwork properly to connect the two zones.

It sounds like the real solution would be to abandon the attic unit (possibly selling it for some quick cash if it still works), and then integrate the second floor ductwork with the first floor ductwork such that the basement-mounted unit can service the whole house adequately.

If your second floor gets really really hot, the first and probably most consequential step is to air-seal and super-insulate the attic floor, and possibly adding a radiant barrier under the roof rafters if you can perform the work yourself (don't hire that part out; the payback time will be on the order of a hundred years). Low-E storm windows can help too if your house's windows are old and crappy.

  • Thanks for the detailed answer. Integrating the ductwork sounds like a great plan, I will now have to research that option, as well as make sure my downstairs unit can service both levels. (14 SEER 2 ton should be good enough for heat & cold for a 2k sqft house correct ?) – killjoy May 21 '15 at 22:53
  • SEER tells you how efficiently it runs, not how much house it can cool; the BTU rating is what you'd need to know. But it's probably fine; most AC units are grossly oversized. You can more or less ensure it'll be fine by performing the attic air-sealing-and-insulation work, since that's where a lot of the heat gain comes from. – iLikeDirt May 21 '15 at 22:55
  • this combining ductwork stuff - is it something that needs to be done by a certified professional and be inspected ? Is it something that can be easily reversed if things dont work out ? Is it something that can be done without messing around with the structure and be seen outside the walls ? I know it depends on the house, lets say a 'standard' house. Thanks again ! – killjoy May 21 '15 at 23:13
  • A pro would probably be best unless you want to learn all about duct design. Which you can and should! A lot depends on the condition of the house: where the ducts are located, what they're made out of, their current layout, etc. Impossible to be more specific without knowing that info. I'd recommend either hiring a pro or becoming an expert in duct design and doing it yourself, if you reasonably feel like it's within your capacity to do. – iLikeDirt May 21 '15 at 23:36
  • @killjoy: in what region is your house? A 2 ton unit for 2k sf would be grossly undersized for most homes in a southern climate (like Texas) but could be sufficient if you are in a cool enough climate or if your house is sealed well enough. – Ryan Smith May 22 '15 at 17:29

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