Anonymous wrote:Re-upping this discussion in 2019 dollars. Has anyone done this in the past year or two? How much did it cost? thanks.

3 years ago (so 2016 dollars) I paid 8k to install a/c to just my upstairs. The handler is in my attic so vents are in the ceiling and no ductwork needed.

I have 2 Story home Southern California, roughly 3400 SFt built in 1989. Have a Single A/C unit providing air to both floors.
Downstairs get freezing cold, however 2nd floor takes a long to reach a comfortable temp.
Any thoughts any thoughts on what could be done and what the cost may be?

Re-upping this discussion in 2019 dollars. Has anyone done this in the past year or two? How much did it cost? thanks.

Dual zones and two units are separate things. Dual zones implies one unit separated into zones. Two units is just that - 2 separate units each with one zone. Neither setup is inherently more or less efficient, although a case can be made for a heat pump being slightly more efficient than a gas furnace. But that implies a two unit system since heat pumps are generally inadequate for all heating needs in this area.

You'll hear a lot of people swear by dual zones - but it is for comfort only. More expensive in short in and long run. That said, if one unit goes out, have at least part of the house cooled / heated is nice.

If you want least expensive in terms of maintenance and energy costs, go with an oversize unit (higher SEER rating) on the inside air handler and outside unit. Talk to a reputable AC company and they can give you the right rating and size for your house, then to price shop it.

Our cape has a separate duct work and a heat pump upstairs. Good solution, but not perfect. Works pretty well, although I don't think it is particularly energy efficient. Electric bills get really high in the peak summer and winter months. Also, it is a bit loud.

We did this last year for about $10k. We added a unit in the attic with vents to the ceilings of all the bedrooms. It's been great.

(not quoted PP, but had a 40s bungalow with added AC) Yes- ductwork goes through the attic and you have ceiling registers rather than floor vents. My house has strong enough supports to put the split unit in the attic too- not sure if this is common or not. Highly recommend a second unit for upstairs rather than trying to use same unit as downstairs since temp will not equalize easily, especially if you have a bonus room over a garage or anything over uncooled space.

Anonymous wrote:We added a second unit, total cost was about $10k including the high efficiency heat pump. Our attic was fully accessible so adding ductwork was easy.

A number oe neighbors in our 1930's cape neighborhood added a supplemental heat pump for the 2nd flr. Great decision.

Other options include a mini-split system, which would be in between a full new unit and window units. Extending ductwork from the basement will be very expensive. But it depends on how your house is built.

could you elaborate? does the ductwork go through the attic somehow? tks.

we paid $10K about 15 yrs ago in our 1915 chevy chase house. Im willing to bet the cost has gone up since then!

If you have the option of adding a second system, I would do this rather than adding ductwork from the 1st floor. Because cold air sinks, it can be very difficult to get both floors comfortable when they are on the same system.

We added a second unit, total cost was about $10k including the high efficiency heat pump. Our attic was fully accessible so adding ductwork was easy.

A number oe neighbors in our 1930's cape neighborhood added a supplemental heat pump for the 2nd flr. Great decision.

Other options include a mini-split system, which would be in between a full new unit and window units. Extending ductwork from the basement will be very expensive. But it depends on how your house is built.

How much does it cost to add (including duct work) a heating and cooling system to a second level? Is it better to do this or just try to extend the duct work that services the main floor/system? What other options (other than window units) are there?