We're looking at a house in southern Alabama that has no central heating and air. I would like to put one in. The house was built in 1950.

What should I be considering about the installation?


The easy challenge is finding somewhere to install the internal half (blower and coils) of the unit. You need to have space, access to service it, a place to run the lines to the outside unit, and power. Power is typically 220, and will need a dedicated circuit, so you'll need to be able to run another line from the breaker panel and have enough additional capacity on the main breaker. Finally, the largest challenge is running the ducts to each of the rooms. In an older home, the joists will frequently be solid and cannot be cut to pass the ducts, so you are left with using the craw space beneath the home, attic space, or enclose them below the ceiling/along the walls.

One final consideration is that a home built this long ago without an hvac unit will likely have little insulation or weather stripping. This means a lot of the energy used to get your home to the right temperature will go right out the walls. To do this right, you could be looking at a situation with all of your exterior walls are opened up to insulate, windows are replaced to prevent drafts, and lots of interior walls and ceilings are opened up to run the lines.

Depending on the home, and especially the layout, it could be cheaper to buy a similar home that already has an hvac installed.


I'm in an older home, and the issues I've run into are all of what BMitch said -- difficulty to run ducts, and lack of existing insulation.

You might be recent enough to have insulation ... if not, they can cut into the top of the walls from the inside and blow in insulation, of take off siding and insert it from the outside. You should also consider your current windows ... if they're originals, they're likely single pane.

To deal with the ductwork issue, I've been considering using a 'ductless air conditioner' aka. a 'mini-split', where there's an outside unit, but you attach a unit into each room that's going to be cooled, and run a ~3" refrigerant line to the outside unit. You can get 'em with as many as four zones, but if you need more cooling (eg, more extreme temps, which is likely for Alabama), or large rooms, you might only get 2 zones per outside unit. All of the internal stuff then just mounts onto the wall, so you don't have to find basement, attic or living space to hide it all.

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    +1 If I could have remembered the name, I would have recommended the mini-split systems myself. I've seen them being used in place of old window units, and they look much better. – BMitch Sep 10 '11 at 14:05

Retrofitting HVAC into a home requires all of the standard trades, and then some. If your carpentry, pipe-fitting, metal-working, electrical and brazing skills aren't up to snuff, consider contracting it out.

In short, depending on the level of accessibility, basically the entire house gets torn apart. That's what's known in the industry as, a can of worms.

  • Coring holes (in brick is no fun) to run power to a disconnect, line-sets to the condenser and the HE furnace exhaust

  • All but guaranteed: existing electrical is in the way of ductwork (other pipes/obstructions likely)

  • A spot outside with enough working space to fit the condenser; one foot clearance on all sides (length of line-set not to exceed 50', ideally)

  • Sufficient capacity of load center and two (laterally adjacent) spaces for a 2-pole circuit breaker (ideally the furnace is also on its own dedicated circuit)

  • New thermostat and wire, condensate drains, gas pipe and power to furnace

  • Destroy parts of your house to install wall registers (avoid floor registers if at all possible)

  • One of the most difficult parts is finding out where to send up the trunk, to the upper floors (entails more investigative destruction)

  • Those who are pregnant and children less than 7yo, should be wary of the (lead) dust this process may create, especially in homes built previous to 1978.


Why bother, unless you have health issues. With the rising cost of oil it is better to look for alternative sources. If its heating you want then try solar warm air, if its cooling then try adding shades to windows, make sure they can open, losing weight so you dont feel the heat, fans, etc.

  • You might be missing the point ... the goal is to answer the question. Sometimes, there are good alternative solutions, but political answers aren't useful. – Joe Sep 10 '11 at 2:13

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