Cost to run central air in 1000 square foot home.

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Old 07-03-14, 10:03 PM
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Cost to run central air in 1000 square foot home.

Hey guys. My house was built in the 30s. My deed list it as 1000 square feet (never really messured it, but its probably about 800 is you subtract the porch). I also have a big storage room (old garage) so that takes it down a little now. Anyway, it has neverh ad central air in it and I would like to have it installed. Anyone know what the estimated cost would be for the unit, duct work, installation?
 
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Old 07-04-14, 07:03 AM
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Where will the furnace be located, do you have a basement?
 
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Old 07-04-14, 08:17 AM
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1930s house?

Your top priority should be reducing heat gain unless the house has already been upgraded -> uninsulated walls + attic + single pain windows + excessive air leakage can more than double heating/cooling costs.

As for installing central air, keep the ductwork out of the attic at all costs. If an attic install is the only option, look into alternatives such as a mini-split system.
 
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Old 07-04-14, 03:57 PM
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I just had a 2ton system, with ductwork, put in my 850 -900 sf house. Most estimates were between $5200 and $7000.
The house is in sw FL and temps since it was installed 3 wks ago have been 85* to 91*.
Based on my usage (FPL) lets you monitor it online) the cost, just to run the AC will be $35/month. $104 total bill. @.11/kwh
The house has old awning windows, and just ceiling insulation.
Have thermostat set to 77 (78 at nite) and it keeps the house at 77, with 52 - 54% humidity. Very comfortable to us. Some times we turn on a ceiling fan.
Hope this helps.
 
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Old 07-05-14, 02:44 PM
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Muggle,

My house has duct in the attic. It is two storys. I had the ducts replaced 5 years ago after discovering that they are asbestos.

Why did you say to keep duct out of the attic?
 
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Old 07-05-14, 03:22 PM
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WRDIY...
Most duct is only about R6-9 I think. At least typical flex is. Since attic temps can get to 130 or so in the summer and get cold in the winter, all that hot/cold air has to get pushed out before the conditioned air starts. Ideally, all ducting should be in conditioned or semi-conditioned spaces.
 
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Old 07-05-14, 03:57 PM
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That is a good point which I have never thought about. I think the duct system was built like that in the 70s, in the attic. So how do ducts get install in new homes today? Do they get install between walls?

The ducts that they replaced in my house is foil and then insulated and then foil. Does that makes a difference?

I live in California. We use ac for about 2-3 months out of the year. We use the heat for about 1-2 months. Regardless, it would be too costly to run the ducts through the walls at this point.

Thanks
 
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Old 07-06-14, 04:27 PM
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I assumed that this house doesn't have heat/air already.

In northern climates ductwork is typically installed in a conditioned basement or crawlspace. Not sure if you have a basement.

Attic systems aren't efficient - the capacity lost to the attic can be really high. (between leakage and conductive heat gain) Some people advocate spray foaming the roof deck and turning the attic into a conditioned space if there's no other place to put the ductwork.
 
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Old 07-07-14, 09:00 AM
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Make sure you have a load calc performed, too many oversized systems being installed these days.
As an example, I'm running a 3 ton roof top unit on our 1835 square foot house in Vegas and it holds a constant 71 all summer. We have neighbors with 5 ton units, same floor plan and high power bills to boot and they're not running the temp as cold as we are.
Many people try to use the bogus 400 square foot per ton rule. Mine works out to 611 square feet per ton and I probably could have went down to 2.5 ton and still been ok.
 
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Old 07-07-14, 09:57 AM
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no basrment.

we in california.
 
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