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AR15.COM
6/13/2017 10:23:56 PM EDT
Looking at a house without any AC.  It was built in 1996.  Original furnace in the basement of a two story house.  No existing AC.  Approximately 4000 sq ft.

Would installing a 5 ton AC unit be adequate for the entire house?  Or do I need to get dual zone AC?

Rough costs on each option?
6/13/2017 10:44:08 PM EDT
[#1]
Not an expert but you need to give some more details. What's the weather like where you live? How's the general layout of the home? What does your existing ductwork look like?
6/13/2017 10:52:29 PM EDT
[#2]
Quote History
Quoted:
Not an expert but you need to give some more details. What's the weather like where you live? How's the general layout of the home? What does your existing ductwork look like?
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Good questions.  It gets hot (90's) during the day about two solid months of the year.  Pretty dry.  Elevation approximately 6500 ft.  

First floor is a typical 90's layout.  Walk into the front door and there's a formal dining and living room.  Then an open kitchen and family room.  Upstairs has 4 bedrooms.  Downstairs with walkout basement felt pretty cool while looking at it today when it was about 82F.  
6/13/2017 10:57:22 PM EDT
[#3]
more details needed. location as in city and state. square footage of house. square footage of exterior windows. u or r value of exterior walls and windows. attic insulation u or r value. orientation of house
6/13/2017 11:04:11 PM EDT
[#4]
Quote History
Quoted:
more details needed. location as in city and state. square footage of house. square footage of exterior windows. u or r value of exterior walls and windows. attic insulation u or r value. orientation of house
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Approx 20 miles west of Colorado Springs.  4000 sq ft.  Not sure on sq footage of windows.  Most windows on E, S, and W sides of house.  Pretty much windows in all rooms of house.  Garage is on north side of house and no windows there.

I have no idea on R value or attic insulation.  Me and the wife looked at it today and we both liked it but no AC has me on the fence.

Wood framed with stucco.  
6/13/2017 11:47:43 PM EDT
[#5]
A ton per 500 SF is the standard, so a 5 ton unit might be too small.  If your house is extremely tight, you can probably get away with a bit less.  If it is pretty loose, you'll need every bit of the calculated required 8 tons.  Otherwise, the 5 ton unit will be working constantly.
6/13/2017 11:53:14 PM EDT
[#6]
With a one-zoned two story house you can either be comfortable upstairs in the summer and too cold downstairs in the winter, or comfy downstairs in the winter and roasting upstairs in the summer.

You can do single zone heat and cool on a 1 story house, and get away with 1 zone heat OR cool on a two story, but for anything else you really need zones.

It's all about airflow and return air.

Minisplit/vrv/vrf might be something to consider
6/13/2017 11:54:14 PM EDT
[#7]
Quote History
Quoted:
A ton per 500 SF is the standard, so a 5 ton unit might be too small.  If your house is extremely tight, you can probably get away with a bit less.  If it is pretty loose, you'll need every bit of the calculated required 8 tons.  Otherwise, the 5 ton unit will be working constantly.
View Quote
Thanks.  That gives me a good rough idea.
6/14/2017 7:07:30 AM EDT
[#8]
You really need someone to do a heat gain/loss calculation on the house, then decide on the systems you would like to install, once you have determined what's needed.
6/14/2017 7:27:20 AM EDT
[#9]
HVAC design guy here, you need to pay someone to do a load calc for you. Then go from there.

You can just guess, i guess, maybe youll get close. You could call up an HVAC company and they can make a guess, which might be closer.

But are you willing to invest between $4000 and $10,000 on a guess?
6/14/2017 7:51:02 AM EDT
[#10]
20 miles west of Colorado Springs? That would put you up in the mountains. I can't see 6500 feet anywhere west. Regardless, it's hard to push air at elevation. Is the walk out basement mostly underground? If so do not include it in your sf or at the most include only the portion fully above ground.

Unfortunately, my experience with older homes out here is the ductwork was never designed for a/c. Smaller trunk lines that don't reduce and lack of return path to second floor sometimes make cooling a challenge.

Adding a 1 1/2 or 2 ton attic system isn't that hard but it can be a bit pricey. My best guess is in the 5 to 10k range. You'd really need to get someone out there to run calculations.

Before 2001 it was the norm not to build for or have a/c. The 2 weeks or so of really high temps, without night time cool downs, are challenging but livable.

What town West of the Springs?
6/14/2017 10:45:56 PM EDT
[#11]
Quote History
Quoted:
HVAC design guy here, you need to pay someone to do a load calc for you. Then go from there.

You can just guess, i guess, maybe youll get close. You could call up an HVAC company and they can make a guess, which might be closer.

But are you willing to invest between $4000 and $10,000 on a guess?
View Quote
I don't know...  I don't think $10k is that bad but I have the feeling it would be more.  

Is $10k or two ac units plus an additional furnace/air handler a realistic estimate if no duct work is needed?
6/14/2017 11:13:45 PM EDT
[#12]
Quote History
Quoted:
20 miles west of Colorado Springs? That would put you up in the mountains. I can't see 6500 feet anywhere west. Regardless, it's hard to push air at elevation. Is the walk out basement mostly underground? If so do not include it in your sf or at the most include only the portion fully above ground.

Unfortunately, my experience with older homes out here is the ductwork was never designed for a/c. Smaller trunk lines that don't reduce and lack of return path to second floor sometimes make cooling a challenge.

Adding a 1 1/2 or 2 ton attic system isn't that hard but it can be a bit pricey. My best guess is in the 5 to 10k range. You'd really need to get someone out there to run calculations.

Before 2001 it was the norm not to build for or have a/c. The 2 weeks or so of really high temps, without night time cool downs, are challenging but livable.

What town West of the Springs?
View Quote
Sorry, about 10 miles west of downtown as the crow flies.  20 miles driving.  Above Crystal Park.  Elevation might be higher than 6500.  Maybe 6500-7000.  

The basement on the front of the house is completely underground and is walkout on the other end.  

I'm just trying to get a rough idea on cost before we decide to make an offer.  Existing furnace is 20 years old and probably needs to be replaced soon.  So really, I'm looking at probably two AC units and two furnaces.