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2 years ago I had a Bryant 2 Ton 13 Seer Air Conditioner + new furnace and coils installed in my 2800 sqft ranch style house with 6 bedrooms and 2 baths split evenly between the basement and main floor. My house was built in 1962 and it has some issues. The AC always has problems keeping up when it's above 90 - 95 degrees out. But, it's gotten worse recently.

2 weeks ago we opened up the basement to the main floor in the living room. Where there used to be a door / hallway and closet, we took all that out and more or less connected the basement main room to the living room in an open floor plan. Thus, there's no closing off the basement anymore. It's always open.

Also, my AC intake is in the upstairs hallway. I have the original ductwork which is 4inch tubes coming off of a 2ft by 1ft high main supply duct. It's all in my floor, none of it is insulated. There are two vents only downstairs, which is more than enough, we usually have them closed off and the downstairs still stays about 65 degrees while the upstairs won't go below 78 on really hot days (95+)

The windows are aluminium single pane. The ceiling has on average, 2 inches of blown-in teddy bear looking insulation. I know my roof has insulation issues because I get ice blocking on the heated part of the house in the winter.

I have a few questions:

  1. Was my AC compressor sized correctly for the house?

  2. Did I completely mess it up by opening up the basement?

  3. Will replacing windows and adding insulation help much?

  4. Finally, what else can I do to make it more efficient?

  • We'd need a lot more information to determine if the unit was sized properly, as square footage is only a small piece of the puzzle. It's also nearly impossible to determine what effect opening up the house could have had, without actually evaluating the house. Reducing cooling losses and heat gains, will almost always improve the comfort in the home. Though it's not possible to say if the improvement justifies the cost. – Tester101 Jun 10 '15 at 22:06
  • Long story short, the only way for anybody to accurately answer your questions. Would be to allow them to inspect the home. – Tester101 Jun 10 '15 at 22:08
  • Ya, i've asked for over-the-phone quotes on previous homes and received similar answers. Let's just say, those companies never got my business. =) Can we try being more general? What info is "evaluated" that I have not provided here? Maybe we could start with some general education on how AC systems are sized for a particular application? Or, how one would evaluate / inspect and apply said calculations? There's attempted answers / general direction that may not be 100% accurate depending on how the requester applies said information. And, there's no-answer answers. I'm looking for the prior. – maplemale Jun 10 '15 at 22:23
  • Have you tried searching this site? If I remember correctly, there's a few good questions that might be of interest to you. – Tester101 Jun 10 '15 at 23:46
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    If I called an HVAC company, and they were willing to give me a quote over the phone. Those companies wouldn't get my business. Using generalizations and "rules of thumb", is a good way to over or undersize a system. – Tester101 Jun 10 '15 at 23:50
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The lack of insulation on the ducts in the floor is of no concern as the floor is in the conditioned space (ie, the area around the ducts is supposed to be cooled.) If the ducts were in the attic that would be a BIG deal.

The very low insulation in the attic seems like both a contributing problem, and the most easily solved one. Either rent a blower and buy some insulation or hire a company to do the whole job and insulate the attic a lot better. Read up carefully before deciding to try the "free blower with 10 bags" at the big box stores. 12-16" is a good number to shoot for, where possible, but you may (probably will) need to baffle for your roof vents at the edges to go that high.

Better windows will HELP but they are more costly and complex to do and involve a smaller area (thus, less overall contribution to the problem) than the attic does - grab the low-hanging fruit first.

Improving attic ventilation along with or before the added insulation will help with both cooling and with ice dams by keeping the attic space above the insulation closer to outside air temperature.

If you find that your system is still undersized, adding a couple of higher SEER mini-split heat/cool systems (on the upper floor, perhaps one at each end of the hallway) might be a better approach than replacing the whole thing. Might not, as well, but should at least be considered, IMHO.

  • But the floor is in a conditioned space that is already conditioned by other means.... I have a hard time thinking it wouldn't help to insulate the ducts, when the conditioned space below is already cooled. Like I said in my question, the basement stays 65 even without AC. With the AC on, it will get down to 58 in the basement when it's 75 above. – maplemale Jun 25 '15 at 16:18

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