Depends on how long you intend to stay in the house.

Hi, Chisue,

I suggest you contact a local HVAC design/testing firm to assess the performance of your existing systems. Once they've assessed your current system's capability, they will be in a position to recommend modifications to, or replacement of your system and you can make a more informed decision. Here's a link to one such firm to get you started:

https://www.priorityenergy.com/service/hvac-residential-design-test

Thank you all! I appreciate your noting our "big picture", beyond just replacing HVAC.

Teardown means only the basement and chimney of the 1950's ranch home remain. Hindsight says we should have dug everything out, despite the permit savings because this qualified as 'remodeling'. To us seniors, 'basement' is where the mechanicals live, but to today's buyers, it's a 9' or greater 'lower level'. (Water over the dam.)

We have only a few more years here, and obviously have to decide about other aspects, such as the 10/12 grade asphalt roof with three years service remaining. Weeks of zero weather cause concern about heat. At the same time, climate change has already pushed up our summer temps.

Our 1.3 acre lot's FAR is 6,000 sq ft. There is another full height 2,000 sq ft in attic over the first floor and attached 560 sw ft garage, if that pertains.

In addition to Charles Ross's kind link, how else would I go about finding the sort of degreed person klem1 recommends?

We have only a few more years here, and obviously have to decide about other aspects,

This aspect is probably going to make the decision more complex, although if you fix these problems it may help you sell the home when that time comes.

If everything was replace in 2001 -- the AC's are likely R22 freon. They could be R410a, but I doubt it. So just about any HVAC company coming into your home is likely going to come there with full on replacement of everything most likely. If that is what you are set to do then it's of no concern then, other than to make sure their plans will fix all your troubles and not create new ones.

I would say right now would be the time to get started as this will increase your choices to maybe include R410a refrigerant options for AC. Given that your time frame at this house is not much longer, that maybe the better choice for you right now.

If you have no AC problems now, finding an HVAC contractor with experience in fixing heating related problems --- you should have plenty of those. Just realize single shop HVAC contractors typically do not advertise heavily, so you have to hunt for them in your area.

Google search look for blogs, maybe you tube as many use these functions as a way to showcase their work among other things. Avoid the free estimate... some of these "could be legit" but most of them are not. Pay for the service... act like this is a paid for interview. Ask questions... if someone seems to dodge a question while being paid?

Like this forum board I merely use it as a way to leave breadcrumbs so people can find me, among other things I do. It's not a perfect source but, there is no perfect source to advertise if you catch my drift.

If you find a single one man licensed HVAC in your area. The HVAC license should include a number that you can look up within your government licensing board on line that licenses trades people. Additionally ask for proof of general liability insurance. I rarely if ever get asked these things probably because of my youtube channel and a lot of documentation of the work I do, not to mention how long I've been in HVAC. I have been asked before like 1 time a few years ago... so while I am prepared for this -- scammers likely will not be.

You want to make sure the person or company you hire is licensed and insured to do what they claim they can do. The take the next step to verify what they provide you, if any red flags seem to be present then keep looking. Remember to treat this as a paid for interview of the company you are hiring.

Free estimate kinds are by and large gimmicks. Not saying that these can't be legit, often they are not. So often in fact I recommend you steer clear of them unless you can't find a one man *licensed* operation in your area.

Thanks, Austin Air. I hope your volunteer efforts here pay off.

Everything here dates from our build in 2001. We've been satisfied with annual maintenance from one 'only HVAC' company for the last dozen years. However, when I asked for replacement info, the response was just as stated above...no recalculating; just same/same based on what we have.

Thanks to thoughtful direction here, I'm leaning towards 'waiting and hoping' for now. I have a managed but terminal disease and am in Year 7 of the 6-to-10 predicted survival. We are both mid-80's.

I can't remember what furnace part our regular HVAC tech has said is most likely to fail -- something that burns out? (These are two Carrier 58TUA furnaces.) Is a furnace not worth repairing when that happens? Having two furnaces has saved our bacon when one of them failed during heating season. Possibly the failure would be in the A/C? Illogical to repair that?

I think a buyer here could be OK with a discount for HVAC and roof. IDK what use another owner would want to make of the house -- one floor as we use it or modify the attic with dormers, or another configuration. The greatest asset is the land and location.

I can't remember what furnace part our regular HVAC tech has said is most likely to fail -- something that burns out?

There's a number of parts that can fail on any furnace made in the last 20 years, no brand is really any more or less immuned to any of it. Especially if the location uses the heat alot like your climate.

Some brands like Carrier have more problems with blower wheels blowing themselves apart, which takes out the blower motor too. But I've serviced Carrier furnaces for some customers for years and years with rarely any trouble and too be clear some other brands blower wheels can do the same thing just not as much as I see Carrier brand do. Although our winters here are mostly back and forth between AC and heat with maybe a week or two here and there of temps low enough to run the heat.

In terms of what burns out? the ignitor. For a place like Chicago, yeah those are going to get a work out. But those kinds of issues are really the least of your worries with the kind of furnaces you have in my opinion. Those are minor cost repairs and no big deal in my opinion more wear and tear part.

The modern gas furnace is only allowed to heat, when the sequence of operations passes all safety checks. Failure of any one of those checks and the furnace won't work. In some scenarios this may or could be an intermittent type problem which are the worst to figure out because it often leads to guessing as to what may or may not be wrong with it.

With what you have going on in your life probably better for you to live with what you have right now.

-- yeah I'm fine I've been in HVAC for over 30 years and towards the end of my career. I often times have more work than I care to take on alot of the time. I merely spend time here of a morning drinking my morning coffee. So what I get from this avenue of the internet or don't get is fine by me. I do what I do here more so because I like what I do and I control all of it. The saying goes something like this: find what you like to do, how to make money at it and you never work a day in your life.

The free part of this ends if someone wants me to investigate and investigations only occur in person. No part of phoning it in works for me, nor am I going to guess to any big extent over the phone.