Cost for replacing HVAC furnaces

[Abe]

Hi everyone, Happy Thanksgiving!

I have a HVAC question on this cold (for Houston) night...

Our house has two systems (one for upstairs, one downstairs). The outside condenser units were replaced 3 and 4 years ago, respectively but the air handler and built-in natural-gas furnaces weren't. Those are now 12 years old, and are used at low to moderate capacity about 5 months of the year (mid October to mid March).

Questions are:
1) what is the normal lifespan of natural gas furnaces? Do they need replacement any time soon?
2) my son's room is always colder or hotter than the rest of the rooms. Basically it seems the problem is the distance from the air handler to his room is too far, and there is no return duct near his room (they are stupidly just below the air handler, so they just recycle air from the vents immediately below the unit).
Things we've done to mitigate this so far are:
- Increased insulation in the walls and entire attic (now R20 and R40). That improved it from 7-10 degrees off to 4 degrees off.
- Put in temporary XPS foam boards to cover the bedroom windows (he's only in there to sleep, and it helps block out the sun in the summers too). That didn't help much.
- Fiddled with closing dampers in other rooms to try to force more air into his room (didn't help).
- Considered a mini-split, but that seems like a costly bandaid for some poor HVAC design.

Any thoughts on how to better mitigate this? Would replacing the air handler and furnaces help? Re-doing the layout seems expensive, but fixing this problem with help with utility bills.

[Papa bear]

Hi everyone, Happy Thanksgiving!

I have a HVAC question on this cold (for Houston) night...

Our house has two systems (one for upstairs, one downstairs). The outside condenser units were replaced 3 and 4 years ago, respectively but the air handler and built-in natural-gas furnaces weren't. Those are now 12 years old, and are used at low to moderate capacity about 5 months of the year (mid October to mid March).

Questions are:
1) what is the normal lifespan of natural gas furnaces? Do they need replacement any time soon?
2) my son's room is always colder or hotter than the rest of the rooms. Basically it seems the problem is the distance from the air handler to his room is too far, and there is no return duct near his room (they are stupidly just below the air handler, so they just recycle air from the vents immediately below the unit).
Things we've done to mitigate this so far are:
- Increased insulation in the walls and entire attic (now R20 and R40). That improved it from 7-10 degrees off to 4 degrees off.
- Put in temporary XPS foam boards to cover the bedroom windows (he's only in there to sleep, and it helps block out the sun in the summers too). That didn't help much.
- Fiddled with closing dampers in other rooms to try to force more air into his room (didn't help).
- Considered a mini-split, but that seems like a costly bandaid for some poor HVAC design.

Any thoughts on how to better mitigate this? Would replacing the air handler and furnaces help? Re-doing the layout seems expensive, but fixing this problem with help with utility bills.

1) normal lifespan - I’ve had furnaces more than 30 years old. If you’re concerned, have an HVAC tech do a once over.  If you need to replace the furnace and air handler, look around 3500 if you find a guy doing side jobs or the friend deal. Go with a company, maybe 5-8k.  Any more and they’re taking you for a ride.
2) sounds like you’re doing everything I’d suggest already.  Sometimes the design isn’t great and there isn’t much you can do outside of tearing it all out and rebuilding over.  If you do find a good tech, they might be able to suggest some better tips to help out. 


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[affordablehousing]

I'm sure you've thought of this but you could probably remedy this with a $30 space heater. I too usually like the $10,000 solution for aesthetic purposes rather than the $30 fix, but a 4 degree difference doesn't seem worth redoing your ducting over.

[Daley]

As long as you have good, sensitive carbon monoxide detectors, and the furnaces are in good shape and there's no cracks in the heat exchangers and you're not feeling woozy or seeing and hearing imaginary things, you can get decades out of a natural gas heater. Papa Bear's price estimates are pretty accurate currently, too.

As far as the heating and cooling issues at the far end, it sounds like the system isn't well balanced. This said, most heater/air exchanger circuit boards have jumpers or micro switches that adjust the fan speed for the cooling and heating, and a lot of installers forget to monkey with those settings. Since its the time of year to do fall maintenance on the heater, maybe pull up the manuals for your upstairs heater and while the tech is there, explain the problem and ask if the fan speeds for both the cooling and heating can run a little faster. Either that, or see if the evap coil fins can be thoroughly cleaned, they might be clogged a bit cutting back airflow.

[uniwelder]

I just wanted to mention that if you’re covering the windows with rigid foam sheet, place it on the outside of the house. Otherwise you’ll create a solar oven that can damage the window or melt the foam.

[Britan]

We have a similar problem in my sons room due to lower insulation (roof and ceiling are too close together for best insulation) and distance from furnace. We considered a lot of pricey options… moving all the electrical and drywall to lower the ceiling, add more insulation to his wall and re-drywall, mini split) but just solved it with a $60 space heater* in winter and window AC in summer. More energy efficient than heating/cooling the whole house, and more sensitive (his room is the exact temp we set it to, rather than trying to set the central air to +/- whatever we want it to be in his room and hope). Double cell honeycomb blinds (custom for best fit) also helped, as did re-caulking the inside and outside of the windows.

* If this is for a toddler or small kids room, spend the money on a space heater that (1) has an anti-tip turn off protection (2) does not get hot to the touch and (3) preferably has a digital temp readout so you can see exactly what you set it to. And then place it up out of reach on a dresser or shelf until you know the kid wont try to mess with it.

[BlueMR2]

1) what is the normal lifespan of natural gas furnaces? Do they need replacement any time soon?

Expect 20+ years with routine maintenance

[Abe]

Thanks everyone for the advice. I think we will go with the space heater - his room is small and well insulated, so won’t need to run it too long to get to temperature. That’s what we did in California in a similar situation (but less insulation).