Why does the a/c guy tell me he wants to insulate instead of fixing new unit?

[quillwise]

Hi all:

I just had a new a/c unit put in 14 months ago. Only had a furnace, so they redid the ducts, as well. Now the unit is not cooling. The a/c guy says he wants to insulate the exterior walls rather than put in a new, larger unit. Does that sound right?

Your thoughts and experience would be much appreciated!

[Syonyk]

Find another cooling guy to look at the system...

Without a lot more details, it's hard to know what the issue is.  If your walls aren't well insulated, you should certainly improve the insulation, but that should have ~nothing to do with an AC unit not working.

[ooeei]

When you say "not cooling" do you mean it's just warm air coming out of the vents? Or is the air cool, but there's not enough of it? Or is it not cool enough? Weirdly enough, bigger doesn't necessarily mean better with an AC system, and sometimes makes things worse.

I'd imagine you have a warranty still on the original unit. Is this the person who installed it to begin with?

[quillwise]

Thanks for responding!

I'll clarify--the a/c cools in the small back rooms (30% of total square feet), but does not come out as strongly through the front vents in the rest of the house (70% of total square feet). So while the thermostat is set at 72, it doesn't cool past 82 in most of the house. So, it's cool air, but not enough of it.

And yes, it is the person who installed it.

[Syonyk]

What happens if you partially close those back vents or otherwise obstruct them to push more cool air to the rest of the house?

[Laura33]

2 thoughts:

1.  Sounds like you have a balancing problem -- if you have too much airflow in one area and not enough on another, he needs to look at the overall airflow balance first.  This sounds like a system design/installation problem, and it is something your guys should fix.

2.  If that gets fixed and the AC still can't keep up, do the insulation.  HVAC systems nowadays tend to be sized for the smallest unit that can meet the heating/cooling demands, because it is better for the unit to be able to operate at a fairly steady-state vs. cycling on and off all the time.  If your house doesn't have insulation, you may have gotten a "standard"-sized unit for that size house, but that is actually undersized for the heat load. 

So there are two ways to fix that.  The "normal" approach is to yell at your HVAC guy for undersizing your unit and make him install one that is a lot bigger.  The efficient, Mustachian, environmentally-beneficial, long-term cost-effective approach is to insulate the house to decrease the amount of cooling needed to a "normal" amount that your unit can handle (also make sure you have an attic fan).  Added benefit that this will cost you significantly less over the long term in operating costs.