Thanks, in advance, for bearing with this long post. I moved into an old (new for me) house recently with pretty ugly air quality. I thought the cause of the smell was just that the house was dirty and sitting empty for a long time. A couple of months later and a lot of cleaning, including having the ducts cleaned, the house still smells bad--kind of like a mix of old house/sheep farm/gas leak (although there is no gas leak.) I've tried Ozone and it doesn't help at all.
The house seems to smell a lot better when the air has been running a lot. When the air is on, the the air coming out of the vents smells fresh. When the air is off but the fan is on, the air coming out of the vents smells funky. The basement is partially finished and it is humid (~70% RH) but doesn't smell at all mildewey or moldy. I just started to run a dehumidifier. The AC seems oversized to me--5 ton and the house is only 1900 SF. It doesn't take long to cool down and then the AC shuts off. The house was built in '62 and has galvanized ducts with partially lined returns. There appear to remnants of a radiant heat system in the basement.
And now my question. Does this sound like an AC/Dehimidification problem that can be solved? My big worry is that I spend a lot of money rectifying the oversized AC and adding a good dehimidifier and still end up with a house that smells like a goat ranch.
Thanks, again, for any help.