"Humidity levels in the house still dip into upper 20's at times. Is this acceptable?"

Depends upon the outside temperature.....

Here is a link to determine the amount of humidity that you should have in your home versus the outside temperature.

http://www.aprilaire.com/docs/default-source/default-document-library/relative-humidity-defined.pdf?sfvrsn=2

Hygrometers are nice, but dependent of the quality not always accurate! 20% humidity is quite low for your area (NC) as that would be a preferable RH% level at a very low outside air temperature.

If you need a whole house humidifier, any good HVAC contractor can install a by pass system for ~$500+/- out the door price

Not certain that nail pops and caulk lines are entirely the cause of humidity levels. You mentioned that your house is two-years old. More than likely your house is going through some natural settling stages.

Thanks bp chill. I called my HVAC installer and he actually recommended the portable unit that I bought. His opinion was that if you were going to buy one for the HVAC then you needed to buy top of the line to avoid mold problems. He said this would run around 2 grand and that he wouldn't even recommend spending that kind of money. Not sure if this is good advice or not. Yes, I have wondered if many of the nail pops, crown molding seperarions, etc aren't part of the settling process as well.

n2lowe - Please know that Aprilaire (one of the major mfr's of whole house humidifiers) has an article or two regarding the misconception of humidification and mold issues. I would assume your HVAC contractor is referencing a steam style humidifier at the cost of $2K.

Not certain if your house has a basement or slab, but a basement would allow you a bypass style - a slab you would need a fan powered humidifier which is between the bypass and steam style. I personally don't think you need to spend $2K. Either way, a furnace mounted humidifier will provide you better results versus a portable humidifier. Been there....done that :)

I have basement but both HVAC units are located in the attic

Our temperatures in NC rarely get low enough to warranty a winter whole house humidifier, unless you are up in the mountains. Nail pops are pretty common due to builders using wet 2x4s in construction.

Makes me wonder about the quality of the insulation I have if the humidity inside my house is reaching 27%.

Good advice regarding the sling psychrometer.

Good advice on checking the hygrometer. Going to get another one to double check. Also checking the current one with a saline water calibration test I read about it. If it does turn out to be reading that lie should I get a blower test to check for leaks? Who would I call and is this expensive. Or would you simply proceed with the humidifier?

n2olowe - If you are interested in a blower test, any energy audit contractor can do so - just be sure to get a reliable company. They will probably want to to do a full energy audit, but in my mind well worth the money to determine inefficiencies within the home. Prices can vary, I would suggest calling around. If you are a AL member you can check out contractors there as well.

Good luck!

A salt solution test for the hygrometer is a good one. I forgot about those. Best would be a two-point calibration above and below the range you will be measuring in while being close to the target range.