I have one in my home, but I live in Michigan and it gets very dry here in the winter. When I lived in Maryland, I wouldn't have had one, because it is much more humid there. Is Haymarket VA dry in the winter or humid like Maryland? You would probably be able to tell (dry in winter = nosebleeds and waking up with horribly dry nasal passages all winter). You also can buy a portable humidity detector (has a proper name, but I can't remember it) at Home Depot or even the grocery store. It's about the size of a cellphone and doesn't cost but about $10. It can tell you if you have the proper humidity in your home. HVAC humidifiers are only for use in the winter, and they shut off once the humidity reaches a set level (so it would be a waste of money if your house is always at that level anyway). Past a certain humidity (it's either 40% or 50%) would cause mold to start growing in your house.
If you were to check your humidity you have to wait until winter to do so, but I can't see how that would be a problem. We had a humidifier installed in a 12 yr. old house and it was no problem. I really don't think it is something that needs to be built into the home originally to save money. We just had an HVAC guy do it. They cut a hole into one of the metal air condiuts (don't know correct term) and stick the humidifier onto it, then attach a water line from an exisiting water pipe.
If it is dry there, then a home humidifier is great. The portable room humidifiers would be the alternative, and those DO grow mold and are such high maintenance. My dad is an environmental engineer and he told me he had no concerns over the use of HVAC humidifiers.
Oh, and yes, they do work. Made a huge difference. No more nosebleeds for my daughter and no more sinus infections for me (due to dry nasal passages). Much more comfortable nasal passages while sleeping in winter. It's also better for your wood furniture/cabinets/floors and prevents nail pops in the drywall due to changes in humidity from summer to winter. The nailpops in our house (we moved in two years ago) are what actually led us to looking into HVAC humidifiers to begin with. They were all over the place and getting worse. After the HVAC humidifier was installed, the nails stopped "popping". (They slowly work their way out of the drywall due to expanding and contracting, creating spots where they drywall "pops" off, exposing the nailhead.)
