Having built a number of times, I've never seen anything movable in the ductwork. Sure there sometimes is debris in there but allergies to drywall are not common.

The allergy "flare" could be humidity related. Do you have a humidifier? Do you know what the RH is?

Generally (always?) running the heat leads to a decrease in the RH. BTW - you probably don't have a furnace or if you do it hasn't run yet. A geothermal heat pump is not usually referred to as a furnace when running in heat mode. You might have a backup heat source that is a furnace but I can't imagine that has been running yet.

Hi David!

Thanks for your helpful reply...

Yes, we have a humidifier...I have a decorative temperature humidity gauge in my kitchen...it says 52% if it's accurate, I'm not sure. Our throats do seem a touch dry.

I turned the humitiy level to 35% and I don't think it's pumped any moisture in the air...I went down there yesterday to watch a couple of times when the heat turned on and haven't noticed the plastic tube thing full of water...if that makes sense!

So, your opinion is that duct cleaning isn't necessary for the most part.

I wonder if my humidity gauge is wrong.

Or...just a plain 'ol dust allergy....I'm ready to get to the bottom of it! Maybe a simple air purifier in her room?

My other thought is that construction debris can be cleaned out pretty easily by anyone without doing the snake oil duct cleaning by the "pros".

Where do you live? Our house is sitting at about 50% this time of year but our furnace hasn't run much yet. I'd imagine, that most of the country still has pretty high humidity in the house right now.

What do you mean by dirtier by the air vents? If the walls surrounding the vents are dirty, it indicates that your home is depressurized and the vents are not well sealed to the area behind them, That draws in dirt from the outside.

David, we live in michigan. So, do you mean that reaching my vacuum hose down each vent should be good enough? I did that when we first moved in...and now a yr later. It wasn't that bad....

Ionized...well...the cold air returns look fine after a yr. there were only a couple of vents (not on the floor...on the side of built in bench seats) where the carpet picks up more dust/debris.

Maybe this is just a case of dust mite allergy that is flaring right now?! I'm just always looking for anything that might help her stuffed up nose.

So, 50-60% is a good level in the cool months?

30-50% year-round is your target for RH.