I have a 2300 sq. ft. 1.5 story home (slab) with a Honeywell TrueSteam 9-gallon humdifier and no zoning. The home has an infiltration rate of 0.37 ACH, so it's not the tightest house, but it's also not loose either. I usually keep the humidifier set to 40% RH, and it will run for several hours from time to time, depending on how cold/dry it is outside.
I wanted to see if I could bring the house up to 45% RH last night. I noticed that it seemed to take quite a while to move the humidity up. The thermostat (VisionPro IAQ) is downstairs, and it was reading 41% humidity, so I decided to take the inside weather station upstairs and see what the humidity was up there. I put it in one of the bedrooms and it was reading 48%. When it's downstairs, it reads exactly what the VisionPro t-stat reads. This leads me to believe that much of the steam from the TrueSteam is going upstairs, and less of it is going to the downstairs branch.
So, my question is, can a zone damper be installed so that the upstairs branch is closed when the call for humidity occurs, but in non-heating mode? I want the zone open if there is a call to heat, but when there is no call for heat, but a call for humidity, I want the zone closed. Is something like this possible? Or does someone have a suggestion on how to make sure an equal amount of steam is fed to both branches?