700M

I won't go over all the humidifiers I tried, just the final system that worked. First of all, I assume you have a forced air furnace. You need to use the air plenum. Next, you will need an Ecobee thermostat. Others may work, but Ecobee was flawless. The Aprilair 700m (m for manual, no need for a humidistat) will do the job. You will need to replace the filter yearly, but they are relatively inexpensive. Finding a spot for the Aprilair will require some searching. It has to attach on the furnace air plenum. I put mine on the return. No, mold will not grow in the plenum. Next, you have three connections; 1) Water; get a plumber to route a copper line to the Aprilair. It is not intuitive, but run the water line to the HOT side. This will make the humidifier run more effectively. 2) Electrical; I mounted my Aprilair next to the furnace, so I routed 120VAC power from the furnace controller to an outlet next to the Aprilair, and plugged the Aprilair into the outlet. 3) Aprilair control wires. There will be two yellow wires. One yellow wire goes to the "C" connection on your furnace controller. The other yellow wire goes to the ACC+ connection on your Ecobee. Tell your Ecobee that you have a STEAM humidifier (I know the Aprilair is not steam, but the system needs to think it does for the fan to run properly). Set the humidity level you want on the Ecobee, and enjoy whole house humidification.

The Ecobee thermostat/Aprilair 700M humidifier is a great combination. Pipe it to your hot water line. One yellow wire to the Ecobee ACC+ and one yellow wire to "C" on your furnace controller board. Setup the 700M as a STEAM type so it will run properly.

I switched from three standalone humidifiers to an AprilAire 700 and it works so well that I haven’t had to run the standalone units anymore. It works really well and way less maintenance once you get it installed.

AprilAire 700 if you’re able to install one in your HVAC. Works way better than the standalone units.

Steam is mainly about control and consistency. It actively generates vapor, so output isn’t tied to furnace runtime and it maintains target RH far more reliably in cold weather. Drip/bypass units like the Aprilaire 700 are cheaper to buy and run, but their effectiveness drops in cold conditions, they only work when the furnace is on, and evaporation leaves minerals behind—causing scale, frequent pad changes, and fine mineral dust entering the airstream, with the issue becoming worse as water hardness increases. Over long periods, inhaling fine particulates is associated with chronic airway irritation, can worsen asthma or other respiratory conditions, and may contribute to long-term lung function decline. Steam still needs maintenance, but it keeps minerals contained in the canister. Cost-wise, bypass units are roughly $20–$40 per season, while steam is closer to $100–$200. In many cold, dry climates, bypass units struggle to get past ~30% RH, while steam remains reliable.

Definitely go with the Aprilaire 700 series for that setup - they're solid and handle that square footage well. Since your heat pump runs most of the time you'll want one that doesn't need crazy high temps to work properly and Aprilaire nails that

We have an aprilaire 700m humidifier built into our hvac and the best it has been able to do is hold at 37% RH. It does help though.

I have one and like it. I have a basic aprilaire bypass unit. If I had the space though I would have gone with the aprilaire 700. And if you have the circuit available and easy to wire, a steam unit is the most ideal.

Thank you for the advice. Is there a recommended evaporative humidifier? I already have aprilaire 700 in the hvac, but that only gets us to 40-45%. Hoping for 50-60% for the young kiddos. Could I replace the aprilaire with something “bigger”? Or wider to have supplemental humidifiers (like I have…but evaporative so I can use tap water). Trying a Canopy in our primary bedroom now, but it appears to lack the ability to get us to our desired humidity levels. It seems to hold around 45%.