Humidity control for home AC unit
June 1, 2021 1:14 PM   Subscribe

I use my AC in the summer more to control humidity than temperature. Does a home Heat/AC controller exist with a humidistat that prioritizes humidity and the temperature setting just sets high and low limits?
posted by Raybun to Home & Garden (8 answers total) 1 user marked this as a favorite
We run a dehumidifier most of the summer in the main area of our house for this purpose. Not as handy as being built in to to the ducting but it works for us so that might be an option if you get stuck.
posted by wwax at 1:55 PM on June 1 [1 favorite]

To some extent an ac dehumidifies as a consequence of cooling. The warm moist air passes over the cooling pipes and, since cold holds less humidity than warm air, water condenses on the cooling pipes and falls to an evaporating tray. Sort of like a glass of cold drink will collect water from the air about it and sweat. That's not to say you couldn't also run a dehumidifier.
posted by tmdonahue at 2:25 PM on June 1 [1 favorite]

I have a Carrier branded Ecobee thermostat that was free with our new furnace, and it has an option to set a desired humidity level and then a maximum amount it's allowed to deviate from the set temperature to achieve the humidity level. Appears this a common feature on their thermostats, so probably also on most smart ones - but I'm not sure how far off "normal" you can set it.
posted by hankscorpio83 at 2:30 PM on June 1 [1 favorite]

I just checked, and Nest has a feature they call 'cool to dry', which is to lower indoor humidity, but it comes with a warning that says it will result in excess energy usage as it may cool below set temperatures. I actually have a house that a dedicated humidity monitor you can set that is no longer operational because the AC unit has been changed once since I've owned the house. So such systems certainly exist in network and wired form.
posted by The_Vegetables at 2:50 PM on June 1 [1 favorite]

BTW, in my house the current indoor humidity is at 64%, the outdoor at 77% at a 62F dewpoint at 70F (insanely humid) and Nest says optimal is 50%, so that's a lot longer of an A/C run time, comparatively, to lower the humidity that much. AC is not running at all today due to the low outdoor temps.
posted by The_Vegetables at 2:55 PM on June 1 [1 favorite]

We had Nest with "cool to dry" in our old house and it did seem to work the way you are requesting, though that wasn't a very humid climate. In our new place, we have a built-in whole house dehumidifier, so it can be controlled independently.
posted by primethyme at 3:01 PM on June 1

A lot of heat pumps (minisplit if you're in the US) have this feature. This is one example.
posted by rednikki at 11:53 PM on June 1

Nthing that living in a high humidity area I have to supplement my AC with dehumidifiers because getting the humidity down with just the AC would push the temperature uncomfortably cold or expensive.
posted by Candleman at 8:07 AM on June 2

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