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Another trend I have seen[1] ] (US market, high performance/high energy efficiency homes) is the use of HVAC and separate, standalone dehumidifier to do the sam

Another trend I have seen[1] ] (US market, high performance/high energy efficiency homes) is the use of HVAC and separate, standalone dehumidifier to do the same thing - take out humidity out of the air that the AC system has to otherwise both cool and dehumidify on it own. The framing (at least as I understood it) was more on the psychometric side - 24C@65% relatuve humidity _feels_ worse than 27C@45%RH, but the energy savings aspect is also non-trivial. As an aside - a fairly large number of central AC systems in the US do not have a humidity censor, so they only go by the temperature set point. Upgrading to control system which does measure humidity, while energy inefficient (because AC would be used to dehumidify the air _below_ the target set point), is an option, though not as good as having a stand-alone humidity control system. Sadly, I am unaware of Nest and/or Ecobee's support for this sort of a setup. Probably not cost effective for them. :\ [1] https://youtu.be/rWWLW4nLNBI?si=Ud1jk3x58H6pnMci https://youtu.be/rWWLW4nLNBI?si=Ud1jk3x58H6pnMci

bob1029 2y ago
Another option is a variable speed condensing unit. This is what I am looking at doing next. A dedicated central dehumidifier is nice, but I've found them to be kind of noisy, especially when installed in the attic. Its got its own compressor, so the vibrations will transfer into the structure.
hunter2_ 2y ago
> Sadly, I am unaware of Nest and/or Ecobee's support for this sort of a setup. Same, and the worst part is that Nest already includes a hygrometer to show humidity in the app. All they need to give the user is a toggle: setpoint in regular dry bulb temperature, or setpoint in calculated wet bulb temperature (or heat index or "feels like" or whatever user-friendly calculation). Although their remote temperature sensors don't have a hygrometer, only the main unit.
kjkjadksj 2y ago
Part of this is solved by sizing the ac correctly. Too powerful an ac and it doesn’t cycle as often and humidity builds.
wongarsu 2y ago
> The framing (at least as I understood it) was more on the psychometric side - 24C@65% relatuve humidity _feels_ worse than 27C@45%RH It's complicated to quantify, but in a sense 24C@65% is warmer than 27C@45%RH. Or rather, maintaining your body temperature is more difficult in the former than in the latter. The human body produces ~100W of heat, and the primary way to get rid of it in warm weather is evaporative cooling: at below 100% relative humidity water slowly evaporates, this takes energy and thus cools down the surface the water was sitting on. We use that by coating us in sweat and letting it evaporate. This is more efficient the lower the relative humidity is. The attempt to quantify this in a nice metric is the wet bulb temperature (what would a thermometer with a wet cloth around it show). 24C@65% is a wet bulb temp of 19.3C, 27C@45% is a wet bulb temp of 18.8C
toast0 2y ago
> Sadly, I am unaware of Nest and/or Ecobee's support for this sort of a setup. Probably not cost effective for them. :\ I've got both of these. Nest has a setting for 'cool to dry', but my climate is usually not humid and hot at the same time. I don't see a similar feature on the Ecobee, but the Ecobee app is perhaps more confusing. It does send alerts when the detected humidity is above set points. Where I do have issues with humidity is in my basement; typically the basement stays around 5-10 F less than the first floor, and if the first floor is 50% relative humidity, moving the air into the basement results in a much higher relative humidity. If the a/c is running for the first floor, there's a good chance of significant condensation on the vents right after the air handler.
johntb86 2y ago
>Sadly, I am unaware of Nest and/or Ecobee's support for this sort of a setup. Probably not cost effective for them. Ecobee has a setting to enable this: https://support.ecobee.com/s/articles/How-to-use-AC-Overcool-Max-to-reduce-humidity https://support.ecobee.com/s/articles/How-to-use-AC-Overcool... They also have a setting to adjust the temperature for humidity: https://support.ecobee.com/s/articles/Adjust-the-Temperature-for-Humidity https://support.ecobee.com/s/articles/Adjust-the-Temperature...
- T3OU-736 2y ago
  Right, I wasn't specofic - Ecobee will overcool with the main AC, but it does not have the 'I have a dehumidifier in my HVAC setup, go use THAT' setting.

bob1029 2y ago

Another option is a variable speed condensing unit. This is what I am looking at doing next. A dedicated central dehumidifier is nice, but I've found them to be kind of noisy, especially when installed in the attic. Its got its own compressor, so the vibrations will transfer into the structure.

hunter2_ 2y ago

> Sadly, I am unaware of Nest and/or Ecobee's support for this sort of a setup. Same, and the worst part is that Nest already includes a hygrometer to show humidity in the app. All they need to give the user is a toggle: setpoint in regular dry bulb temperature, or setpoint in calculated wet bulb temperature (or heat index or "feels like" or whatever user-friendly calculation). Although their remote temperature sensors don't have a hygrometer, only the main unit.

kjkjadksj 2y ago

Part of this is solved by sizing the ac correctly. Too powerful an ac and it doesn’t cycle as often and humidity builds.

wongarsu 2y ago

> The framing (at least as I understood it) was more on the psychometric side - 24C@65% relatuve humidity _feels_ worse than 27C@45%RH It's complicated to quantify, but in a sense 24C@65% is warmer than 27C@45%RH. Or rather, maintaining your body temperature is more difficult in the former than in the latter. The human body produces ~100W of heat, and the primary way to get rid of it in warm weather is evaporative cooling: at below 100% relative humidity water slowly evaporates, this takes energy and thus cools down the surface the water was sitting on. We use that by coating us in sweat and letting it evaporate. This is more efficient the lower the relative humidity is. The attempt to quantify this in a nice metric is the wet bulb temperature (what would a thermometer with a wet cloth around it show). 24C@65% is a wet bulb temp of 19.3C, 27C@45% is a wet bulb temp of 18.8C

toast0 2y ago

> Sadly, I am unaware of Nest and/or Ecobee's support for this sort of a setup. Probably not cost effective for them. :\ I've got both of these. Nest has a setting for 'cool to dry', but my climate is usually not humid and hot at the same time. I don't see a similar feature on the Ecobee, but the Ecobee app is perhaps more confusing. It does send alerts when the detected humidity is above set points. Where I do have issues with humidity is in my basement; typically the basement stays around 5-10 F less than the first floor, and if the first floor is 50% relative humidity, moving the air into the basement results in a much higher relative humidity. If the a/c is running for the first floor, there's a good chance of significant condensation on the vents right after the air handler.

johntb86 2y ago

>Sadly, I am unaware of Nest and/or Ecobee's support for this sort of a setup. Probably not cost effective for them. Ecobee has a setting to enable this: https://support.ecobee.com/s/articles/How-to-use-AC-Overcool-Max-to-reduce-humidity https://support.ecobee.com/s/articles/How-to-use-AC-Overcool... They also have a setting to adjust the temperature for humidity: https://support.ecobee.com/s/articles/Adjust-the-Temperature-for-Humidity https://support.ecobee.com/s/articles/Adjust-the-Temperature...

T3OU-736 2y ago
Right, I wasn't specofic - Ecobee will overcool with the main AC, but it does not have the 'I have a dehumidifier in my HVAC setup, go use THAT' setting.