When you think of humidity what comes to mind.Mist ,fog,dew,wetness.Well all these conventional picture of humidity tells that it is related to amount of moisture in the air.But our comfort level is not just related to moisture present in the air.A more important and useful term is relative humidity and temperature that affects our level of comfort inside our house or outside.When accessing IAQ(Indoor air quality) both these factor must be taken into account.
So what is relative humidity(RH)?
Well in simple terms it is the amount of moisture present per cubic meter of air.Now while the volume of given air remains fixed the number of molecules of air,in other words how dense the air is depends on the temperature of the air.Now obviously dense air which is colder can hold less moisture than hot air because as air expands when heated there is more space between molecules in hot air to accommodate water molecules than in colder air
So if we take air of fixed amount of moisture content in it and heat it its RH will decrease and if we cool it RH will increase.You can test it by measuring RH at inlet and outlet of your furnace or AC respectively.
But there is a paradoxical effect seen in weather conditions.
You may have seen that hotter seasons are high in humidity while colder seasons are dry.This is because it generally rains or water evaporates faster in hot season so no of water molecules per cubic meter of air is higher than is in winter.
While in winter the air saturates and the water condenses to form droplets or ice.But we don’t see droplets forming on window panes in summer.
We know that AC coil takes up the latent heat from water vapor molecules and removes moisture and but it increases RH.It is only when this cool air mixes with indoor hot air that the RH of supply air decreases while of whole house increases.
Similarly a furnace makes the air less dense so reduces RH of supply air but when it mixes with the colder air of whole house the RH of supply increases while of whole house decreases.
How humidity affects us.
High humidity levels in the home creates allows for growth of for mold ,dust mites,powerful allergens and irritants which is not good especially for people with asthma.
On the other hand if humidity is below 30%,
- It causes irritation of the mucous membranes in nose and throat, leading to breathing difficulties.
- Dry air is adds to discomfort to people with skin or eye conditions.
- It is also dry wood made items them too much creating cracks in them.
HVAC components that control your indoor humidity.
Whole house Humidifier-Used in winter season.Introduces water molecules into the draft air by intake from a solenoid valve and pouring it on a meshed plate.The water evaporates and is then taken away by the air draft on the duct it is installed.
Dehumidifier-Can be used in extension to AC.Work almost like AC but do not cool the air but help in making you cool since it removes the stickiness and mugginess from air so your sweat evaporates faster and make you feel cool.
Dehumidity-stat-It is a simple device that operates and control the dehumidifier or AC But it is more used for energy saving device when you are gone for extended period of time or vacation rather than humidity control and prevent growth of mold or mildew inside your home.
The setting of the nob is like follow.
When Away-Set the Knob(Used for dehumidification) to 60 % and temperature your desired cooling temperature Ex-80 degree F and set your fan switch to auto.When away your thermostat wont work if humidity is less than 60% but dehumidifier would.
When Home-Set the Knob to about 100% and operate the thermostat normally.
control(that lets water in to the humidifier) valve to humidify(when connected to humidifier) or dehumidify(when connected to dehumidifier).
Check out popular humidifier on amazon.
This humiditistat comes with the company making your whole house humidifier.In winter when humidity is low Set the humidistat knob to 55 % which in summer would have been in off position.Also you need to adjust the humidity level according to the temperature outside to prevent formation of dew on windows etc and dry the house furniture or wood work beyond acceptable limits.However people generally forget to change it from time to to time.
An alternative to all this could be a humidity controlling thermostat which can control both humidifier or dehumidifier according to the weather and RH present outside.Below we have listed some good wifi thermostat with humidity control feature that is easy to set and forget type.
1.)Honeywell YTHX9421R5101WW/U Prestige IAQ Kit with Redlink technology
Although this thermostat is not programmable it is a full on solution for your indoor air quality including temperature and humidity.It comes with multiple temperature and humidity wireless sensor that you can install inside or outside home and based on inside and outside reading it will smartly adjust your AC or dehumidifier or Humidifier.It says DIY type but it is recommended to install it through professionals.
Other than that it uses red link technology by Honeywell which is secure and reliable in terms of communication between devices.Here is a video explaining Red link technology.
2.)Aprilaire 8620W WiFi Thermostat
Aprilaire is an HVAC manufcacturer that makes humidifiers,dehumidifiers air purifiers,home automation using zoned temperature control and of course thermostats.The above model of Aprilaire thermostat can control both your humidifier and your dehumidifier from the thermostat itself.Along with humidity it also has event based air cleaning and ventilation controls.It has an auto mode which allows you to control humidity hands free.
Temperature we feel is also a affected by humidity so if you can control that with other parameter other than heating and cooling it can lower your energy cost. At least that is what the company claims.In all it is a decent thermostat that allows auto humidity control.
3.)Venstar T7900 Programmable WiFi Thermostat
Venstar is a US based company which exclusively makes thermostats for residential and commercial use and energy management system for small businesses. The above model is T7900 which is only residential model with humidity control humidifier and dehumidifier. It has color touch screen which also allows you to set wallpapers and sd card into the Thermostat.You can add voice control by connecting Alexa device.(only).You set the humidity set point and it will humidify using humidifiers or dehumidify using cooling mode.It also auto adjust recovery time using changing seasonal trend.It calls it smart recovery.Overall its a little pricey but good addition to add to your comfort level.
4.)Honeywell TH9320WF5003 Wi-Fi Touch Screen Programmable Thermostat
Also called Honeywell vision pro 9000 this thermostat is an upgrade to vision pro 8000 which also have wifi and humidity control for humidifier and dehumidifier in auto mode.The same design type model is RTH9580WF. The difference is that later is a smart thermostat with auto adjust feature like nest or Ecobee. But with price consideration you may be quite satisfied with the above model.It comes for around $140 in comparison to RTH9580WF which is about $230.
The setting for humidity control is quite easy.
In summer months.
1.)Go to Menu>Select Humidification>Goto help to know how each setting works>Seleect dehumidification>Set your humidity level to about 60%>Select done and go back to home screen.
In winter months
Got to Menu>Scroll down to find humidification>Click on help meny know how different setting works>Set humidity to about 35 %>Tap on done and go back to home screen.
Your system ability to reach that humidity in winter or summer will depend on outdoor temperature and humidity and also on your home age structure and insulation levels.
5.)Ecobee3 smart thermostat
Ecobee 3 is the middle ground in the whole range of ecobee smart thermostat interms of price and features.But it has what you need.That is ability to control humidifier or dehumidifier uses its ACC+/ACC- terminals to control any other accessory other than heating or cooling.In summer moth you can adjust humidity by setting the humidity set point and also AC over cool max setting so you don’t over run Ac to lower the humidity.
For winter moths it has a frost control which lowers humidity set point as the outside temperature falls.This prevent frost on windows and save them from damage.
Here is a video how to set humidity in summer .Setting in winter will go along the similar process and or you can refer your manual.
6.)Nest smart thermostat-When it comes to thermostat we know nest is the market leader.It comes with almost all feature you need in a thermostat.Only drwback is that it is not cheap and maybe not for everybody if you dont need most of its other feature like geofencing etc basically what makes it a smart thermostat.
In Nest controlling humidity after wiring is just as simple as setting the humidity set point and over.You will be done. It will start controlling your Ac dehumidifier or humidifier according to your humidity set point.See i this video.
7.)Cielo Breez Plus, Smart Air Conditioner Remote Controller
This probably a new entrant into thermostat market is meant only for those who suffer from hot and humid climate.Its is cost effective way of controlling Ac to keep temperature as well as humidity into your desired range.Works with most of the Ac brands and models and is also compatible with Alexa and Google assistant. It also has Geofencing. However if you want to control your Furnace or humidity in winter as well this is totally not the thermostat you need.Other than that it has overall good customer feedback and ratings.