In the past posts in this blog, we have mentioned that temperature and humidity are strongly related. However, a temperature and humidity relationship chart can demonstrate this in a much better way.
Today, we are going to delve deeper into what relative humidity means and how it is related to temperature. Since it is expressed as a percentage, we are also going to find out why.
What is the relationship between air temperature and relative humidity?
In layman’s terms, the relationship between temperature and humidity in an enclosed space is inversely proportional.
Inverse means that when one variable increases, the other decreases. But it is not always as simple as that because other dynamics can come in.
For instance, hot air can hold more moisture than cold air. Therefore, when there is more heat, the humidity is going to be high. It is for this reason that hot places such as Florida have high humidity throughout the year.
Also, in summer, the air holds more humidity than in the cold seasons. Thus, to stay comfortable in your indoor spaces, you need both a humidifier and a dehumidifier.
BUT LOOK HERE …
If you increase the temperature in your indoor space without increasing the moisture, the air will become dryer. Heat makes moisture evaporate. Thus, the humidity will fall!
This explains why we have low humidity indoors in winter because we turn on the heat, but we don’t increase the humidity. Thus, the heat is high and it makes the air drier, dropping the humidity.
Temperature and humidity relationship formula
When you hear of the temperature and humidity relationship formula, it is usually about calculating the RH – relative humidity level you need in your house.
It is not too hard to do this really. You could just use an online calculator to find out. On the tool, you will have to enter a few values.
Enter the temperature in degrees Celsius, divided by the dew point temperature in degrees Celsius. You can then multiply the result by 100 to get your RH level in percentage.
In simplified form, the formula for calculating relative humidity would look like this:
This means that relative humidity is the percentage of vapor pressure divided by vapor pressure saturation at a certain temperature.
Understanding the 30 to 50 Percent Indoor RH Rule
The relative humidity range given for the indoor living spaces is 30 to 50 percent. This means that at low temperatures, your indoor humidity should never go below 30 percent
In high temperatures, the humidity level should never rise above 50 percent.
Some sources may give the best range as 35 to 55 percent and some may even go to 60 percent. However, 70% humidity is too high indoors and outdoors.
What happens when humidity dips below 30 percent?
Your books and paintings might become brittle and dry, wallpapers start peeling off and indoor plants might start drying up.
Static electricity starts forming and you experience nasty shocks when you are wearing clothes. Also, the air can feel colder than it actually is.
When the humidity is too low, it affects your health. For instance, the skin becomes dry, your lips become chapped and your hair brittle.
Too dry air is also not good for people with allergies or with chronic respiratory conditions such as asthma. It can cause inflammation of the airways and the sinuses.
Indoor allergens such as dust and pollen will float about in the air. Thus, you will inhale them easily and they might trigger allergic reactions.
What happens when humidity rises above 50 percent?
There are many effects of high humidity indoors. First, it can provoke allergic reactions in people who have asthma, since like dryness, wetness can also cause an inflammation of the airways.
There are many health effects of high humidity on the body. For instance, it causes your body to overheat because humidity retains more heat.
Your body is tricked to start sweating in an attempt to cool down. This can even lead to dehydration.
Too much moisture in the air leads to the growth of mold in your house. The dark spaces in the kitchen, basement and bathroom are notorious for growing mold. Mold spores can fly in the air and when you inhale them, they trigger certain illnesses.
High moisture in your indoor air makes ideal conditions for pests, worms, dust mites, pet dander and other indoor allergens to thrive.
Overall, low and high humidity are really bad. Maintain your indoor humidity within the recommended range.
Relative Humidity vs temperature chart
There are two types of humidity. One is Absolute Humidity and the second one is Relative Humidity.
In a closed room where there is no influence of sunlight, moving air, wind and other external factors, the fixed amount of vapor that the air holds at a given temperature is called absolute humidity.
In a regular room, say your sitting room, the water content in the air is best expressed as relative humidity.
This means the amount of water in the air at that temperature, in relation to the total amount of water that the air should actually hold at 100 percent saturation.
If relative humidity is 100 percent at 25°C, then that is the maximum amount of water that the air can hold at that temperature. That is its 100 percent saturation point.
If the relative humidity is 70 percent at 25°C, that is 70 percent of the maximum amount of water that the air can hold at that temperature.
Thus, Relative Humidity is expressed as the amount of moisture in the air divided by the maximum amount of moisture the air can hold at that temperature, multiplied by 100.
Relative Humidity and Temperature: Vital Things to Know
There are two types of humidity, which we have already discussed. However, we need to mention that absolute humidity rises with rise in temperature. It is also expressed in grams of water per cubic meter of air (g/m3).
RH is the percentage of water that air holds at a given temperature, in relation to the total amount of water it could hold (at that temperature).
For instance, the amount of air that water could hold at 20°C is different from what it would hold at 10°C.
When measuring Absolute Humidity, remember that humidity is directly relational to temperature.
When measuring RH, remember that humidity is inversely proportional to temperature.
Like other materials, air has its saturation point at different temperatures. At higher temperatures, it has a lower saturation point, meaning that it becomes more saturated faster.
The three types of temperature
There are three types of temperature. These are dry bulb, wet bulb and dew point temperatures.
Dry bulb temperature is the type of temperature measurement that is used for homes, schools, offices and other living settings.
To preserve artifacts in the right conditions, a different type of temperature may be used in museums, galleries and other similar settings.
Dry bulb temperature is recorded using a thermometer that is not affected by the amount of moisture in the air.
Wet bulb temperature is taken using a thermometer that is moist or a thermometer bulb that is affected by moisture.
Dew point temperature is the temperature taken at the point of saturation or 100 percent humidity when water vapor condenses and forms droplets on windows and other surfaces.
Is humidity directly proportional to temperature?
It is inversely proportional. If you increase the temperature of an enclosed space without increasing the water vapor, the humidity drops. However, outdoors, in summer, an increase in temperature can lead to an increase in humidity.
Whether you get the relative humidity chart or relative humidity temperature chart, the fact remains that living out of the recommended RH range of 30 to 50 percent can be uncomfortable and it can even cause certain illnesses.
The temperature and humidity relationship chart supports the general consensus that high indoor temperature will cause high humidity and vice versa.
Thus, in summer, you need a dehumidifier and in winter, a humidifier.