The informational landscape surrounding the topic of home renovation is overrun with articles written by companies that sell various goods. Making up fairy tales is one of the well-liked methods, and their sole objective is to persuade people to buy things. The situation with relative humidity in residential settings is particularly interesting, especially when articles are published in one magazine recommending the purchase of both a humidifier and a dehumidifier. What should be done to the air in the apartment, humidify it or continue to drain it? What is the ideal relative humidity and how do you measure air humidity?
There is a discrepancy between the room’s relative and absolute humidity.
Let’s start by remembering that there are two types of air humidity: absolute and relative.
- Absolute measures the amount of water in the form of steam (gas) that can be found in one kilogram or one cubic metre of air.
- The percentage ratio of the actual water content to the highest amount attainable at a particular temperature is represented by relative humidity. We frequently talk about the relative humidity of the air in ordinary conversation, which can result in misunderstandings.
How does a residential area’s relative humidity level develop?
There are primarily two sources of water vapour in an apartment that has been occupied for a long period. One source is the water that residents emit during daily activities (washed clothes, washed under a hot shower, etc.). Another component includes providing ventilation air. Additional sources of moisture from building materials are introduced if construction and finishing operations are done indoors.
Why is the apartment’s air dry in the winter?
The temperature of the air has a significant impact on its capacity to contain water vapour. The Mollier curve, which describes this relationship, makes it simple to calculate the moisture content of air at a particular temperature. For instance, even at 100% humidity during winter frosts, the air is relatively dry, with only around one gram of water present per cubic metre.
After entering the room and warming to room temperature, the relative humidity of such air will only be a few percent. That is, because the heating radiators are running at full capacity throughout the winter, the air does not simply (or not as much) grow dry.
Factual statement: In the winter, dehumidification of spaces happens right when ventilation (ventilation) takes place. The end outcome is changes in humidity. It turns out that internal moisture release occurs more or less continuously in persons. However, the water vapour flow outdoors varies. These additional indications cause relative humidity to fluctuate across a wide range. This is manifestly demonstrated by the internal wood’s drying out.
Normal humidity levels in the apartment
What level of relative humidity should one aim for when purchasing a humidifier or dehumidifier, and what is “normal” for an apartment? It’s common knowledge that +20 degrees and 50% humidity are considered typical. On the comfort zone diagram, this is actually the last point from the top.
When is the apartment’s air humidity at its best?
Not dryness, but excessive humidification of the apartment’s air poses a considerably larger health risk. Not the water vapour itself, but the effects of excessive humidity, such as mould and fungi on windows and building materials, are detrimental. For kids, in particular, mould spores in the air can cause asthma attacks and allergic reactions.
In severe circumstances, too much moisture during the cold season in the form of condensate can cause the collapse of building structures. “Wet” labour done during the wintertime when a building is being decorated and repaired is especially risky due to the increased humidity of the internal air.
How can the humidity in a room be raised? Technically, the appropriate humidity indication can be achieved using specialised humidifiers (steam, ultrasonic) that produce water vapour. Based on the specified value of air exchange, the local environment, and the acceptable level of room humidity, it is simple to assess their performance in terms of water vapour.
However, you’ll probably need to replace the windows before humidifying the air in the space. On a typical double-glazed UPVC window with an aluminium spacer, the figure depicts the real temperature distribution during the winter. Temperature lowers to 0.4 degrees in the lower portion of a double-glazed window that is already frosty at -18 degrees. At an air temperature in the room of +20 degrees, the “dew point” is realised in this place at relative humidity of roughly 30%.
If we use a humidifier to try to increase the humidity in this condition, we will end up with condensate that will collect as a puddle on the windowsill. The window will begin to convert vaporise water to liquid water, acting as a dehumidifier. The “dew point” is +9.3 degrees with +20 degrees air temperature and 50% relative humidity. Therefore, it is essential to use windows that won’t have any places in the winter during frosts when the temperature would be lower.
By switching from aluminium spacers to “warm” frames, it is possible to increase the temperature of the double-glazed window’s edge zones. Additionally, by using low-emission glass and filling the windows with inert gases, it is possible to raise the temperature of the glass in the double-glazed window’s central zone. In challenging situations, you can also think about electrically heated glass.