How Important Is Managing Air Humidity in Buildings?

Controlling air humidity within buildings is crucial for maintaining the well-being of both occupants and the structural integrity of the environment. Excessive dryness can lead to material damage, discomfort, and health problems, while overly high humidity can promote mold growth and discomfort. In this article, we will explore the importance of keeping relative humidity within the optimal range and the methods for achieving this balance.

The Impact of Low Humidity

Low humidity levels can cause a variety of issues, ranging from damage to materials to health concerns. For instance, wood tends to deform and crack when air humidity is too low, while paint may begin to peel off surfaces. This not only affects the aesthetic appeal of buildings but can also lead to significant repair costs. Additionally, low humidity can increase the likelihood of electrostatic discharges, which can potentially damage electronic equipment. Data centers, in particular, are at risk, as these discharges can harm expensive equipment and compromise critical data.

Furthermore, low humidity can irritate the skin, eyes, and respiratory system, leading to discomfort for occupants. Additionally, small particles, such as dust and viruses, tend to remain airborne for longer durations when humidity levels are low. This can result in an increased prevalence of allergies and viral illnesses among building occupants.

Maintaining Relative Humidity Within the Optimal Range

The optimal range for indoor relative humidity, as recommended by both the US Environmental Protection Agency (EPA) and the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), is from 30% to 60%. Achieving this balance is essential for preventing the problems associated with extreme humidity levels.

One of the primary methods for controlling humidity is through the use of humidification and dehumidification systems. These systems work to adjust air moisture levels to keep them within the recommended range. However, it’s important to note that these systems come with a cost, both in terms of initial investment and ongoing operating expenses.

To effectively manage humidity, it’s essential to size HVAC (Heating, Ventilation, and Air Conditioning) equipment to provide optimal control over both temperature and humidity. This means using additional humidification or dehumidification measures only when necessary. Oversized air conditioners, for example, can lead to humidity issues. In such cases, upgrading to appropriately sized units with higher energy efficiency can be a more effective solution compared to adding a separate dehumidification system, which may increase energy expenses.

Integration of Humidity Control in HVAC Systems

Some HVAC configurations come with built-in features for dehumidification, reducing the need for additional components. For instance, air handlers equipped with both heating and cooling coils can effectively control humidity:

1. The cooling coil can lower air temperature and humidity, and if further dehumidification is required, the cooling output can be increased.
2. To prevent excessive cooling, the heating coil can then raise the air temperature to a comfortable level.

In certain cases, steam-based heating systems can provide simultaneous heating and humidification, particularly during cold and dry winter days. While hot water is more commonly used in space heating applications, steam-based humidification can be beneficial if the infrastructure already employs steam in other processes, such as healthcare institutions or industrial facilities.

Energy-recovery ventilation systems are another option that not only exchange heat between outdoor air supply and exhaust but also humidity through a concept called enthalpy-recovery ventilation:

1. When outdoor air is dry, an ERV system can recover moisture from the exhaust air.
2. Conversely, when outdoor air is too humid, the exhaust air can assist in removing excess moisture.

In essence, ERV systems can complement both humidification and dehumidification efforts, contributing to a more balanced indoor environment.

Conclusion

Maintaining the relative humidity of indoor air within the recommended range is essential for the comfort, health, and longevity of buildings and their occupants. A well-designed HVAC system should not only control temperature but also humidity. While humidification and dehumidification systems play a crucial role in achieving this balance, it’s important to consult with HVAC engineers to ensure that the existing infrastructure is optimized for humidity control. In some cases, improving the overall HVAC system’s performance may yield more effective results than adding additional humidity control equipment. A moderate level of air moisture is key to a healthier, more comfortable, and longer-lasting indoor environment.