The Role of Humidity Control...
January 16, 2025
The Role of Humidity Control in Balancing Occupant Comfort and System Performance
Humidity is a very important factor governing the behavior of occupant within the space, impact on building envelop and operation of equipment serving the space. So, what is humidity? The term humidity refers to the amount of moisture or water vapor present in the air. The concentration of water vapor can be higher or lower depending upon the capacity of air to hold water vapor until precipitation, which is known as relative humidity
Both higher and lower humidity levels are undesirable and have adverse effects on people and surroundings. The uncontrolled level of humidity leads to poor indoor air quality (IAQ) as per the report from Amercian Industrial Hygiene Association (AIHA). Hence, optimum humidity level is maintained during operational hours of any building to enure occupant comfort, good health and higher productivity. It also plays a crucial role in maintaining integrity of buiding materials and equipment.
What is the Source of Humidity ?
- Geographic Location
The area located near coastal region experience moisture-rich air due to evaporation of water based on the change in temperature from dawn to dusk. - Leaks or Spills
Water spilled or leaked can contribute to rise in humidity level in a building. They can cause growth of bacteria, mold, fungi etc. which can lead to serious respiratory problems. - A/C Malfunction
Routine maintenance is an effective way to improve the overall performance of air conditioning systems. Dirty air filters, frozen evaporator coils, clogged drain line, poor insulation, undersize/oversize unit etc. may result in an increase in humidity level. - Vent Termination
The positioning of vent close to the opening in the conditioned space can significantly buildup humid environment and increase unnecessary load on air conditioner. - Kitchen Activity
An appropriate measure to exhaust steam generated while cooking food or from dishwasher can add moisture laden air to the space.
Understanding Buiding Humidity Levels
Various types of building structures such as residential, commercial, mixed-use, healthcare facility, industry, institution, hotel, public safety, aviation, rail, port etc. is more susceptible to different levels of humidity. The American Society of Heating, Refrigerating, and Air Conditioning Engineers, Inc (ASHRAE) provides guidelines or recommend definite range of relative humidity that are intended to satisfy functional requirement of a particular building. So, what should be an ideal humidity level for a given space type? Let us investigate in each zone or room of a building and identify whether there is condensation on windows? Mold growth? Occupant discomfort? Effect on appliances or artifacts? Therefore, for a given space type humidity control is utmost important and challenging.
What will Happen at Lower Humidity
- Occupant Discomfort
There is a risk of respiratory illness like asthma and bronchitis. Dry air symptoms include dry skin, lips and hair, sore throat, dehydration, eye irritation, nosebleeds and susceptibility to cold. - Static Electricity
The absence of thin molecular layer of water with plenty of free ions that can instantly dissipate any built-up static electricity causes release of static electric charge with no barrier tends to experience electric shock on exposure to any conductive surface of an appliances. - Airborne Dust
Dry air makes it easier for allergens like pollen and duct can remain airborne for a longer period. Dust particles may also contain harmful chemicals and contaminants directly affecting occupant health. It causes wear and tear of equipment with sensitive instruments that requires precise calibration on too much exposure to dust. - Power Consumption
The equipment will work overtime to manage predefine humidity along with desirable temperature within the space. This extra usage of the equipment tends to increase energy bills with more wear and tear. - Specific Issues
Lower humidity has a huge impact on paper and textile industries as it can cause hardwood separation, shrinkage and cracking or warping, wallpaper peels at the edge etc. Distortion of expensive artifact in museums and libraries. Extremely low humidity can obstruct plant growth and may dry out to defunct in greenhouse.
What will Happen at Higher Humidity
- Occupant Discomfort
There is a risk of adverse effects on the human body and can contribute to issues such as fatigue, muscle cramps, fainting, heat stroke, hyperthermia, lethargy etc. - Growth of Mold and Mildew
Molds are microscopic fungi that settle on damp surfaces and mildew are grey or white patches that are formed on shower curtains, tiles or windowsills. It weakens the structural integrity of buildings and damage ceiling or walls. - Decrease Air Circulation
Pollutants and other harmful particles are trapped in the air causing poor air circulation affecting overall indoor air quality. - Poor Condensation
An inappropriately sized HVAC system provides ineffective dehumidification resulting in an increase in humidity, more power consumption and increase in wear and tear of equipment leading to potential system failure. - Rotting Furniture and Furnishing
Excess moisture due to high humidity causes irreversible damage to hardwood floors, window frames and other wooden artifacts.
Understanding the Significance of Humidity Control
Higher humidity level feels damp and creates an oppressive environment, while on the other hand lower humidity level feels dry and causes respiratory issues. Moreover, excess humidity promotes mold and mildew growth, which can create unhealthy surroundings and deteriorates the building structure. Therefore, overall productivity of occupant is sacrificed with poor indoor quality at a higher cost of energy consumption. Hence, for most buildings, effort towards achieving ideal humidity level with an adequate measure to control or maintain optimal humidity level is an objective of a good HVAC system.
Strategies for Effective Humidity Control
- Monitor Humidity Levels
Installation of humidistat to continuously monitor indoor humidity levels. The data is integrated with HVAC unit, which increases or decreases the cooling coil temperature to maintain the required level of humidity. - HVAC System
Engineer’s best practice to avoid selection of oversized or undersized unit followed by planned maintenance approach offers precise control and regulation. - Dehumidification
Installation of an additional dehumidifier in the circuit or stand-alone unit within the space with high humidity removes excess moisture from the air reducing overall latent load on HVAC system. - Humidification
Installation of humidification system for an addition of moisture to space with arid conditions prevent discomfort and protect sensitive equipment’s. - Ventilation
Adapt proper ventilation technique for effective air circulation and prevent moisture buildup. - Building Envelope
Insulation of building with high quality material having required R-value to minimize heat transfer and a well-sealed building to prevent air intrusion from gap around window, door and through cracks. - Building Automation System
Integration of smart building technologies in order to analyze and optimize HVAC system parameters based on the type of occupancy and weather conditions.
