A Solution that Saves: Adiabatic vs. Isothermal Humidification

May 28, 2020 / by Casey Jon McKay

When it comes to managing environments for mission critical applications, the discussion often surrounds precision cooling. However, in addition to temperature, controlling humidity is essential. From eliminating static electricity to preserving works of art, there are as many benefits of humidity control as there are unique applications.


The type of humidification implemented in mission critical environments can make a significant difference in operating expenses and maintenance costs. Understanding the difference between adiabatic and isothermal humidification can illuminate the potential to capitalize on true energy savings and a quicker ROI.

What is Isothermal/Steam Humidification?

Isothermal/steam humidification systems use electricity or gas as an external heat source to boil water creating steam as water vapor is dispersed in the air. During the isothermal process, the air temperature essentially remains constant. Energy consumed from an external energy source is approximately 1,000 BTU/LB of moisture. Isothermal humidification types include:

  • Electrode canister
  • Infrared
  • Electric resistance
  • Direct steam injection (building steam)
  • Steam-to-steam
  • Gas-fired

What is Adiabatic/Evaporative Humidification?

Adiabatic/evaporative humidification systems use mechanical energy to generate finely atomized water particles that are introduced to the air and/or evaporated to/from media. The adiabatic process does not require thermal energy from an external source. There is no heat added. Energy extracted from air stream is approximately 1,000 BTU/LB of moisture. Typical types of adiabatic/evaporative humidification are: 

  • Ultrasonic - piezoelectric transducer
  • High pressure water nozzle
  • Compressed air nozzle
  • Centrifugal atomizing (sling type)
  • Evaporative pad

Adiabatic Cooling During the Humidification Process  

Adiabatic humidifiers produce tiny water droplets that are released into the air, thus increasing the absolute humidity. Those tiny water droplets absorb heat energy from the environment and cool the surroundings. Through the cooling process, total enthalpy – the sum of the internal energy added to the product of the pressure and volume of the system – remains constant. This process consumes less than 10% of the energy required to boil water into steam.


Benefits of Adiabatic Humidification

Perhaps the most notable benefit of adiabatic humidification is air cooling. Because adiabatic humidifiers draw heat from air for evaporation, they can produce a 20+ °F temperature drop. Every pound of adiabatic humidification added to the air removes approximately 1,000 BTU of heat. This is a significant benefit in climates where air is consistently warm and dry, such as a data center, or in spaces where there is an additional heat load, from equipment in a computer room for example.

Because adiabatic humidifiers use heat present in the air to change water to vapor, they consume less energy to operate compared to isothermal humidifiers, which require external energy to boil water into steam. Additional benefits offered by adiabatic humidifiers are:

  • Increased efficiency data centers
  • Significant energy savings
  • Helpful when steam or gas are not available
  • Precise humidity control
  • Quicker ROI

STULZ Ultrasonic Humidification Systems


STULZ offers two Ultrasonic Humidification systems: Direct Room Humidifiers (DRH) and Duct and Air Handler Humidifiers (DAH). Multiple piezoelectric transducers immersed in a water bed impart high-frequency oscillation allowing the distribution of very fine water droplets – 90% smaller droplets than nozzles – into the air.

Mixed Bed Deionization (DI) provides high-purity water quality for small capacity and light commercial humidifier applications. Culligan® High-Purity Reversed Osmosis (RO) plant pre-conditioner is ideal for large capacity humidifier applications. 100% of the demineralized water in the humidifier is utilized; no flush cycle is required.

STULZ Ultrasonic Solutions provide precise static electricity and product quality control at a minimal operating cost. Direct Room (DRH) and Ducted (DAH) Humidifiers provide a clean, efficient, and precise humidity control solution. These units keep operational costs lower allowing for a quicker ROI, typically 1-2 years, verses that of steam applications. Additionally, a 93% energy savings over steam humidifiers makes these units ideal solutions for mission critical applications.

Energy efficiency is a cornerstone of the STULZ mission. Delivering world-wide, purpose-built products that not only provide solutions, but also save energy and money is essential to the brand. For over 40 years, STULZ has lead the precision heating and cooling industry with an entrepreneurial spirit and a client-focused mindset. In collaboration with valued customers, STULZ continues to innovate for mission critical applications, locally and across the globe.

Learn more about STULZ Humidifiers

Topics: Humidification

Casey Jon McKay

Written by Casey Jon McKay

Casey Jon McKay is the newly appointed Product Line Manager at STULZ USA, the world’s leading provider of energy efficient temperature and humidity management technology. Prior to championing various industry segments such as hyperscale computing, colocations, precision agriculture and humidification, Casey served as the STULZ USA Director of Engineering. He has overseen product design, development, testing and validation of the entire STULZ USA product portfolio and has over 20 years’ experience focused on both commercial refrigeration and the precision climate control industry. When he's not obsessing over temperature and humidity, you'll find Casey in his studio or on the stage singing and playing bass guitar.

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