In-Duct Evaporative Cooling

Q: What is in-duct evaporative cooling and how does it work in air handling units (AHUs)?

In-duct evaporative cooling integrates adiabatic humidification media within an AHU’s airflow stream, reducing air temperature by leveraging the natural heat absorption of water evaporation before air is supplied to conditioned spaces—enhancing cooling efficiency with minimal additional mechanical load.

Q: What maintenance or operational considerations should be addressed when deploying in-duct evaporative cooling?

Proper media selection, water quality control, airflow design and duct-integration are key operational factors; ensuring the evaporative media remains clean, saturation is maintained, and the increased humidity (if direct cooling) is compatible with the conditioned space are all essential for reliable long-term performance.

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Benefits

Modern evaporative cooling systems use the natural adiabatic process to efficiently regulate indoor air conditions while minimizing energy use. With the ability to deliver powerful cooling from minimal electricity, they offer a cost-effective solution for air handling units. There are three primary in-duct cooling strategies—direct, indirect, and exhaust air—each designed to optimize performance based on system design and climate.

Direct cooling efficiency

Adds humidity directly to the incoming air stream to lower temperature and boost cooling performance in AHUs.

Indirect cooling power

Uses humidified exhaust air to transfer cool energy through a heat recovery system without adding moisture to the supply air.

Exhaust air optimization

Recovers cooling energy from humidified exhaust air to pre-cool incoming air, reducing load on mechanical chillers.

In-duct evaporative cooling

Top of page Benefits References FAQs

Direct evaporative cooling: powerful adiabatic cooling with low energy demand

Direct evaporative cooling delivers high-efficiency temperature reduction by introducing moisture directly into the incoming air stream. This adiabatic process lowers supply air temperatures while using only a fraction of the energy required by traditional cooling systems. It’s ideal for AHUs serving industrial, commercial, or mission-critical environments where both cooling performance and humidity balance are key. Condair’s in-duct humidifiers ensure precise control and dependable operation even in high-demand applications.

Indirect evaporative cooling: boost efficiency without compromising humidity control

Indirect evaporative cooling allows facilities to reduce air temperatures without adding moisture to the conditioned space—making it a perfect fit for environments that require tight humidity parameters. By pre-humidifying the external air before it passes through the heat recovery unit, Condair’s systems enhance heat exchange efficiency and extend the operating range of your AHU. This strategy supports year-round performance improvements, even when ambient temperatures rise, while keeping energy use remarkably low.

Exhaust air evaporative cooling: energy recovery that reduces mechanical load

Exhaust air evaporative cooling reclaims energy from the exhaust airstream to pre-cool fresh intake air through a heat recovery unit. This method decreases the burden on chillers or DX systems, cutting both energy consumption and peak demand. Condair’s evaporative technology provides consistent performance across a variety of climate conditions, offering an effective, sustainable way to retrofit efficiency into existing ventilation and cooling systems.

"Use case" is beneficial in many industries and applications

Data Centers

Humidity Control for Electronics Manufacturing

Warehousing and Logistics

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Projects and References

Apple Campus, Cupertino

Cupertino, California, located close to San Francisco, is home to the headquarters of American technology company Apple. The building was designed by British architect Norman Foster, who realized the idea of an oversized ring in connection with the former Apple Campus at Infinite Loop No. 1 in Cupertino.

At a diameter of almost half a mile, the building complex offers a massive 2.8 million sq ft of usable space and accommodates 12,000 employees. The ring surrounds a 1.4 million sq ft park featuring rest areas, cafés, sports facilities and a rainbow-colored festival stage that was inaugurated by Lady Gaga in 2018. Powered entirely by renewable energy, the building features a 17-megawatt rooftop solar array and energy-efficient evaporative cooling from Condair.

Weatherite, UK

When Weatherite needed to develop an innovative cooling solution that didn't rely on man-made refrigerants, it turned to Condair's adiabatic cooling expertise. The partnership resulted in Weatherite's innovative AdTec-D direct cooling system, which is now a highly proven free air-cooling unit, used by leading telecoms and data centre clients.

Facebook / Meta, Sweden

This data centre in Lulea Sweden is one of the world's most efficient and sustainable data centres. Condair evaporative humidifiers add up to 22,800 litres per hour to the air in the penthouse ventilation systems to maintain the humidity to ASHRAE standards across the data halls.

Microsoft, Ireland

Microsoft Dublin uses an "open air cooling" system rather than mechanical chillers to maintain the low internal temperatures required around its servers. Fresh air is continuously introduced into the building and mixed with recirculated indoor air.

35 Condair evaporative humidifiers provide up to 8C of energy-efficient evaporative cooling to its huge data rooms. This combined use of fresh air and evaporative cooling has enabled the data center to eliminate the need for mechanical cooling for 95% of the year.

Cork Internet Exchange, Ireland

The Condair ME evaporative humidifier is providing adiabatic cooling in an innovative indirect cooling system at the Cork Internet Exchange (CIX) in Ireland. An indirect air-to-air evaporative cooling system maintains the temperature across CIX's data halls without using any chillers and with 75% less energy than a traditionally cooled data centre.

A cool recovery with Konvekta

The Condair ME evaporative humidifier is being used by energy recovery specialists, Konvekta, as one of its standard adiabatic cooling solutions. As an example, a recent installation at a clinic in Tyrol, Austria, resulted in a confirmed annual energy recovery across the Konvekta systems of 92% for the building. A single Condair ME humidifier contributed more than 60,000kWh/a of cooling during this period from just 3,800kwh/a of consumed electricity.

Frequently asked questions

In which environments or applications is in-duct evaporative cooling most effective?

In-duct evaporative cooling is especially effective in commercial, data-centre or industrial facilities where large fresh-air intake volumes exist, and where controlling supply air temperature or pressure drop is critical; it performs best when outdoor or intake air streams have sufficient capacity for moisture absorption and when humidity limits allow meaningful cooling through evaporation.

What is in-duct evaporative cooling and how does it work in air handling units (AHUs)?

What maintenance or operational considerations should be addressed when deploying in-duct evaporative cooling?

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