DOAS vs RTU vs HOAS – Compare Operating Differences

DOAS vs RTU vs HOAS

Improving indoor air quality (IAQ) by increasing the amount of outdoor air (OA) entering a building is necessary for many facilities. The downside of adding outdoor air is it also admits excess moisture into the facility. Dedicated Outdoor Air Systems (DOAS), High Outside Air Systems (HOAS), and Rooftop Units (RTU) are a family of packaged units that contain similar factory features but have a distinct sequence of operations and responsibilities.

The most energy-efficient method to remove moisture is through the use of a Dedicated Outdoor Air System (DOAS). A DOAS unit is a packaged unit that is installed outside and is used with other HVAC equipment. DOAS units are designed to bring fresh air into building spaces delivering neutral air discharge air temperatures of 70F to 75F @ 50% RH. The DOAS supply air dew point design temperature is lower than a standard air conditioner to ensure the maximum amount of moisture from the outside air.

A Rooftop Unit (RTU) is a packaged unit that is installed outside of a commercial building and operates in either cooling, economizer, or heating mode responsible for providing comfort cooling of space.

A High Outside Air System (HOAS) has operational characteristics of both a standard rooftop unit and a dedicated outdoor air system. The HOAS provides high outside air into space or building like a DOAS and it will provide comfort cooling/heating operation similar to an RTU.

To compare the operating differences between the DOAS, RTU, and HOAS view the compiled table. For more information, visit our website york.com.