The mechanical engineer of a new low-rise commercial building is proposing DOAS (dedicated outdoor air system) units as a means of complying with the owner’s sustainable design requirements.

What is the principal benefit of using a DOAS system?

The explanation of the answer cites Pg 668 - 669 of MEEB.

I went to these pages and was sadly disappointed to find only a single paragraph that does not explain how it works, and summarizes that a DOAS is “more of a potential than an actual trend.”

However, the explanation states that a DOAS is “often used on projects with high sustainable performance criteria. The ability to provide 100% fresh outside air reduces energy dependence because the return air system is powered and used far less frequently than in a conventional HVAC system.”

I have a 5th edition of The Architect’s Studio Companion, which is almost 10 years old and doesn’t have anything about DOAS.

The 12th edition of Architectural Graphic Standards isn’t much better.

I did find this website extremely helpful and wanted to pass along:
Radiant cooling/DOAS | HVAC Selection (

Any other resources?

@gerald -

The principal benefits of using a DOAS system are the following;

  • It combines ductwork which leads to lower initial costs.
    -Because it combines airflow it also reduces air volume and thus decreases the fan energy use.
  • It does a really good job of mixing fresh outdoor air and return air for a space, reducing cold and hot spots for the users.


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