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.
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.
I was also reading in MEEB about DOAS. I understood it as the following:
There is a dedicated outdoor air duct system. It is continually moving fresh outdoor air through the building. Heating and/or cooling was a separate system, for example, a chilled beam. It sounded like DOAS was more of an add on to a system that is already providing heating/cooling.
Could you clarify or elaborate a little? Thank you
Thanks for your question! You are correct, it is system that is used in combination with a heating or cooling system. By divorcing heating and cooling requirements from ventilation requirements, a DOAS can maintain consistently high indoor air quality. Check out page 165 in the Architect’s Studio Companion for more information and reach out with any additional questions. Thanks!