Hi all,
I have a doubt regarding a CI project. The building is served by Dedicated Outdoor Airflow Systems (DOAS) that serves several floors. Our project is regarding only one floor. As per ASHRAE 90.1 - 2010, section 6.4.3.9, DCV controls are only required for spaces with high occupancy density served by systems with 1400 l/s of outdoor airflow or more. We know that each DOAS that serve the building (and the project) have more than 1400 l/s, however, each DOAS provides around 1200 l/s to the floor under certification.
As such, must spaces that have a high occupancy density in our project (as per the 6.4.3.9 section) need to comply with DCV controls?
The doubts is: each system's total outdoor airflow is higher than 1400 l/s (as a total), but each DOAS provides less than that threshold to our project.
Thank you very much in advance!
Tyler Thumma
7GroupLEEDuser Expert
62 thumbs up
May 23, 2024 - 9:24 am
Yes, spaces meeting the size and density requirements of 6.4.3.9 would need to be designed with DCV controls, unless any of the exceptions to 6.4.3.9 apply, since the airflow defined by 6.4.3.9(c) is the system airflow, not the airflow to the project space only.
Luis Andrade
2 thumbs up
May 23, 2024 - 10:02 am
Hi Tyler, thank you very much for your comment.
Adding up to the question above, please consider that the central DOAS units are not interviened (not in the scope of the tenant), only the air distribution on the floor under certification. The DOAS are landlord's propriety, constant volume and do not have any frequency driver installed, how would that be possible? My doubt here would be: if the system does not have a VSD or a pressure sensor to maintain setpoint, under controlled CO2 values wouldn't the space's VAV dampers that close just revert the outdoor air to the other rooms? If there is no pressure sensor nor a DSV for it to act, perhaps in this case it doesn't make sense to have the VAV dampers there.
Please let me know if I wasn't clear here..
Again, thank you very much in advance!
Tyler Thumma
7GroupLEEDuser Expert
62 thumbs up
May 23, 2024 - 10:51 am
Your explanation was clear. However, I am unable to provide design guidance for how to achieve this requirement with the system that's been installed. This would need to be coordinated with the landlord and the project's design engineers.
Luis Andrade
2 thumbs up
May 24, 2024 - 5:35 am
Hi Tyler,
Your answer back there was good enough to at least confirm my suspicious that this is not an easy and quick answer. It makes total sense to apply the DCV control. I'll have to double my efforts here to try to figure out a solution to this one.
Meanwhile, if someone else has experience in this situation, please do leave here your insight.
Thank you!