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A building has fan-assisted ventilation and no mechanical cooling system. Does this qualify as natural ventilation?

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NC-v4 EQp1:Minimum indoor air quality performance

CO2 monitoring for exhaust fan system?

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Dang Thi
ESD Engineer
GreenViet Consultancy Company
LEEDuser Basic Member
3 thumbs up

Our project are factory, the ventilation system use exhaust fans combined with louvre / open door to tranfer outside air direct from outside. 
To monitor, we consider that is natural ventilation case so we suggest owner/MEP designer install CO2 sensor at between 3 and 6 feet above the floor combined with audible alarm when CO2 concentration exceeds the setpoint by more than 10%.
Recently, in our projects, LEED Reviewers don't approve CO2 monitor, they require exhaust fans greater than 1000 CFM (1700CMH)  must be provided with monitoring devices.
It is correct?

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Wed, 04/12/2023 - 16:23

Has anyone come across an answer to this? Is an exhaust fan with outdoor air intake louver considered mechanical or natural ventilation?

Wed, 04/12/2023 - 16:34

Since it requires a fan to draw ventilation air, it is mechanically ventilated.  Natural ventilation would only rely on passive strategies - such as convection induced from process heat.  
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Dave Hubka
Practice Leader - Sustainability
EUA
LEEDuser Expert
510 thumbs up

Wed, 04/12/2023 - 16:47

I agree with Candice. When electricity is needed for ventilation it is no longer "natural".

Thu, 04/13/2023 - 12:14

Thanks, Dave and Candice. Saw some posts that seemed to hint otherwise and got confused.
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Afogreen Build
www.afogreenbuild.com
Green Building Consultant
LEEDuser Premium Member
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Tue, 07/25/2023 - 09:36

Hi Kelsey,  Yes, agree with Candice and Dave,
It can be mechanical ventilation because it has fan to draw air. As define in ASHRAE STANDARD 62.2-2016, natural ventilation is define as ventilation occurring as a result of only natural forces, such as wind pressure or differences in air density, through intentional openings such as open windows and doors.
While, mechanical ventilation is the active process of supplying air to or removing air from an indoor space by powered equipment such as motor-driven fans and blowers.  Best regard – Afogreen Build Team
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Afogreen Build
www.afogreenbuild.com
Green Building Consultant
LEEDuser Premium Member
249 thumbs up

Tue, 07/25/2023 - 09:36

Hi Kelsey,  Yes, agree with Candice and Dave,
It can be mechanical ventilation because it has fan to draw air. As define in ASHRAE STANDARD 62.2-2016, natural ventilation is define as ventilation occurring as a result of only natural forces, such as wind pressure or differences in air density, through intentional openings such as open windows and doors.
While, mechanical ventilation is the active process of supplying air to or removing air from an indoor space by powered equipment such as motor-driven fans and blowers.  Best regard – Afogreen Build Team

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