[Equest-users] LEED Increased Ventilation Credit and Energy Modeling

[Joseph Lewis]

You are going to follow 90.1 Appendix G for the model.  This means both the baseline and proposed design outdoor air flow rates will need to be the same except if you are using demand control ventilation in the proposed and it is not required by 90.1 section 6.

In the case where you have demand controlled ventilation in the proposed and it is not required in the baseline then the USGBC has stated that they would like the baseline to be modeled as compliant with 62.1 without the system level corrections.  There also should not be any temperature difference corrections because the other appendix G rules require your CFM sizing to be based up on a 20 °F delta T.

If demand controlled ventilation is required by 90.1 then it must be modeled in the baseline and proposed with the same design flow.

I personally take credit on my models for where the proposed VAV system has controls to maintain a constant OA flow across from design to minimum supply, by modeling the baseline as just proportional.  I have not been flagged for it, but I also have not found any definitive ruling that what I am doing is allowed.    

Joe Lewis
Fortier Engineering

From: Joe Chappell 
Sent: Thursday, March 06, 2014 3:50 PM
To: mailto:equest-users at lists.onebuilding.org 
Subject: [Equest-users] LEED Increased Ventilation Credit and Energy Modeling

Good day,

 

I have a question regarding the LEED credit for Increased Ventilation (IEQc2).  This is the credit awarded for exceeding ventilation in all spaces by 30% beyond the ASHRAE standard 62.1 requirements.  It seems obvious that the design model ventilation rates would be those 30% higher than 62.1 requirements.  What then would the baseline model ventilation rates be?  

 

If you strictly follow 90.1 Appendix G, you should always model baseline and proposed equivalent except for when taking credit for demand controlled ventilation.  However, it seems in this case that it could also be argued (by LEED) that you should model the ASHRAE 62.1 required ventilation rates in the baseline model, not those that are 30% higher and therefore pay the energy expense( most climates) for increased outside air.

 

Does anyone have any experience with LEED on this issue?  Thanks in advance.

 

Kind regards,

Joe Chappell

 
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