[bldg-sim] Modeling buildings with natural ventilation for Appendix G

["Mike Tillou" <miket@xxxxxxxxxx>]

Title: Message

Ramana,

 

The ASHRAE 90.1 ECB sub-committee is working on a methodology for simulating natural ventilation within the framework of Appendix G but I don't think its finished yet.  In the meantime here is what I would recommend.

 

Appendix G / 90.1 ECB allows you to use an exception calculation method to simulate hybrid systems or unique efficiency measures to demonstrate above-standard performance.  I think this would certainly apply in your case.  

 

Here's what I have done on projects requiring an exception calculation method. 

1. Establish your energy cost budget and your design energy case following the Appendix G guidelines.  

2. Create a second model using the Design Energy Case as the baseline and make the necessary modifications to simulate radiant heating / no cooling via natural ventilation. 

3. Report the energy savings from your exception calculation as a line item at the end of your LEED EA-1 summary table (similar to how renewable energy is reported). 

4.  Include a seperate summary table  for the exception calculation showing the energy end-use breakdown and how you arrived at the cost savings.  Show both the baseline and proposed energy use. 

5. Make sure the savings are reasonable and prudent for the system you are proposing. 

6. Document any changes to the model especially changes to schedules that were necessary to properly simulate your system.

7. Make it easy for someone to review your assumptions and the methodology you used to estimate the savings

 

I hope this helps.  Good luck.

 

Mike

 

Michael Tillou, PE
ETC Group, Inc - Energy Engineering for a Sustainable Future
Ph:413-458-9870

-----Original Message-----
From: bldg-sim@xxxxxxxx [mailto:bldg-sim@xxxxxxxx] On Behalf Of Ramana Koti
Sent: Monday, December 18, 2006 4:53 PM
To: bldg-sim@xxxxxxxx
Subject: [bldg-sim] Modeling buildings with natural ventilation for Appendix G

Dear all,

Is ignoring natural ventilation in both proposed and baseline designs an accepted/fair way of modeling based on Appendix G (ASHRAE 90.1-2004)?

Part of the proposed design has (radiant heating + natural ventilation) with no cooling which was modeled as a radiant slab, no cooling, natural ventilation ignored.

But the Baseline HVAC system based on Appendix G is System 5: Packaged VAV w/Reheat. (Natural ventilation can be modeled based on Air Change method or Sherman Grimsrud method though I do not know how to do it).

I cannot decide how to make the baseline and proposed comparable with respect to Natural Ventilation (in a manner acceptable to LEED review), suggestions will be appreciated.

Thanks,

Ramana Koti, Sustainable Building Analyst
LEED AP

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