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ASHRAE 90.1-2010 – Recirculation in Baseline Systems 4 and 6?

asked 2025-07-05 04:54:10 -0500

Anurag_G
91 ●4

Hi everyone, I'm working on an energy model following ASHRAE 90.1-2010 and I have a question regarding the baseline systems. Specifically, for System 4 (PSZ-HP) and System 6 (Packaged VAV with PFP Boxes & Reheat) — are these systems modeled with air recirculation in the baseline case? I'm trying to ensure my unmet hours are within limits and want to confirm if recirculation is assumed or if it's 100% outdoor air. Any insights or references from Appendix G or modeling guidelines would be greatly appreciated. Thanks in advance!

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answered 2025-07-05 13:11:28 -0500

Greg Estep
1009 ●33 ●6

Hi Anurag, Systems 4 and 6 include recirculation. They also includes a dry bulb economizer and heat recovery with sensible and latent effectiveness set to 50%.

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Hi Greg, the economizer applicability depends on climate zone right? Also, does heat recovery apply even if there are no heat recovery systems in actual design?

Anurag_G ( 2025-07-05 21:27:48 -0500 )edit

Hi, yes, economizer is climate zone dependent, per table G3.1.2.6a. Heat recovery (energy recovery) is required if it meets the criteria of table 6.5.6.1.

Greg Estep ( 2025-07-06 19:52:11 -0500 )edit

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Asked: 2025-07-05 04:54:10 -0500

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ASHRAE 90.1-2010 – Recirculation in Baseline Systems 4 and 6? edit