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NC-v4 EAp2:Minimum energy performance

Baseline Required Outdoor Airflow for Toilets

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Junaid Mujahid
Sustainability Engineer
PNC Architects (Sobha Realty)
LEEDuser Basic Member
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Hi Forum Users!

The MIAQ LEED Calculator does not have any space category for Toilets/Washrooms/Showers. Considering ASHRAE 62.1-2010 requires exhaust for these spaces and obviously makeup air will be required to replace the exhausted air, how can this makeup air be reflected in the minimum outdoor air requirement in the IAQ calculator for the Baseline Case model?

Since if this is not included, it imposes an energy penalty on the proposed case energy model for supplying additional outdoor air

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Fri, 01/30/2026 - 16:19

Exhaust-only spaces are not intended to be included in the calculator, since the calculations are for outdoor air requirements only. However, the exhaust makeup air requirements of the exhaust-only spaces should be added to the outdoor air requirements when determining the Baseline ventilation rates. 
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Junaid Mujahid
Sustainability Engineer
PNC Architects (Sobha Realty)
LEEDuser Basic Member
2 thumbs up

Mon, 03/30/2026 - 06:31

Hi Tyler,

The reviewers on multiple projects of ours have always insisted that the Baseline Outdoor Airflow reported in the MEPC must exactly match the MIAQ Sheet. So if exhaust-only spaces are not to be included in the MIAQ sheet, then the additional outdoor air is not acceptable apparently in the Baseline model.

Would a narrative explaining the additional outdoor air requirement for the exhaust-only spaces in the Baseline case be acceptable? Or is there another approach to this?

Mon, 03/30/2026 - 12:22

Reviewers should not be requiring the Baseline OA to exactly match the MIAQ sheet if an explanation is provided to justify the difference. Here is the language directly from the LEED v4 Reference Guide > Minimum Energy Performance > Further explanation > Common Issues with Energy Modeling > Table 5 > Ventilation:"Exception (c) penalizes projects for providing more ventilation air to the space than is required by ASHRAE 62.1–2010 or a local code, whichever requires more ventilation air. If the proposed project provides outdoor air in excess of the amount required, the baseline must be modeled with the required ventilation rates, which will be lower than the proposed ventilation rate. This creates an “energy penalty” for the additional fan and conditioning energy.For various reasons, however, it is common practice to specify slightly more ventilation air than required. A project team that has specified up to 5% more total ventilation air than required may model identical ventilation rates. If exhaust requirements dictate the amount of ventilation air that must be provided to the building, as indicated in Section 5.9.2 of ASHRAE 62.1–2010, provide an explanation, documentation, and calculations as necessary to show that exhaust requirements exceed the minimum ventilation flows, and model the ventilation rate identically in both buildings."

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