#1175 WHF Penalty in Shoulder Months and Troubleshooting

[Dee Anne Ross]

User complained of insufficient credit for WHF in 2019. The files they provided as proof were recreated and each difference identified. It has a VERY poor envelope. Our findings: (1) The worse the envelope, the less credit. (2) When compliance goes negative, there is sometimes no benefit to the WHF. (3) In some climate zones there is a credit for removing the WHF.

High level issues:
1. In 2016 removing a WHF increased site kWh. In 2019 removing a WHF decreases site kWh.
2. In 2016 a building poor envelope get more benefit (TDV margin) from a WHF than a more efficient envelope. The opposite seems to be true in 2019.
3. Builder’s compliance model from 2016 is an extreme case of the above. With this model, in some climate zones there is a large EDR credit for removing a WHF.

Goals is to remove some or all of the penalty from months when WHF uses more energy (and TDV) than non-WHF models. Considerations/possibilities:
1. Possibly only run if the current day dry-bulb high temperature is above a certain value. However, the cut off temperature is not the same for all climate zones so no final value.
2. Do not want a standard WHF to be as smart as a NightBreeze which would not mimic a typical homeowner.
3. Need a middle ground between the current model and the NightBreeze.

Files with and without WHF in ribd16 and ribd19 attached.

[RJ Wichert]

In addition to revisions to address the above issues, we'd like to add a limit to the cooling ventilation airflow of 3.5 cfm/ft2 of conditioned floor area. This is a building wide limit, so the total cooling ventilation airflow for a building can't exceed 3.5 times the total conditioned floor area of the building.

• We'd like this to behave like IAQ where an error is triggered (after hitting run simulation) when the min IAQ airflow is not met.
• We'd like there to be a UI message on the project level Cool Vent tab stating that the project exceeds the cooling ventilation airflow limit (if it exceeds the limit) (similar to how a "NOT MET" message appears on the IAQ tab if the minimum is not met)

[Dee Anne Ross]

From RJ: In addition to revisions to address the above issues, we'd like to add a limit to the cooling ventilation airflow of 3.5 cfm/ft2 of conditioned floor area. This is a building wide limit, so the total cooling ventilation airflow for a building can't exceed 3.5 times the total CFA of the building.
• Want it to behave like IAQ (when the min IAQ airflow is not met) where an error is triggered after hitting run simulation.
• We'd like there to be a UI message on the project level Cool Vent tab stating that the project exceeds the cooling ventilation airflow limit (if it exceeds the limit) (similar to how a "NOT MET" message appears on the IAQ tab if the minimum is not met)