Interpretations No. 301-2014-018 and No. 301-2019-002 Ventilation Run Time go into effect on May 10, 2020
The interpretations state:
Where Dwelling-Unit Mechanical Ventilation Systems are specified but at the time of rater inspection lack controls to provide continuous or programmed intermittent operation, or where controls are not powered, wired, or set-up to enable verification of mechanical ventilation system operation, the system does not meet the definition of a “Dwelling-Unit Mechanical Ventilation System,” and the Rated Home is therefore considered a residence “without Dwelling-Unit Mechanical Ventilation Systems” in the context of Air Exchange Rate.
Dwelling-Unit Mechanical Ventilation System “daily run hours” entered into the Approved Software Rating Tool shall be based on the ventilation controller run time setting present at time of rater final inspection.
This means that ratings on dwelling units without mechanical ventilation controls installed at the time of final inspection should be modeled without mechanical ventilation. If the rater is able to go back for a re-inspection and the mechanical ventilation controls are installed, then the rating file can be updated to include mechanical ventilation. In addition, the daily run hours should be based on the ventilation controller run time at the time of the inspection.
Homes permitted before the effective date of this interpretation do not have to follow this interpretation.