The ASHRAE standard refers to “installed” LPD, so all the light fixtures installed during design and construction must be included in the calculation. Often, designs will provide two fixtures to supplement each other at different times. For example, task

The ASHRAE standard refers to “installed” LPD, so all the light fixtures installed during design and construction must be included in the calculation. Often, designs will provide two fixtures to supplement each other at different times. For example, task lights may be designed to be used only intermittently, but for LPD calculation purposes, you should assume that all lights are switched on.