Changes to Lighting Schedule Library in v7.1 and Later

Starting from DesignBuilder v7.1.3, some lighting schedules and target illuminance library values have been changed due to an update in the UK NCM 2021. This article summarises these changes and their likely impact on the results when loading v7.0 and earlier simulation models into more recent versions.

UK NCM 2021 Library Lighting Schedules No Longer Include Fractional Values

DesignBuilder lighting operation is governed by the General Lighting > Operation schedule. This schedule is used to multiply the design lighting gains by the time-varying factor in the schedule to give the gain for each timestep in the simulation.

In DesignBuilder v7.0 and earlier, the lighting schedules provided by the UK NCM (and adopted for use in the DesignBuilder schedules library) included a few, mostly plant room, NCM lighting schedules with fractional values. However, in DesignBuilder v7.1.3 and later, these lighting schedules mostly have fractional values replaced by 1.

These changes can significantly affect results in EnergyPlus simulation models that use the affected lighting schedules.

The affected lighting schedules are listed below:

UK NCM 2021 Library Activities Have Different Target Illuminance Values

DesignBuilder daylight dimming control uses target illuminance setpoint values to govern when electric lighting is required to supplement low daylight levels. The default target illuminance values for each Activity template are sourced from the UK NCM. In the 2021 NCM, included in DesignBuilder v7.1.3 and later, these target illuminance values have been updated, and the changes are reflected in the DesignBuilder Activity templates library.

More Details and Example

1. In DesignBuilder v7.0 and earlier, plant room lighting schedules used fractional values of 0.01, but these are now set to 1 in v7.1.3 and later. This results in a 100x increase in general lighting power consumption! These schedules operate between 8 and 16 hours a day during the week. Some will also operate at the weekend or on holidays.
   The default target illuminance is 200 lux in all these plant room activities, unchanged from the previous Schedule library, apart from Hosp_Plant, which was previously 150 lux.
2. The Dwell_DomBed  lighting schedule previously had fractional values in the evening and values of 1 at times during the day. The fractional values are now replaced with 1. As a consequence, lighting energy consumption will be approximately doubled. The default target illuminance of the corresponding activity template is unchanged at 100 lux.
3. The Hosp_OpTheatre lighting schedule had fractional values in the early morning and evening, but these are now set to zero. The default target illuminance of the corresponding activity template is reduced from 1000 to 500 lux. The combined effect is that annual lighting energy consumption will typically be around 45% of that calculated previously.
4. The Hosp_Bed lighting schedule previously had mainly fractional values: 0.25, 0.5 & 0.75 which have now been changed to 1. The default target illuminance of the corresponding activity template was 125 lux, but is now 100 lux. The overall effect is to increase in Lighting energy consumption by about 25%.
5. The Hosp_WardPatients & 24x7_Bed lighting schedule previously had a mix of fractional and values of 1. These are now all 1. The default target illuminance of the corresponding activity template has been reduced from 150 lux to 100 lux, typically resulting in a ~10% increase in annual lighting energy consumption.
6. The LibMusGall_Display lighting schedule previously had a mix of fractional and values of 1. These are now all 1. The default target illuminance of the corresponding activity template remains at 200 lux, typically resulting in a ~15% increase in annual lighting energy consumption.