IES Consulting were commissioned to perform Climate Based Daylight Modelling (CBDM) and ASHRAE 55 thermal comfort analysis for the LEED v4 certification of the Schneider Electric X-Pole headquarters in Grenoble, France.
The consultants used RadianceIES CBDM technology to model the space performance of an exemplar floor for the purposes of targeting the LEED v4 IEQ Daylight credit. The analysis utilised Option 1 of the credit with performance against spatial daylight autonomy (sDA) and annual sunlight exposure (ASE).
CBDM utilises an annual simulation linking location, shading, climate data (including solar intensity and cloud cover) together with the building properties. This provides a complete overview on how the daylight performance varies throughout the year due to any changes in these factors. The CBDM approach is much more detailed than a static calculation, which provides only a snap shot, and provides a much more comprehensive analysis of the impact of daylight on building design, in line with actual daylighting variance throughout the year.
The sDA calculation required the consultants to run individual simulations both with and without shading systems. This creates limits on the maximum and minimum daylight entering the space and from these datasets a parsed result is created by defining a threshold for when the blinds will operate throughout the occupancy period, this captures the true condition of daylight performance. For example, blinds will not always be called at the same time everyday due to seasonal changes, solar intensity and cloud cover variation.
By contrast, the ASE required a more straightforward approach with only one simulation process, since the methodology never employs blinds and therefore determines the solar exposure the spaces experience. Its purpose to prevent the space being overlit.
Dynamic Thermal Simulation was used to perform an ASHRAE 55 analysis to determine the Predicted Mean Vote (PMV) and Percentage of People Dissatisfied (PPD) as indicators of occupant comfort. The modelling aimed to demonstrate conditions would be maintained between a PMV range of ±0.5, corresponding to a PPD level of less than 10% of occupants dissatisfied with the thermal environment.
While these thresholds were exceeded in some instances, primarily due to differences in air temperature (to which the HVAC system responds) and operative temperature (which influences thermal comfort), the consultants were able to demonstrate that threshold conditions could be met for the vast majority of the time.