A comparison of scale-model photometry and computer simulation in day-lit spaces using a normalized daylight performance index

•A new daylighting performance metric, Normalized Daylight Index (NDI), is proposed and examined.•NDI simplifies the comparison of alternate design solutions.•NDI was applied to a comparison of computer validations with scale model photometry.•The paper outlines the sources of errors in the reported scale model photometric investigation.

A process to compare results of building daylighting computer simulations to the results obtained using scale-model photometry under real skies is outlined. The process uses the illuminance values in a subject space under study and normalizes the values with those obtained in a space considered to be the base case. The normalized factor is termed Normalized Daylight Performance Index (NDI). An example on how this can be done is applied to an open plan office space with two different furniture layouts. Sources of experimental errors are outlined. NDI was found to be a viable metric for comparing daylighting simulations with scale-model photometry.