Lark Spectral Lighting is a new plugin for grasshopper that helps architects, lighting designers and researchers investigate circadian light metrics within a daylighting workflow. Lark allows designers to define the color of skies, glazing and building materials based on spectral data. Furthermore, luminance renderings and irradiance data can be used to analyze the relative impact of design options on the non-visual, circadian system. Lark Spectral Lighting is a collaboration of University of Washington and ZGF Architects LLP.