This paper examines the relationship between lighting energy savings from daylighting and daylight-imposedscooling loads. From DOE2.1C simuIation results for specific commercial buildings and glazingsoptions, we show that for any daylighted or electrically lighted space, the cooling load component fromsnatural or artificial lighting can be broken into three component factors. Each of these factors can besexpressed mathematically as constants that are a function of glazing characteristics and illumination levelsswithin the space. These three constants can then be combined into a single daylight coolness index.sThus, from (model or simulation) illuminance measurements for a proposed daylighted space, a designerscan quickly compare the relative cooling load impacts of different daylighting designs.