Annual Sunlight Exposure (ASE) is the percent of an analysis area that exceeds a specified direct sunlight illuminance level (e.g. 1000 lux) for more than a specified number of hours (e.g. 250 hours) per year. As such, a Full year (365 days) should be used for meaningful results. ASE is meant to complement sDA, as a metric to help designers limit excessive sunlight in a space. ASE can suggest a higher risk of glare but is not a definite metric for glare or visual discomfort occurring.
The purpose of ASE is to demonstrate if a space is over lit. Blinds or shades are not modelled as they are for sDA. For example, ASE1000,250: denotes the percentage of area that exceeds 1000 lux for more than 250 hours per year. It can also suggest a risk of excessive solar heat gain in spaces.
This simulation could be used, for example, for LEED IEQ-Daylight (Option 1), as this metric follows the guidance of the Illuminating Engineering Society guide LM-83, Approved Method: IES Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE).
Note: ASE is not the same as the BRE metric Annual Probable Sunlight Hours (APSH). APSH can be assessed using IES’s SunCast tool. ASE also differs from Annual Light Exposure (ALE) which can be used in settings such as art galleries or museums to check cumulative light exposure, for example on artefacts.
