Balancing Daylight & Energy

How should we measure daylighting?

Daylight Factor

● Ratio of internal to external

illuminance under overcast

sky

● Used in early versions of

LEED

● Pro: Simple annual metric

● Con: Inaccurate in most

localesGraphic of Daylight Factor, by Max Pierson(http://www.maxwellrosspierson.com/)

How should we measure daylighting?

Moment-in-time Illuminance

● Minimum illuminance levels

at a point in time (e.g. min.

24 fc on Sept 21 at 9am and

3pm)

● Used in LEED 2009

● Pro: Clear snapshot of

performance

● Con: Not annualizedGraphic of illuminance at 9am on Sept. 21, by Max Pierson (http://www.maxwellrosspierson.com/)

How should we measure daylighting?

Dynamic metrics

● Use solar irradiances from a

weather file

● Annualized (summary metric

for an entire year)

● Used in LEED v4

● Pro: accurate predictors

Graphic of Daylight Autonomy, by Max Pierson(http://www.maxwellrosspierson.com/)

Daylighting Metrics in Sefaira for SketchUpSpatial Daylight Autonomy (sDA)

● How much of a space receives

satisfactory daylight

● sDA300, 50% - Percent floor area that

has at least 300 lux for at least 50%

of the annual occupied hours

Daylighting Metrics in Sefaira for SketchUp

Annual Sunlight Exposure (ASE)

● How much of a space receives too

much direct sunlight

● Indicator of possible visual or thermal

discomfort

● ASE1000, 250 - Percent floor area that

has at least 1000 lux for at least 250

annual occupied hours

Daylighting Metrics in Sefaira for SketchUp

● Real-time feedback on

daylighting (sDA) & glare

(ASE)

● Enables trade-offs between

energy & daylighting

● Uses cloud-based

deployment of Radiance and

DAYSIM

Learn more or Watch a demo

www.sefaira.com