Objectives Learn about daylighting Review lighting -terminology -technology -design

Review of zonal cavity design method Calculate CU Calculate number of fixtures need for a specific space Do not ignore S/MH ration when you distribute lamps

Terminology and technology Numerical Example: Measurements from the previous class Find Luminous flux F [lm] Luminous Intensity I [cd] Efficacy EF [lm/W] Coefficient of utilization (CU) for each of the three lamps/fixture assuming that working area is 0.5m x 0.5m below the lamp Illuminance per W of electric energy (E/P) Solution on the whiteboard LampIncandescentFluorescentLED Electric power [W]59128 illuminance E [lux] at distance l = 0.5m760 lux880 lux1100 lux Lamp surface temperature °C

Photometrics Luminous intensity [candela, cd] Define the ability of light source to generate light (illumination) in given direction Power – luminous flux [lumen, lm] Quantity of light Illuminance – light power density [foot-candela, fc] [lux, lx] SI units Density of light (illumination) incident on a surface Luminance - surface brightness [foot-lambert, lm/ft 2 ] directional emission of visible light

Relation between: 1) Luminous intensity [cd] and 2) Illuminance [fc] fc = cd / distance 2

Units and conversion 1 cd = Area of unit sphere = 4·π = lumens Luminous flux [lumen]= Luminous intensity [cd] · (4·π) Luminance [ Foot-lambert ] = lumen/ft 2 from surface in the direction of view – define the brightness of surface – important for contrast r=1 1cd

Daylighting computer simulation Radiosity method

What about lighting quality? Zonal cavity calculations focus on light quantity Quality can not be ignored CRI, evenness of illumination, transition between light and dark, flicker, glare, color temperature Quality is very important

Daylighting Scientific and psychological studies have found: People prefer buildings where changes in sunlight exterior affect interior lighting Properly lit spaces are preferred to underlit or overlit spaces Diffuse lighting is preferred to direct lighting North sky lighting is ~universally preferred

What are problems with daylighting? Can require extensive controls Requires extra hardware to avoid direct lighting Can require expensive glazing Can damage works of art Need to limit the amount of heat associated with solar gains

Strategies for Daylighting Orient your building on an East-West axis Limit direct sunlight with exterior shades, light shelves, clerestory windows, translucent glazing Control glazing and conventional lighting with controls Occupancy sensors Automatic blinds Light-level sensors

Reading Assignment Tao and Janis Chapter 16 and section 17.1, 17.2, and 17.4

Project 2 Measurement and analysis of environmental parameters a)Lighting - Measurements - Calculation b)Thermal comfort in ECJ classroom c)Noise measurement d)Report e)Daily oscillation measurement (HOBO)