L16: Daylighting Flashcards
(51 cards)
What is daylighting?
The use of light from the sun and sky to complement or replace electric light
What are the goals of high-performance daylighted commercial buildings?
- Meet design objectives and adopt holistic design
- Maximise occupant comfort and productivity
- Maximise building value
What is the visible spectrum?
Wavelength range of electromagnetic radiation visible to human eye
What do treatments to glazing aim to do?
Stop infrared without stopping visible light
What is visual transmittance?
A measure (0-1) of the amount of visible light that passes through the glazing material of a window
Why is the VT for single pane clear, double pane clear, double pane reflective and double pane low-e clear?
Single pane clear - 0.89
Double pane clear - 0.8
Double pane high reflective - 0.1
Double pane low-e clear - 0.7
What are the types of glare?
Disability glare
Discomfort glare
What is the efficacy of clear sky?
150 lumens/watt
What does direct sunlight provide?
Illuminance too intense for task lighting
What does direct sky light provide?
Less illuminance than direct sunlight but still intense; daylighting design focuses on diffusing light
What are indirect natural light sources?
Matte reflective surfaces or translucent glazing to diffuse direct light eg. light scoop, tubular skylight, switchable privacy glass
What is the daylight factor?
Ratio of interior to exterior illuminance (gives illuminance as a % of what it would be without building and just under overcast sky)
How are designs tested?
Scaled, physical models with light cells which measure interior light levels to assess character, glare, adequacy and balance of light
OR software to assess daylighting and electric lighting
What ist he 15/30 rule?
Tasklighting in15ft perimeter zone is daylight; next 15ft is daylight and electric; beyond 30ft only uses electric
= Work areas must be kept within 30ft of exterior
What can be used when straight plans are undesirable?
Finger plans - but can obstruct sky if too tall
Where is light most abundant and uniform?
North facade
What is the second most important exposure after north facade?
South - light less abundant but uniform diffuse
Why is east and west exposure minimised?
Glare, unwanted solar heat transfer
What is a courtyard?
Most compact variation of finger plan; creates more obstruction to sky and blocks East/West sun
What are atriums?
Similar to courtyards except glazing at roof replaces wall glazing but still obstructs sky and heat gain in summer
What are light wells?
Atriums below clearstories or roof monitors; less light but reduced heat gain
What are translucent partitions used for?
Allows side light to be borrowed by deeper spaces
How does the height of the window effect the daylighting zone?
Higher window = deeper daylighting zone
height x 1.5
How does adding a light shelf affect the daylight zone depth?
Height x 2.0
