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Environmental Systems Ch13
Transcript of Environmental Systems Ch13
To me natural light is the only light, because it has mood – it provides a ground of common agreement for man – it puts us in touch with the eternal. Natural light is the only light that makes architecture, architecture.
Louis I Kahn
13.1 Gothic - Result of the quest for maximum window area.
Roman groin vault supplanted the barrel vault partly
because it allowed large windows in the vaulted spaces.
Renaissance - use of large numerous windows continued.
“Hardwick Hall, more glass than wall”
Crystal Palace – Joseph Paxton
modernist and contemporaries of daylight
frank lloyd wright
Electric lighting made design concerns about lighting a non-issue – bring in more light (more electricity)
Electric lighting affects/confuses our perception of space/time
About ½ of all electric lighting used in buildings could be saved with effective use of daylight
In office and schools – about 70% energy use could be saved
Much of the work done in offices is done during daylight hours
Power plants are built and sized for – not total energy used, but amount of energy used during peak times – reduce demand, reduce power plants
Austin Texas story
Daylight satisfies the biological need to respond to natural rhythms of the day.
Research shows –
Student performance increased 20% when daylight was added
Retails sales increased by 3% (remember exponential growth)
In Europe, building codes require workers to have access to both daylight and views of the exterior
13.2 why daylighting
marcel sembat high school of technology, france, archi5
13.3 Daylight entering a window can have several sources:
Direct sunlight, clear sky, clouds, diffuse sky radiation (pollution-dust), or reflections from the ground and nearby buildings
Light from each source varies in quantity and heat content, and also in quality –
Color, diffuseness, and efficacy
Important to understand daylight from 2 extreme conditions:
Overcast sky and clear sky with sunlight
Daylighting that works in these conditions, will work in most all other conditions
On a clear day – illumination is 100-200 x greater than the requirements for good indoor illumination.
13.5 How does daylight vary within a space?
Depends on: Brightness of source, size of source, exposure angle (clear vs overcast, aperture opening, location of work surface)
Daylight Factor – ratio of the illumination indoors to outdoors on an overcast day, which is an indication of the effectiveness of a design in bringing daylight indoors
This means – that a 5% daylight factor on an overcast day when the illumination is 2000 footcandles the illumination indoors will/should be 100 footcandles
2000fc x 0.05 = 100fc (this model can be tested under any time of year or day).
Remember – absolute illumination does not = good visibility. Relative brightness between interior and the window is a critical consideration
850 fc x 0.05 = 42.5 fc for a studio space in memphis
fc for studio work should be between 20fc and 200fc depending on size and complexity of task
13.6 Light without Heat – light is filled with infrared radiation and electric lights also produce much sensible heat:
Maximize light in winter
Minimize direct light in summer due to associated heat
Direct sunlight can be well distributed so as not to create excessive heat:
Incandescent lamps introduce about 6x more heat than daylighting
Fluorescent lamps – 2x more heat
13.7 VT – visible transmittance – factor that quantifies amount of visible light passing through glass (.9 clear - .1 very reflective)
SHGC – Solar Heat Gain Coefficient – factor which quantifies the total solar radiation (visible + infrared)
LSG – Light – to – Solar Gain – Ratio the higher the ratio, the cooler the light (ratio of VT to SHGC)
Rule of Thumb – the VT factor should be much larger than the SHGC when one is choosing glazing for cool daylighting purposes
13.8 Goals of Daylighting – supply sufficient light of quality with minimum glare.
Get more light deeper into the building to raise illumination levels in rear & reduce illumination gradient across the room (fig. 13.8b)
Reduce or prevent direct glare of unprotected windows & skylights
Prevent excessive brightness ratios (especially those caused by direct sunlight)
Prevent or minimize veiling reflections (esp. From overheated skylights/windows, fig 13.8d)
Diffuse light by means of multiple reflections off ceilings/walls – (Kimbell Art Museum)
Use full aesthetic potential of daylighting (in spaces with no critical visual tasks)
Daylight strategies: 2nd Tier strategy utilizing 1st Tier aspects.
South is Best
North next-best due to consistency & quality
East/West are worst – received sun only half a day, with low sun angles, difficult to shade
1. Lighting thru the Roof 13.9d
a. Use skylights in conjunction with light wells to take light deeper into building
b. Horizontal windows at roof are better:
1. allow uniform illumination over large interiors
2. receive much more light than vertical openings
2. Form – determines the mix of vertical & horizontal openings, but also how much of the floor area will have access to daylighting
a. TYPICAL – 15’ perimeter is fully daylit
b. another 15’ zone is partially daylit (Fig. 13.9e)
3. Space Planning – open space planning is good for light distribution within interior
4. Color – light colors are good:
a. reflect light farther into room
b. diffuses light to reduce dark shadows
c. ceiling should have highest reflectance factor (order: ceiling, back wall, side wall, floor, furniture)
5. Use separate openings for viewing & daylighting – high windows for daylight, low windows for viewing.
Basic Window Strategies: pg 416-419
Windows should be high on the wall, widely distributed, and of optimum area 13.10a
Place window on more than one wall
Avoid unilateral lighting (one wall)
Use bilateral lighting (two walls) fig. 13.10d
Place windows adjacent to interior walls (to use their surface for reflectivity 13.10f)
Splay walls to reduce the contrast between windows and walls (fig. 13.10g)
Filtered daylight (goetz gallery)
Shade windows from excessive sun in summer 13.10j-k
Use moveable shades 13.10m-n
pg 402, 403, 405
13.14 Skylight & Top Lighting – both likely to cause glare or veiling reflections.
Due to likelihood of a collecting so much light and heat from summer sun, it is suggested one use clerestories.
Space skylights to achieve uniform lighting
Spacing is equal to ceiling height when NO windows are present
Spacing is equal to double ceiling ht. w/windows
Use “splayed” openings to increase size of opening
Place high in the space (get diffused light at floor, not direct glare)
Place near walls to use walls as reflector
Use interior reflectors to diffuse light
Use exterior shades & reflectors to improve the summer/winter balance
Use steeply sloped skylights to improve summer/winter balance (note sun angles)
Use sunlight for dramatic effect (church of light, Tadao Ando)
13.15 Clerestories, Monitors, & Lightscoops – all involve a large space raised above the roof to bring light into a space.
Monitor – windows face more than 1 direction and are operable
Lightscoop – windows face 1 direction and opposite is curved surface which reflects light downward
South-facing clerestories can actually collect more sunlight in winter instead of summer due to lower sun angles
**All produce a diffused, soft light – but direct glare can still be a problem.
Special Daylighting Techniques:
Light wells / shafts – used on deep plans
Fiber-optic & light pipes (Phoenix Central Library – light-emitting concrete)
Glass Floors (Wiel Arets’ Maastricht Academy of Art & Architecture)