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DAYLIGHTINGCONCEPTS

Mt. Angel Library by Alvar Aalto; featuring a major daylight “fixture”

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Daylighting

Daylighting has always been of major importance, but somehow during the 1960s, we forgot everything we knew

about the art and science of daylighting. Cheap energy and air conditioning

did us in.

William Caudill in the Foreword to Daylight in Architecture

an example of the allure and power of active systems

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^^ Kimbell Art Museum, Ft. Worth, TX

Mt. Angel Library, Mt. Angel, OR >>

daylighting offers great opportunities for creative design

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Daylight Components

The daylight reaching a given point within a building generally consists of a mix of the following components (which show up as elements in some design analysis methods):

-- a sky component (SC)

-- an externally reflected component (ERC)-- an internally reflected component (IRC)

these “internal” components are related to—but not the same as—the direct, diffuse, and reflected resource components that comprise light falling on an aperture

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Daylight Components

DF = SC + ERC + IRC

the “sky” component is not the same as a “direct solar” component

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A Daylighting Design Process

• Establish lighting system design intent and criteria• Daylighting may be a reasonable method to achieve intent• If so, select a likely daylighting implementation method

(an approach or approaches)• Validate that the approach actually works (that the result

meets intent and criteria) using appropriate design tools• Refine the initial design solution as required using

appropriate analysis tools; validate the final design solution• Develop construction drawings and specifications• Commissioning the daylighting system design (critical)• Construct• Commissioning the daylighting system (especially controls)• Occupy building; validate system in place and in use; learn

and communicate the lessons learned

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Daylighting Design Issues

• The source of light is variable– addressed through the design process– addressed via coordination with electric lighting– addressed in usage by space occupants

• The source of light is outside the building– light must be brought into a building– light must be skillfully distributed from an aperture located at

the periphery of a space

• These are primarily architectural design issues– architects must take the lead– daylighting potential is established with the first design moves

(plan, orientation, and massing)

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General Daylighting Approaches

• Sidelighting– Unilateral or bilateral– Windows– Clerestories (if low)

• Toplighting– Skylights– Clerestories (if high)

• Hybrids and combinations

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what about “bottomlighting”?

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Sidelighting (if unilateral)

illuminance drops off fairly quickly as distance from aperture increases

illuminance (lux, FC or DF) on horizontal task plane

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Sidelighting (if bilateral)

illuminance drops off fairly quickly as distance from aperture increases;but two opposing apertures help to balance light distribution across space

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Toplighting (if single aperture)

illuminance drops off fairly quickly as distance from aperture increases

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Hybrid Approaches

illuminance from skylight fills in “gap” caused by sidelight distribution pattern

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Daylighting System Components

• Light source the sky not direct sun• Apertures (openings—such as windows or skylights)

• Aperture modifications (lightshelves, shading devices, glazings, jambs, …)

• Space geometry (length, width, height of room)

• Surface reflectances (of ceiling, walls, …)

• The illuminated thing (task, surface, …)

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Daylighting System Components

• Source (the sky not direct solar)– On a macro scale this resource is a function of

geographic locale and site conditions

• Apertures (openings)– Are a function of design decisions (placement in

building, size, number, orientation)

• Aperture modifications (lightshelves, shading devices, glazings, …)– Are a function of design decisions

the site presents an opportunity that the designer can run with

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Daylighting System Components

• Space geometry– Is a function of design decisions

optimize space layout and use the space itself to help distribute light

• Reflectances – Are function of design decisions use

reflective surface finishes to spread light

• Illuminated thing (task, surface, …)– A function of space type and usage

… good daylighting design is good architectural design

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More on Daylighting Glazing

• Glazing location (orientation, tilt, surroundings) is important

• Glazing area and DF are related in a generally linear manner

• Usually, daylighting glazing should have a high VT (visible transmittance) and a low SHGC (solar heat gain coefficient)—characteristics that will be incompatible in many products

• Generally daylighting should involve no direct solar radiation (provide shading devices to ensure this without blocking diffuse daylight)

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More on Lightshelves

These elements are used with daylighting windows to more evenly distribute daylight in a space; they do not substantially increase the amount of daylight that is captured

– They can be external, internal, or both

– When used, they split a window area into “view” and “non-view” components

– They can assist with shading against direct solar radiation (thus reducing heat gain and glare)

– Performance is not well documented—lightshelf design is more an art than a science

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Lightshelves

Inland Revenue (UK), image from LBL

exterior lightshelves, Milwaukee, winter

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Philips Exeter Academy, Exeter, NH; Library, Louis Kahn (1967)

campus contextbuilding context

Daylighting Example

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building massing

façade texture and layers

Philips Exeter Academy

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reading carrels and lounge area

Philips Exeter Academy

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grand entry staircase and structure

Philips Exeter Academy

note difference in “warmth” of light

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various views of structure (contrast of wood and concrete)

Philips Exeter Academy

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views up into central volume, showing minimal toplighting and smoke vents

Philips Exeter Academy

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bookshelf engages structure

user of stair engages structure

Philips Exeter Academy

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exterior courtyard (note vegetative shading) meeting room

Kimbell Art Museum, Dallas, TX; Louis Kahn (1972)

Daylighting Example

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images from: http://www.kimbellart.org/

exterior view

gallery interior

Kimbell Art Museum

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images from: http://www.kimbellart.org/

gallery interiordaylighting fixture

Kimbell Art Museum

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images from: http://www.kimbellart.org/

gallery open to courtyardexterior view

Kimbell Art Museum

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Emerald People’s Utility District Offices, Eugene, OR; Equinox Design

south façade with fixedand vegetative shading

Daylighting Example

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lightshelf

north façade, note glazing, no shading

Emerald People’s Utility District Offices

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south façade, note fabric shading devices

Emerald People’s Utility District Offices

break room, note direct solar infusion

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it takes more than an aperture to make a daylighting system

skylight, unnamed architecture building (think about maintenance)

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Phoenix Convention Center

some serious external shading shading, more and less, from glass

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Why CarbonDioxide Matters

http://img257.imageshack.us/i/3way8fp.png/

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Why Reducing Carbon Emissions Matters

http://www.msnbc.msn.com/id/9527485/

Fall 1979 Fall 2005