Transcript Daylighting combined presentation

Daylighting:
Accident or Technology?
Marc Schiler
Schiler & Associates /
University of Southern California
Technical Approach to
Natural Lighting
 Provide the light:
• Building plan, section and orientation
• Fenestration location and sizing
 Lighting circuits and controls
• Balance the availability of natural light
• Shutoff in stages
 Sensors
• Occupancy sensors
• Photosensors
Aesthetic Approach to
Natural Lighting
 Provide the space:
• Building plan, section and orientation
• Fenestration location and sizing
 Colors, reflective forms and gradation
• Show the sensuous nature of the space
• Reinforce the design concept and parti
 Reinforce the function
• Avoid glare
• Provide visual terminus(humans are
phototropic)
Five Topics:
 Topic One: Technical
– Concepts and Strategies
 Topic Two: Aesthetic
– Examples and Images
 Topic Three: Models
– Simulating Daylight with Physical Models
 Topic Four: Calculations
– Rules of Thumb and Calculations
 Topic Five: Equipment
– Sensors and Controls
Topic One
 Technical: Concepts and
Strategies
Agenda for Topic One
 Benefits
 Strategies and Elements
 Definition of Terms
 Design Guidelines
Benefits
 Quantitative
– Cost savings for
user
– Peak Reduction
– Sustainability
 Qualitative
– Color Rendering
– Productivity
– Connection
Prototype Strategies
 Foot Prints
 Clerestories
 Sawtooth
 Skylights
 Light Shelves
 Atria
 Exotica
Foot Prints
Clerestories
Sawtooth
Skylights
 Caveat:
– Lower winter angles = less light
– Higher summer angles = more heat
Light Shelves
Light Pipes
Atria / Light Wells
Fresnel Lenses and
Holographic Films
Design Guidelines
 Basic Principles
– illuminance vs. luminance
 Glare
– discomfort glare vs. veiling reflections
 Vertical vs. Horizontal
 Tips
– Bring it in high
– Bounce it or filter it
– Control it
– Harvest it
Vertical vs. Horizontal
 Solar Control vs. Lighting per glazing
area
– more light from horizontal glazing, more
heat gain in summer, less heat gain in
winter
– less light from vertical, better distribution,
overhang controls for southern orientations,
fins for eastern and western orientations
(and northern)
Single Story
 Warehouses
 Supermarkets Bldgs.
 Light Industrial
 Suburban sites
Multiple Story
 Offices
 City Bldgs.
 Urban sites
Summary (of Topic One)
 Strategies and design
elements
 Design “Tips”
Break
 Take a break
– Stretch your legs
– Get some coffee
– Get rid of some coffee
– Call home
Daylighting:
Accident or Technology?
Marc Schiler
Schiler & Associates /
University of Southern California
Topic Two: Aesthetics
 Classics
– Older buildings with natural
lighting often stand the test of
time very well.
 Current Examples
– Newer buildings enjoy the
technique and the technical.
Good Examples, Old to New
 St. Gallen Abbey Library, Peter Thumb
 Bradbury Building
 Ventura Coastal Building by Scott
Ellinwood
 Mt. Airy Library by Ed Mazria
 Boy’s / Ralph’s Supermarket
 Lyons School of Architecture by
Jourda and Peroudin
Examples for Varying
Functions and Climates
 Arab Center, Paris, Jean Nouvel
 Episcopal Church, Phoenix
 MIT Chapel, Boston, Aero Saarinen
 Wells Branch Bank, Minnesota
 BRF Office Building, Copenhagen
More Examples
 Crystal Cathedral, Philip Johnson
 North Jutland Art Museum, Alvar Aalto
 Menil by Renzo Piano
 Kimbell Museum, Louis Kahn
 Ronchamps, Le Corbusier
 La Tourette, Le Corbusier
Note -
 The preceding three pages
refer to 35mm slide
collections of each building.
Summary of Part Two
 The greatest designs include natural lighting.
– Natural light saves energy
– Natural light can project in dramatic fashion
– Natural light can be bounced and diffused to fill a
space
 This has proven true throughout history
– Rather than fight the architecture, we wish to work
with the architecture in the designing the natural
and “artificial” lighting to work together.
Daylighting:
Accident or Technology?
Marc Schiler
Schiler & Associates /
University of Southern California
Topic Three: Models
 Using Scale Models to Study
Light Distribution
Daylight Harvesting
 Provide the light:
– Building plan and orientation
– Fenestration location and sizing
 Test the design
– Physical models
– Computer simulations
 Lighting circuits and controls
– Balance the availability of natural light
– Occupancy sensors, Photosensors
Agenda for Topic Three
 Scales
 Examples
 Model Craft
 Measurement
 Photography
 Computations
Scale #1 - Quick and Dirty
 Simple question:
– skylight in middle or by the wall?
– horizontal skylight or monitor?
– eyeball assessment of question
 Small Scale:
– 1/16”=1’-0” to 1/2” = 1’-0” or about
1:200 to 1:20
Quick and Dirty (cont’d)
 Construction
– time: one hour or less
– foamcore or chipboard, approximate
reflectances
– tacky glue, masking tape or even pins
– scissors, scrap materials at hand
 Time and cost
– 1/2 hour, $0 - $20
Scale #2 - Developmental
 Developmental issues:
– Sizing issues: “How big should the skylight
be?”
– Placement/Light distribution: “How close to
the wall?”
– Details: “How wide or deep should the light
well be?”
– Actual measurements taken at different
times and seasons
 Middle Scale:
– 1” = 1’-0” or about 1:10
Developmental (cont’d)
 Construction
– Correct reflectances, some details like
baseboards
– simple furniture, critical objects to be lit
– more detail, such as mullions to show shadow
patterns
– specular and diffuse surfaces are differentiated
 Time and cost
– 2 to 4 hours, $30 - $100
Scale #3 - Presentation
 Qualitative issues:
– Calibration against existing space to test
proposed renovations
– Color interaction, mood, ambience,
personal reactions
– Search for glare sources, veiling reflections
– Photographs taken at different times and
seasons
 Large Scale:
– 2” = 1’-0” or about 1:5 or larger
Presentation (cont’d)
 Construction
– Correct colors, complete details like
return air grills, blackboards
– Complete furniture, with simulated
textures
– Ceiling treatments, light fixtures, ducts
– Dirty surfaces, where appropriate
 Time and cost
– 20 to 100+ hours, $100+
Review - Solar Angles
 Altitude
 Azimuth
Solar Gnomons
 One for each latitude, gnomon at
correct height
 Glued to model in relation to model
compass
 Manipulated to get shadow in the
correct position
– Azimuth first
– Altitude second
Solar Gnomon Example 1
Model Craft
 Joints must be sealed
– electrical tape, or aluminum foil taped over all
corners and seams
 Walls must be opaque
– construction paper, opaque internal surface
treatments glued to internal surfaces
– aluminum foil covering all exterior surfaces
(exception: any surface which might reflect light
into the model, such as a roof adjacent to a roof
monitor or sawtooth)
Model Craft (cont’d)
 Replaceable parts or oversized parts
– Whatever is being tested should fit into a lightleak-proof slot
– Prepare modules for each variation in
developmental or presentation models
– In some cases, testing skylight placement can be
done by making an oversize roof, and then sliding
it around so that the skylight sits over different
areas. One roof and skylight can then simulate
many positions without any cutting.
Model Craft (cont’d)
 Portholes for measurement
– allow access for meters and wires, if
necessary, and cover the hole if it is
possible to read the meter from
somewhere else.
– if necessary, cut holes in the floor to allow
the meter surface to be at the workplane
height in the scale of the model
Model Craft (cont’d)
 Portholes for photography
– plan the access for the camera from the
desired viewpoints
– place portholes at in scale eye position,
e.g. 5’-3” in model scale
– if multiple views are desired, cover
portholes with scale blackboards or
paintings so that one porthole is not
visible from the other camera angle
Review - Measurement
 Footcandle or Lux
 Suggested Daylight Factors
(DF)
– What the heck is a daylight
factor? Ein / Eext hor
Measurement Procedures
 Grid Record Sheet
– Draw a grid of expected measurement
points on a sheet of paper, along with
headers recording actual time of day and
simulated time of day
– Xerox enough copies of the sheet for
different date or design variations
– Record each set of readings onto
separate sheets
Measurement (cont’d)
 Don’t let light in over your shoulder
– shade the meters from direct beam for DF
values
– Don’t let light in through the measurement
port (it screws up the measurement)
– put a shroud over your head, and tape it
to the model, if necessary (black plastic
trash bag, double thick, is usually
sufficient)
Measurement (cont’d)
 Do let light in over your shoulder!
– when measuring through the active
window, be sure that your body stays
below the field of view of the window and
the meter
– don’t shade the meters from direct beam
for absolute values
Photography
 Record date and time
– Include the date and time you
are simulating within the image
itself
Photography (cont’d)
 Provide a porthole
 Don’t let light in over your
shoulder
– again, put a shroud over your head,
and tape it to the model, if
necessary (a black plastic trash bag,
double thick, is usually sufficient)
Slides
 Note. At this point the
presentation proceeds to proof
that this can be done at each
scale in the form of a series of
35mm slides of the interiors of
real buildings followed by
models of the same space,
generally indistinguishable.
Summary of Topic Three
 Scales, costs and functions
 Examples
 Model Craft
 Measurement
 Photography
Break
 Take a break
– Stretch your legs
– Get some coffee
– Get rid of some coffee
– Call home
Daylighting:
Accident or Technology?
Marc Schiler
Schiler & Associates /
University of Southern California
Topic Four: Calculations
Rules of Thumb and
Calculations
Agenda for Topic Four
 Rule of Thumb Computations
– Width to Depth
– Percentage Glazing
 IES calculation methods
– sidelighting
– toplighting
Design Guidelines (Reminder)
 Basic Principles
– illuminance vs luminance
 Glare
– discomfort glare vs veiling reflections
 Vertical vs. Horizontal
 Tips
– Bring it in high
– Bounce it or filter it
– Control it
– Harvest it
Reminder of Application
Guidelines
 Different functions and building
forms will require different
calculation methods.
Vertical vs. Horizontal
 Solar Control vs. Lighting per glazing
area
– more light from horizontal glazing, more
heat gain in summer, less heat gain in
winter
– less light from vertical, better distribution,
overhang controls for southern orientations,
fins for eastern and western orientations
(and northern)
Single Story
 Warehouses
 Supermarkets Bldgs.
 Light Industrial
 Suburban sites
Multiple Story
 Offices
 City Bldgs.
 Urban sites
Rules of Thumb for Aperture
Sizing
 Suggested Daylight Factors (DF)
– What the heck is a daylight factor?
 Sizing to obtain the suggested DF
– What glazing area in which kind of
element
 Computer Programs
– If the client’s got money
Suggested Daylight Factors
Function
DF
Comment
Circulation
Public Spaces
Warehouse
Office area
Detailed office work
Factory work
Detailed manf’g
Manual drafting,
color comparison
1%
>1%
1.5%
2-4%
5%
2-4%
5%
vertical surfaces are important
more light, more drama
higher for tightly packed shelves
filing, reception, general area
focus on work surface
dependent on function and danger
tasks requiring high visual acuity
6%
provide one area within the space
Sizing
From Sidelighting (d < 2.5 x h)
near the front of the space
at the middle of the space
near the back of the space
Suggested Glazing Area
DF x Af / 0.5Tg
DF x Af / 0.2Tg
DF x Af / 0.1Tg
From Toplighting
Vertical monitors
North facing sawtooth
Horizontal Skylights*
Suggested Glazing Area
DF x Af / 0.2Tg
DF x Af / 0.33Tg
DF x Af / 0.5Tg
Example #1
 2,000 sf of warehouse, toplighting
–
–
–
–
forklift access, generous aisles
suggested DF = 1.5%
Transmissivity of glazing = 62%
Horizontal skylights
 Go for uniform 1.5%
– Ag = DF x Af / 0.5 Tg
–
= .015 x 2,000sf / (0.5 x .62)
–
= 96 sf
Example # 2
 2,000 sf of simple office space,
sidelighting
–
–
–
–
non strenous tasks, filing, some computer terminals
suggested DF = 2-4%
depth within 2.5h of window (20 ft of 8 ft window)
Transmissivity of glazing = 75%
 Do layout, decide desired daylit depth

Go for 3% at middle
–Ag = DF x Af / 0.2 Tg
– = .03 x 2,000sf / (0.2 x .75)
– = 400 sf

Go for 3% at back
–Ag = DF x Af / 0.2 Tg
– = .03 x 2,000sf / (0.1 x .75)
– = 800 sf
IES Lumen Method
 Tracks light from sky and sun
separately
 Applies form and reflectance factors to
light from ground
 Assumes a strip window for the entire
length of one wall (as might be found
in an office.)
IES Lumen Method (cont’d)
 Calculates a Coefficient of Utilization
(CU) for five locations within the cross
section of the space
Basic Equation
 Ei = Ex NT CU
 where
 Ei = interior illuminance in lx,
Ex = exterior illuminance in lx,
NT = net transmittance,
CU = coefficient of utilization.
Sidelighting
 Ei = Exv τ CU
 where
 Ei = interior horizontal illuminance on a
reference point from sidelighting, in lx,
Exv = exterior vertical illuminance on
the window wall in lx,
τ = net transmittance of the window
wall,
CU = coefficient of utilization.
Ground Exitance
 Mg = ρg (Exh sky + Exh sun)
 where
 Mg = exitance from the ground in
lm/m2,
ρg = reflectance of the ground,
Exh sky = horizontal illuminance from the
sky in lx,
Exh sun = horizontal illuminance from the
sun in lx.
Illuminance from Overcast
Sky
 Refer to IESNA Lighting Handbook, Ninth Edition for complete
tables
Illuminance from Clear Sky
 Refer to IESNA Lighting Handbook, Ninth Edition for complete
tables
Illuminance from Sun
 Refer to IESNA Lighting Handbook, Ninth Edition for complete
tables
Net Transmittance
 τ = T Ra Tc LLF
 τ = net transmittance of window
LLF = light loss factor representing dirt
accumulation
Ra = the net-to-gross window area
ratio representing such elements as
mullions and glazing bars;
Tc = other elements such as shades
and drapes
Light Loss Tables
Location
Clean area
Industrial area
Very Dirty area
(used to be slide 87)
Glazing Position
vertical
sloped
horizontal
0.9
0.8
0.7
0.8
0.7
0.7
0.6
 Refer to IESNA Lighting Handbook, Ninth
Edition for complete tables
0.6
0.5
CU Sky Component = 0.75
 Refer to IESNA Lighting Handbook,
Ninth Edition for complete tables
CU Ground Component
 Refer to IESNA Lighting Handbook,
Ninth Edition for complete tables
Clear Window Illuminance
 Ei = τ (Exv sky CUsky + Exv g CUg)
 Ei = interior illuminance at a reference point
in lx,
τ = net transmittance of the window wall,
Exv sky = exterior vertical illuminance from the
sky on the window in lx,
CUsky = coefficient of utilization from the sky,
Exv g = exterior vertical illuminance from the
ground on the window in lx,
CUg = coefficient of utilization from the
ground.
Diffusing Window Illuminance
 Ei = 0.5 τ (Exv sky + Exv g ) ( CUsky + CUg)
 Ei = interior illuminance at a reference point
in lx,
τ = net transmittance of the window wall,
Exv sky = exterior vertical illuminance from the
sky on the window in lx,
CUsky = coefficient of utilization from the sky,
Exv g = exterior vertical illuminance from the
ground on the window in lx,
CUg = coefficient of utilization from the
ground.
Toplighting
 Ei = Exh τ As / Aw
 Ei = average incident illuminance on the workplane
from skylights in lx,
Exh = horizontal exterior illuminance on the skylights
in lx,
As = gross projected horizontal area of all the
skylights in m2
Aw = area of the workplane in m2,
τ = net transmittance of the skylights and light well,
including losses because of solar control devices
and maintenance factors,
CU = coefficient of utilization.
Toplighting (cont’d)
 TDM = 1.25 TFS (1.18 - 0.416 TFS)
 TDM = dome transmittance,
TFS = flatsheet transmittance.
Toplighting (cont’d)
 T = (T1 T2) / (1 - ρ1 ρ2)
 T1, T2 =diffuse transmittances of the
individual domes,
ρ1 = reflectance from the bottom side
of the upper dome,
ρ2 = reflectance from the top side of
the lower dome.
Light Well Equation
 WCR = 5h(w +l) / wl
 WCR is the well cavity ratio, used to
look up the well efficiency Nw
 h is the well height,
w is the well width,
l is the well length.
(The dimensions h, w, and l must be
expressed in the same units.)
Light Well Cavity Ratio
 Table from IESNA Lighting Handbook,
Ninth Edition
Diffuse Transmittance
 τd = Td Nw Ra Tc LLF
 Td is equal to the diffuse transmittance
 Nw is the well efficiency
 Ra = ratio of net to gross skylight area
Tc = transmittances of diffusers,
lenses, louvers, or other controls
LLF = the light loss factor from IES
tables.
Direct Transmittance
 τD = TD NW Ra Tc LLF
 TD is equal to the direct transmittance
of the dome
 Nw is the well efficiency
Ra = ratio of net to gross skylight area
Tc = transmittances of diffusers,
lenses, louvers, or other controls
LLF = the light loss factor from IES
tables.
Room Cavity Ratio
 RCR = 5 hc (l + W) / lw
 hc is the height from the workplane to
the bottom of the skylight well,
l is the length of the room,
w is the width of the room.
(All three parameters must have the
same units.)
Room Cavity CU Tables
Ceiling
Reflectance
Wall Reflectance (%)
RCR
50
30
10
80
0
1.19
1.19
1.19
1
1.05
1.00
.97
2
.93
.86
.81
3
.83
.76
.70
4
.75
.67
.60
5
.67
.59
.53
6
.62
.53
.47
7
.57
.49
.43
8
.54
.47
.41
9
.53
.46
.41
10
.52
.45
.40
 Refer to IESNA Lighting Handbook, Ninth
Edition for complete tables
Overcast Sky
 Ei = Exh sky τd CU N (A / Aw)
 Exh sky = exterior horizontal illuminance due to the
sky only, in lx,
τd = net diffuse transmittance,
τD = net direct transmittance,
CU = coefficient of utilization,
N = number of skylights,
A = area of each skylight in m2,
Aw = area of the workplane in m2.
Clear Sky
 Ei = (Exh sky τd + Exh sun τD) CU N (A / Aw)
 Exh sky = exterior horizontal illuminance due to the
sky only, in lx,
Exh sun = exterior horizontal illuminance due to the sun
only, in lx,
τd = net diffuse transmittance,
τD = net direct transmittance,
CU = coefficient of utilization,
N = number of skylights,
A = area of each skylight in m2,
Aw = area of the workplane in m2.
Daylight Factor
 CIE (European) methods
 Less accurate, more flexible, in
allowing asymmetrical window
placement
 PSALI
 Some methods only account for
overcast conditions
Computer Programs
 More accurate predictions or renderings
–
–
–
–
Lightscape
Radiance
Lumen Micro (et al)
Superlite
 Payback period, including effect of HVAC
– DOE2.1E
– MicroDOE, PowerDOE, CECDOE, etc.
– HEED, Solar 5
Summary of Topic Four
 Computational Rules of Thumb
 IES Lumen Method
– sidelighting
– toplighting
 Daylight Factor
 Computer programs
Break
 Take a break
– Stretch your legs
– Get some coffee
– Get rid of some coffee
– Call home
Daylighting:
Accident or Technology?
Marc Schiler
Schiler & Associates /
University of Southern California
Part Five: Equipment
Natural Lighting:
Control Devices and Systems
Daylight Harvesting
 Provide the light:
– Building plan and orientation
– Fenestration location and sizing
 Test the design
– Computer simulations
– Physical models
 Lighting circuits and controls
– Balance the availability of natural light
– Occupancy sensors, Photosensors
Agenda for Topic Five
 Controls
 California Codes
 Typical Circuits
 Demonstration
 Possible Savings
 Dangers and Pitfalls
 Walkthrough
Review - Terms
 Design Level
 Circuits
 Devices
– sensors
– power packs
– switches
Basic Strategy
 Circuit layout and sensor
placement, daytime
Basic Strategy
 Circuit layout and sensor
placement, nighttime
California Code
 Must provide possibility for 50%
reduction in any room over 100 sq. ft.
 Provide separate switching for daylit
areas, to allow harvesting
 Allowable Lighting Power Density and
Actual Lighting Power Density
– Credits for daylight sensors
– Credits for occupancy sensors
– Credits for automatic time controls, etc.
California Code (cont’d)
 Credit factors for occupancy sensors
Type of Control
Type of Space
Factor
Occupant Sensor
with separate sensor for each
space
any space  251 square feet enclosed
by opaque floor to ceiling partitions; any size classroom, corridor,
conference room or waiting room
0.20
rooms of any size that are used solely for storage
0.60
other spaces greater than 250 square feet
0.10
Occupant sensor with a separate
sensor for each space used in
conjunction with daylighting
controls and separate sensor for
each space
any space  250 square
feet within a daylight area
and enclosed by opaque
floor to ceiling partitions
0.10 (may be added
to daylighting control
credit)
California Code Required
Layouts
Control types
 Occupancy Sensors
 Photosensors
 Continuous Dimming vs. Step
Dimming
 Occupancy and Photosensor
Interaction
Occupancy Sensors
 Ultrasonic
–
–
–
–
sees around corners
quartz crystal oscillator
multiple receivers
sees inanimate movement, sometimes vibrations
 Infrared
– line of sight only
– ignores movement of same temperature objects
– can be aimed and masked
Comparison
Function or characteristics
partitioned areas
restrooms with stalls
long enclosed hallways
very large low ceilinged areas
small enclosed offices
areas with high ceilings
areas with high vibration or airflow
open areas which need to be subdivided
ultrasonic
good
good
good
good
OK
OK
bad
bad
infrared
bad
bad
OK
OK
good
good
good
good
Ultrasonic
Infrared
Photosensors
 Ceiling mounted, viewing workplane
Continuous Dimming vs.
Step Dimming
 Low natural light + single step = no
savings
 (single step is never activated, light too
low)
Continuous Dimming vs.
Step Dimming
 Continuous dimming harvests
immediately
 (begins @ 100%, reduces to 30%*)
Continuous Dimming vs.
Step Dimming
 Large natural light + single step = big
savings
 (single step is activated, goes to zero)
Continuous Dimming vs. Step
Dimming
 Plentiful daylight + single step = best
value
 Lower natural light levels require
continuous dimming
Typical circuits
 Power Pack
 Separate low voltage signal
 RS-232, EPROM, Carrier Wave and
X-10
Power Pack
 Switches, sensors and outside sources
Staged Signals
 Interim logic box collects signal data
“Intelligent Ballasts”
 Separate low voltage signal from sensor
to ballasts
Possible savings
 DOE2.1E
–
–
–
–
–
STEPPED vs.CONTINUOUS
LT-REF-PT-1 ( x, y, z)
LT-FRACTION-1
DESIGN LEVEL
Lighting ->HVAC -> plant -> Economics
 HEED, DAYLIT
– STEPPED vs. CONTINUOUS
– 3 zones
– DESIGN LEVEL
Dangers and Pitfalls
 Users
– Sensitivity and Time Delay
– Incorrect Placement
– “Know it All”
 Contractors
– Upside Down
– Wrong Voltage
– Passive Circuit to Active Circuit
– No Calibration
Summary
 Controls
– Occupancy Sensors
– Photosensors
– Continuous Dimming vs. Step Dimming
– Occupancy and Photosensor Interaction
 Code Requirements and Benefits
Summary (cont’d)
 Typical Wiring Diagrams
– Power pack vs. “intelligent ballasts”
 Typical Pitfalls
 Energy saved
 Quality Environment!
Overall Summary
 Natural Light in Buildings
– Provide the light:
• Building plan, orientation and section
• Fenestration location and sizing
– Lighting circuits and controls
• Balance the availability of natural light
• Shutoff in stages
– Sensors
• Occupancy sensors
• Photosensors
Sources for further study
 Books:
– Ander, Gregg; Daylighting Performance
and Design, Van Nostrand Reinhold, New
York 1995
– Kaufman, John, et al; IES Handbook;
Illuminating Engineering Society (IESNA),
New York
– Schiler: Simplified Design of Building
Lighting, Wiley & Sons, New York 1992
– Schiler et al: Simulating Daylight with
Architectural Models, DNNA report
Sources for further study (cont’d)
 Monographs:
– ____; RP-5 Recommended Practice of
Daylighting; Illuminating Engineering ,
Society (IESNA), New York
– ____; RP-21 Calculation of Daylight
Availability; Illuminating Engineering
Society (IESNA), New York
– ____; RP-23 Calculation of Daylight;
Illuminating Engineering Society (IESNA),
New York
Finis
 Daylighting:
Accident or Technology?

Marc Schiler
Schiler & Associates /
University of Southern California