State of california

air resources board

Manufacturer’s Advisory Correspondence (MAC) 2010-XX

sUBJECT:	Optional Test Procedure For Certifying Model-Year 2016 And
Later Vehicles Under The Cool Cars Alternate Performance Compliance
Option

aPPLICABILITY:	2016 model year (MY) and later vehicles < 10,000 GVWR
produced by manufacturers who have chosen to have some or all of their
product line comply with the Cool Cars regulation by demonstrating
equivalent solar control using the alternate performance option.

rEFERENCES:

1.	Section 95603 of Title 17, California Code of Regulations (CCR),
“Cool Car Standards and Test Procedures – 2012 and Subsequent
Model-Year Passenger Cars, Light-Duty Trucks, and Medium-Duty
Vehicles”

The following sections and topics will be presented in this MAC.

I. 	Background and Discussion

II. 	Alternate Performance Option Test Procedure Overview

	A. 	Assembly and Requirements of Test Stand

	B. 	Vehicle and Cabin Equipment

	C. 	Preconditioning

	D. 	Test

III.  	Certification Requirements

	A. 	Cool Cars Group Determination

	B.	Data Vehicle Selection

	C. 	Testing Requirements

	D.	Durability Requirements

	E.	Records Retention

	F.	Carry-Over and Carry-Across

i.	Background and Discussion:

Subarticle 9, sections 95600, 95601, 95602, 95603, 95604, and 95605,
under title 17 of the California Code of Regulations established the
Cool Cars regulation.  The regulation aims to reduce the solar heat gain
of vehicles parked in the sun by requiring manufacturers to equip new
vehicles with solar control glazing.  Specifically, beginning in model
year 2012, manufacturers must use solar control windshields that meet a
50 % total solar transmittance (Tts) standard, side and back windows
that meet a 60 Tts standard, and rooflights that meet a 30 Tts standard.
 Beginning with model year 2016, further control of solar heat gain is
required; reductions in solar heat gain can be achieved either through
solar control of all glazing at 40 Tts (rooflight at 30 Tts), or through
a performance-based option where a combination of solar control
technologies may be used as long as they result in equivalent solar
performance to the glazing alone.  In addition to solar control glazing,
several approaches to reducing solar heat gain have been identified,
including solar reflective paints, passive or active ventilation
systems, solar reflective or thermoregulating materials, and vehicle
insulation.  These and other technologies may be used to meet a
performance-based option.  The purpose of this Manufacturer’s Advisory
Correspondence (MAC) is to provide manufacturers with guidance in
complying with the Tier 2 alternate performance option, should this
option be chosen in lieu of glazing meeting the standard.  

The test protocol presented in this MAC is approved for 2016 MY and
beyond.  However, the ARB may revise this guidance in the future if
additional data become available that warrant reassessment of the test
procedures and certification guidelines identified herein.  

ii.	Alternate Performance Option Test Procedure Overview

The Cool Cars performance option test procedure includes the testing of
a vehicle in two configurations, one of which is installed with the
solar control glazing meeting the Tier 2 standards, and the other is
installed with a package of alternate solar control technologies. 
Through the test procedure outlined in this MAC, manufacturers must show
that the package of alternate solar control technologies results in a
reduction in air temperature within the vehicle that is equal to or
greater than that achieved with the solar control glazing.  The
following procedures should be followed in the preparation and testing
of vehicle:

A. 	Assembly and requirements of the test stand 

The goal of a thermal soak test facility is to simulate the impact of an
ambient heat load on the heat transmittance properties of technologies
installed on vehicles in lieu of solar control glazing meeting the Tier
2 Cool Cars requirements. The environmental facility control elements
that are discussed are ambient air temperature and humidity, minimum
test cell size, solar heating, and vehicle frontal air flow.

Ambient Temperature.  (a) Ambient temperature during the test shall be
maintained at 23 °C ± 2 °C (during the heating phase the temperature
is allowed to rise to 35 °C) 

	(b) Air temperature shall be recorded continuously at a minimum of 30
second intervals. Records of cell air temperatures and values of average
test temperatures are maintained by the manufacturer for all
certification related programs.

Humidity.  (a) Ambient humidity is controlled, within the test cell,
during all phases of the test sequence to an average of 100 ± grains of
water/pound of dry air. 

	(b) Humidity is recorded continuously at a minimum of 30 second
intervals. Records of cell humidity and values of average test humidity
are maintained by the manufacturer for all certification related
programs.

Minimum Test Cell Size.  The recommended test cell size shall conform to
the recommendations in the EPA Solar Loading Procedure – SC03 Federal
Code of Register part 86.161–00 Air conditioning environmental test
facility ambient requirement.

Solar heating.  Vehicle heating shall be obtained through the use of
lamps with solar irradiance according to EPA Solar Loading Procedure –
SC03 Federal Code of Register Section 40 part 86.161–00 Air
conditioning environmental test facility ambient requirement.

Air Flow.  (a) The minimum air flow nozzle discharge area must be equal
or exceed the vehicle frontal inlet area. Optimum discharge area is 18
square feet (4.25 x 4.25), however, other sizes can be used. 

		(b) Air flow volumes shall be equal to 2.0 ± 0.25 m/s throughout the
duration of the test.

B. 	Vehicle and Cabin Equipment

Test vehicles from each Cool Cars group shall be chosen according to the
certification guidelines detailed in Section III.   For each test
vehicle, the test procedure shall be conducted twice: once with the test
vehicle equipped with 40 Tts glazing on the
windshield/sidelights/backlights and 30 Tts on the rooflight (if
applicable), and once with the test vehicle equipped with the
manufacturer-designed solar control package.  The same test vehicle
shall be used for both tests.  When equipped with the Tier 2 solar
control glazing, any means may be used to reach the specified level of
solar control, including temporary films.  If metallic reflective
glazing is used to comply with the 40 Tts standard, deletion windows may
be used to improve the operation of electronic devices; deletion windows
may be used on each piece of glazing (windshield, sidelights, and
backlight) and be up to 10% of the glazing area for that piece as
defined in the regulation.  

For each test, the test vehicle shall be instrumented as follows:

    

Temperature sensor accuracy shall be better than or equal to ± 0.25
°C.

The temperature measurement shall be an arithmetic mean of eight
measurements: interior breath level air and foot level air in the front
row (left and right seating positions) and back row (left and right
seating positions).  If there is no back row, only four measurements
from the front row shall be averaged.  

Temperature sensors shall be equipped with radiation shields to prevent
direct heating from lamps and/or potential cooling from ventilation
systems.

Front seats shall be placed in the rearmost and lowest position,
seatback angle 90°, headrest down – Figure 1.

Breath-air thermocouple locations shall be at the seat centerline, 660
mm from the seat bottom and 250 mm forward.  If there is only one front
row seat use only one sensor.  If there is only one bench type seat use
the centerline of the left and right front head rests to orient
temperature sensor placement.  

Foot-air thermocouple locations shall be at [tbd…FORD has proposal]. 

Data shall be collected at one second intervals.

Figure 1.  Seat Position and Temperature sensor location

C. 	Preconditioning

≥ 4 hours with windows open, lamps off.  Prior to starting test, close
vehicle windows.  Soak location and test cell location can be in
different locations as long as the vehicle cabin air temperature is
maintained within 23°C ± 2 °C during transport.

D. 	Test

The test vehicle shall be tested according to the procedure below.

Start recording temperature readings.  Temperature readings shall be
taken and logged at one second intervals.  

Record temperatures for minimum of 15 minutes with solar lamps off.

If any temperature reading is outside of the 23°C ± 2 °C the vehicle
must be preconditioned again. 

Turn solar lamps on, set to 850 W m-2; energy intensity is determined
according to 40 CFR 86.161–00 as an average of the two points measured
at the centerline of the test vehicle at the base of the windshield and
the centerline of the vehicle at the base of the rear window (truck and
van location defined as bottom of vertical window or where an optional
window would be located).

Heat vehicle for 150 minutes while continuing to record temperatures.

Turn lamps off.

Record temperatures for minimum of 15 minutes after lamps are off.

Report average temperature of the eight sensors during final 30 minutes.
while lamps were on.

III. CERTIFICATION REQUIRMENTS

A. 	Cool Cars Group Determination

Manufacturers shall divide their product line into cool cars groups
based on the following criteria that must include but not be limited to:

1. The vehicles covered by a certification application shall be divided
into cool car groups of vehicles which are expected to have similar
thermal responses to a solar load based on vehicle geometry, glazing
area, interior volume, and solar technology package.  Manufacturers
shall use the following guidelines for grouping vehicles:

Vehicle Group	Description

Two-seaters	Cars designed to seat only two adults

Sedan	Cars designed to seat 2+ adults, including hatchbacks

Wagon/Crossover	Utility vehicle built on a car chassis designed to seat
4+ adults

SUV	Utility vehicle built on a light truck chassis designed to seat 5+
adults

Minivan

	Pick-up Trucks

	Van/MDPV	< 10,000 pounds



B. 	Data Vehicle Selection

Within each cool car group the manufacturer shall select the vehicle
which is expected to be worst-case for interior heating due to solar
load.  The manufacturer shall use good engineering judgment in making
selections of vehicles under this section.

1. The worst-case test vehicle for a cool car group shall be the vehicle
with the greatest ratio of top-view glazing area to interior volume. 
Top-view glazing area is defined as the total area of glazing determined
by viewing the vehicle from a plane parallel to the roof of the vehicle
rounded to the nearest 0.1 square feet.  Interior volume is the sum,
rounded to the nearest 0.1 cubic feet, of the front and rear seat volume
measured in accordance with the SAE standard “JXXXX” United States. 
In the case of vehicles with a cargo area open to the passenger area
(e.g., hatchbacks, crossovers, SUVs) the cargo volume shall be included
in the vehicle volume.  In the event that two vehicles have identical
top-view/volume ratios, the vehicle with the largest total glazing area
shall be used.  

2. The test vehicle shall be equipped with all equipment that would
affect solar loading that is standard on that model or is optional
equipment (e.g., rooflights) that is projected to be installed on > 33%
of vehicles produced.  

3. The test vehicle shall be equipped with the worst-case interior and
exterior colors and materials offered on that model.  Worst-case colors
and materials are those with the highest solar absorbance.  

C.	Data Vehicle Testing Requirements

1. Each test vehicle with alternative technology shall be used to
demonstrate equivalency to a test vehicle which is equipped with glazing
meeting the 2016MY standard with respect to interior temperature under
the specified conditions of the test procedure detailed in Section II.

2. Demonstration of equivalency shall be conducted to demonstrate that
the interior temperature of the test vehicle with the alternative
technology is equal to or less than the interior temperature of the test
vehicle with glazing meeting the 2016MY standards.  

3.  Temperatures demonstrating equivalency must be the arithmetic mean
of the four breath air and four foot air temperatures recorded during
the final 30 minutes of the soak period.

D. 	Durability Requirements

1. Manufacturers must submit data to replicate the equivalent of 12
years durability (accelerated aging is acceptable with prior EO
approval).  For example, if on average based upon customer data a shade
on it expected to deploy 6 times/day, then the manufacturer must show
durability data for 12 years of shade deployment 6 times/day. 

 

2. Manufacturer must calculate a deterioration factor for each solar
control management system.  The deterioration factor is the reduction of
a solar control system that may be expected during the useful life of
the system.  For example, an active ventilation fan may at the end of
its life not pull the same volume of air out of the cabin then when it
is new.  The deterioration factor in degrees Fahrenheit must be
subtracted from the temperature reduction seen by the Cool Cars data
vehicle installed with that technology.   

E. 	Records Retention

1.  As specified in 17CCR § 9.95603, manufacturers must maintain
records of the direct solar reflectance, solar absorptance, and total
solar transmittance of the glazing utilized for each model vehicle for
ten (10) years after the end of that model-year.  

2.  For those vehicles utilizing the alternate performance option,
manufacturers must maintain records of what technology(ies) was
utilized, if any, and data demonstrating the expected durability of the
alternate approach. 

3.  For those vehicles utilizing the alternate performance option,
manufacturers must maintain records of the ambient cell conditions
(temperature and humidity) and vehicle interior temperatures measured
during the test.

4.  The records in (1), (2), and (3) must be provided within 30 days of
request by the California Air Resources Board. 

 

5.  The records must include the following information:  model-year,
engine test group, model name, cool car group, direct solar reflectance,
solar absorptance, and total solar transmittance for each type (e.g.,
absorbing, reflecting, privacy) and position (e.g., windshield,
sidelight, rooflight(s), backlight) of glazing used.  The records must
also include necessary and appropriate details for alternate
approach(es) utilized.

F.  Carry-Over and Carry-Across 

Certification of a cool car group may carry over model years unless the
vehicle selection is no longer representative. In determining if the
test vehicle is no longer representative, any of the following
conditions may apply:

1. A new model or model design within the cool car group has a top-view
glazing to interior volume ratio greater than the current test vehicle.

2. The solar management technology package changes in such a way as to
reduce the solar control of any piece of the technology package.

3. If the test vehicle did not have a rooflight and projected production
of vehicles with rooflights increases to above the 33% threshold.

 This is the threshold used for emissions certification regulations for
establishing vehicle mass.  See 40CFR §86.1832-01

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DRAFT Cool Cars MAC		03/04/2010

  PAGE  5 

