M e t a l M a t t e r s
Solar Reflectance and Aluminum Framing Energy Efficiency
By Dean Lewis
t began over a decade ago with the “cool roof”
movement—the concept that products made with
materials or finishes with greater solar reflectance
minimize the transfer of heat to the building.
in the laboratory, enabling monitoring of changes
in solar reflectance due to aging and exposure.
Per the Cool Roof Rating Council Product
Rating Program (CRRC-1), color family elements
product specimens are tested for absolute Hunter
“L”, “a” and “b” values in accordance with ASTM
D2244-15a, Standard Practice for Calculation of Color
Tolerances and Color Differences from Instrumentally
Measured Color Coordinates.
• On the L scale, a low number (0-50) indicates
dark and a high number (51-100) indicates light.
• On the “a” scale, a positive number indicates
red and a negative number indicates green.
• On the “b” scale, a positive number indicates
yellow and a negative number indicates blue.
The SR of a surface is measured on a scale
from 0 to 1, the latter indicating 100 percent
reflectance of the incident radiation, which would
mean no effect on surface temperature, while an
SR of 0 would indicate all radiation absorbed.
Accelerated outdoor weathering using concentrat-
ed natural sunlight (as defined in ASTM C90)
with night-time wetting for 870 megajoules Total
Now, advances in coatings technologies for
architectural products other than roofs are lead-
ing to solar reflective coatings to keep surfaces
cooler. Enter reflective fenestration framing sys-
tems—“cool frames,” if you will.
AAMA 643-16, Voluntary Specification,
Performance Requirements and Test Procedures for Solar
Reflective Finishes covers performance requirements
and test procedures for organic coatings such as
acrylics, polyesters, siliconized polyesters and vari-
ous types of fluoropolymers. It applies to coatings
on aluminum, fiber-reinforced thermoset or wood
and cellulosic composite profiles for fenestration
products (vinyl profiles excluded) that are partic-
ularly reflective to sunlight, and so tend to keep
buildings cooler. This is a particular boon to com-
mercial buildings, which tend to be cooling-inten-
sive, rather than requiring much heating.
This specification supplements the existing
AAMA coating specifications, which include AAMA UltraViolet Radiation is an approved alternative
603, 2604 and 2605 for aluminum substrates – a
to the South Florida testing. Actual South Florida
exposure positions sample at a 45-degree angle fac-
ing south for a minimum of three years.
“good, better and best” triumvirate of increasingly
stringent performance criteria.
The entry requirements for an AAMA
603-compliant finish include 20 microns (0.8
mil) thickness, while 2604 and 2605 require 30
microns (1.2 mil). All three standards test for
The Table of Color Families and Characteristics
per CRRC-1 contained in AAMA 643-16 gives
different ranges of L, a and b values and for default
SR as the minimum acceptable values for 17 color
color uniformity, specular gloss, dry film hardness, groups. These are light and dark versions of reds,
film adhesion, impact resistance, chemical resis-
tance, resistance to corrosion caused by humidity
and salt spray, and resistance to color fading or
deterioration based on weathering tests.
beige/tan shades, blues, browns, greens, whites and
gray-black. In general, L values are less than 45 for
dark colors and more than 60 for light colors. The
“default SR” ranges from 0.25 to 0.70 (dark to light).
AAMA 643-16 can assist architects, owners
and contractors in specifying “cool frame” finish-
es with higher-than-standard SR values and still
maintain a high level of performance in terms
of film integrity, exterior durability and general
appearance over a period of many years. AGG
AAMA 643-16 prescribes a test for determining
the solar reflectance (SR) of flat opaque materials
using a commercial portable solar reflectometer
per ASTM C1549-09 (2014), Standard Test Method
for Determination of Solar Reflectance near Ambient
Temperature Using a Portable Solar Reflectometer. The
SR is determined before and after either acceler-
ated simulated outdoor weathering or actual out-
door weathering at a designated Florida test site.
Periodic testing can be performed in the field or
Dean Lewis is the technical manager of
training and education for the American Architectural
Manufacturers Association in Schaumburg, Ill.
Architects’ Guide to Glass & Metal