M e t a l M a t t e r s  
Cool Coatings  
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