| Low-E Finish Hits U.S. Market 
With a lower-emissivity coating
on interior walls and ceilings, the radiant energy of the warmer interior walls, furniture
and people in the room will all be partly reflected.
Germany has confirmed that the product's e value is between
0.46 and 0.71, compared to around 0.9 for standard latex. The lower e value of Radiance
reduce the emission into interior rooms by up to 40%, but also releases the remaining 60%
at a much slower rate than normal painted, unpainted or wallpapered walls. This
helps keep the interior cooler in summer and more comfortable.
For maximum comfort, the product should be applied to all
interior wall and ceiling surfaces, because radiant heat, unlike convective heat that
rises, travels randomly in all directions. Just like standard latex, it can be
applied by brush,roller or sprayer, and a gallon will cover 350 to 400 square feet
depending on surface porosity. It can be applied over acoustic tiles, masonry and
most previously primed surfaces.
How Low-E Wall Coatings Work
There are two fundamental ways an interior low-e wall
coating will have an effect on the energy consumption in a building. First, it will
raise the thermal resistance of the building's outer walls. Secondly, it will increase the
thermal comfort in a building in winter and summer by changing the median radiant
temperature.
| Table 1/Test
Results |
| Sample |
Maximum (°F) |
Minimum (°F) |
Mean (°F) |
| Radiance Eg-Shel |
80.42 |
75.92 |
78.44 |
| Standard latex |
84.38 |
79.88 |
82.04 |
| Ceramic Coating |
85.28 |
79.52 |
82.04 |
Walls coated with a standard interior latex will have an
emissivity around 0.9 to 0.95 and a radiant-heat reflection of 5% to 10%. A lower
emissivity of the wall will result in a smaller radiant heat transfer coefficient and a
higher thermal resistance of the wall. Coating all interior walls and ceilings can
increase radiant-energy reflection to up to 40%, as well as reduce the radiative heat flow
from the warmer interior walls to the cooler outer walls of the building. In summer,
it has the same effect; only the direction of the heat flow is changed.
With a lower-emissivity
coating on interior walls and ceilings, the radiant energy of the warmer interior walls,
furniture and people in the room will all be partly reflected. Even if the inner
surfaces of an exterior wall are slightly colder when covered with a low-e finish, the
apparent temperature will be higher and have a positive effect on the room's operative
temperature, which is the temperature experienced by occupants of the room as too hot or
too cold.
Early Testing
The main concern when introducing any new technology to a
mature market is to ensure that the product receives extensive input at each of the
research, development and testing phases.
Before the product was introduced, low-e wall coatings and
the standardized equipment needed to measure their performance did not exist. To solve the
problem, the help of Germany's highly acclaimed Fraunhofer Institute for
Construction-Related Physics was enlisted to create test apparatus to rate the performance
of Radiance* against other paint and coatings.
Tests were conducted using Eg-Shel white, a standard
interior latex white and a brand-name interior ceramic coating. Using a radiant
heater with an even surface and a surface temperature of 1250F, three test
plates (one for each type of coating) were tested. |
