While Solar Shades play a key role in daylighting concerns with LEED, the USGBC does not address fabric content, glare control performance, the differences in the openess of the various weaves available or the color choices of the fabrics.
Fabric Content:
Let’s take a look at the back of the fabric card for Mermet’s M-Screen.
Across the top of the chart are codes: Ts, Rs, As and Tv. These codes are interpreted as:
Ts = Solar Transmittance is the energy that passes through the fabric
Rs = Solar Reflectance is the percentage of solar energy reflected
As = Solar Absorption is the amount absorbed by the shade fabric.
Ts + Rs + As = 100%
Tv = Visual Transmittance is the measure of Glare
Visual Transmittance
The number is a ratio of the amount of total solar energy which passes through the glass and screen combined.
M-Screen 5% White/White = 15
This fabric reduces glare by 85%
M-Screen 5% Charcoal/Sky = 5
This fabric reduces glare by 95%
As you can see, the darker the color, the better the performance for reducing glare.
Shading Coefficient
Shading Coefficient is the percentage of solar heat gain through a combination of glass and screen. Light colors have lower shading coefficients and darker colors have higher shading coefficients. Lower shading coefficients means lower heat gain and better thermal performance.
M-Screen 5% White/White = .36
This fabric allows 36% heat gain
M-Screen 5% Charcoal/Sky = .65
This fabric allows 65% heat gain
In terms of reducing heat gain, the lighter the color, the better the performance.
Openness
The most common weaves in solar shades are 1%, 3%, 5% and 10%. You can also look at it as the 3% open weave is also 97% closed. To determine which weave is the appropriate percentage, I usually recommend 1% for areas where light and privacy are needed such as bathrooms. 3% and 5% are great for intense sun exposure such as south and west orientations. For northern exposures, 10% is adequate. Eastern facing windows will get morning sun, so 5% works well.
Fabric Options
We offer a wide range of fabric options from several weavers such as Verosol, Hunter Douglas Contract, Draper, Mermet, Rockland and Phifer. In addition we also have several PVC free fabrics and blackout fabrics. To see the slide show of our fabrics please click here>