VLT is impacted by the openness factor, fabric color, and the amount of light that transmits through the fabric. Visible light transmittance (VLT): The percentage of the available visible light allowed to pass through the solar screen shade and window combined. Fabric color itself does not affect openness across a fabric product line. The more open the fabric, the more solar radiation passes through open space rather than fabric, affecting the overall performance and amount of glare protection, heat protection, and view-through. Openness factor (or Density): Measurement of the relative area of the fabric’s openings, or holes. The total value of all 3 percentages equals 100% of the available solar radiation. A low percentage indicates fabrics that absorb little solar energy.Īll of the available solar radiation is either transmitted through, absorbed by or reflected by the fabric. Solar absorptance (As): The proportion of solar energy absorbed by the fabric alone. A high percentage indicates fabrics that reflect solar energy well. Solar reflectance (Rs): The proportion of solar energy reflected away by the fabric alone. A low percentage indicates fabrics that reduce solar energy well. Solar transmittance (Ts): The proportion of solar energy transmitted through the fabric alone. The visible and invisible combined, or “spectrum”, make up what we see as light, feel as heat, and UV (ultraviolet) rays that are not seen or felt, but have damaging effects on skin, eyes and furnishings. Some of it is visible, some is not visible. What we call “sunlight” is the energy, or radiation that comes from the sun.

Part of the information collectively known as “fenestration data” Understanding solar/optical/thermal factors

Screen shade