What do fabric specifications mean? Transmission, Reflectance and Absorption.

General Information

External blinds provide better protection thermally than internal blinds because the sun’s rays that are partially absorbed by the fabric before reaching glazing and are pushed back outwards by the fabric. 

Darker colours absorb more solar energy and thus offer more protection  against  heat than light colours. On the other hand, bright colours are more suited for indoors. They absorb less heat and reflect it more than dark colours.


Different manufacturers have varying measures and technical information they publish about fabric specifications.  Generally speaking the specification falls into two main sections: thermal factors and optical factors.  This is generally published as a percentage between 0-100 or as a decimal between 0-1. 1 or 100 would be the highest and 0 would be the smallest with 0.5 or 50 being mid range.  

Thermal factors


Solar Transmittance (Ts)

Solar transmittance often referred by the letters TS is the percentage of solar energy that is transmitted through the fabric. A low percentage indicates that the fabric is effective at limiting heat gain.

Solar Reflectance (Rs)

Solar Reflectance often referred to by the letters RS shows how much solar radiation is reflected by a fabric. A high percentage indicates that the fabric is effective at limiting heat gain..

Solar Absorptance (As)

Solar Absorptance referred by the letters AS is how much solar energy or radiation is absorbed into the fabric. A high percentage means it absorbs a high amount of the solar energy so is more effective at limiting heat gain.  

Optical factors


Openness Factor (OF)

Openness factor is only used for screen fabrics and refers to the surface area of the fabric that is open. You can learn more specifically about this in our previous post (insert link here) 

Visible Light transmittance  (Tv)

The overall proportion of light transmitted through the fabric.  The lower the percentage, the better the fabric is at providing shade. 

Visible light reflectance (Rv)

Visible light reflectance is the percentage of light that is reflected by the fabric.  The higher the percentage the better the fabric is at providing shade.

Sample Testing

Before making a decision for a large quality of blinds it is always worth installing a single blind or even just getting a large piece of the proposed fabric to physically test in the space you will be using it in.  Whilst the manufacturer’s specifications provide a guide.  You can not get better than physically seeing the fabric in the room and visually testing it yourself to make sure it provides the relevant level of performance.

To find out more please get in touch below.

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