What is openness factor in roller blind fabric?
Updated
Openness factor is the percentage of a sunscreen roller blind fabric that is open gaps rather than solid woven yarn. A low openness factor, such as 1 to 3 percent, blocks more light, glare and view for more daytime privacy, while a higher factor lets in more light and gives a clearer view out.
Sunscreen or screen roller blind fabric is woven from yarn with small, regular gaps between the threads, rather than being a solid sheet. Openness factor is the industry term for how much of that weave is open space compared with solid yarn, usually given as a percentage.
How the percentage works
A fabric with an openness factor of 3 percent has solid yarn covering roughly 97 percent of its surface, with only 3 percent left as open gaps. A fabric with an openness factor of 10 percent has far more open gap, so more light and a clearer view pass through, but less glare, heat and UV are filtered and daytime privacy is lower. In short, a lower figure means a tighter weave, less glare and less view.
Sunscreen fabric does not give privacy at night with the lights on. From inside you can see out through it in daylight, but at night the effect reverses and people outside can see in, so a sunscreen blind is often paired with a blockout blind or a curtain.
What a lower number is best for
- Rooms that get strong afternoon sun, where cutting glare and heat matters most.
- Windows close to a street or neighbour, where daytime privacy is a priority.
- Screens and media rooms, where reducing reflections on a screen is useful.
What a higher number is best for
- A view worth keeping, such as a garden or water outlook.
- A room that already gets limited natural light.
- Windows where UV and glare control matters less than keeping the room bright.
What to ask your retailer
Openness factor is only one part of how a fabric performs. Weave pattern, yarn thickness and fabric colour all affect the final result too, so two fabrics with the same openness number can still look and perform differently. Ask your retailer to show a sample of the exact fabric against the actual window, at the times of day the room is used, so the trade off between view, glare, heat and privacy can be judged for real rather than from a number alone. A blind retailer can show you each fabric against a window, in the colours available.
Other ways people ask this
Is a lower openness factor always more private?
Generally yes for daytime privacy, though colour and the light balance between inside and outside also matter, and no sunscreen fabric gives privacy at night with the lights on.
Does openness factor affect how much heat a blind blocks?
Yes, a lower openness factor generally blocks more heat and glare along with more light, while a higher factor lets more of all three through.
How do I choose an openness factor for my window?
There is no single figure that suits every home. The right one depends on the window and the room, so ask your retailer to show the fabric against the actual window.
This answer is general information. For your own windows, your retailer's advice and your order with them come first.