What Openness Factor Means On A Solar Shade

Every solar shade sample has a number on the back. 1%, 3%, 5%, 10%. That number is the openness factor, and all it tells you is how much of the fabric is open space rather than yarn. A 5% fabric is 5% holes and 95% thread. Almost everything you will notice about the shade once it is hanging on your window comes out of that one figure.

What The Number Actually Measures

Solar screen fabric is a woven mesh. Yarn runs one way, yarn runs the other way, and between the threads there are tiny square gaps. The openness factor is simply how much of the surface those gaps add up to. Nothing more complicated than that.

Here is why it matters so much. The open part of the weave passes sunlight straight through, unchanged. Direct sun, full glare, no filtering at all. A 10% fabric always lets at least a tenth of whatever hits it come through as raw light, whatever colour the fabric is. The yarn handles the rest, reflecting some of that energy back out through the glass and absorbing the remainder.

So the number is a ceiling on how much sun control you can get from that fabric. Colour and weave quality move things around at the margins. The openness sets the range.

One thing the number does not tell you is how dark the room goes in the evening. Solar shades are not a darkening product at any openness. If that is what you are after, you are shopping for a different fabric on the same roller, and our page on custom shades covers where each one fits.

What Changes As You Go Down The Scale

1%. The tightest fabric in normal residential use. Glare drops away, the room reads noticeably dimmer, and the view outside goes soft and slightly grey. You still see shape and colour and movement. You stop seeing detail. This is as close to daytime privacy as a solar shade gets.

3%. Most of the glare control of a 1%, with a good deal more of the view kept. Outlines stay legible. Trees still read as trees. On a window that is genuinely punished by afternoon sun, this is usually the right compromise.

5%. The most popular choice, and for good reason. The view outside reads clearly. Glare is cut to something a room can live with. If you have no idea where to start on a normal window, start here.

10%. A much looser weave. The view is close to unobstructed and the room stays bright. Sun control is modest, so save this for glass that does not take direct sun in the first place.

Fabrics above 10% exist, up to around 14%, and they are really a view product with a little insect-screen haze to them. Manufacturers publish UV and heat figures for each individual fabric, and those figures track openness closely but not perfectly. Ask for the numbers on the exact fabric you pick rather than trusting a rule of thumb about the family it belongs to.

Picking A Number Room By Room

West and southwest glass. This is the North Texas problem, and 3% is the honest default. On the worst window in the house, the one that turns a room unusable from three in the afternoon, 1% earns its keep. We wrote about the whole west-wall problem in covering west-facing windows.

A home office with a screen. 1% or 3%. Screen glare comes from a bright surface sitting in your field of view, so cutting the brightness of the window matters more here than total room light does.

Kitchens and family rooms where the backyard is the point. 5%. You bought the house for that view. Keep it.

North-facing glass, or a window shaded by a deep porch. 10%. There is little direct sun to fight, so buy the view.

Bedrooms. Openness is the wrong question for a bedroom. Pick the darkening layer first and decide about a solar shade second.

Why Dark Fabric Sees Out Better Than White

This surprises people, because white feels like the cooler, brighter choice. It is, for heat. For seeing out, dark wins every time.

A pale mesh lit by direct sun becomes a bright glowing surface hanging in front of the view. Your eye stops at the fabric and reads the weave instead of what is past it, which is why a white solar shade can look hazy in strong light. Dark yarn absorbs that light rather than scattering it back at you, so your eye travels through the holes and lands on the yard.

The trade-off runs the other way on heat. Light fabric reflects more solar energy back out through the glass before it becomes warmth in the room. Dark fabric absorbs it and gives some of that heat up on the inside face.

Charcoal or bronze mesh at 3% or 5% is where most people land once they have held both against their own window. If heat is your loudest complaint rather than glare, go lighter and accept the haze.

The Night Problem Nobody Puts On The Sample Card

A solar shade works on a difference in light levels. During the day it is brighter outside than in, so the fabric face catches the light and you get a one-way effect: you see out, nobody sees in.

After dark that reverses completely. Your lamps make the room brighter than the street, and anyone outside is now on the dark side of the glass. What they get is shapes, outlines and movement. Going down to 1% softens it. It does not solve it.

So for any street-facing room, and for every bedroom, plan a second layer from the start. Drapery panels on a rod above the window handle it well. So does a dual roller with a room-darkening fabric on the second tube. Our post on room-darkening and blackout shades explains what each of those fabrics really does, including the light that still comes around the edges.

Front rooms sit close to the sidewalk in a lot of the newer neighborhoods, which is why this comes up on nearly every consultation in Frisco.

What To Sort Out Before You Order

Four things decide whether you like the shade a year from now.

• The openness number on the exact fabric you picked, not the collection it sits in.
• The fabric colour, judged in your own light at the hour the sun is actually a problem.
• Whether that window needs a second layer for evening privacy, and what it will be.
• Whether the roll is exposed or sits in a cassette, and whether side channels are worth it where light slips past the edges.

Sheila brings the samples to the house and holds them against your own glass, in the afternoon if that is when the window misbehaves. A 3% and a 5% look nearly identical in a sample book and behave like different products on a west wall. Book a free in-home consultation and see them on the window before you decide.