7 Things Architects Should Know Before Specifying Solar Shades

A practical guide to fabric openness, exposure, glare, transparency, and solar performance

Solar shades can seem like one of the simpler elements of a project.

Select an openness factor.

Choose a color.

Coordinate the hardware.

Approve the sample.

But solar shade fabric is not simply a finish. It is a performance material that directly affects solar heat gain, glare, daylight, transparency, and the occupant's relationship with the exterior.

The fabric, glazing, orientation, and location of the shade all work together. Change one of those variables and the performance can change dramatically.

Before specifying a solar shade, architects should understand these seven principles.

1. Openness Is Only the Starting Point

Openness factor describes the percentage of open area in a solar shade fabric.

A 5% openness fabric, for example, is approximately 5% open and 95% closed.

Common openness factors include:

• 3% — tighter weave with stronger solar and glare control

• 5% — a balance between control and transparency

• 10% — greater view-through with less solar protection

As a general principle, the tighter the weave, the greater the fabric's ability to limit solar energy entering the space.

But openness alone does not tell you how a shade will perform.

A 3% fabric is not automatically "better" than a 5% or 10% fabric. The correct openness depends on what is happening at that particular window.

The specification should begin with the condition, not the sample.

2. Window Orientation Should Influence the Specification

A single shade fabric does not necessarily make sense on every elevation of a building.

Northern-facing windows typically require less solar protection and may accommodate a more open fabric.

Windows receiving significant direct sunlight generally require tighter fabrics—often in the 3% to 5% range—to provide greater solar control.

This becomes particularly important on demanding exposures where direct sunlight can create excessive brightness, heat, and visual discomfort.

Rather than asking:

"What solar shade are we using on the project?"

ask:

"What does this elevation require?"

The ideal specification may change from one façade to another.

That is not inconsistency.

It is responding to architecture.

3. Look Beyond Openness: Understand AS, RS, and TS

Openness describes the physical weave.

Solar performance tells us what actually happens when sunlight reaches the fabric.

Solar energy interacting with a shade can be divided into three components:

AS — Solar Absorptance

The percentage of solar energy absorbed by the fabric.

RS — Solar Reflectance

The percentage reflected away by the fabric.

TS — Solar Transmittance

The percentage transmitted through the fabric.

Together:

AS + RS + TS = 100%

These values provide a much more complete picture of fabric performance than openness alone.

Two fabrics can have identical openness factors but behave very differently because one reflects more energy, while the other absorbs or transmits more.

For performance-sensitive spaces, the specification should therefore move beyond simply saying:

"3% solar fabric."

The solar-performance data matters.

4. Fabric Color Is a Performance Decision

Color has a major effect on how solar fabric behaves.

Generally:

Light colors reflect more solar energy.

Dark colors absorb more solar energy.

Consider two versions of the same 5% openness fabric.

In one performance example, the white fabric allowed approximately 49% solar heat gain, while the comparable black fabric allowed approximately 56%.

For solar heat-gain reduction, the lighter fabric performed better.

But that is only half of the story.

When glare and view-through are considered, the darker fabric can have a substantial advantage.

This is why the color of solar shade should never be treated solely as an aesthetic choice.

Color changes performance.

5. Glare Control and Heat Control Are Not the Same Thing

A fabric that performs well at reducing solar heat gain may not provide the best glare control.

Glare is fundamentally about contrast.

If someone is working at a computer while a bright window occupies the field of vision, the difference in luminance between the screen and window can make the visual task uncomfortable.

A useful principle is the 1-3-10 luminance ratio:

• approximately 1:3 between a visual task and an adjacent surface

• approximately 1:10 between the visual task and a non-adjacent surface

Solar shades reduce the difference between these light levels.

And darker fabrics can perform particularly well.

Using comparable 5% openness fabrics:

• a white fabric reduced glare by approximately 57%

• a black fabric reduced glare by approximately 90%

The dark fabric absorbs more visible light, significantly reducing brightness at the window.

This creates an important specification tradeoff:

Light fabrics can offer stronger solar reflection.

Dark fabrics can offer stronger glare control.

The correct choice depends on the problem the room is trying to solve.

6. Darker Fabrics Can Actually Improve the View

This may seem counterintuitive.

Many clients assume a light-colored shade will feel more transparent.

In practice, darker solar fabrics frequently provide better view-through.

The eye tends to look past a dark mesh more easily, while lighter fabric can become visually prominent when illuminated by daylight.

Openness still matters.

A 10% fabric generally provides more transparency than a 3% fabric.

But color also plays an important role.

That means increasing openness is not the only way to preserve a view.

In certain conditions, selecting a darker fabric may allow an architect to maintain strong exterior visibility while using a tighter openness factor to better control glare.

And that matters because there is always a tradeoff:

Increasing openness improves view-through—but also allows more solar energy through the shade.

The objective should not be maximum transparency.

It should be the best usable view while maintaining the required level of solar and glare control.

7. Interior and Exterior Shades Perform Very Differently

The location of the solar shade relative to the glass can have an enormous impact on performance.

With an interior shade, sunlight first passes through the glazing.

The shade then reflects, transmits, or absorbs that solar energy.

When a dark interior fabric absorbs large amounts of solar radiation, some of that energy is converted to heat and released toward the interior.

An exterior shade changes the sequence.

Solar radiation reaches the shade before it reaches the glass.

The fabric can intercept much of that energy outside the building, where the absorbed heat dissipates into the exterior environment.

The difference can be dramatic.

For one 3% ebony fabric paired with non-reflective double glazing:

• Interior installation: approximately 50% total solar heat gain

• Exterior installation: approximately 8%

For a comparable white fabric:

• Interior installation: approximately 37%

• Exterior installation: approximately 14%

The same fabric can therefore behave very differently simply because its relationship to the glass has changed.

This is why some of the most demanding solar-control conditions should begin with a larger architectural question:

Should the sun be controlled before or after it reaches the glazing?

An Additional Tool: Solar Reflective Fabrics

There is another way to address the conflict between solar performance and interior aesthetics.

Solar Reflective Coatings, sometimes called metalized fabrics, use a highly reflective layer on the window-facing side of the shade.

This allows the exterior-facing surface to reflect more solar energy while the room-facing side can retain a darker or more design-appropriate appearance.

The concept is important because it separates two performance requirements that normally compete with each other:

Solar reflection toward the glass.

Glare control and aesthetics toward the room.

For demanding interior applications, this can provide architects with another valuable specification option.

Start With the Problem, Not the Fabric

The strongest solar shade specifications begin before the fabric is selected.

Start by asking:

What are we trying to control?

• Glare?

• Solar heat gain?

• Daylight?

• View?

• Privacy?

Then consider:

• What is the window orientation?

• How much direct solar exposure does it receive?

• What openness is appropriate?

• What are the fabric's AS, RS, and TS values?

• How will color affect heat, glare, and transparency?

• Should the shading occur inside or outside the glazing?

Only then should color and texture become the final design decision.

The sequence should be:

Purpose → Performance → Fabric → Design

Because a solar shade is not simply something placed in front of the glass.

It is part of the architecture's response to the sun.