Why Office Glare Gets Worse in November: Seattle’s Low Winter Sun and How to Fix It

In July, window complaints in a Seattle office are about heat. By November, they sound different. People squint at monitors at 3 p.m., turn laptops away from the glass, and ask facilities to do something about the sun. The cause is the low winter sun, and office window glare film is one of several ways to handle it.

We see this pattern every fall on office jobs in Seattle, Bellevue, and Redmond. This guide explains why glare gets worse as the days get shorter and which windows take the worst of it. It also covers what to try before film, and what 3M’s own data says about glare reduction window film.

The Sun Angle Problem: 66 Degrees in June, 19 in December

Seattle sits far enough north that the winter sun never climbs high. KIRO 7 Chief Meteorologist Morgan Palmer puts the noon sun at about 66 degrees above the horizon on June 21. By November 7 the daily peak drops to about 26 degrees. On December 21 it tops out near 19 degrees.

A high summer sun lands on the floor close to the window. A low winter sun travels almost flat across the room. It passes the first row of desks, hits monitors at eye level, and shines into the faces of anyone turned toward the glass.

The geometry is easy to check. The table shows how far direct sun can reach across the floor at noon through a south-facing window whose top edge sits 8 feet above the floor.

Sun heights from KIRO 7. Reach is an illustrative calculation: 8 feet divided by the tangent of the sun angle. Overhangs, blinds, and nearby buildings change it.

Noon is the mildest case. Through the afternoon the sun sinks lower, and the beam reaches deeper until sunset.

The clock makes it worse. Daylight saving time ends on November 1, 2026, when 2 a.m. becomes 1 a.m. The sun keeps its path, but the office clock moves. Low sun that crossed desks near 4 p.m. in late October now shows up near 3 p.m., in the middle of the workday.

Which Windows Get Hit Hardest

In late fall and winter, the sun crosses the southern half of the sky. It rises in the southeast and sets in the southwest, so south-facing glass gets the most hours of low, direct sun. Southwest and west glass take the late-afternoon beam, which sits lowest and is hardest to dodge. North glass gets little direct sun until spring.

On November site walks, the same spaces come up again and again. These are the places we check first:

• South and southwest perimeter desks, where the beam crosses screens for hours
• West-facing offices and corner suites, where the 3 p.m. sun sits at eye height
• Glass meeting rooms, where a wall display faces a window or a glass partition
• Reception desks behind a glass lobby wall, where staff face the entrance all day
• Training rooms and classrooms with projectors or large screens

If complaints cluster in these spots, the sun angle is the cause. It won’t ease until early February, when KIRO 7 says the noon sun climbs back to the 26-degree peak it had on November 7.

What to Try Before Window Film

Film is not the first fix for every desk. OSHA’s computer workstation guide says window light reflected on a monitor makes images harder to see and leads to eye strain and fatigue. Its fixes cost little, and several work well. We tell clients to start there, so film only has to solve what is left.

These are the OSHA steps we see help most in Seattle offices:

1. Turn the monitor so the screen sits at a right angle to the window.
2. Use the blinds you have. OSHA notes that vertical blinds work best on east and west windows, and horizontal blinds on north and south windows.
3. Tilt the monitor down slightly and clean it often, since dust adds to glare.
4. Add a glare filter to the screen, as long as the image stays easy to read.

These steps fix one desk at a time. Start with the worst seats and see how far they get you.

They fall short in a few places we see often. Open offices with dozens of screens can’t all turn sideways to the glass. Glass meeting rooms lose their purpose when the blinds stay shut. A floor where everyone closes the blinds by 2 p.m. stays dim and closed in for the rest of the day.

How Glare-Control Film Works and How Much Daylight It Takes

Solar film cuts glare by cutting the visible light that passes through the glass. So every glare film also takes some daylight with it. On 3M’s data sheets, the glare reduction figure tracks the drop in visible light almost point for point.

On 1/4-inch clear glass, the 3M Prestige Series data card lists Prestige 40 at 39% visible light let in. Bare glass of the same type lets in 88%, per 3M’s data sheet. That is a drop of about 56% by our math, and 3M lists glare reduction for Prestige 40 at 55%. Prestige 70 lets in 69% of visible light and cuts glare by 22%, again close to its drop in light.

What Prestige adds is control over heat and fading without a mirror look. The data card says the films reflect much of the sun’s infrared energy, the part you feel as heat. It also lists 99.9% UV rejection for every film in the line. 3M’s Prestige specification puts interior reflection at 5% to 9%, close to the 8% of plain clear glass.

Film also has a limit we state up front. The darkest Prestige film, PR20, still lets in 21% of visible light, so a bare 19-degree sun can still dazzle someone facing it. Film turns a blinding window into a bright one. In the offices we work in, that usually lets people keep blinds open most of the day and close them only when the sun is lowest.

Picking a Film That Cuts Glare Without Making the Office Dark

The right film depends on how bright the room is now and who sits closest to the glass. A dim, north-facing floor has little light to spare. A southwest corner office in Bellevue or Lynnwood can give up half its daylight and still feel open. That is why we often specify two or three films for one building, one for each problem side.

The table lists 3M’s published numbers on single-pane 1/4-inch clear glass, plus two exterior films. Use it to narrow the choice before a site visit.

Sources: 3M Prestige Series data card, Prestige 70 Exterior data sheet, Prestige 40 Exterior data sheet. The last column reflects our field practice, not 3M guidance.

Treat these figures as a starting point. Your glass type moves every number in the table.

On double-pane clear glass, the same data card shows Prestige 40 letting in 35% of visible light and Prestige 70 letting in 62%. Glare reduction stays the same on both. Tinted and Low-E glass shift the numbers again, which is one reason we identify the glass before we quote. If your team worries about a darker office, our article on what employees notice after tinting covers that question.

Test One Window Before You Film the Floor

A data sheet can’t show how a film looks from one desk at 3 p.m. in November. The fastest way to find out is to film one problem window and work next to it for a few weeks. Pick the window behind the person who complains most, on the worst side of the floor. Then check it on a clear afternoon in November or December, when the sun sits lowest.

Give the test time to settle. 3M’s Prestige specification says new film can look dimpled from leftover moisture and should dry flat within 30 calendar days. The spec ties that window to reasonable weather, so a test installed during a cold, wet Seattle week may need the full month. The same spec says to wait 30 days before washing the film.

Before any film goes on, ask for a glass check. 3M’s spec lists a glass stress analysis among the services an authorized dealer provides on request. Our article on whether window film can crack glass explains what we look for. Where interior film fails that check, exterior film may still work.

You can also preview tint levels before the test with 3M’s window film simulator. It shows how different 3M films change the look of a room. It can’t show your glare, but it helps a team agree on how dark is too dark.

Book a November Glare Walk-Through

November is the best month to see office glare at its worst, since the sun sits near its lowest and the clock has pushed it into working hours. We walk the floor in the afternoon and mark the desks and rooms that take the low beam. We also identify the glass on each side of the building. You get a written recommendation for each side, with 3M’s data behind every film choice.

We work with offices across Seattle, Bellevue, Redmond, Lynnwood, Tukwila, and the wider Puget Sound. Learn more about our office window tinting and solar film work. Contact our team to book a glare walk-through, or call 206-484-0489.