# Documenting Seasonal Sun and Shade at a Window Film Site Visit

Source: https://precisionfilmsystems.com/learning-center/documenting-seasonal-sun-shade-site-visits/

A window can be shaded when you measure it and receive direct sun when the customer uses the room. A tree can shade the glass during one season and leave it exposed during another. One visit gives you useful evidence, but it does not show the entire year.

The job record should make clear what you saw, what the customer reported and what you predicted. Keep those separate from the decision about which film is suitable for the glazing.

## Begin with the time and place of the problem

Ask where the customer is when the problem occurs and what time it usually starts. A desk, checkout counter or chair is more useful than a general note that the room gets too much sun.

Record the months or season, approximate start and finish times, and whether the issue happens on clear days, cloudy days or both. If the customer says “late afternoon,” ask for the best available time range rather than converting that phrase into an exact hour yourself.

Distinguish direct sunlight from other observations. Sun reaching a work surface, a bright window in the field of view and a reflection on a screen can produce different site evidence. Do not assign a cause solely from a phone photo.

A customer report is valuable even when you cannot reproduce it during the visit. Label it as a report, including who provided it, instead of writing it as something the installer observed.

## Put every observation on a named pane

Use the same pane or window IDs as the measurement schedule. Record the date, local time, time zone and weather conditions with the observation.

Identify the elevation and how its direction was established. If a phone compass is the source, say so. Note whether the reading is magnetic or true north when using it with a sun-position reference. Magnetic or environmental interference can affect a phone compass, so do not imply survey-grade accuracy from a casual measurement. [Apple compass guidance](https://support.apple.com/en-au/guide/iphone/iph1ac0b663/ios)

Photograph the whole opening as well as the relevant shadow boundary. An isolated patch of sunlight without a pane ID is difficult to use later. Where appropriate, include an interior view showing the customer's position and an exterior view showing the obstruction.

Avoid capturing people, confidential screens or unrelated private material. You need evidence of the glass and shading, not a record of the business's activity.

## Describe the shade instead of labeling the whole window shaded

Record whether shade covers the whole pane or only part of it. Identify what causes it: an overhang, adjacent wall, neighboring building, tree, sign or another object.

A note such as “upper third shaded by fixed overhang at 10:20 a.m.; lower portion in direct sun” can be revisited. “Shaded window” loses both the pattern and the time.

Also note which conditions may change. Trees may lose leaves or be pruned. An awning may retract. A delivery truck is a temporary obstruction. A neighboring building is more persistent, but planned construction can change the surroundings.

Interior conditions belong in the record too. Note blinds, curtains, displays or furniture near the glass, their position during the visit and whether the customer uses them differently at the problem time.

Do not treat partial shading as merely a reason to expect less heat. The IWFA's solar-control education guide identifies uneven glass temperatures as the basis of thermal stress and lists shading and restricted airflow among relevant factors. That makes the observed pattern useful technical information, not a film approval by itself. [IWFA solar-control education guide](https://iwfa.com/wp-content/uploads/2026/01/Advanced-Solar-Control-Education-Guide-2026.pdf)

## Keep a small evidence table

Here is a hypothetical record for one office. The entries illustrate how to label evidence; they are not observations from a real customer.

| Evidence type | Record for pane W03 |
| --- | --- |
| Observed on site | October 15, 10:20 a.m. local time, clear sky; upper third shaded by fixed overhang; remaining glass in direct sun |
| Customer reported | Direct sun reaches the west-side desk approximately 3:30 to 5:00 p.m. during part of autumn |
| Unknown | Exact dates of the reported problem and afternoon shadow boundary |
| Next evidence needed | Dated afternoon photos from the same location, with the blinds in their normal position |
| Product status | Glazing details and selected-film suitability still under review |

The morning observation does not confirm or disprove the afternoon report. The useful next step is to obtain evidence at the relevant time, not to argue from the time when the installer happened to arrive.

## Use a sun-position prediction for a defined question

A sun-position tool can help investigate where the sun is expected to be for a specified location, date and time. Check the coordinates, local time, UTC offset and daylight-saving setting. A one-hour input error can undermine a comparison even when the display looks precise.

Azimuth describes the direction around the horizon, while elevation describes the angle above it. NOAA's glossary defines those terms relative to true north and the horizon. [NOAA solar-position glossary](https://gml.noaa.gov/grad/solcalc/glossary.html)

A predicted position is not proof that sunlight reaches the glass. The local obstructions must still be accounted for. It also does not tell you how much heat enters the room, whether the customer will find the result comfortable or whether a product is suitable for the glass.

Label the tool, inputs and assumptions in the record. If the obstruction was estimated visually rather than measured, say so. Do not turn an approximate tree line into an exact minute when shade will end.

For a seasonal comparison, choose dates that relate to the reported problem. A midsummer view may not answer a question about autumn sun. Use the prediction to identify a useful observation time or a question for further review, rather than presenting it as a guarantee of daily conditions.

## Ask for follow-up evidence that can be compared

If another site visit is not justified, the customer may be able to provide a short sequence of photos. Ask for the same viewpoint, a visible pane reference, the date and time, and a note about blinds or other movable shading.

Request the period that matters. In the hypothetical office, one photo near the reported start and another later in the afternoon could help establish where direct sun reaches. A photo taken at noon would leave the main question open.

Weather matters. A cloudy-day photograph cannot establish the clear-sky shadow boundary. Record the limitation and decide whether more evidence is needed before finalizing the recommendation.

## Use the record in product review

The sun-and-shade record should travel with the glazing information. It does not replace glass identification, product data or manufacturer approval where required.

As one manufacturer example, 3M's glass checklist asks about glazing construction, pane dimensions, interior shading and outdoor shadow patterns. Use the current requirements for the film you are actually considering rather than assuming every manufacturer's review is identical. [3M glass checklist](https://multimedia.3m.com/mws/media/1705610O/glass-checklist.pdf)

Keep the final conclusion proportionate to the evidence. You may have confirmed direct afternoon sun, identified a likely seasonal pattern or found that a key condition remains unknown. Those are different results.

A useful site record lets the next installer or technical reviewer see those distinctions without repeating the conversation. It also gives you a clear reason for the next measurement, photo or product question before the material is ordered.

## Related Learning Center Articles

- [Plan Oversized Panes and Seams Before Buying Film](https://precisionfilmsystems.com/learning-center/oversized-panes-seam-planning-before-purchase/)
- [What to Write Down Before You Leave the Job Site](https://precisionfilmsystems.com/learning-center/what-to-write-down-before-you-leave-the-job-site/)
- [Glass and Film Compatibility: What to Check Before Recommending Film](https://precisionfilmsystems.com/learning-center/glass-film-compatibility-what-to-check-before-recommending-film/)