What TSER Means and Why It Is Not the Whole Story

TSER describes solar heat rejection for a rated glass-and-film system. It helps compare solar-control performance, but it does not predict a percentage drop in room temperature or establish whether a film is suitable for the glass.

What TSER Measures

TSER stands for total solar energy rejected. It accounts for incoming solar energy reflected away and the portion absorbed by the glazing system that subsequently flows outward. Energy that passes directly through, plus absorbed energy released inward, contributes to solar heat gain inside. LLumar technical definitions

Calling TSER a solar heat rejection rating is appropriate. The problem is presenting that rating as a guaranteed improvement in the customer's room. Keep the claim attached to the specified glass-and-film combination and its rating conditions.

How TSER Relates to SHGC

Solar heat gain coefficient, or SHGC, describes the fraction of incoming solar energy admitted as heat. For the same system and rating conditions, the relationship is:

TSER (%) = (1 − SHGC) × 100

An SHGC of 0.30 corresponds to 70% TSER. These are complementary descriptions of solar performance, rather than two independent benefits to add together. Match the reporting basis: a center-of-glass value should not be paired with a whole-window value that includes the frame. IWFA 2026 Flat Glass Solar Education Guide, performance definitions; IWFA 2026 Advanced Solar Control Education Guide, window performance measurements.

What a 70% TSER Rating Does Not Promise

A 70% TSER rating does not establish that a room will be 70% cooler, that cooling bills will fall 70%, or that all heat entering the building will decrease 70%. A room also gains and loses heat through other parts of the building. Window area, orientation, shade, weather and the heating or cooling system affect the outcome. IWFA 2026 Advanced Solar Control Education Guide

The customer's existing window also rejects some solar energy. To describe improvement from adding film, compare the original and proposed systems on the same basis.

For illustration only, suppose the existing glazing has an SHGC of 0.80 and the proposed glass-and-film combination has an SHGC of 0.30:

Measure	Illustrative result
Existing glazing TSER	20%
Proposed glazing TSER	70%
Reduction in admitted solar heat relative to the original glazing	(0.80 − 0.30) ÷ 0.80 × 100 = 62.5%

The proposed system has 70% TSER, while the calculated reduction from the original glazing is 62.5%. Neither percentage predicts the room's temperature or energy bill. These are hypothetical matched-condition values, not a product recommendation. The relative-reduction method compares the change in solar heat gain with the original solar heat gain. LLumar technical definitions: Summer Solar Heat Gain Reduction

Why UV Rejection, VLT and IR Rejection Cannot Be Added Into TSER

Sunlight includes ultraviolet, visible and infrared radiation. All can contribute to heating when absorbed; infrared is not the only part relevant to heat. IWFA Flat Glass Solar Control Education Guide, solar heat and absorbed-energy sections.

The headline percentages on a sample card are not interchangeable inputs to a simple TSER calculation. VLT is weighted for human vision. IR figures may use different wavelength ranges and reporting methods. Absorbed energy must also be accounted for because some can flow inward. LLumar technical definitions; IWFA 2026 Advanced Solar Control Education Guide

For example, 40% VLT does not establish that the other 60% is energy rejected outside. Some of the non-transmitted light can be absorbed. Use the manufacturer's published TSER or corresponding SHGC for the stated glazing system instead of estimating TSER from UV rejection, VLT and an IR headline.

Check Suitability Before Comparing Performance

For an installer, film selection starts with the glass and the job conditions. Review construction, coatings, condition, exposure and shade against the manufacturer's current film-to-glass guidance. Absorption deserves attention early because it affects glass heating, but a percentage alone is not a universal approval for every window. LLumar technical definitions: Solar Absorptance

Build the comparison from films that are suitable for the application. Then consider solar control alongside the customer's daylight, glare and appearance preferences. Review physical samples and the other specifications rather than selecting from the largest TSER number alone. Keep the supporting glass notes and manufacturer guidance with the job file.

For the field review, see Glass and Film Compatibility: What to Check Before Recommending Film and Why Manufacturer Film-to-Glass Guidance Should Stay With the Job File.

Explaining the Rating to a Customer

Keep the explanation tied to the job: this rating helps compare solar heat rejection on the stated glass, while the recommendation also accounts for the customer's window conditions and priorities. Avoid turning the number into a temperature or savings promise. If you discuss improvement over the existing glazing, make the baseline and calculation clear.