Choose ComforTech 35 if you want a lighter, less noticeable tint that still cuts substantial heat and glare. Choose ComforTech 25 for rooms with punishing sun, monitor or television glare, or a need for stronger daytime privacy. The 25 rejects more solar energy and admits less visible light, so it also looks darker.
Both shades belong to Concord’s ComforTech Ceramic Series. Their published figures were measured on 1/8-inch (3 mm) clear glass using NFRC-guideline methods, and Concord identifies the values as representative. Your glass type, pane construction and exposure can change the result.
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The short decision: 35 for balance, 25 for maximum control
The shade numbers describe how much visible light passes through the film. ComforTech 35 has a 35% visible-light transmission (VLT); ComforTech 25 has 23% VLT. In practical terms, 35 keeps a room brighter and has a subtler appearance, while 25 produces a noticeably deeper tint.
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- Pick ComforTech 35 for living rooms, home offices and street-facing windows where you want useful solar and glare reduction without a dark look.
- Pick ComforTech 25 for south- or west-facing glass, rooms that overheat, screens that wash out in direct sun, or windows where daytime privacy is important.
- Use curtains or blinds at night. Neither transparent shade is a night-privacy solution when the interior is brighter than outside.
There is no single “better” film. The choice is whether preserving daylight or increasing solar, glare and daytime-privacy control matters more in each room.
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Published performance compared
Concord’s 2023 technical sheet reports these representative results on 1/8-inch (3 mm) clear glass:
| Metric | ComforTech 35 | ComforTech 25 | What the difference means |
|---|---|---|---|
| Visible-light transmission (VLT) | 35% | 23% | 35 keeps more daylight; 25 appears darker. |
| Total solar energy rejected (TSER) | 58% | 69% | 25 blocks more of the sun’s total energy. |
| Solar heat gain coefficient (SHGC) | 0.41 | 0.31 | Lower is generally better for limiting solar heat entering through glazing. |
| Glare reduction | 61% | 74% | 25 provides the stronger published reduction. |
| Ultraviolet rejected | More than 99% | More than 99% | Both report the same high UV rejection. |
| Exterior visible-light reflectance | 25% | 40% | 25 has the more reflective exterior appearance. |
The figures are not guarantees for every installation. Concord says actual performance varies with glass type and its properties, and the sheet’s values are representative samples rather than a promise of a specific room temperature or utility-bill reduction.
How to read the numbers in a real house
Visible-light transmission: the brightness trade-off
VLT is the percentage of visible light that passes through the glazing and film. A 35% VLT window transmits about half again as much visible light as a 23% VLT window under the published comparison. That does not mean a room will measure exactly 35% or 23% as bright: wall color, blinds, exterior shade, weather and the direction of the window all matter. It does predict the basic visual difference. ComforTech 35 is the easier choice when you want daylight and an unobtrusive tint; ComforTech 25 is more suitable when reducing brightness is part of the goal.
Total solar energy rejected: the broad solar-control measure
TSER describes the share of the sun’s total energy that the film rejects. The published 69% for ComforTech 25 is higher than the 58% for ComforTech 35, so 25 is the stronger solar-control option on the stated test glass. TSER includes more than the visible portion of sunlight, which is why it is useful when the problem is heat as well as brightness.
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Solar heat gain coefficient: heat entering through the glazing
SHGC indicates how much solar heat enters through the window system. Lower values generally indicate better reduction of solar heat gain. ComforTech 25’s 0.31 is lower than ComforTech 35’s 0.41. If a room becomes uncomfortable during peak sun, that difference supports choosing 25, provided the darker appearance is acceptable.
Glare reduction: comfort for screens and eyes
Concord reports 61% glare reduction for 35 and 74% for 25. The stronger 25 figure is relevant to a television, monitor, reading area or any seat that receives direct reflections. Glare is affected by the position of the sun and the screen, so film may reduce the problem without eliminating every reflection.
Ultraviolet rejection: effectively tied
Both shades report rejection of more than 99% of ultraviolet radiation. UV control is therefore not a useful way to choose between 25 and 35; the daylight, heat and glare figures are the meaningful differentiators. UV film performance does not make the window a substitute for curtains when you need privacy.
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ComforTech 25 has a 40% exterior visible-light reflectance compared with 25% for 35. That higher reflectance contributes to 25’s more pronounced exterior appearance and can help explain why the darker shade feels more private in daylight. It does not create one-way privacy in all lighting conditions.
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Which shade fits each room and exposure?
Living rooms and common areas
ComforTech 35 is the balanced default for a living room that needs less heat and glare but should still feel open and bright. Its 35% VLT and lower exterior reflectance are less likely to dominate the view from inside or change the room’s character. Use 25 when the seating area faces intense afternoon sun or when reflections on a television are a persistent problem.
Home offices and study areas
Start with 35 when the desk receives ordinary daylight and you want to preserve a bright workspace. Move to 25 for a west-facing desk, direct sun across the monitor, or a room that becomes hot during working hours. The 25 shade’s 74% published glare reduction gives it the edge for difficult screen reflections.
South- and west-facing windows
These exposures commonly receive stronger or longer periods of direct sun. On the supplied performance data, 25 is the more protective choice because it has higher TSER, lower SHGC and greater glare reduction. If the room is used mainly in the morning or is shaded by trees or an overhang, 35 may provide enough control without the darker look.
Street-facing and front-room glass
ComforTech 35 generally suits a front room where you want a subtle exterior appearance and useful daytime comfort. Concord identifies 25 as a privacy shade and 35 as not a privacy film, so choose 25 when reducing daytime views into the room is a priority. Test a sample at the actual window if the exterior look is important.
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Bedrooms, nurseries and media rooms
Choose according to exposure and use rather than the room name. A shaded bedroom may benefit from 35’s lighter appearance; a sunny bedroom with early heat or strong reflections may justify 25. A media room usually favors 25 when glare is the overriding concern, although blackout blinds remain the way to control light completely.
Daytime privacy is not nighttime privacy
ComforTech 25’s darker tint and 40% exterior reflectance can make it harder to see into a brighter room during the day, which is why Concord positions it as a privacy shade. ComforTech 35 is described as a solar-control film rather than a privacy film. In either case, the effect depends on relative indoor and outdoor brightness. After dark, lights inside can make the room more visible from outside; use blinds or curtains for reliable night privacy.
Shared construction and appearance
Both products are in Concord’s ComforTech Ceramic Series, described as dual-reflective nano-ceramic film with a neutral color, uniform appearance and low reflectivity. The comparison information lists a 2 mil thickness, dry adhesive, scratch resistance, UV protection and DIY-oriented application for both shades.
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Double-pane windows and installation limits
Concord’s safety guidance says every ComforTech shade is safe for double-pane windows up to 40 square feet under its stated conditions. That is a conditional limit, not a universal approval for every insulated-glass unit. Before ordering or applying film, verify:
- The total glass area of each pane is no more than 40 square feet under the conditions covered by Concord’s guidance.
- The window is actually the glazing construction covered by the manufacturer’s safety information.
- The glass manufacturer, warranty and local requirements do not prohibit or restrict applied film.
- Frames, seals, muntins and operating clearances can accommodate the installation without damage.
The published performance values were measured on 3 mm clear glass. Tinted, coated, laminated, low-emissivity or otherwise specialized glass can produce different heat behavior. A film may be listed as double-pane safe while still requiring a glass-specific review for a particular window.
A practical selection process
- Identify the problem window. Note its direction, the hours of direct sun, whether the problem is heat, glare, brightness or views into the room, and whether the pane is single- or double-glazed.
- Set the daylight priority. If preserving a bright, natural appearance is more important than maximum solar control, shortlist ComforTech 35. If reducing brightness is acceptable, keep 25 in consideration.
- Check the exposure. South- and west-facing glass with strong sun generally favors 25; shaded or moderately exposed glass often fits 35.
- Decide whether daytime privacy is required. Choose 25 when that requirement is material. Do not treat either shade as a night-privacy system.
- Compare the published performance. Use 25’s 69% TSER, 0.31 SHGC and 74% glare reduction when control is the priority; use 35’s 35% VLT and lighter 25% exterior reflectance when daylight and a subtle appearance lead.
- Confirm glazing compatibility. Check pane size, construction, manufacturer restrictions and local installation requirements before purchasing film.
- View a sample in place. Look at the film from inside and outside in both sunny and overcast conditions. The actual glass and surroundings can make a shade appear lighter or darker than a product photograph.
Planning a DIY or professional installation
The series is presented as DIY-oriented and uses a dry adhesive, but “DIY-oriented” is not the same as risk-free. The quality of the result depends on accurate measurement, clean glass, careful handling and compatibility with the window. A professional installer may be preferable when panes are large, difficult to access, unusually shaped or covered by a valuable glazing warranty.
Before film is applied
- Measure each pane rather than assuming every window in a room is identical.
- Record the glass type, pane count and approximate area so the double-pane guidance can be checked.
- Inspect seals, edges and existing coatings; film does not repair failed insulated-glass seals or damaged glass.
- Compare the intended appearance from the street and from the room, especially when considering the more reflective 25 shade.
During the decision about who installs it
Use the manufacturer’s application instructions and safety conditions as the controlling requirements. If a local rule, glazing warranty or window manufacturer imposes a stricter condition than the general product description, follow the stricter condition. Do not infer that a result measured on clear 3 mm glass will apply unchanged to every double-pane or specialty window.
What the published figures cannot promise
The technical sheet does not establish a universal percentage reduction in a home’s energy bill, a guaranteed indoor temperature, or an exact payback period. Those outcomes depend on window area, orientation, shading, climate, HVAC operation, insulation and occupant behavior. The figures support a relative choice between the shades, not a prediction for a particular house.
There is also no current price comparison established for these exact products here. Obtain a current quote or sample-kit price directly from the seller and account for pane size, access and whether installation is DIY or professional. Avoid substituting generic film specifications for the ComforTech values above; a different product can have a different VLT, SHGC, TSER and warranty.
Room-by-room recommendation checklist
- Bright but comfortable living room: ComforTech 35.
- West-facing room that overheats: ComforTech 25.
- Office with manageable daylight: ComforTech 35.
- Office with direct monitor glare: ComforTech 25.
- Front room needing daytime privacy: ComforTech 25, with curtains or blinds for night.
- Window where the lightest visual change matters: ComforTech 35.
- Any double-pane installation: Either shade only after checking the 40-square-foot guidance, glazing construction and applicable restrictions.
Bottom line
ComforTech 35 is the safer all-around choice when you want solar and glare control while keeping rooms bright and the film understated. ComforTech 25 is the performance choice for stronger sun, heat, glare and daytime privacy, accepting a darker interior and more reflective exterior. Select by the problem each window has, then confirm the glass and pane-size limits before installation.
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