Technical guide to 3M LE20, LE35, LE70 and Thinsulate CC75 insulating window film — VLT, U-value, reflectance and shading coefficient, plus Delaware retrofit applications.
Two windows that are both described as double pane can need different films, or no film at all. Compatibility depends on how the insulated unit is built and where any coating sits.
Glass make-up: Pane thickness, whether either lite is tinted, tempered or laminated, and the overall unit size all affect how much solar heat the inner pane can absorb.
Low-E coating and surface: For a conventional two-lite IGU, surfaces 1–4 run from outside to inside: 1 outdoors, 2 and 3 facing the cavity, 4 room-side. Obtain the actual Low-E coating type and surface from the supplier; do not assume a universal coating position or film compatibility.
IGU construction and seal: Spacer type, seal condition, age and any existing fogging matter. Film does not repair a failed seal, and a failing unit is usually a replacement conversation.
Thermal stress: Film changes solar absorption in the glass assembly. Large panes, partial shading, existing edge damage, heat sources and glass construction affect thermal-stress risk; review the manufacturer’s guidance for the exact film and glass.
Legacy performance tables: Published performance tables show results for defined reference glass. They are not blanket statements that a film is compatible with every double-pane or Low-E window.
Window manufacturer warranty: Some window manufacturers address aftermarket film in their own warranty terms. Check that document alongside the film manufacturer’s warranty.
Spacer and glass labels: A close photo of any etched or printed mark in a glass corner, and the spacer bar text between the panes if legible.
Window maker and age: Manufacturer name, sticker or paperwork, and approximate installation year if known.
Each elevation: Wide photos showing which way the glass faces and any partial shading from overhangs, trees or neighboring buildings.
Pane sizes and problems: Approximate sizes of the largest panes, plus any fogging, cracks or failed seals already visible.
Request a free estimate or call (302) 947-4624. Shore Tint & More (Delaware Window Film) — 3M Authorized Dealer, IWFA accredited, serving Delaware and the Maryland Eastern Shore since 1989.