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Window Film: A Myth-Busting Report

August 30, 2013 | 0 comments

Any change made to improve window insulation performance can make a significant difference in the energy that is lost through the building envelope.

With solar heat gain reductions of up to 75% (equaling average energy cost savings of between 5% and 15%), window film improves insulating performance of a commercial building’s windows. In fact, the newest low-e window films can improve window insulating performance by as much as 92%. In many cases, building owners and facilities managers receive a complete ROI on window film within three years (or less with utility rebates).

Still, myths persist about the characteristics of window film. Do any of these sound familiar to you? If so, read on to find out why they’re not true …

Myth #1: Installing window film will cause window glass to break

Window film application typically isn’t the sole cause of thermal breakage of window glass if it’s installed according to manufacturer specifications. If the glass isn’t manufactured and/or installed to meet industry standards, or if the wrong kind of window film is applied to the glass type, then the application of window film may be a contributing factor to breakage. To reinforce this point, some window film manufacturers offer a warranty that includes glass and film replacement if thermal shock fractures do occur.

Myth #2: Window film makes the windows look shiny or iridescent

Older, conventional types of low-e film can display an iridescent appearance when installed near certain types of energy-efficient lighting (such as compact fluorescents); however, newer low-e coatings are available that virtually eliminate this iridescence and shine.

Myth #3: Window film makes it too dark in my building, so we’ll have to install more lighting

Newer low-e films are designed to be spectrally selective and reduce infrared heat while allowing most visible light to pass through. This allows natural lighting into a space comfortably while minimizing heat allowed through the windows.

Installing window film can actually decrease the need for artificial lighting. It sounds counter-intuitive, but here’s how this happens: Before film is installed, blinds or shades are often used to reduce sunlight and heat. Once window film is in place to reduce solar heat gain and glare, people often open blinds to reconnect with the outdoors. As a result, window film provides more light plus a view to the outdoors.

Myth #4: Window film only works in the summertime or in warm climates

Windows typically account for 25% of annual heating and cooling costs, but they can be responsible for as much as 40%. To help control energy costs year-round, the right kind of window film can improve energy efficiency across all seasons in every possible climate. Today’s high-performance, low-e window film can substantially improve the efficiency of existing windows by keeping solar heat out during summer and retaining heat during winter.

Low-e windows have U-value and emissivity values that range from 0.02 to 0.20, which means that 80% to 98% of the room’s heat is reflected back into the room in the winter. The insulating power of some low-e films (with emissivities as low as 0.07, reflecting 93% of room heat back indoors during winter) can give single-pane windows the annual insulating performance of double-pane windows, and give double-pane windows the annual insulating performance of triple-pane windows. This not only reduces HVAC loads and runtimes, but also lengthens HVAC equipment life and offers year-round utility cost savings.


Which window film myths are we missing? Can you think of others we could address?


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