International Window Film Association

Guide To Avoiding Glass Failure

Examination Procedure

This document presents an extensive list of factors which need to be considered when the application of window film to a particular set of windows is under consideration. This material can be applied directly, to a make a reasonable judgment as to whether or not window film should be applied to a particular window system. This would be an acceptable procedure if the installation under consideration involves a set of windows with similar characteristics such as would occur in a small residential application. In this case, it is recommended that the window film installer carefully examine a representative sample of the windows on which window film is to be applied prior to acceptance of the job. If the number of windows to be filmed is less than twenty, all of the units should be included in the sample. If the number of units to be filmed exceeds twenty, then a representative sample of twenty units should be selected for examination. The representative sample of windows should then be subjected to the examination described in this guide. If any of the window units fail to successfully pass the examination, it is not recommended that window film be applied without consultation with the window film manufacturer.

If the job under consideration is more complicated, involving significantly different types, sizes, etc. as might occur with a large residential project or commercial application, it is recommended that a more detailed procedure be followed. The more detailed procedure involves the production of a detailed set of documentation.

First, it is recommended that a sketch of the overall project be prepared on the project plan sheets provided at the end of this document. Indicate the project name, the date, and the individual's name who is responsible for taking the data. In addition, indicate the approximate scale used in the drawing and provide an accurate indication of North on the sketch based on a reliable compass reading. All of the windows to be filmed should be clearly indicated and labeled with a unique identification number which should be entered in the film decision table described next. If the project involves a one-story structure, the sketch can be presented on a single page. Use additional pages as necessary for large or multistory structures.

In addition, it is recommended that the film decision table be filled out. The film decision table presents a full description of each window identified with a unique number in the sketch of the proposed project. Indicate in the blanks provided the project name, the date, and the individual's name who is responsible for taking the data. This table incorporates different listings for items that relate to thermal stress fracture or insulating glass seal failures. There are a total of 17 entries in the table. The table should be filled out in its entirety for all types of windows to be filmed. The following discussions provide guidance for completing the table. The final entry in the table indicates whether or not it is recommended that film be applied to the window. If any entry in the table is unacceptable, the window film application should not be performed without consultation with the window film manufacturer.

Guide Topics

The following provides a brief commentary of the information that is to be recorded in the film decision table for each entry listed.

1. Window Number. Enter the unique number that identifies each window examined in the building.

2. Glass Type. Enter the type of glass being examined -- annealed or heat-treated.

3. Glass Color. Enter the color of the glass -- clear or tinted/coated. If the glass is tinted/coated enter the total solar absorption of the glass. If the glass color is tinted/coated and the total solar absorption is unknown, window film should not be applied.

4. Glass Construction. Enter the type of the glass construction -- monolithic, laminated or insulating glass.

5. Simplified Frost Point Test. Enter the results of the IWFA frost point test if the windows are insulating glass. The entry is either pass/fail.

6. Glass Thickness. Enter the thickness of the glass. Check the thickness against restriction presented in this document.

7. Window Size. Enter the area of the glass. The area of the window is required to determine when the window is larger than the guidelines for certain types of annealed and insulating glass products.

8. Framing System. Enter whether the window frame system is acceptable -- pass/fail. Factors involved in the evaluation of the framing system include edge bite, moisture conditions (whether or not moisture accumulates around insulating glass) as well as overall glass support conditions.

9. Moisture in the Glazing System. Enter whether the glazing system has moisture problems or not -- pass/fail. For insulating glass it is important to establish whether the system retains water or moisture in the vicinity of the glass edge sealants. If it does the glazing system fails.

10. Glazing Materials. Enter a brief description of the glazing materials used to provide perimeter support, cushioning, and sealing for the glass.

11. Condition of Glazing Materials. Enter whether the conditions of the glazing materials are acceptable -- pass/fail. The gaskets, sealants, and tapes should be investigated to determine if the glass product provides cushioning and thermal isolation around the perimeter. If these have deteriorated, the glazing materials fail.

12. Solar Exposure. Enter the direction of each window to the nearest quarter compass -- N, NE, E, etc.

13. Exterior Shading Condition. Enter whether the exterior shading conditions are acceptable or not based on discussions presented in this document -- pass/fail. Review all shadow conditions that can affect the window.

14. Interior Shading Device. Enter whether or not the interior shading device clearances are met as discussed -- pass/fail.

15. Glass Surface Condition. Enter whether or not the surface of the glass has obvious damage, scratches, or flaws, the surface of the glass is judged to be damaged -- pass/fail.

16. History of Glass Breakage. Enter the percentage of unexplained glass breakage for this type of window. If the percentage of unexplained glass breakage exceeds 1%, then film should not be applied to this type of window.

17. Final Recommendation. Enter whether or not window film should be installed for this type of glass based on the outcome of examination -- film/no film. If any of the previous entries are negative, or if any conditions noted are not acceptable based on discussions presented in this document the entry should be no film. Window film should not be applied to this type of glass without detailed consultation with the window film manufacturer.

Once it has been determined that the windows under consideration have no inherent or latent defects, the film manufacturer's guidelines and recommendations should be consulted for individual film types for the application