Field Evaluation of Windows

Last Updated: 10/20/2009

Various tools can be used to evaluate windows in the field. Unless a new window still has the NFRC label attached to it, it is nearly impossible to determine by sight what the thermal and optical performance of a window is. These tools can provide information, such as low-e coating, gap width and gas fill,  that can be used to approximate the performance of a window.

 

Solar gain and Low-e detector

This device can be used to determine if a low-e coating is present in the window, what type of coating it is, and where it is located. The type of low-e coating will indicate the amount of solar gain that is admitted through the coating. Readings can be "low", "medium" or "high". The device will also indicate on which glass surface the low-e coating is in relation to the position of the device. Limitations: Only works on glass of 1/8" (3 mm) or thinner. Cost: around $350 from EDTM.com
  Glass and air space thickness meter

Two versions of this device exist, one is a ruler which visually shows the thickness of the air gap and glass by laser reflections, the other device has a digital readout. These devices can also be used to measure at various locations on the window surface to determine deflection. When glass panes are deflected in, the resulting air or gas space is smaller, which reduces the U-factor. These devices cost $550-$750 depending on the model. They are available from FDR Design and EDTM.com
Gas concentration detector

This device can measure the concentration of argon or krypton gas in a glazing unit, without destroying the glazing unit. Initial gas fill for new windows ranges from 90-95%, and this device can verify the current gas concentration. Limitation: only produces accurate results for gas fills >50%, only works when the low-e coating is on the other pane. Cost: around $12,000 from FDR Design or SparkLike

With help from the above listed devices, the following parameters can be determined:

By using the WINDOW5/6 program the user can generate a window system, based on the parameter, and estimate a U-factor and SHGC.