OT-88-07-1 -- Laboratory Determination of the Thermal Resistance of Glazing Units PDF

A test facility and procedures to determine the thermal characteristics of window products were developed at The Institute for Research in Construction (IRC), National Research Council Canada (NRCC). Initial work was conducted on the following types of glazing units:

- sealed double-glazed, clear glass
- sealed double-glazed with low emissivity coating on clear glass
- sealed triple-glazed, clear glass
- sealed triple-glazed with thin plastic film with low emissivity coating
- unsealed double-glazed without spacer

All units were tested to determine their thermal resistance (surface to surface R-value) at the following test conditions:

- room-side temperature: 21°C - weather-side temperature:
-7, -21, and -35°C, and some units were also tested at -14, -18, and -28°C.
- pressure difference across the test specimen was kept less than 3Pa.
- weather-side airflow was perpendicular to specimen.

Overall heat transmission coefficients (U-value) are also provided combining the surface heat transfer coefficients, as recommended by ASHRAE, with the R-value determined for each speclmen. Although there is at present no standard test procedure for the determination of the overall coefficient of heat transmission (U-value) sealed units, these test results indicate the relative performance of the samples tested.

The experimental results of some of the specimens are compared with values predicted using the computer program VISION developed, through NRCC, to evaluate the thermal performance of glazing systems.

Units: SI