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Surface #1 is facing outside, surface #2 is the inside surface of the exterior pane, surface #3 is the outside surface of the interior pane, and surface #4 is the inside surface of interior pane. The window frame is labelled #5, a spacer is indicated as #6, seals are shown in red (#7), the internal reveal is on the right hand side (#8) and the ...
The above equation only takes into account the temperature differences and ignores two important parameters, being 1) solar radiative flux; and 2) infrared exchanges from the sky. The concept of T sol-air was thus introduced to enable these parameters to be included within an improved calculation. The following formula results:
R-value is the temperature difference per unit of heat flux needed to sustain one unit of heat flux between the warmer surface and colder surface of a barrier under steady-state conditions. The measure is therefore equally relevant for lowering energy bills for heating in the winter, for cooling in the summer, and for general comfort.
The difference in temperature between the inside and outside of the building is at least 5 °C (9.0 °F). The weather is cloudy rather than sunny (this makes accurate measurement of temperature easier). There is good thermal contact between the heat flux meter and the wall or roof being tested.
A European standard (EN 673) uses 20 °C difference between the inside and outside temperature which results in an optimal simulated gap width of about 17 mm for a standard double glazed window. A US standard (NFRC) uses a 39 °C difference which yields a smaller optimal gap width of about 13 mm.
Process window index (PWI) is a statistical measure that quantifies the robustness of a manufacturing process, e.g. one which involves heating and cooling, known as a thermal process. In manufacturing industry, PWI values are used to calibrate the heating and cooling of soldering jobs (known as a thermal profile) while baked in a reflow oven .
Shading coefficient (SC) is a measure of thermal performance of a glass unit (panel or window) in a building. It is the ratio of solar gain (due to direct sunlight) passing through a glass unit to the solar energy which passes through 3mm Clear Float Glass. [ 1 ]
The first of the cooling load factors used in this method is the CLTD, or the Cooling Load Temperature Difference. This factor is used to represent the temperature difference between indoor and outdoor air with the inclusion of the heating effects of solar radiation. [1] [5] The second factor is the CLF, or the cooling load factor.