Window Energy Efficiency: Solar Heat Gain and Visible Transmittance

By | 2017-11-21T12:51:26+00:00 April 4th, 2016|Mechanical Engineering, Thermal Management|

Conduction and Radiation of Thermal Energy In my last blog post, I wrote about the conduction and radiation of thermal energy through windows and the thermal transmittance value, called the U-Factor, that characterizes that heat transfer.  The U-factor is useful in evaluating window performance and making wise decisions when specifying components for a building, but it is only one piece of the puzzle.  The National Fenestration Research Council (NFRC) mandates a second value alongside U-factor in its certification process, called the Solar Heat Gain Coefficient (SHGC).  SHGC represents the ability of a window to resist [...]

Window Energy Efficiency: Thermal Transmittance

By | 2017-11-07T15:14:36+00:00 March 30th, 2016|Mechanical Engineering, Thermal Management|

Figure 1: Windows catching sunlight By Magda S [FreeImages.com Content License] In our last blog post, I wrote about the thermal resistance (R-value) and transmittance (U-factor) of insulation and windows.  The R-value represents how well a material prevents heat transfer through its thickness, and U-factor is its inverse, representing how much heat a material will conduct through.  These values are fairly simple to calculate for most building materials materials like the bricks and panels in Figure 1, as they primarily experience only conductive heat transfer.  Windows are a more challenging proposition, however, since the heat transfer through them [...]