Superimposed on the solar spectrum are 4 curves representing the performance of 4 different insulated glass types. Everything falling below the curve is transmitted through the glass. Note that all glass blocks the very short wavelength radiation below 300 nm.

There is also heat contained within the visible part of the spectrum admitted along with the daylight. However, the low solar low-E is formulated to admit the daylight (and its associated heat) while rejecting the near infrared radiation which contains heat but NO daylight.

The black dashed line represents CLEAR insulated glass. It transmits a high fraction of UV and daylight and near infrared solar heat. The green dotted line shows TINTED glass, which cuts UV, drastically blocks daylight, and also reduces significant near infrared heat.

The yellow line represents LOW SOLAR heat gain low-E glass which greatly cuts UV, maintains high visible light levels, and blocks the great majority of near infrared solar heat.

The blue line represents NORTHERN low-E glass designed for colder winter climates. It reduces some UV, allows high daylight transmittance, but does not block nearly as much solar infrared heat. It is useful where there is little cooling load and a desire to utilize as much solar heat as possible to warm the house.