The window heating offset is a measurement error that is introduced by the heating of the CG 3
window by the sun. It only occurs during the day. During a sunny day, the upper CG 3 will suffer
from this. This error cannot be avoided except by shading or ventilating. On a sunny windless day
with a solar irradiance of 1000W/m2
, an error of 25 Watts per square metre can be expected. The
window will absorb part of the solar radiation and will heat up. As a result of this heating, heat will
irradiate towards the thermopile. This results in a significant error source, in the Infrared range. This
error is neglected, however, in the net radiation calculation This is justified because the solar
radiation is always dominant when this error occurs.