The scope of the 2D g-value measurement application is to obtain the 2D-angular behaviour of complex fenestration systems. As an extension of the in-situ g-value device, a moveable 2D g-value measurement apparatus including a 2-axis movable mirror as well as a small horizontally rotatable measurement box, allows to measure instantaneous g-values under real sun conditions and definite incident angles. The sample probe of 0,6 x 0,6m is installed in the measurement box, which includes the controlled g-value device for measuring the resulting heat flux trough the sample.