Murkka Primus Fixed is a closed wood-aluminium window with an aluminium external sash. The advantage of closed windows is the possibility to build large sized windows.
Heat retention:
U-value of standard glass is 0.89
U-value of special glass is to 0.82 (VTT estimated, size 1230×1480)
Sound insulation:
Rw = 32-41 dB, Ctr = 27-37 dB