STM offers energy-saving and environmentally friendly solutions in Timber, Alu Clad and Oak.



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STM manufactures windows that meet the strictest statutory requirements - A-rated

The windows are one of the building materials that have historically caused the greatest loss of heat in buildings. That’s why it’s important to choose the right energy class for your home.


The heat loss through windows and doors is calculated in U-value and is an expression of the energy that passes through 1 m2 of a part of the building per second at 1 degree between outdoors and indoors and is denoted as W/m2K. The U-value can be up to 6.0 W/m2*K, which is very high compared to an insulated building. The best windows have 3-layer energy glass with low energy loss of under 1 W/m2*K.


The G-value is an expression of free heat. It says how big a part of the solar energy that hits the glass outside passes through the pane and into the room. The G-value is a figure between 0 and 1 and the higher the G-value, the more free heat comes into the room.