Occurrence of condensation on different surfaces depends on the temperature of surface and relative air humidity. The lower the surface temperature, the less air humidity is needed in order for condensation to happen. Condensation or ‘’dewing’’ can be avoided by using better insulated glass units (triple paned glass unit, better interpane spacer) or decreasing the relative air humidity of the room by ventilating it or by using dehumidifiers. Insulated glass unit (IGU) is in most cases composed of two or three panes whereas the space between the panes is filled with inert gas such as argon or krypton. Distance between the panes depends on the geometry of window profile, which limits the width of IGU. Distance between the panes is kept constant by interpane spacers which are installed on the edges of IGU. These glazing bars can be made of aluminium, combination of stainless steel and polymer materials, silicone foam or solid polymer materials. Thermal conductivity of the glazing bar depends on the material of which spacer is made of. This consequently affects the insulation of IGU edge which is the weakest part of IGU. If the thermal conductivity increases, thermal insulation decreases which leads to lower surface temperature on the edge of the glass which is crucial for the occurrence of condensation. In winter months, when the outside temperature drops below 0 °C, it is crucial if IGU has an aluminium spacer or spacer made of better material which are so called ‘’warm – edge’’ spacer. Nowadays it is not advised to use aluminium spacers as the warm-edge glazing bars are much better and easily accessible.