The only guarantee of quality may be the presence of manufacturer's "Voluntary certification (manufacturer of doors shall not be subject to compulsory certification). – Warping. Quality doors are not subject to warping (above normal), even under the most barbaric conditions. For example, when the summer heat in an urban high-rises temperature "scale" for the 40 and the humidity drops to 20%. The quality of sound insulation door. (The index of airborne sound insulation). As well as the thermal insulation (thermal resistance) and breathability.
All these features are optional and are described in the relevant snip. For door of the main practical value is "index of airborne sound insulation. What does this mean in practice? For example, you put a child to bed, closed his room door, and can lead a full life or communicate in a whisper and walk on tiptoe. Or another example: the sound of a toilet room you let the household and guests of a pleasant conversation. From what depends on: – From what made the door leaf. Very good performance in special noise-reducing doors, more conventional. Panel paintings with a solid filling in special extruded chipboard, paintings on panel with the filling of honeycombs. The door to the completion of honeycomb insulation index essentially depends on the size of applied cells.
Cell with a cell size 13h13mm. provide acoustic insulation equal to paintings with a solid fill. The worst indicator of panel doors made of pine. She is being well dried, still resonates in some parts of the sound spectrum.