The invention relates to a pressed composite heat-insulating board or panel to be used for low-cost manufacturing of insulating panels and consisting of: a) a standard building board or panel having a composite structure or not and forming a support (1) for the application of a layer on one or both sides; b) an adhesive layer (2) resistant to high temperatures; c) a layer of insulating material (3) consisting essentially of layer silicate and/or volcanic rock, especially vermiculite; and d) optionally a further layer of insulating material (4) consisting essentially of one or more finely distributed metal oxides and/or highly dispersed pyrogenic silisic acid and optionally one or more of the insulating materials listed under c). The invention also relates to methods for producing such boards or panels.