A heating device equipped with a chamber defining a cavity, includes a door or wall incorporating a triple glazing including three transparent substrates defining, from the interior to the exterior of the cavity, faces numbered 1 to 6 respectively, at least the faces 1 and 2 of the first substrate and 3 and/or 4 of the second substrate being covered with heat-reflecting coatings, wherein the mean spacing e1 between the first substrate and the second substrate and the mean spacing e2 between the second substrate and the third substrate is different, the ratio between the largest spacing and the smallest spacing being greater than 1.1, and e1 and e2 being between 2 and 20 mm.