A coke oven of a horizontal construction of the non-recovery or heat recovery type is shown. The oven has at least one coking chamber, in which laterally vertical downcomers as well as horizontal bottom flues extend underneath the coking chamber for indirect reheating of the coking chamber. At least a part of the interior walls of the coking chamber is configured as a secondary heating source by coating it with a high-emission coating (HEB) that shows an emission degree equal to or higher than 0.9, and consists of the substances Cr2O3 or Fe2O3 or a mixture containing these substances, with the portion of Fe2O3 amounting to at least 25% by weight in the mixture, and with the portion of Cr2O3 amounting to at least 20% by weight in the mixture.