An electric kiln for firing ceramic pieces, comprising a succession of modules (M), each comprising an upper roof structure (Z1), a lower floor structure (Z3), and two opposite side wall structures (Z2); wherein the three structures (Z1, Z2 and Z3) include various insulating materials for the purpose of maintaining the internal temperature within a firing chamber (C), along which a motorised roller conveyor (16) runs which is located within a firing chamber (C); and wherein above and below the motorised roller conveyor (16) within the firing chamber (C) a heat system is applied to raise the temperature; characterised in that: - the upper roof structure (Z1) comprises at least one upper insulating body (1) formed by a folded and pressed ceramic fibre blanket which is formed by a ceramic fibre material with elongated threads; where this entire folded and pressed package of the ceramic blanket is nailed and fastened to a metal frame (2); where lateral ceramic fibre plates (3) are fixed on two opposite sides of the roof insulating body (1); and where this entire assembly of the metal frame (2) with the ceramic fibre blanket (1) and the lateral ceramic fibre plates (3) is located under an upper enclosure (5) located above the metal frame (2); - each of the two side wall structures (Z2) comprises a lateral insulating body (1') also formed by a folded and pressed ceramic fibre blanket; where the two lateral insulating bodies (1') include longitudinal recesses (23) on which end sections of the assembly of the insulating body (1) and the two lateral ceramic fibre plates (3) of the upper roof structure (Z1) rest; and where each lateral insulating body (1') is fixed to a side frame (2'); - the lower floor structure (3) comprises a horizontal floor structure (6') formed by refractory bricks, and two side walls (6) on both opposite sides which are seated on the horizontal floor structure (6'); where said side walls (6) comprise layers of refractory brick and outside these at least several side plates of ceramic material; - the heating system comprises electrical resistors (12) coupled around two groups of tubular ceramic rollers (13) above and below the motorised roller conveyor (16); where end sections of the ceramic rollers (13) are coupled in pairs of aligned holes (20, 21) which are located in the two side walls (6) of the lower floor structure (Z3), and in the lateral insulating bodies (1') which form part of the two opposite side wall structures (Z2); - the motorised rollers (16) of the conveyor are coupled by their end sections in holes in two opposite longitudinal alignments of perforated bricks (19) which separate the lateral insulating bodies (1') from the side wall structures (Z2) and the side walls (6) of the lower floor structure (Z3). (Machine-translation by Google Translate, not legally binding)