A modular fire proof cold room wall arrangement to be formed between - a first module having at least a first module end formation and - a second module having at least a second module end formation to join them together at said first module end formation and said second module end formation at a mutually compatible mating face, comprising in each said first and second module (100a, 100b), between respective two metal foils (103, 105) a therebetween (103,103; 105,105) laminated thermal isolation material layer,, wherein at the mating face it comprises, - at said first module end a line formation with a protruding member at a first side of said first module to be joined, - at said second module end a line formation with a recessing part at a second side of the second module to be joined, wherein the protruding member at the first module end formation and the recessing part at the second module end formation have such a mutually compatible formation pair to form a matching pair (106p, 106r) so that the protruding member is dimensioned (r, p, α, β) to fit into the recessing part at the mating face, characterized in that at the first module a first module end formation at the mating face comprises - a first metal foil part with its length (n) at the protruding member at a distance (d) from an aligning metal foil at the opposing side of the first module end formation, and - a second metal foil part (105c, 105b) of the metal foil partly being twisted into a deepness (k) into the isolating material by the length (k) of a part of the metal foil part (105b, 105c) and in that at the second module a second module end formation at the mating face comprises - a third metal foil part with its length (n') at the recessing part and - a fourth metal foil part (103a, 103b) of the metal foil, partly being as twisted into a deepness (m') into the isolating material by the a length (m') of a part of the metal foil part (103b, 103c). - a first module having at least a first module end formation and - a second module having at least a second module end formation to join them together at said first module end formation and said second module end formation at a mutually compatible mating face, comprising in each said first and second module (100a, 100b), between respective two metal foils (103, 105) a therebetween (103,103; 105,105) laminated thermal isolation material layer,, wherein at the mating face it comprises, comprising in each said first and second module (100a, 100b), between respective two metal foils (103, 105) a therebetween (103,103; 105,105) laminated thermal isolation material layer,, wherein at the mating face it comprises, - at said first module end a line formation with a protruding member at a first side of said first module to be joined, - at said second module end a line formation with a recessing part at a second side of the second module to be joined, wherein the protruding member at the first module end formation and the recessing part at the second module end formation have such a mutually compatible formation pair to form a matching pair (106p, 106r) so that the protruding member is dimensioned (r, p, α, β) to fit into the recessing part at the mating face, characterized in that at the first module a first module end formation at the mating face comprises wherein the protruding member at the first module end formation and the recessing part at the second module end formation have such a mutually compatible formation pair to form a matching pair (106p, 106r) so that the protruding member is dimensioned (r, p, α, β) to fit into the recessing part at the mating face, characterized in that at the first module a first module end formation at the mating face comprises - a first metal foil part with its length (n) at the protruding member at a distance (d) from an aligning metal foil at the opposing side of the first module end formation, and - a second metal foil part (105c, 105b) of the metal foil partly being twisted into a deepness (k) into the isolating material by the length (k) of a part of the metal foil part (105b, 105c) and in that at the second module a second module end formation at the mating face comprises - a third metal foil part with its length (n') at the recessing part and - a fourth metal foil part (103a, 103b) of the metal foil, partly being as twisted into a deepness (m') into the isolating material by the a length (m') of a part of the metal foil part (103b, 103c).