A curable epoxy resin composition of an epoxy resin (a) and a combination (b) of an antioxidant (b1) and a UV absorber (b2). The UV absorber (b2) is a benzotriazole. The antioxidant (b1) is a compound of general formula I: wherein: R1=—H, —OH, —O—C1-18 alkyl, —C1-18 alkyl, —C5-12 cycloalkyl being unsubstituted or being substituted with C1-6 alkyl or C1-6 alkoxy, or —CH2—C5-12 cycloalkyl being unsubstituted or being substituted with C1-6 alkyl or C1-6 alkoxy; R2,3,4,5=independent from each other —C1-6 alkyl; and R6=a bivalent aliphatic, cycloaliphatic or aromatic residue. The weight ratio of (a) to (b) is from 90.0:10.0 to 98.5:1.5, with the proviso that the weight portion of (b1) is at least 0.5. The cured product has very good weather resistance after curing by polyaddition with a polycarboxylic acid anhydride or by homopolymerization. The cured product is suitable as an electrical insulation material.