The insured value of works of art is determined by their market value. The market value is the amount needed to buy a replacement of the same grade.
If an insured item increases in value, the increase is insured in the current year. If an artwork loses value as a result of damage, the insurance replaces the reduction in value.
No, household contents insurance does not comprehensively insure your artworks. In order to protect your valuable art collection against all risks we recommend that you take out separate art insurance.