They are allowed to deduct value-preserving investments and energy renovations that save energy and protect the environment. For example, sanitary, plumbing, painting or carpentry work, heating maintenance, oil tank cleaning or washing machine repairs and gardening work, such as the replacement of perennial plants, are considered value-preserving. Energy-saving measures include new windows and doors, façade insulation and heat pumps. You can deduct the costs as a lump sum or the actual costs (with proof). The Confederation and most cantons allow a flat rate of 10 percent of the imputed rental value for newer properties and 20 percent for older properties. In addition to this, homeowners may deduct the premiums for building and building liability insurance and supplementary insurance. Condominium owners can deduct their contributions to the renewal and management fund of the owners association, provided they are used for value-preserving measures.