The annual passive-energy building congress, held in April this year in Bregenz, attracted more than 1,000 participants. The relevant technology has long advanced beyond the pioneering phase. The passive-energy building concept is based on a few clear principles: a compact volume with a high level of thermal insulation; the use of triple glazing; and the installation of ventilation plant with a heat- recovery facility. The low heating energy needs of such buildings allow those renewable sources of energy to be exploited that are regionally available. The congress was attended by architects, specialist engineers, contractors and energy consultants, as well as local government officials, product manufacturers and trade firms. Participants had to choose between a wide range of lectures, which took place parallel to each other in four halls over a period of two days. Ample space was also provided for an exchange of ideas in the large foyers between the halls.