Many modern office buildings have highly glazed facades. Their energy efficiency and indoor climateis, however, being questioned. Therefore, when a modern office building (new construction) with larger glazing areas was planned, an investigation was carried out to determine the possibilities to:- efficiently use the increased access to daylight and thereby reduce the use of electricity forlighting and at the same time improve the visual comfort- ensure good thermal comfort- arrive at a reasonable total energy use, which is at the same level or preferably lower level than atraditional office building.The work was done by a project group that supported the design team with advanced energy, indoor climate and daylight simulations. Detailed performance specifications on energy use and indoor climate were worked out. The results show that the aims can be fulfilled if the following mainrequirements are fulfilled :- The glazing area should not exceed 45 % of the faade area.- The total solar transmittance of the glazing combined with solar shading must be lower than 0.1.- The U-value of the windows must be lower than 1.1 W/mK.A double skin faade was chosen. An important conclusion is that coordination and cooperationthroughout the building process is absolutely necessary. The building will be finished in 2007.