Concrete is after water the second mostly used material and the most widely used construction material in the world. The production of cement creates more than 7% (calculated from WBCSD data) [7] of worldwide man-made $CO_2$ emissions. Therefore optimization of concrete structures can lead to the significant environmental savings. Experimental investigation and case studies performed by authors in the frame of long term research, focused on environmental optimization of building structures, support the expectation that it will be possible to reach factor 3 or even more through utilization of high performance concrete (HPC) while keeping structural reliability on the needed high level. Developed structural concepts have been proved not only by theoretical and experimental results, but also by practical application in construction of several buildings. Paper presents three case studies - ribbed / waffle floor structure with minimized thickness of upper deck to 30 mm, light precast RC balcony element and light precast RC frame for passive house.