For a transparent meeting centre at the Green Village of TU Delft, the Co Creation Centre, a large air-to-air PCM battery was integrated in an air handling unit. Based on the experiences with this battery, a new battery was applied in an office building, the Office Lab. Both buildings were used as research facilities. The PCM uses of outdoor and indoor temperatures such as a flexible thermal mass with a high thermal capacity, flattening high and low indoor temperature peaks. In case of very warm of very cold outdoor night temperatures the battery can additionally be loaded with a heat pump. In this way the thermal and electrical capacity of the heat pump can be reduced significantly as well. The battery can be an economic and energetic favourable alternative. Additionally, there is a water-to-PCM battery in the crawl space with the same kind of panels. In the heating season heating energy from the heat pump with a higher temperature can be stored, making use of low, zero or negative electricity prices via solar panels or the grid. A thermal battery can reduce grid congestion as well. The performance of the PCM-batteries is evaluated with a CFD-program (Phoenics), a building simulation program (Design Builder), and additional calculations and measurements as far as possible.