The aim of this study is to define several methods that enable to estimate the heat exchanged in the different components of an air handling unit (AHU), and propose control strategy optimizations. The AHU studied is a part of a low energy office building located in Norway. The focus is especially made on its rotary heat recovery system, its heating/cooling coil and its heating coil. The data of one month recorded by the building energy management system (BEMS) have been used. The heat exchanged estimation methods presented in this paper are based on heat balances, valve positions and heat exchangers number of transfer unit (NTU). Comparison of the results obtained with the different methods outlined a poor quality of the valves positions signals. This fact has also been confirmed using a statistical method, the principal component analysis (PCA). Because of this issue, the methods proposed have not been validated. Regarding control strategy optimization, the use of a heat exchanged estimation method is required. The estimation method based on NTU has been used as reference, since this method does not use the valves positions signals. The goals of control strategy optimization are to reduce the energy costs and the CO2 emission. The proposed improvements are based on a new distribution between components of input heat, regarding the specific energy cost and CO2 emission of components. The tested optimizations gave better results that the current control strategy, but since the method used as reference has not been validated, these conclusions have to be confirmed after a resolution of the valves positions signals problems.