This bachelor work is focused to design low-energy family houses or passive houses where traditional heating or cooling system are not present and energy consuption is close to zero. The other solved issue is water vapour diffusion through the house walls. This work considers the draft of the family house with vapour diffusion open walls study in details. Construction details were evaluated by software AREA (“Building phisics“ software package).The end of the work considers energy consuption of the house by ISOVER software Project evaluation.The goal of the work was family friendly to enviroment house design.