The paper deals with risk analysis of insufficient airtightness of the envelope construction. The risk analysis is a systematic and structured data processing to identify potential hazards. The main aim of paper is to qualified risks which arise from the danger, i.e. insufficiently airtight of the building envelope. The quality of airtight building envelope except for low energy consumption also minimizes the risk of damage to the structure associated with the spread of the heat, water vapor in the structure and fungal growth. The qualification of risks consists of choice of method and determinative indicators, input data and simulation of model with drawing results.