Improved energy efficiency of the buildings is the most cost effective measure in mitigation of CO2-emissions. Improvement of thermal insu- lation level of the building envelope is one of the possible measures in both cold and warm climates. Integrated life-cycle design of build- ings is responsible for a number of issues affecting the sustainability of a building, e.g. energy efficiency, healthy indoor climate, life-cycle emissions and costs, service life, and quality. Good and healthy indoor condition is the target for designing and delivering buildings. Moisture damages are one of the main causes deteriorating the indoor air quality. Mould growth index is a tool for assessing mould growth risks in building structures. Connected to dynamic moisture calculations the tool can help designers to make the right choices in design for better energy performance.