The main purpose of the model is that it is supposed to be used in future evaluation of buildings and to be an easy to use tool for aiding decisions. Life cycle economics is about mixing capital costs with future costs. Life cycle economics is usable when calculating over short time periods or someone building for its own management. The models used in life cycle economics are suitable for calculation in Microsoft Excel. The future is uncertain, thatÌs why uncertainties should be added into life cycle economics. By adding Monte Carlo simulation its possible to use uncertainties in calculations and get results with probabilistic outcome.