Natural ventilation is the usual mode of ventilation of residential buildings. There is no fan. People think, this system has no energy requirements, but continuous air flow causes heat loss by ventilation. This energy consumption is higher then energy for controlled forced ventilation.

Author raises discussion and proposed changes in the rules of the energy audit. Draws attention to the criteria for evaluating alternatives and to small requirements for variability solutions. Read controversy of the author and reviewer who considers the methodology as sufficient and sees a problem in processing audits.

Water consumption in 2009 was significantly lower. Price of water in the CR is already in some regions the same as in Germany. Six of the ten water companies got in r.2009 checks penalty for wrongly calculated the price of water and sewage. Price increase is avoided.