Optimization of the airtightness and the flow rate of air in nearly zero energy buildings

The control of heat losses, inwards/out, in nearly zero energy buildings is of high importance. The transmission losses through the building envelope are easily reduced using larger amounts of insulation. Calculation of the impact of this action on the total energy demand of the building, is quite standard. It’s however much more difficult to determine the efficiency of actions to increase the airtightness of the building and the influence of the ventilation system. A valid model for these calculations is important, as the calculation of intelligent ventilation systems is much more complex due to constant air flow rate changes, which depend on the occupancy. The flow rates fall back to the hygienic minimum when no occupancy is detected, thereby reducing heat losses and lowering fan consumption. The investment cost for the ventilation system management however, increases. This paper focusses on the optimization of these two objectives using a case study.

As first result a cost optimal solution for the project is achieved, lowering the energy consumption and reducing the investment cost of the building, due to the adjustment of the ventilation parameters and the building parameters. As second result the cost optimization, combined with dynamic simulation, learns that no extreme airtightness is needed to achieve a nearly zero energy building.