permeability

Resulting from experiences of a project by the German National Energy Research Foundation (NEFF), and further investigations, a recommendation is presented on the permeability of building envelopes in residential buildings, according to on hand ventilation devices. To find out the permeability, the air leakage at 50 Pa is evaluated. This can be found out with the differentiated pressure reading of the building.

Studies the direct coupling of ventilation heat and solar gains to increase the performance of passive solar systems. Examples of particularly suitable buildings are described. The thermal model FRED, based on a thermal resistance network representing a three-zone building, is modified to include a simple airflow model driven by wind speed and temperature difference. The simulated building is ascribed symmetric permeabilities, then asymmetric permeabilities.

The R-values of permeable insulation systems are generally determined in test apparatus designed to assure one-dimensional heat transfer and to assure no air intrusion effects. Such classical R-values are used to help describe insitu heat-tra

Studies the effects of permeability on the wind loading on a building. Compares experimental results from wind-tunnel tests with theoretical methods for estimating the mean and fluctuating internal pressures for various permeability. Observations show that the internal pressure can be estimated from known external conditions in terms of mean RMS and spectral values to a reasonable level of accuracy for the case where the permeability consists of circular apertures. Effects on the external pressure distribution due to permeability are found to be significant under certain circumstances.

Calculations show that natural ventilation exploiting wind and specific gravity differences may reduce the need for ventilation heat. This is not done as usual by ventilation through open doors and windows but through fine porous air-permeable outside walls. The optimum thickness of the heat insulation layer is defined, giving maximum saving of total heating and ventilation energy.

This work deals with different aspects of air movements in building components. The investigation shows to what degree the concept of fluid mechanics can be applied to problems concerning air flows in building componenets. The applicable parts of fluid mechanics are presented as thoroughly as possible. Based on this concept, routines are outlined to make it possible to handle complex flow and pressure distribution problems. Both manual and computer calculation routines are described and the way they can be used is demonstrated in a number of examples.