TN 27: Infiltration and Leakage Paths In Single Family Houses - A Multizone Infiltration Case Study

This document describes preliminary work towards validating models that predict airflow rates between several zones. It is preliminary in the sense that it examines the quality and definition of physical data needed for a more testing and thorough validation. The exercise has used a version of the multi-zone computer model developed by Walton at the National Bureau of Standards with some modifications to the treatment of wind pressure coefficients. The experimental data consisted of airflows between the subfloor, living space, and roof space zones for five single storey houses, together with air leakage rates from outside. There were approximately 300 data points supported with climatic data measured on site, and individual zone airtightness data. Satisfactory agreement was generally achieved between measured and calculated infiltration rates in each of the three zone types. The most uncertain components of input data were the wind pressure coefficients and the distribution of leakage openings to different parts of the building. Literature values for pressure coefficients and a simple area-based rule for allocating leakage openings to different surfaces was followed. In many cases, calculated inter-zone airflows were similar to measured airflows and in others, better definition of inter-zone airflow characteristics was clearly necessary.