Building leakage analysis and infiltration modelling for an Italian multi-family building

Abstract

The presented paper aims at detailing the results of an investigation that was recently conducted in Italy to evaluate the contribution infiltration makes to meeting ventilation needs in a recently renovated apartment building and the corresponding energy costs. It is years that increasing importance has been placed on the energy efficiency in residential buildings as about 70% of the existing Italian residential building stock was built before 1976 (i.e. before any measure related to the energy efficiency in buildings). As existing dwellings have been traditionally considered ‘leaky’, the actions for improving their energy efficiency have often determined tighter buildings, raising concerns about whether the amount of infiltration is sufficient to provide occupants with acceptable indoor air quality (IAQ). The current state of knowledge on infiltration in multi-family buildings in terms of measuring procedures, corresponding air change rates and airflow patterns was reviewed. The air tightness of a three-storey, six-unit, multi-family building which can be considered representative of the existing recently renovated Italian building stock was characterized by means of a series of fan pressurization tests. The performed blower door tests are documented and results of the data analysis are reported and discussed. A simulation model was developed; simulations were performed to analyse in detail the winter magnitude of air infiltration. Winter is usually detrimental to IAQ, as severe outdoor weather prompts occupants to keep closed any opening that could allow cold drafts into their homes. Modelling results were validated on the basis of a 3-week monitoring campaign. The developed model enabled to estimate the variation with time of infiltration rates and therefore the influence of infiltrating air on the resulting heat loss and IAQ. Numerical predictions were derived using the EnergyPlus simulation tool which allowed to combine whole building thermal simulation and detailed multi-zone airflow modelling. Results show that, during the considered heating season (October–April), the average air change rate due to infiltration was approximately 0.1 h−1. It was concluded that infiltration cannot be relied upon to provide adequate ventilation air and, if not assisted by other means of ventilation, IAQ deterioration is likely to occur.