Experimental Study of Multizone Air Leakages in Low Energy Houses

As airtightness is recognized as an essential issue for low energy dwellings, it is nowadays generally included in EP (energy performance) calculations, often through single zone models with uniform air leakage. Because more consideration is often given to energy performance than to indoor air quality issues, air leakage through internal partitions is often disregarded. In order to confirm or infirm such simplification, additional studies are needed. Therefore in the present study air leakage through building envelope and through internal partitions is investigated. Firstly, the paper describes the experimental study, conducted in order to measure multizone air leakages, using the guarded zone pressurization technique. Air leakages of 695 external and internal walls were measured on 28 detached houses with different levels of envelope airtightness. Envelope airtightness varies between n₅₀=0.5 and 8.8 h^-1, with a majority of values under n₅₀= 2.1 h^-1. Secondly, the paper presents the database, which includes for each internal or external wall: building general information, special requirements, building main characteristics (main material, constructional type, ventilation system, insulation type, number of levels, envelope airtightness), measurement protocol, type of wall, measurement input data (altitude, wind velocity, temperatures, area, volume), measurement results (C_L, n, q₅₀, as well as uncertainties). The paper presents in a third part a first analysis of this new database, in order to find most important relationships. For instance, internal and external envelope airtightness levels are not connected: we can obtain high internal leakage with an airtight envelope and respectively, building construction techniques have more influence. As a perspective, the paper concludes with on-going developments concerning another numerical multizone study using these new data. Through these studies, we underline the impact on building airflows of a fine modelling of internal and external airleakages, with consequences on IAQ-bedrooms where people stay the most part of their time.