IAQ 2016 Defining Indoor Air Quality: Policy, Standards and Best Practices Co-Organized by ASHRAE and AIVC

Pressurization (Blower door) test is a well-established method, performed in order to quantify the total leakage in a building envelope. However, the Blower door results are not really adequate to use when air leakage through the building envelope during natural conditions (non-pressurized) is to be estimated. A common assumption made when estimating air leakage during natural conditions, is to assume that air leakage paths are evenly distributed in the areas of the building envelope. This assumption gives quite poor numerical model results since different leakage configurations are often situated unevenly in the envelope. In order to improve the correspondence between Blower door and air leakage model results, more information on the types and locations of the leakage paths are required as input to simulation models. This paper investigates if additional information from visual inspection and IR-thermography observations at site can increase the precision when estimating air change rates due to air leakage in natural conditions. A numerical model is developed in this study by allocating leakage in various parts of the building envelope. Leakage allocation is assessed by visual inspection and IR-thermography observations at site during the Blower door test. This procedure is tested in the case study of a large single zone church. Blower door and leakage allocation results are used in the numerical model. Model results are compared with tracer gas measurements.

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.

Since 2008, every measurement of building envelope airtightness performed in France in order to justify an airtightness value for EP-calculation has to be performed by a qualified operator. With the introduction of the French BBC-Effinergie label in 2007 which imposed a limit value for residential buildings airtightness, and then with the application of the current French EP-regulation (RT2012) which imposes those limits to all new residential buildings, the number of qualified operators has been increasing until almost 1,000 in 2015. Each year, those qualified operators fill a database which gathers now information about 90,000 airtightness measurements on residential and non-residential buildings. The Cerema is in charge of this database and performed each year some analyses of those data. It includes 39 fields about building general information (owner, location, use, year of the construction, year of the rehabilitation), special requirements (label, certification), building main characteristics (main material, constructional type, insulation, ventilation system, heating system), measurement protocol (operator, date of measurement, measurement device, time of measurement, method), measurement input data (envelope area, floor area, volume), measurement results (CL, n, qa4, n50, uncertainties) and classification of the leaks (46 categories). In a first part, this paper presents a study of the impact of the leaks distribution on the measurement result, depending on the main material of the buildings, the ventilation system and the insulation. In a second part, this papers proposes an evaluation of the impact of the season of measurement on the measured airtightness for several French regions with different climates, for wood constructions, concrete construction and brick construction. The last part of this paper presents a first analysis of the correlation between the n value and the uncertainties of the measurement result for single-family houses built according to the RT2012.

Infiltration is the ingress of ambient air under normal operating conditions through adventitious openings located in the façade of a building. The importance of reducing infiltration to save energy is highlighted by standards and building codes in many countries. The mean heating season, or other typical, infiltration rate is often inferred from a measurement of an air leakage rate at a pressure differential of 50 Pascals from a whole building pressurization test, often made using a blower door. A simple linear relationship between the air leakage rate and the infiltration rate (infiltration equals air leakage divided by 20) is sometimes assumed to exist and is known by many terms, such as the rule-of-20, leakage-infiltration ratio, Sherman’s ratio, or the Persily-Kronvall rule. The value of 20 is not always fixed, and can be adjusted according to a number of factors, such as building height, shielding, air leakage path size, and climate. The origins of this relationship have previously been unclear, which is problematic if a ratio is to be used with any confidence. This paper investigates the origins of leakage-infiltration ratios (LIRs) and shows that they emerged in the early 1980s from various studies (some unpublished) that measured airtightness and air change rates in a range of single-family dwellings and established empirical relationships between them. It is shown that there is no technical basis for LIRs, yet they are applied by building codes around the world and used to make policy decisions. There widespread use is likely a function of their simplicity, yet they have significant limitations. Accordingly, limitations their use are recommended and more complex alternative models are presented that can be used when more rigorous predictions of infiltration rates are required.