Methodology for the characterization of the envelope airtightness of the existing housing stock in Spain
Poza-Casado, Irene; Feijó-Muñoz, Jesús; Padilla-Marcos, Miguel; Meiss, Alberto.
It has already been proved that air leakage causes a great impact in the energy performance of buildings in cold climates. In recent years, many studies have been carried out in northern Europe, US and Canada. Regulations in these countries establish maximum air leakage rates for the construction of new dwellings and the refurbishment of the existing ones. However, there is a lack of knowledge relating to the housing stock in Spain. In temperate climate countries, air leakage has traditionally been part of natural ventilation. On the one hand, current Spanish building regulations (CTE) establish controlled ventilation in dwellings to ensure indoor air quality (IAQ). On the other hand, air leakage is only considered concerning windows characteristics. Ventilation rates are calculated based on ideal airtight envelopes. Therefore, problems of over-ventilation, uncontrolled air flows, poor indoor air quality and energy consumption are caused. A national research is being accomplished within INFILES project (2016-2018), where nine Universities on different locations are participating with coordinated field measurement campaigns. The dwellings to be tested were chosen by establishing a nonprobability statistical sampling method. With the aim of representing the major characteristics of the Spanish housing stock in the most reliable way, a proportional quota sampling scheme was designed: as a consequence, 411 tests are being carried out in order to characterize the airtightness of the construction system of the envelope and to determine typical air leakage paths in dwellings. Stratification was performed with real data by taking into account different variables which have been proved to be relevant concerning airtightness: climate zone, year of construction and typology (single-family houses or multi-family buildings). The air leakage rate is being determined using a standardized building pressurization technique, in accordance with UNE-EN 13829 and ISO 9972:2006 regulations. Typical air leakage paths are determined using infrared image technique. A specific software has been developed to retain dwellings characterization data: location, year of construction, typology, size, height, construction technology, property developer, retrofitting state, window area, energy systems, and others, up to a total of 140 parameters. The aim of the project is to develop a wide database with representative samples of residential buildings in Spain. In this way, it will be possible to relate the main factors that have an impact on airtightness. The main objective is to know ventilation rates due to air leakage and its energy impact in order to design guidelines with real data, which is obtained from the tests. A subsequent control regulation proposal for the envelope airtightness will be developed. Consequently, Spanish regulations will be consistent with European directives.
Palabras clave: Air leakage; residential buildings; fan pressurization test; Blower Door.