A framework for integrating indoor air quality into the life cycle assessment of buildings: application to the sizing of ventilation rates
Résumé
Abstract Purpose Life cycle assessment (LCA) methods are used in building ecodesign, but do not currently consider indoor air quality (IAQ). Since we spend about 85% of our time indoors, and are exposed to potentially hazardous substances, IAQ is of particular importance to human health. Its consideration in LCA could help make adequate design choices (e.g. materials, window layouts or ventilation rates) and reduce the building’s impacts, while avoiding their transfer to other life cycle stages. Methods To address this gap, we propose a methodology combining building LCA and models that encompass the whole pollutant pathway, from emission to quantified impacts on human health using the disability-adjusted life years (DALYs) indicator. We account for volatile organic compounds (VOCs) and fine particulate matter (PM 2.5 ), emitted from materials and indoor activities. An optimal ventilation rate allowing to reduce overall IAQ and LCA impacts (namely from energy for space heating and ventilation fans) is identified. The framework’s applicability is demonstrated on a case study: different rooms having distinct uses, occupancy and activity patterns, lead to different emission rates, impacts and optimal ventilation rates. The influence of heat sources (gas, electricity, wood) on optimal rates is assessed and different window layouts for natural ventilation are tested. Results and discussion PM 2.5 and heating are the main sources of impacts, respectively ranging from 40–94%, and 1–31% of total impacts of each room, which range from 2500 µDALY/year to 14200 µDALY/year. Rooms with higher indoor emissions have higher optimal ventilation rates: 1.2 ACH (air changes per hour), 2.9 ACH and 13.2 ACH in the meeting room, office and kitchen respectively. These rates also vary for different heat sources due to their different IAQ and LCA impacts: 2.7 ACH, 5 ACH and 15 ACH for coal (still a common fuel in rural Asian countries), gas and electric fan heating respectively in the living room. The combined use of double-flow ventilation to lower heating needs and filters that reduce PM 2.5 concentrations leads to a 56% decrease in total impacts of the meeting room. Conclusions This study shows the applicability of the framework to building ecodesign. For instance, distinct optimal ventilation strategies can be devised, depending on the room or building use. The framework can also have a regulatory application in public health, through representative archetypes, by providing general recommendations in the tertiary and residential sectors.