Marc Abadie

Indoor particle pollution: effect of wall textures on particle deposition

Abstract The aim of this study is the experimental determination of deposition constants for several wall textures in order to predict indoor particles concentration. Experiments involved the injection of spherical particles (0.7, 1.0 and 5.0 μm in diameter) in a cubic box whose internal faces are covered by the texture to be tested. Global constants of deposition are determined by regression fitting of the concentration exponential decay curves. Deposition constants are deduced for each orientation from the Crump and Seinfeld theory (J. Aerosol Sci. 12(5) (1981) 405). This decomposition method has been tested for 5.0 μm and then been extended to smaller particles.

Cool roof and ventilation efficiency as passive cooling strategies for commercial low-rise buildings – ground thermal inertia impact

Commercial low-rise buildings are often characterized by weak energy performances, and heat transfers through roof and ground are prevalent. The roof design and its opening system is a key factor of the thermal performance. Skylights and radiative properties of roof coating have a direct impact on solar gains, thermal losses and natural ventilation potential. The overall performance depends on the combination of these design parameters (solar reflectance and opening size), on the weather conditions and on the inertia given by the slab on the ground. The roof design performance depends on the ground which determines the dynamic behavior of these buildings. A generic case study is modeled and an extensive parametric study (about 840 annual simulations) is performed to point out these key parameters’ impacts on energy demand and comfort. The combination of efficient roof techniques (skylights and cool roof) along with a high thermal inertia of the building can be an adequate passive cooling solution in summer, with a 99.8% drop in degree-hours above the discomfort temperature in summer. Nevertheless, we show that these passive strategies could not be totally efficient without taking care of the ground thermal inertia which account up to 58.6%.

Comparative Analysis of Response-factor and Finite-volume based Methods for predicting Heat and Moisture Transfer through Porous Building Materials:

Many of the now well-known building energy simulation programs use the response factor method developed in the early 1970s by Stephenson and Mitalas. These are TRNSYS, EnergyPlus, Blast, and DOE-2, to name but a few. Others, such as PowerDomus, ESP-r, and BSim, perform finite-volume or finite-difference calculations to solve the heat and mass transfer through the building envelope. These two different approaches are known to have strengths and weaknesses. The main objective of the present exercise is to compare the prediction of both methods. A two-step procedure is employed here. The first deals with the pure thermal problem, i.e., without moisture calculation. Three different cases of increasing complexity are studied and compared to analytical solutions. The second step focuses on the moisture problem alone by comparing the responses obtained with a two-layer buffer storage model and a finite-volume discretization for moisture transfer. Results show that time step values are determinant even for pure thermal cases where the classical value of 1 h can lead to notable errors. For problems with moisture sorption in the wall, it has been shown that grid refinement is a very decisive parameter, while the time step has to be set, to unusually small values, to achieve a good response.

PANDORA database: A compilation of indoor air pollutant emissions

Modeling indoor air quality (IAQ) in real buildings still remains difficult because of the limited data regarding the pollutant outdoor concentrations and indoor sources. The characterization of indoor sources is currently problematic, as most of studies have focused solely on measuring indoor concentration levels instead of determining the source emission rates that are required to model the indoor concentration changes with time. The present work aims at compiling the available data regarding the emission rates of both gaseous and particulate pollutants in a systematic way into a unique database called PANDORA (a comPilAtioN of inDOor aiR pollutAnt emissions) to provide useful information for IAQ modelers. In addition to the presentation of PANDORA, the elaboration of a target volatile organic compounds (VOC) list based on the emission rates implemented in the database is also described. Results show that the obtained target VOC list is similar to those based on actual indoor VOC concentration measurements, demonstrating that PANDORA alone can be used to produce such a list and that, considering the data integrated in the database, formaldehyde, acetaldehyde, and benzene are the three VOC that should be carefully accounted for in IAQ analysis.