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Controlling air leakage through the building envelope remains a challenge, especially in light of the imperative to transition to a net-zero energy building sector and the increasing importance of indoor air quality during extreme weather events such as wildfires. The British Columbia Energy Step Code is a performance-based compliance option in the British Columbia Building Code which is intended to provide a transition pathway to net-zero energy ready construction by 2032. For small residential buildings, performance targets entail thresholds for the measured air leakage rate through the building envelope. This paper reports on the airtightness of the first 145 single- and two-family dwellings built under the Energy Step Code in Richmond, BC. Although the first phase of the implementation of the Energy Step Code in Richmond entailed no airtightness targets (only testing), results indicate improvement compared to the historical levels of airtightness in the region. Key words: airtightness, air leakage measurement, infiltration, blower-door test. Le controle des fuites d'air a travers l'enveloppe du batiment demeure un defi, surtout compte tenu de l'imperatif de passer a un secteur de batiments a consommation energetique nette zero et de l'importance croissante de la qualite de l'air interieur lors d'evenements meteorologiques extremes tels que des feux de forets. L'Energy Step Code de la ColombieBritannique est une option de conformite fondee sur le rendement dans le code du batiment de la Colombie-Britannique (<< British Columbia Building Code >>) qui vise a offrir une voie de transition vers une construction a consommation energetique nette zero d'ici 2032. Pour les petits immeubles residentiels, les objectifs de rendement comportent des seuils pour le taux de fuite d'air a travers l'enveloppe du batiment. Le present document fait etat de l'etancheite des 145 premieres habitations unifamiliales et a deux logements construites en vertu de l'Energy Step Code a Richmond, en Colombie-Britannique. Bien que la premiere phase de la mise en oeuvre de l'Energy Step Code a Richmond n'ait comporte aucune cible d'etancheite a l'air (seulement des essais), les resultats indiquent une amelioration par rapport aux niveaux historiques d'etancheite a l'air dans la region. Mots-cles : etancheite, mesure des fuites d'air, infiltration, test d'infiltrometrie., 1. Introduction Uncontrolled flow of air through the building envelope, namely air leakage or infiltration, can cause a wide range of problems including reduced durability of the envelope, energy loss, [...]

Preventing and alleviating heat stress remain an enormous challenge in dairy farming. Although enhanced air distribution techniques have been developed and deployed in many barns, ventilation alone is no longer sufficient even in regions with historically mild climates. There is an increasing need for cooling of the intake fresh air. Evaporative cooling is a cost-effective sustainable technique used in many applications, including livestock farming. This paper presents a graphical method for preliminary evaluation of evaporative cooling as a viable and effective solution. Thermodynamic principles are combined with models for heat transfer in dairy cattle to develop a set of criteria on the psychrometric chart. The proposed method is demonstrated for a naturally ventilated dairy barn located in the continental central European climate and in two locations with hot climates, a semi-arid/Mediterranean and a humid subtropical climate. • Thermoregulation models combined with thermodynamic principles. • Limits for effectiveness of evaporative cooling derived. • Developed criteria mapped onto psychrometric chart. • A graphical method to assess effectiveness of evaporative cooling proposed. • Proposed method demonstrated for sample barn in Europe. [ABSTRACT FROM AUTHOR]

Laminar free convection in a vertical channel with isothermal walls is a classical heat transfer problem. In general, the channel walls may be at different temperatures, leading to a difference in the rate of heat transfer at the walls. Although numerical and experimental results are often presented in terms of average wall Nusselt numbers, separate correlations for heat transfer at each wall are rarely available. The few existing relations are complex in form due to the extra parameters introduced to facilitate the correlation of results. Moreover, the existing correlations do not reflect the physics of the problem in full. In this work, the three-temperature problem of laminar-free convection of air in a tall vertical channel with isothermal walls is studied in a new theoretical framework, namely the extended Newton formulation. This formulation eliminates the need for an effective temperature difference, hence simplifying the presentation and correlation of the results. The dQdT technique was utilized along with computational fluid dynamics to calculate the average paired Nusselt numbers that characterize the extended Newton formulation of the problem. The dQdT results were then used to derive heat transfer correlations which are both simpler in form and more accurate than the existing correlations. The proposed correlations are applicable to cases of both channel walls hotter or both colder than the ambient air. [ABSTRACT FROM AUTHOR]

This paper examines engineering students' misconceptions of thermodynamics. A summary of the pedagogical theories of misconceptions is presented and the cognitive roots of misconceptions are briefly reviewed. Concept tests are discussed as one of the most effective tools for diagnosing misconceptions, followed by a summary of the available thermodynamics concept tests. Finally, an overview is presented of the most frequent thermodynamics misconceptions among engineering students. [ABSTRACT FROM AUTHOR]

This paper examines the three-temperature problem of convection at the indoor side of a complex fenestration system (CFS) based on recent theoretical developments, namely the extended Newton formulation and the dQdT technique. CFD solutions were obtained for natural convection at the indoor side of various CFS configurations. The dQdT technique was then implemented numerically to obtain the paired heat transfer coefficients of each configuration. The results were used to assess the approximate relations used in the ASHRAE Window ATachment (ASHWAT) tool. The comparison shows that while there is remarkable agreement between the ASHWAT estimates and dQdT results for roller blinds, discrepancies exist between results for venetian blinds. Furthermore, although use of a delta resistor network to model convection at the indoor side is valid and relatively accurate for roller blinds, the application of this model to CFSs with venetian blinds requires additional levels of approximation. Nevertheless, the heat transfer rates calculated based on the approximate resistor-network model are in close agreement with the CFD results. [ABSTRACT FROM AUTHOR]