Journal of Building Physics

Air transport control has been recognized as critical to the proper functioning of buildings. Airflow is related to all facets of environmental control because it influences transport of heat and moisture and affects indoor environment as well as the durability of the building enclosure. To a lesser degree, we also recognize that contamination of wall cavities in building assemblies by organic materials from inside or outside provides both the nutrients and the inoculation potential for mold growth. Moisture carried by air may also increase the rate of emission of volatile organic compounds from these materials. While keeping rain out of building enclosures is a primary consideration in design, controlling airflow through the building enclosure comes a close second in importance to allow environmental control within buildings. Yet, an increase in the airtightness comes with a cost as well as an increased risk of moisture entrapment in case of any failure, and this, in turn, relates to the type of the building.

Modelling the hygrothermal behaviour of crop-based insulation products is essential to assess their impact on the energy performance of the building, predict indoor climate conditions, and prevent any risk of unexpected degradation. Traditionally, transient numerical models that predict internal conditions of construction materials consider that the variation of moisture storage with temperature is negligible although the sorption behaviour is known to be temperature dependent. This paper investigates this particular effect for crop-based materials and uses a refinement of standard mathematical representations. For this purpose, the effects of a thermal shock on the evolution of hygrothermal conditions inside a straw-bale wall are studied with several versions of a flexible research model. The latter is capable of incorporating the temperature dependency of the sorption curve with both a physically-based and an empirical description. A large climate chamber is used to gather experimental data and is able to host a full-size straw bale prefabricated panel. Internal conditions of straw bales are obtained with proper sensors bars. Results show that when large temperature gradients occur in a crop-based material, a model that considers temperature effect on moisture storage enhances greatly the prediction of internal conditions.

This article presents one of the applications of fractional-order models in modelling the dynamics of air temperature changes in residential spaces. The characteristics of these models include the order of the derivative which is a real number and, in more general cases, a complex number. These models are a further generalization of the traditional dynamic model but, thanks to the fact that derivatives are not real numbers, they can be used to model dynamics of much more complex physical phenomena. This article undertakes to identify the parameters of the fractional-order model which models the dynamics of air temperature changes inside buildings. Measurement data which were registered during experiment were used in the identification process.

Measurements obtained from two non-air-conditioned outdoor full-scale test cells during a year in Torreón, Coahuila, Mexico, are used to compare the thermal performance of two envelope constructive systems for walls and roofs of monolithic concrete buildings. The two constructive systems have the same thickness, one is mono-layered and other is two-layered. The two-layered constructive system has a better thermal performance due to its larger thermal resistances and thermal capacity, and the more-layers effect. The experimental data were compared with numerical simulation results obtained with EnergyPlus using the time-dependent heat transfer model. The numerical results are, in general, in good agreement with the experiments. The surface lag time is the variable with the largest differences.

The article examines air channels formed as simple geometrical figures along the slab length to determine their influence on thermal insulation value of the slab. The channel designer in the slab is intended to help lessen the weight of the slab, with simultaneous preservation of the actual thermal parameters. The solution is aimed at the rigid as insulation materials, and its objective is to design a prefabricate for renovation of the external walls.