Evy Vereecken

In situ determination of the moisture buffer potential of room enclosures

Indoor air quality, occupant’s comfort, durability of building parts, and energy consumption are highly related to the variations in indoor relative humidity. Since interior finishes and objects assist in dampening the peaks in relative humidity, the knowledge of the moisture buffer potential of room enclosures is necessary to include its effect in whole-building simulations. In this article, a method for the in situ determination of the moisture buffer potential of room enclosures is presented. During a period of some days, a humidifier is placed in a room and a moisture production scheme is implemented. Based on the measured RH-increase and decrease during loading and unloading steps, the ventilation rate and moisture buffer potential of the room are determined inversely by solving the moisture balance of the room using the effective capacitance and effective moisture penetration depth models. The methodology is validated by well controlled experiments in a large climatic chamber with known hygric inertia, and afterwards applied to real room enclosures. Main advantage of the proposed method is that a simple and fast experiment allows obtaining a comprehensive characterization of the hygric inertia of the whole building enclosure — including all interior finishes and multidimensional interior objects such as furniture, carpets, drapes, books, etc.

Towards a more thoughtful use of mould prediction models: A critical view on experimental mould growth research

To assess the mould risk on materials, different mould prediction models are available. However, each of these models struggles with shortcomings, which might result in widely varying conclusions. A view on the challenges might come in use when developing novel or upgraded models in view of a more reliable risk assessment. Additionally, this knowledge will stimulate a more thoughtful use of the current models. This article shows a preliminary evaluation of some mould prediction models, and this based on experimental literature data on wood. Although experiments are the input for the model development, discrepancies are observed. Therefore, the difficulties and challenges in experimental mould research are discussed.

Capillary Active Interior Insulation Systems for Wall Retrofitting: A More Nuanced Story

ABSTRACT To thermally upgrade exterior masonry walls, interior insulation is often the only possible retrofitting technique, especially when dealing with historic buildings. Unfortunately, it is also the riskiest post-insulation technique, as frost damage, interstitial condensation, and other damage patterns might be induced. To diminish those risks, nowadays so-called capillary active interior insulation systems are often promoted. These systems aim a minimal reduction of the inward drying potential, while interstitial condensation is buffered. Currently, several capillary active systems are on sale. These different types have, however, widely varying properties. In this article, a closer look at the hygrothermal properties and the working principle of a number of “capillary active” interior insulation systems is made. The spread in capillary absorption coefficients and the vapor diffusion resistances of the different systems is discussed and their influence is illustrated. Based on all this, a more nuanced view on capillary active insulation systems is pursued. Abbreviations: AC: aerated concrete; CaSi: calcium silicate; GM: glue mortar; GB: gypsum board; HAMFEM: Heat Air and Moisture Finite Element Method; MW: mineral wool; PE: polyethylene; PIR: polyisocyanurate; PUR: polyurethane; VIP: vacuum insulation panel; WFB: wood fiber board; XPS: extruded polystyrene; sddry: dry vapor diffusion resistance factor; µdry: dry vapor diffusion resistance

A determination methodology for the spatial profile of the convective heat transfer coefficient on building components

Several experimental procedures have been established to determine the convective heat transfer coefficient, a frequently used parameter in many engineering disciplines. Almost all of these methodologies focus on point or spatially averaged values. Yet, in many studies the spatial profile of the local convective heat transfer is of importance. In this paper, a methodology to determine such spatial profile is proposed. In this method, experiments are combined with Monte Carlo simulations. Such an approach makes it possible to account for inaccuracies in the input data. As an example, the methodology is applied to determine the spatial profile of the local convective heat transfer coefficient near a corner for two thermal bridge configurations. The temperature difference between interior surface and indoor air is found to restrict the applicability of the method. Nonetheless, for the case with a sufficient temperature difference, the order of magnitude of the convective heat transfer coefficients further away from the corner is in line with literature data. An important limitation of the technique at this stage of its development is, however, its requirement for prior knowledge of the equation that describes the spatial profile of the convective heat transfer coefficient. Despite these drawbacks, the methodology shows much potential and can be valuable for other applications as well.