• Energy Research

Abstract Naturally ventilated buildings have been worldwide increasingly welcomed, given the current global awareness toward environmental sustainability, indoor health-quality and renewable energy. As Natural Ventilation (NV) performance relies on building design and interaction with the local environment, its potential benefits are not always easy to take advantage of, and thus sets up a vital field of study. This paper provides an overview of investigations on the subject by collecting researches focused on thermal comfort, energy efficiency and indoor air quality. Reviews were gathered, and their contributions compiled, showing challenges and opportunities regarding the NV use as a sustainable alternative. Moreover, the parameters and metrics used in the assessment of NV performance were summarised, and the trends discussed. The findings of the reviewed studies showed an increased number of investigations since 2015, with a tendency towards the use of numerical models to evaluate NV performance, as well as works on parametrization and optimisation. A balanced share of the different climates around the globe considered in the NV potential investigations was also identified, showing a worldwide spread interest and effort on the subject. However, detailed studies concerning ventilation strategies are mainly performed in hot and humid or Tropical climates, which proves that the added value of applying NV in other climates might be further explored. Finally, the review pointed out future works opportunities.

Abstract Highly efficient insulating systems help reduce heat losses and promote building energy efficiency due to their very low thermal conductivity. However, when applied to outdoor surfaces, climate conditions exposure might deteriorate the material's properties, compromising the building's energy performance over its lifetime. In the framework of a European research project (Horizon2020 - Wall-ACE), a novel aerogel-based insulating external render was developed, characterized, and submitted to a large-scale weathering test to assess its durability. The test rig was equipped with hygrothermal, impedance, and heat flux sensors, used as reference data to create and calibrate a 2D heat and moisture transfer (HMT) model that compared impedance readings and predicted water content. Before and after the test, thermal properties, e.g., U-Value, were measured to assess the weather impact on the exterior render performance, which were also investigated through building energy simulation (BES). In this article, both experimental and numerical procedures are described. Results show high water absorption in the analyzed render systems during weathering, especially at the innermost layer, demonstrated by both impedance and simulation outputs. An adjusted base coat and attention at the execution phase can avoid such intrusion of water. Nevertheless, a low thermal conductivity degradation was measured after the large-scale test, showing that the aerogel-based insulating system's effectiveness is not harshly compromised throughout its life-cycle.

Predicting building air change rates is a challenge for designers seeking to deal with natural ventilation, a more and more popular passive strategy. Among the methods available for this task, computational fluid dynamics (CFD) appears the most compelling, in ascending use. However, CFD simulations require a range of settings and skills that inhibit its wide application. With the primary goal of providing a pragmatic CFD application to promote wind-driven ventilation assessments at the design phase, this paper presents a study that investigates natural ventilation integrating 3D parametric modeling and CFD. From pre- to post-processing, the workflow addresses all simulation steps: geometry and weather definition, including incident wind directions, a model set up, control, results’ edition, and visualization. Both indoor air velocities and air change rates (ACH) were calculated within the procedure, which used a test house and air measurements as a reference. The study explores alternatives in the 3D design platform’s frame to display and compute ACH and parametrically generate surfaces where air velocities are computed. The paper also discusses the effectiveness of the reference building’s natural ventilation by analyzing the CFD outputs. The proposed approach assists the practical use of CFD by designers, providing detailed information about the numerical model, as well as enabling the means to generate the cases, visualize, and post-process the results.

Research and development of cost-effective, high-performance thermal insulation materials for the construction sector has to be focused on their final application. In particular, solutions for refurbishing historic buildings, which represent 40% of the European building stock, have to offer a good compromise between environmental quality, energy efficiency and conservation aspects. In this paper, the experimental assessment of an insulation material based on aerogel technology, recently developed in the European project EFFESUS, is presented with regard to the material's thermal performance, compatibility with historic fabric and reversibility. The overall results obtained in laboratory testing on a real-size mock-up and in a real-world case application indicate that the new material is a promising solution for retrofitting historic buildings, thanks to its thermal properties, easy application, reversibility and material compatibility.