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This article was presented at the ICACER 2022 conference. The energetic performance of a building insulation coating is assessed by means of simulations of a dynamic RC model and by carrying out a parametric analysis based on Design of Experiment techniques. The external insulation coating is characterized by three parameters: the thermal conductive resistance, the shortwave solar absorptivity, and the longwave emissivity. The façade of the building is modelled with two lumped thermal capacitances on the internal and the external surfaces, and two thermal resistances representing the conduction through the wall and the internal convective and radiative phenomena. The external insulation is modelled by two more thermal resistances, which simulate the external convective exchanges and the conduction through the insulation, and one thermal capacitance in the insulation external surface. The inputs to the model are the external ambient temperature, the internal temperature, and the weather conditions (the wind convective heat transfer coefficient and the incident shortwave and the longwave radiative heat fluxes). The analyzed output parameter of the model is the internal surface heat flux, which has a direct impact on the heating and cooling loads. The Box-Behnken Design has been used to select the optimal values of the parameters of the insulation coating that result in a maximized internal heat flux during winter months and a minimized flux during summer months. The use of the Box-Behnken Design permits to assess the combined effect of the input parameters on the output parameter and the formulation of a simplified compact model to predict the latter as a function of the formers. The outcomes of the models suggest that surface emissivity is a key factor in summer periods while winter periods are mostly dominated by the thermal resistance in the wall.

Despite significant development in the performance and efficiency of solar thermal technology, little consideration has been given to its interaction within building envelopes, aside from mechanical fixing systems. The lack of solutions for the architectural integration of solar collectors and the complexity of their assembly process remain important barriers for the widespread adoption of this technology. An innovative approach is proposed in which solar collectors are not merely integrated into conventional building envelopes, but instead these envelopes are hybridized and activated to house solar thermal systems. This poses the challenge of adapting solar thermal technology to the capacities and limitations of architectural skins. The paper presents results from three ongoing projects. BATISOL and BASSE investigate the development of solar thermal technology so as to fulfil the functional, constructional and formal requirements of building skins. Fa��ade assemblies are turned into active skins by integrating unglazed solar collectors in the place of conventional renders and claddings. RETROKIT explores the usage of renewable energy gains within an alternative environmental control strategy, by direct supply of heated air into the ventilation system. Finally, a discussion is presented on architectural, constructional and thermal performance aspects of these solutions, based on both design assessments and experimental data., DOI of full conference proceedings: https://doi.org/10.7480/isbn.9789492516299

The greatest difference between buildings of traditional and non-traditional construction design lies not so much in the building materials used, but in the way they are used to construct the external envelope of a building – in the way they are assembled. One may say that the defining approach of traditional construction is the management of moisture and, in contrast, one can say that modern construction systems generally (but not always) depend on blocking, not managing, moisture. The deterioration and decay that occurs in buildings almost always involves moisture. Three relevant moisture sources are identified in this report: indoor vapour, rain water (including wind driven rain) and ground water. Since heat, water vapour and liquid water are all driven by different forces, they can ‘move’ in different directions at different times within the same wall. However, because the forces driving these transport phenomena are coupled, retrofit strategies to address one issue may have unexpected effects on another. Retrofitting building elements to improve thermal performance can carry an unestablished level of risk of moisture-related damage occurring, to the detriment of existing and newly installed portions of the building fabric as well as for occupants. The report discusses two available methodologies for conducting hygrothermal risk assessments: steady-state condensation risk assessments, using the Glaser method, and transient hygrothermal performance analysis, using numerical simulation. In Ireland and the UK, construction guidance and practice are still heavily influenced by the diffusion paradigm, a reductionist but deeply held view that vapour diffusion is the only relevant moisture transport mechanism in building fabric and the use of a vapour barrier to control it is always best practice. The case study in this report has demonstrated, by comparing Glaser method and numerical simulation assessments (using BuildDesk U and WUFI software respectively), that (a) their results can be diammetrically opposed, (b) moisture transport in solid, unrendered stone walls is predominantly in the form of liquid migrating through the materials’ capillaries, due to capillary action and surface diffusion. The report demonstrates that choosing the most appropriate risk assessment method is important to ensure that retrofits are durable, sustainable and create healthy environments.

Plane element heat loss[1] and thermal bridging[2] together constitute all the conduction heat loss (measured in W/K, watts per kelvin) through the thermal envelope[3] of a building. Perversely insulating the plane elements more and more without carefully dealing with junctions can lead to a significant increase in thermal bridging heat loss. This is often more significant in poorly thought-out energy-focused retrofits than in existing or new buildings.