Development of Clay Tile Coatings for Steep-Sloped Cool Roofs

Abstract

Most of the pitched roofs of existing buildings in Europe are covered by non-white roofing products, e.g., clay tiles. Typical, cost effective, cool roof solutions are not applicable to these buildings due to important constraints deriving from: (i) the owners of homes with roofs visible from the ground level; (ii) the regulation about the preservation of the historic architecture and the minimization of the visual environment impact, in particular in historic centers. In this perspective, the present paper deals with the development of high reflective coatings with the purpose to elaborate "cool" tiles with the same visual appearance of traditional tiles for application to historic buildings. Integrated experimental analyses of reflectance, emittance, and superficial temperature were carried out. Deep analysis of the reflectance spectra is undertaken to evaluate the effect of different mineral pigments, binders, and an engobe basecoat. Two tile typologies are investigated: substrate-basecoat-topcoat three-layer tile and substrate-topcoat two-layer tile. The main results show that the developed coatings are able to increase the overall solar reflectance by more than 20% with acceptable visual appearance, suitable for application in historic buildings. Additionally, the effect of a substrate engobe layer allows some further contribution to the increase of the overall reflectance characteristics.

Evaluation of Different Urban Microclimate Mitigation Strategies through a PMV Analysis

“…In order to recognize the characteristics of each plant, Table 4 reports: the height zP, albedo coefficient αF and the "Leaf Area Density" (LAD) [49]. This is why each plant was assumed to be divided into 10 blocks, each with a height of 1/10 of the total height and for every block the "Leaf Area Density" was calculated through the following relationship [49]: Then, Table 5 reports some thermophysical properties of the materials characterizing the limits surfaces of the structure in every configuration: In detail, the high albedo material coefficients were chosen according to previous research [50] related to the development of innovative materials with the same spectral response of those used in historical centers in the visible region, but high reflectance in another solar spectrum range. In this way, it is possible to respect the architectural restrictions of the historical buildings.…”

Development of Innovative Heating and Cooling Systems Using Renewable Energy Sources for Non-Residential Buildings

“…The depletion of fossil fuel reserves and the pressing target for CO 2 emission reduction is pushing the international community to search for valid alternatives to conventional fossil resources [1]. Worldwide energy policies encourage both the energy savings from passive solutions and the exploitation of renewable energies (solar and wind energy, geothermic, biomass and bio-fuels, and fuel cell technologies) [2][3][4][5][6][7][8][9]. The European Community [10] specifically promotes the transition to nearly-zero energy buildings [11][12][13], characterized by high energy performance and renewable energy exploitation.…”

On Innovative Cool-Colored Materials for Building Envelopes: Balancing the Architectural Appearance and the Thermal-Energy Performance in Historical Districts

“…Three scenarios of the same case study were taken into consideration for comparison purposes, with increasing levels of cool, passive solutions implemented on the building envelope: Case 0, the reference case with no retrofit solution; Case E, with the cool red mortar on the vertical envelope, and finally Case E+R, with both cool red mortar as the envelope finishing layer and cool clay tiles [33] as roof elements. By comparing the energy demands for cooling, Case E was able to reduce demands by 1.2%, when compared with Case 0, while Case E+C allowed 3% energy to be saved for cooling with respect to Case 0, combining both the benefits of the vertical and horizontal envelope.…”

“…With respect to the cool-colored tiles, thermal-optic characteristics were measured and thoroughly described in Pisello and colleagues' work [33]. The optimized tiles displayed a thermal emissivity equal to 0.89, while the solar reflectance was around 0.7.…”

“…In Case E and E+R, increasing levels of passive solutions were applied to the envelope to improve the thermal-energy performance of Palazzo Gallenga. In Case E, the cool red mortar finishing layer was applied on the vertical envelope, while in Case E+R, representing the maximum level or cool retrofit solution, the combination of the cool red mortar finishing layer for the vertical envelope, and the cool clay tiles [33] for the roof, was simulated. With respect to thermal emissivity and thermal conductivity, they were the same in both prototype sets, and they did not change with the addition of IR pigments.…”