The “urban heat island effect” is defined as an increase in air temperature (from 1 to 6°C) in urban areas compared to surrounding rural areas due to human activities and housing; higher temperatures also give rise to an increase in thunderstorm activity and a decrease in wind. Several techniques are available to mitigate the impact of urban heat islands, one of which is the use of reflective materials. Also known as cool materials, they offer a high capacity to reflect incident solar radiation and to re-emit thermal energy in the IR spectral range. A combination of these properties contributes to lower roof and surface temperatures in the buildings, thereby reducing the release of heat into the atmosphere with significant energy savings (from 10 to 30%) in air conditioning.
The Solar Reflectance Index (SRI) is an indicator of the ability of a material to reflect solar energy compared to the reference values of a standard white (SRI=100, maximum value) and black surface (SRI=0, minimum value). The higher the SRI Index, the greater is the capacity to reflect incident radiation of a given material.
A number of protocols for the certification of buildings set a threshold value for solar reflectance – or SRI index – for exterior surfaces and low and steep sloped roofs. LEED (Leadership in Energy and Environmental Design) certification system, for example, which is now in its 4.1 version, is a standard applied in 165 countries in the world providing a global approach to sustainability and a rating from Base to Platinum for the recognition of virtuous performance in human health and environmental key areas. The LEED rating system awards credits to products that, as new and after a 3-year usage period, exceed the SRI initial and aged threshold values fixed.
Any certification concerning buildings necessarily includes the materials used, e.g. ceramic tiles or slabs, that are often chosen according to their high-durability, physico-chemical characteristics; they potentially represent optimum high solar reflectance solutions in calls for tender and public procurement contracts for obtaining credits related to the mitigation of the heat island effect.
From its own experience, Centro Ceramico has observed that the number of tests on ceramic tiles has doubled over the last few years in line with growing awareness of environmental issues.
Ferro Corporation, a major international producer of chemical and performance products for the ceramic industry, this year commemorating its centenary of research and innovation, cooperates with Centro Ceramico in Bologna within the project “INVOLUCRO”*. Aim of the project is the radical transformation of the traditional ventilated facade into a smart membrane, dynamically adapting to environmental conditions and producing energy to provide increased energy and acoustic performance. Cladding solutions include high SRI (Solar Refectance Index) ceramic slabs, that can reduce summer thermal load and improve inner comfort.
The prime object of the research study involving Centro Ceramico and Ferro Corporation is to improve Total Solar Reflectance values of ceramic tiles using “cool” pigments. Ferro can offer a long experience in the production of cool pigments, already widely employed to colour roofs and facades in different materials, such as sheet metal, bricks and plastics.
After a first phase focused on the research and development of two “cool” solutions suitable to ceramic tiles – one paint and one enamel – the project has now reached a final phase based on the production of prototype porcelain stoneware tiles, 60x60cm, to be fixed on the ventilated facade on prototype turrets manufactured by Aliva Srl, member of IVAS group in San Mauro Pascoli, a company specialized in facade systems. The outdoor performance of both “cool” solutions will be compared to that of traditional ventilated facades to highlight the desired benefits through a testing process in the relevant environment.
A successful experimentation will allow the launch of innovative ceramic claddings on the market. Let’s make it happen!
* INVOLUCRO PROJECT : Regional Operational Programme of the European Fund for Regional Development 2004-2010 co-financed by Emilia Romagna region; coordination: CIRI-Edilizia e Costruzioni, Bologna University. Partnership: Centro Ceramico, CertiMac, CNR ISTEC, LARCOICOS