Construction materials vary consistently county by county (not just country by country). Factory manufactured products (e.g., glazings, steel, etc.) have quite constant properties and are available on broader areas, whilst products realised in the construction yard, offer higher variability (e.g., plasters).\u00a0<\/span>Generally speaking, we may isolate three classes of variation of material properties:<\/span><\/p>\n – Small variability, once the specific product has been identified: steel; aluminum; roofing membranes;<\/span><\/p>\n – Average variability: tiles; masonry; paints (paint are prepared in the factory, but their final reflectance depends on the thickness, influenced by application, and on the substrate);<\/span><\/p>\n – Large variability: concrete; mortars; plasters.<\/span><\/p>\n However, all built surfaces might offer large variations in their optical properties, regardless the intrinsic standard deviation of their product category, because of:<\/span><\/p>\n – Ageing, especially (but not limited to) <\/span>soot, dust and dirt deposition<\/span><\/a>, mould growth, etc.;<\/span><\/p>\n – Deposition of snow, water, etc.<\/span><\/p>\n – Influence of angle of incidence on total value;<\/span><\/p>\n – Rate between beam and diffuse radiation, and air mass (all available for building products reflectance data are generally calculated for AM1.5, with reference to the ASTM G 173 solar irradiance spectral distribution).<\/span><\/p>\n <\/p>\n Green procurement will yield to deploy cool roofs everywhere… but how long will they stay cool?\u00a0In the US, this issue has been addressed and state regulations (e.g., California Title 24) and environmental rating schemes (e.g., LEED) already require ‘aged’ values, as not all products and materials perform the same over time.<\/p>\n This is to avoid to compute the energy needs of a building considering the initial albedo = 0.80, while after 1.5-2 years it gets to 0.56<\/a>, because of weathering, soiling, and, at times, biological growth. This is what, in average, happens in Milano, which increases peak exterior surface temperatures by 19\u00b0C, for highly insulated roofs.<\/p>\n If you don’t have data for a specific site, a robust approximation can be granted by an accelerated weathering and soiling protocol, devised by the Lawrence Berkeley National Laboratory. It has been recently accepted as ASTM standard D 7897-15<\/a>, and its repeatability and reproducibility assessed with an international laboratory study<\/a>, joined by Polimi too.<\/p>\n An extension of the protocol to mimic the weathering & soiling in EU urban areas is coming, likely to be used by the EU-CRC. It will extend the method to fa\u00e7ade materials too, including photocatalytic ones.<\/p>\n <\/p>\n <\/p>\n Under construction, for the moment. We exposed to the urban environments of Milano and Roma roofing and fa\u00e7ade materials, and we measured their optical-radiative performance over time. Measurements include UV-Vis-NIR reflectance (from 300 to 2500 nm @ 5nm, with a Perkin Elmer Lambda 950, equipped with an integrating sphere), and thermal emittance.<\/p>\n At the present time, we exposed [within brackets start and end date of the exposure campaign]: – 3 fabrics for tensile structures\u00a0[Apr 2012 – Apr 2014]. Something is here:\u00a0http:\/\/dx.doi.org\/10.1016\/j.egypro.2014.02.147<\/a>;<\/p>\n – 4 types of glazing\u00a0[Apr 2013 – Apr 2014]. Unpublished;<\/p>\n – 6\u00a0types of fa\u00e7ade finish [Oct 2011-Oct 2013; Apr 2012 – ongoing]. Something is here: http:\/\/dx.doi.org\/10.1016\/j.conbuildmat.2015.08.028<\/a>;<\/p>\n – 8 types of shading devices and glazing [Nov 2014 – ongoing].\u00a0Unpublished.<\/p>\n For scientific purposes only: if you need data please contact: riccardo . paolini (at) polimi . it<\/em><\/p>\n Please note that if the dataset is unpublished we may decide not to release it until the related paper is out there.<\/p>\n <\/p>\n <\/p>\n Reading’s Spectral Library of Urban Materials:\u00a0http:\/\/www.met.reading.ac.uk\/micromet\/LUMA\/SLUM.html<\/a><\/p>\n Glazing\u00a0<\/b>International Glazing Database<\/span><\/a> (managed by Windows Group – LBNL)<\/span><\/p>\n Cool Colors Project Pigment Database<\/a>\u00a0<\/b>[Project funded by California Energy Commission and developed by <\/span>Heat Island Group<\/span><\/a> – LBNL: <\/span>Cool Colors Project<\/span><\/a>]<\/span><\/p>\n Contents: spectral library of 88 pigments used for paints adopted in the construction sector. Plots of spectral reflectance (300 nm – 2500 nm), transmittance and absorbance are available; spectral data with password, to be required. A method is described for calculating the spectral reflectance of a coating film over a given substrate, known the spectral data of the film (over void) and of the substrate.<\/span><\/p>\n Cool Roofs\u00a0<\/b>Cool Roofing Material Database<\/a>\u00a0<\/b>[Developer: Heat Island Group – LBNL]<\/span><\/p>\n Contents: solar reflectance (300 nm – 2500 nm) , emissivity and SRI (solar reflectance index) for: <\/span>asphalt shingles<\/span><\/a>; coatings (<\/span>white<\/span><\/a>, <\/span>tinted<\/span><\/a>, and <\/span>aluminum<\/span><\/a>); <\/span>roofing membranes<\/span><\/a>; <\/span>metal roofings<\/span><\/a>; and <\/span>tiles<\/span><\/a>.\u00a0<\/span><\/p>\n Note<\/b>: these products are used in the US market. They might not be widespread (or even not available in EU, particularly asphalt shingles).\u00a0<\/span><\/p>\n <\/p>\n US Cool Roofs Council<\/a>\u00a0<\/b>[Developer: CRRC – Cool Roofs Rating Council, i.e. network of US National labs, manufacturers, ASTM representatives, etc.]<\/span><\/p>\n Contents: solar reflectance (300 nm – 2500 nm) , thermal emittance for all kind of roofing products used in the US market. Initial values and, for some products, after 3 years of natural exposure.<\/span><\/p>\n Rated products directory<\/span><\/a>\u00a0<\/span> C<\/b>ool roof database<\/b><\/a>\u00a0<\/b>and\u00a0<\/span>COOL ROOFS_database_report<\/b><\/a><\/p>\n DESCRIPTION OF MAIN ROOF PRODUCTS<\/b><\/a><\/p>\n Contents of the first release (2009): more than 100 products, including tiles, paints, membranes, and coatings.<\/span><\/p>\n All downloads from the project<\/span><\/a><\/p>\n <\/p>\n Nasa Spectral Library<\/a>\u00a0<\/b>[Developers: NASA, California Institute of Technology]<\/span><\/p>\n Contents: spectral library including 84 materials (under Man-Made)\u00a0adopted in the construction sector [not specified where, supposed USA]. Spectral reflectance (420 nm – 14000 nm) plots and spectral data available.<\/span><\/p>\n <\/p>\nWeathering and soiling of building envelope materials and components<\/h2>\n
Polimi database on aged solar spectral reflectance and thermal emittance of building envelope materials<\/h2>\n
\n– 16 roofing materials including single-ply membranes, field applied coatings on modified bitumen, roofing felts, clay tiles. These are exposed low sloped, in Milano and Roma, and tilted by 45\u00b0 facing south, in Milano only [Apr 2012 – ongoing].\u00a0http:\/\/dx.doi.org\/10.1016\/j.enbuild.2014.08.008<\/a>;<\/p>\nOther databases on the topic<\/h2>\n
\nEU Cool Roofs Council<\/b><\/a> (ongoing)\u00a0<\/b>[Developers: EU project, <\/span>project partners<\/span><\/a>]<\/span><\/p>\n