![]() ![]() There are other court cases that have arisen from special reflective paint claims in the US too. Taking away the sunlight provides no building performance benefit.ĭulux went down this path, and they paid a heavy price of $400000 in Australia. White Paint and Solar Reflective Coatings are only effective in reflecting/rejecting sunlight or energy from the sun. Myth #1 Solar reflective paint can be applied to the inside of a building to keep it warm. At the bottom of this article, we modelled different solutions for keeping heat out of a building and keeping heat inside of the building, using different building envelope materials. ![]() Moving onto the myths that are doing the rounds, regarding high reflective/white paint benefits. The earth radiates heat back to space mostly at much longer wavelengths (Middle to far Infrared at a much lower intensity). This spectrum is highly dependent on the effect of the atmosphere. The sun emits strongly in the visible light range, but it also produces ultraviolet and near-infrared radiation. The sun is only actively forcing its energy on our buildings during 3-4 peak hours of the day and yet we expect comfort 24 hours of the day.Įarth receives energy from the sun in the form of solar radiation-radiation with varying wavelengths along the electromagnetic spectrum. It’s huge! But it only benefits energy efficiency for a few hours of the day. The above chart looks at how much energy makes the earth’s surface in the visual spectrum range. High solar reflectance (white paint) reduces direct sun energy absorption (albedo), hence a cool roof energy-saving claim is supported. 05, where most homes in Australia require ceiling insulation of R 4.1. As an example to justify this claim, the best insulation in the world (aerogel, k=0.02, so R=t/k=0.001/0.02=R 0.05 m².K/W) has an R-value of. Insulation with an R-value can also block this form of energy transfer because this type of energy is transferred into the building envelope via conduction.Īs a silver bullet argument, A paint/coating, 1 mm in thickness does not provide any meaningful insulation. Radiation - which is countered with a radiant barrier, eg, Low-E films, shiny metallic surfaces and white paints, with additives claiming better near-infrared deflection performance.Convection: which is countered with an airtightness layer.Conduction : which is countered using an insulation R-value.There are 3 methods of energy transfer, that affect energy efficiency in the building envelope. When considering different building envelope products, it’s important to understand that energy radiates from all objects, the sun radiates energy primarily on the visual spectrum and near-infrared, and Indoor objects in a house here on earth radiate on the middle to far-infrared spectrum. ![]() Let’s start firstly with an explanation of what the building envelope actually is: It includes the external walls, ceiling, and floor that connects you to the outside environment.Ĭonsidering that reflective paint works by deflecting radiant visual energy, we decided to model radiant energy transfer comparisons using different building envelope products.īefore we go into the modelling of what white paint and what solar thermal reflective paints can do, let’s talk about the different spectrums of energy that comes from the sun and the spectrum of energy that comes from building materials and materials that the earth is made of. Here at Efficiency Matrix, we are not rocket scientists but some of the claims/assumptions out on the internet really needs to be straightened out and explained in a manner where most people will be able to understand cool roofs. Solar Thermal Reflective Coatings, and having a Cool Roof. ![]()
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