The total heat gain includes heat from the sun, internal heat gain and heat gain resulting from the transfer of heat from rooms with a higher temperature. If they are too high, the temperature in the room increases, which often leads to a decrease in the comfort of the people inside, losses in stored products, but also an increase in air conditioning and ventilation maintenance costs during summer. Cool roof technology significantly reduces the heat gain through the largest part of large-scale buildings.
Profits as well as losses
In recent years, a lot has been said about reducing heat losses. All over the world, the requirements for thermal resistance of building envelopes are increasing. Lawmakers strive to minimize energy consumption both in winter for heating and in summer for cooling. When designing and manufacturing, as well as modernizing roofs, the main concern is to use a suitably thick and moisture-proof thermal insulation layer. This solution perfectly reduces heat loss in the winter months, and protects against overheating in the summer. This is particularly important because overheating buildings negatively affect the efficiency of employees and air-conditioning devices which causes higher CO2 emissions. That’s why it’s worth considering strengthening the building’s thermal insulation system with an additional element, such as a cool roof with COOL-R coating, which protects against excessive heat from solar radiation. Will it be a way to reduce thermal gain?
Need for regulation
Heat transmission through partitions depends on their thermal resistance and the temperature difference on both sides of the partition. If the temperature inside and outside is the same, heat transmission doesn’t take place. The COOL-R coating regulates the temperature of the roof outside, thus reducing the temperature inside the building. Interestingly, the term „cool roof” doesn’t actually refer to the partition as such, but only to the material used as the top layer. What properties lie behind this technology?
Cool roof coatings
Cool roofs have an albedo of 0.70 and a minimum thermal emission of 0.75. These are essential factors for getting an appropriate energy balance. For example, the reflectivity of the COOL-R liquid coating is 85.7% ± 0.2, and the emissivity value is 0.85 ± 0.03. The first is a ratio of the sum of the solar energy hitting the roof to the amount of energy reflected by it. The second parameter is the ability to remove absorbed thermal energy. This means the coating is highly reflective and therefore reflects the light. At the same time, it has a high emissivity, so it doesn’t absorb or transfer excess heat inside. For example, a roof covered with aluminum greatly reflects light, but due to its low emissivity it absorbs energy and transmits it inside. What’s important, COOL-R works with any type of roof, both flat and sloping, and it can be applied to all popular bases in construction.
The reflective and emission properties of the roof covered with the COOL-R coating
High temperature eliminated step by step
As mentioned already, low heat gain can be obtained by using materials (i.e. a cool roof) with high reflectivity and emissivity, making it difficult to transmit heat into the building. On top of those, it would be worth considering other elements that affect heat gain.
The color and texture of the roof affect the temperature, just like a black sweater is not a good idea to wear in hot weather. Why? Because dark colors absorb heat. For example, on a warm summer day, the temperature on a galvanized steel roof will average around 60°C, and on an anthracite roof it will oscillate around 80-85°C. The texture is also important. Smooth surfaces have a lower heat dissipation capacity due to the smaller surface area through which heat can radiate. Surfaces with a more porous structure are a better solution since they reflect the accumulated heat more easily. As a result, the highly reflective COOL-R layer has a bright colour and creates a seamless, waterproof coat that adapts to the surface to which it is applied.
Roof with a highly reflective COOL-R coating, Bolesławiec, Poland
In buildings with an air conditioning system, uncontrolled excessive heat gain generates a number of problems, such as high energy consumption used to cool the building, which translates into a high value of the EP index and high electricity bills. For that reason, it’s worth making a heat balance calculation before and after installing a cool roof.
All investors who choose to use COOL-R will get a tailored calculation. The company not only performs a heat balance analysis before and after installing a cool roof, as our experts will additionally calculate how much annual savings investors will gain due to better efficiency of the air conditioning and ventilation systems after a roof renovation, based on detailed data of the investment (heat transfer coefficient U, cost of 1 kWh, wall and roof area, location). Based on this data, you can also determine the payback time for a cold roof investment. COOL-R experts also take into account a number of other elements into their calculations, such as energy-consuming points, climate, location, daily temperature distribution, type and thickness of partitions. Each investment is treated individually. Additionally, the cool roof coating is applied by certified contractors trained according to the highest international standards. They are responsible for the entire implementation process and as-built service.