Hello slate people
We all know that the most important part of the building, the element that create and define a dwelling, is the roof. Without a roof to cover you from the weather, you don´t have a house. The roof is also the main and most critical component in terms of thermal regulation. To achieve the best thermal performance, your roof must be properly designed, using the best available materials.
In this sense, a recent research paper from the prestigious journal Solar Energy has highlighted some interesting facts on this thermal efficiency of roofs. The paper studies the effect of the roof geometry and the used materials., taking into account two different parameters, the Energy Use Intensity (EUI) and the Thermal Discomfort Hours (TDH). The authors use a sophisticated methodology based on computer simulations, which allows to perform more than 24,000 cases for roof geometry, and 1470 cases for the roof material tests. The study considers up to nine different finishing materials: asphalt shingles, metal roofing, concrete tiles, clay tiles, terracotta tiles, slate, wood shingles, cool roof (PVC, white), cool roof (acrylic, white), and green roof, in combination with different roof shape and underlying insulation materials.
Results show that slate and clay tiles, being the finishing materials with higher thermal mass (the ability of keeping temperature), have the best TDH values, so they keep the temperature of the house in the optimum range of comfort for the inhabitants. However, due to this thermal mass, slate and clay tiles consume more energy for cooling. At this point it is important to bear in mind that the authors of this study are from Egypt, an African country with warm winters and extremely hot the rest of the year. In the capital city, El Cairo, the average temperature during the summer is around 35°C (95°F), while during the winter is around 20°C (68°F). These temperature range are far from those we have in Europe or North America, where it is much more important to heat the house than to cool it. Therefore, clay tiles are a good option for temperate and continental climates, but if you take into account price and durability, then slate is the best option.
(Wait, slate is more expensive than clay¡, why do you say price is better?)
Well, do not forget that life expectancy of an average clay tile is around 30 years, while a slate cover will easily last more than 100 years. It is not about the money you pay when installing the cover, it is about the money you will save in the following years. Replacing a clay tile roof is not really cheap.
Have fun¡
Reference:
Alaa, H., Yehia, M., & Ayoub, M. (2025). Metaheuristic optimization of roof designs to enhance energy performance and thermal comfort using parametrization and machine learning. Solar Energy, 286, 113186. doi: https://doi.org/10.1016/j.solener.2024.113186