Abstract
Many previous studies by the authors of this paper and others have shown that installing white/reflective/cool roofing systems resulted in energy savings. The amount of energy savings depended on the longwave thermal emissivity and the short-wave solar reflectivity of the rooftop surfaces. The question is “what is the percentage energy savings for the whole building as a result of using cool roofing systems instead of conventional/black roofing systems? To answer this question, three-dimensional energy simulations are conducted for typical Saudi buildings when they are subjected to the natural weathering conditions of the Eastern Province of Saudi Arabia. Several Window-to-Wall Ratios (WWRs) having different thermal resistances (R-values) and Solar Heat Gain Coefficients (SHGCs) are considered in the study. The windows are located in the different main solar orientations. To investigate the effect of the area ratio of the roof to the walls on the potential energy saving due to using cool roofs, one storey and two-storey are considered in this study. Results showed that using reflective materials with lower short-wave solar absorption coefficients in the roofing systems have resulted in a decrease in the yearly total energy loads of one-storey building and two-storey building.
Highlights
In regions with harsh climatic conditions, a substantial share of energy is used for heating the buildings in cold climates, and cooling the buildings in hot climates such that in Gulf Cooperation Council (GCC) countries
Results showed that using reflective materials with lower short-wave solar absorption coefficients in the roofing systems have resulted in a decrease in the yearly total energy loads of one-storey building and two-storey building
Numerical simulations were conducted to investigate the potential energy savings as results of using white roofing systems of single-zone buildings and two-zone buildings when these buildings were subjected to weather conditions of Saudi Eastern Province
Summary
In regions with harsh climatic conditions, a substantial share of energy is used for heating the buildings in cold climates, and cooling the buildings in hot climates such that in Gulf Cooperation Council (GCC) countries. The design of building envelopes with the intent of achieving energy savings can necessarily help reduce building operating loads and the demand for energy over time. This research study mainly focuses on the performance of the whole building with reflective roofing systems and non-reflective (i.e. conventional/black) roofing system. When solar radiation hits the building envelope (i.e. roofs, walls, curtain walls, windows and skylight devices), a part of solar energy is reflected and the other part is absorbed. The absorbed part of solar energy results in an increase of the surface temperature of the building envelope. Reflective/white/cool roofing systems use bright surfaces to reflect a significant portion of the incident short-wave solar radiation, which lowers the surface temperature compared to conventional roofing systems. White roofing systems help reduce the urban heat island effect and the cooling loads during the summertime
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