The building envelope's overall thermal transfer value (OTTV) is an essential aspect of creating sustainable and energy-saving architecture. The original OTTV formula makes it difficult for any user who is not an expert to calculate OTTV. Designers usually need an empirical formula to determine the design direction in the initial design stage. Instead of replacing the previous SNI (The Indonesian National Standard) 6389:2011, this paper will introduce several simple equations as empirical

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... as covering solar factor (SF), effective shading coefficient (SCeff), and OTTV. Three hundred architraves units of facade models were investigated to make the formulas or equations. Regression analysis was used to make three practical formulas in this paper. The research validation consists of first and crossed-validation to determine the Root Mean Square Error (RMSE) and Average Percentage of Error (APE) between the rule of thumb and original equation of OTTV from the Indonesian standard. The results show that the RMSE is only 1.12 W/m2, while the APE is 1.05%. By these results, the empirical formulas can be implemented to be the rules of thumb in the first stage of the design process because the values of RMSE and APE are still under the design margin of thermal design in the building.