Designers need sufficient knowledge about insulation characteristics for buildings to be constructed in areas subjected to transportation noises. Existing standards for facades do not seem to be satisfactory in taking into account the type of source, and, at present, there is no international standard for this purpose. In this paper, the effective factors in proposing insulation standard for facades are analysed and the previous literature regarding insulation studies and insulation criteria are briefly reviewed. A set of rating curves which can be implemented in various situations are introduced in order to determine the minimum required noise reduction for facades exposed to three types of transportation noises, such as road, railway and aircraft noises. The input data are simply the most available factors in design: (1) type of source, (2) noise level at the facade in L(eq), dB(A), (3) function of rooms behind the facade. The charts have been prepared by using typical source spectra measured in the field and the indoor noise criteria proposed by Beranek (NCB), so as to give the required insulation values both in terms of frequency dependent transmission loss and the single number weighting (R(w)). An analytical expression is also given based on a regression analysis for the above parameters as independent factors. A comparison is made between the National Standard Curve recommended in Belgium Legislations and the proposed rating curves, yielding higher insulation values depending on the sound frequency and source type.