This paper focuses on the limits of measurement of the sound insulation of building façades at low frequencies. Three standard methods are compared mainly for the position of the equipment. In particular, the positions proposed by the international standard ISO 140-5 and the national standards ASTM E 966 (USA) and JIS A 1430 (Japan) are considered. The limits of measurement of the sound pressure level in front of the façade are investigated. Different placements of the external source and receiver are considered. Moreover, different placements of the receiver inside small rooms are compared by focusing on corner vs. center room positions. The uncertainties of room averaged sound pressure levels measured according to different standards are discussed. The problems of measurement of the reverberation time in small rooms and of sound insulation in irregular shaped rooms are introduced because these measurements present several critical challenges. Finally, suggestions to improve the future version of the ISO 140-5 are reported.