In composite membranes, non-woven substrates are often included to offer higher mechanical strength. The use of non-wovens is currently limited in electrochemical applications, apart from lab-made electrospun non-woven membranes. In this manuscript, three commercial non-wovens are compared to test their potential use in acid-based electrochemical applications, for instance redox flow batteries, and are also compared to a woven fabric substrate. The three non-wovens are found to have variable suitability in terms of the stability of solvents used in further membrane processing. However, all are deemed limiting due to their relatively high area resistance (0.37–1.47 ohm.cm²). In comparison, free-standing and selective commercial ion exchange membranes have area resistances around 0.08–0.27 ohm.cm². More open substrate backings such as a woven structure are recommended instead to allow for lower resistance of the resulting composites.