A microporous film comprising: 75 wt. % or greater of a high density polyethylene resin having a density of 0.957 g/cc-0.970 g/cc, a melt index of from 0.2 to 10 g/10 minutes, a molecular weight distribution, Mw,cc/Mn,cc, of greater than or equal to 6.0, and a Mz,abs of greater than or equal to 500,000 g/mol, wherein the microporous film is oriented in the machine direction and exhibits a normalized water vapor transmission rate greater than 50 g mil/(100 in2·day).