Described herein are methods for increasing strength of blown films, by forming the films using a film blowing apparatus where the film is formed from a blend of a first polymeric material and a renewable carbohydrate-based polymeric material having particular characteristics. By using such a blend, and ensuring that the film blowing apparatus is operated at a high blow up ratio of at least 2.0, and/or using a narrow die gap of no more than 500 microns, Applicant has discovered that increased strength in the film can be obtained, as compared to where (i) the renewable carbohydrate-based polymeric material is not included or (ii) where the film is blown at lower blow up ratios and/or wider die gaps.