Good Building Score: 46

Recommendation: Nopal Favorite

Vapor variable membranes are often the best option when adding an interior side airtightness layer. Their biomimetic design adapts permeability to varying conditions; nearly vapor closed during winter to keep interior moisture out of insulated cavities and highly vapor open during summer for drying to the interior. Proper airtightness stops drafts and increases insulation performance by factors, not percentages.

While there are a growing number of options in this category, Intello Plus has the ideal permeability curve, absolute air tightness and 100+ year durability.