Breathable roofing underlays, more correctly referred to as a vapour permeable or Low Resistance (LR) underlay, is designed for use under slate and tile roofs and can reduce the requirement for roof ventilation in order to prevent interstitial condensation and consequential damage and decay. Depending on the strength and weight of the underlay, there may be limitations on where it can be used in different wind zones. The product data and packaging should identify these limitations.