Most alternative membranes have functional layers that are even thinner than a human hair which make them more vulnerable to degradation.
It is the functional layer, not the upper or lower fleece, that is protecting the roof from the elements during the building phase.
Only when the roof is fully covered does the functional layer then provide its secondary water shedding role.

Tests of installed roofing membranes proof that alternatives can leak very quickly after less than 10 years, whereas your roof should last for years to come.

UV exposure during the building phase is pre-damaging the roof underlay. Heat, once the roof is covered, also adds additional stress, affecting the membranes functionality.

Scientific theory, independent laboratory tests and now the independent real life ageing tests on installed membranes show that alternatives are much more sensitive to UV and heat compared to Tyvek^®. These tests clearly prove that alternative roofing underlays can fail very quickly after less than 10 years.