Allvent is Allbuild's breathable underlay; BBA Approved and CE marked. Not only is it breathable, it is water vapour permeable too and is suitable for both vertical and horizontal appliances.
Does every building need roof ventilation and breather felt?
More often than not the answer will be yes. Everything we do within the house from cooking to bathing and showering causes moisture. As the moisture rises it becomes trapped in the roof space, this can lead to mould and dampness. Items stored in the loft space will also be affected and most importantly the structure itself can become damaged which can be extremely costly to repair.