Unvented Shed Roof Barrier

Yes unvented roof assemblies can be insulated with fiberglass a wufi post and not just in climate zones 2b amp.

Unvented shed roof barrier.

Potential pitfalls to avoid include. As the osb or plywood roof sheathing absorbs moisture the sheathing expands and decreases the space between adjacent sheets. Unvented roofs are increasingly common due to design priorities. This causes the roofing paper and shingles to buckle.

The roof is an insulated unvented shed roof which slopes down from the second story to the north side and on the interior it s a cathedral ceiling half of a cathedral. However designers of compact roof assemblies must consider vapor permeance and arrangement of the roofing materials to produce acceptable hygrothermal performance and low. Most building codes allow for unvented roof construction. However creating a vented roof gives a thermal separation between the roof and the conditioned heated and cooled spaces of the house so the sun baking on your metal roof won t over stress your air conditioning in the summer and snow will melt off your roof slower in the winter causing fewer ice dams and other water worries.

Martin s post focuses on the marketing of owens corning 039 s propink unvented attic insulation system. Unvented roofs have a number of advantages. Unvented roof systems where the insulation and air barrier are applied directly to the underside of the roof deck are common in applications where designers are seeking cost effective and energy efficient roof assemblies. Ventilation becomes more difficult the more complicated a roof s construction is.

An understanding of heat air and moisture as well as the causes of condensation is critical in detailing unvented roof assemblies. Traditionally we ve insulated the roof panel to try and keep the temperature on the panel from reaching the dew point. We ll add a vapor barrier so the moist air does not flow up through the insulation and condense on the roof. Unvented low slope roofs are never designed to dry to the exterior because low slope roofing membranes are vapor barriers.

As a result unvented roofs have become popular in homes with feature dense roofs think multiple skylights dormers and other aesthetic flourishes. While this fact adds some risk to these assemblies compared for example to a traditional vented unconditioned attic with asphalt shingles this type of roof is very common. But a preinstalled membrane may be even more effective at removing condensation. This phenomenon occurs regardless of whether the roof is vented or unvented in the absence of a vapor barrier between the asphalt shingles and the roof deck.

These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck.