Unvented Flat Roof

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.

Unvented flat roof.

Unvented flat roofs a technical discussion flat roofs have often been built with the insulation all on top of the vapor closed drainage plane as this avoids dew point condensation issues inboard of the roofing. These roofs can lower your heating costs in the winter. Unvented roof assemblies should be insulated either with air impermeable insulation rigid foam or spray polyurethane foam or with a combination of foam and air permeable insulation. If water or air ducts run through your attic space they are less likely to be affected by extreme temperatures and this can save you money on utility costs.

Un vented roofs operate on the principle that moisture entering the roof assembly can be controlled and that there is no need for venting to control moisture accumulation. Martin s post focuses on the marketing of owens corning 039 s propink unvented attic insulation system. Low slope and steep slope unvented roof systems i e. In order for an un vented roof assembly to function properly the following conditions must be in place.

In unvented flat or low slope roofs with parapets perform a full flood test to ensure leak free installation of roofing membrane. However architects of these compact roof assemblies must consider vapor permeance and arrangement of the materials to produce acceptable hygrothermal performance and low risk of condensation in the resulting conditioned attic space. Systems where condensing surface temperatures are controlled and systems where condensing surface temperatures are not controlled. Yes unvented roof assemblies can be insulated with fiberglass a wufi post and not just in climate zones 2b amp.

These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck. Four options for building an unvented roof assembly. If you don t want to use sips or nailbase there are four basic approaches. Unvented roof design falls into two categories.

When properly installed unvented roofs perform well and cause no excess moisture accumulation.