Unvented Flat Roof

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.

Unvented flat roof.

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. 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. Systems where condensing surface temperatures are controlled and systems where condensing surface temperatures are not controlled. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction.

When properly installed unvented roofs perform well and cause no excess moisture accumulation. These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck. Drying of unvented roofing assemblies is by definition only provided to the interior. Four options for building an unvented roof assembly.

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. If you don t want to use sips or nailbase there are four basic approaches. Low slope and steep slope unvented roof systems i e. These roofs can lower your heating costs in the winter.

Martin s post focuses on the marketing of owens corning 039 s propink unvented attic insulation system. In order for an un vented roof assembly to function properly the following conditions must be in place. 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. In unvented flat or low slope roofs with parapets perform a full flood test to ensure leak free installation of roofing membrane.

This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction.