Unvented Roof Systems

Air permeable insulation such as fiberglass batts dense packed cellulose or blown in fiberglass can t be used alone for an unvented assembly since these types of insulation can allow moist indoor air to reach the cold roof sheathing leading to condensation or moisture accumulation.

Unvented roof systems.

Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck. Controlling ice damming by keeping the roof cold. 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.

Removing moisture from roof cavities structural members sheathing and insulation. While unvented attics are gaining acceptance homeowners must realize their limitations including. A system most likely to be found in newly built homes. When properly installed unvented roofs perform well and cause no excess.

However designers of compact roof assemblies must consider vapor permeance and arrangement of the roofing materials to produce acceptable hygrothermal performance and low. Unvented roof systems can be safely used in many different climates. These roofs have some pros and cons as explained in the article. Sc historically typical construction of homes in canada and the us have vented attics between the ceiling of the interior space and the roof.

An unvented assembly can perform well but it s important to get the details right to avoid sheathing rot. Enhancing roofing material life span by reducing sheathing temperature. The term hot roof is something of a misnomer as the attic space will only be a few degrees warmer than in a traditional roof. Many local building codes do not account for non standard construction alternatives such as unvented attic assemblies.

Unvented roofs have a number of advantages. As a result unvented roofs have become popular in homes with feature dense roofs think multiple skylights dormers and other aesthetic flourishes. An unvented roof assembly is constructed without any ventilation and is fully sealed on all sides and filled with insulation. Ventilation becomes more difficult the more complicated a roof s construction is.

Also unvented roof assembles make complicated roof geometries more viable as they are difficult to ventilate effectively.