Vented Vs Unvented Attic

A properly constructed unvented attic is immune to the moisture problems that occur in vented assemblies and is much more likely to be energy efficient.

Vented vs unvented attic.

Section r806 4 unvented attic assemblies. Don fugler research director canada mortgage and housing corporation. In other words vented roofs may well be the best design for one home while an unvented roof will be a better solution for another home. Let s dive a little deeper into what that means exactly.

Note that this would not apply where an unvented roof assembly is used as indicated in section r806 4. Unvented roofs which provides a detailed explanation of each. Airtight ceilings are a more reliable way to ensure a dry attic than venting but in practice most houses fall into a middle ground where venting balances moisture input. When insulating your attic the contractor can either spray the attic floor to keep a vented attic or spray the roof deck for an unvented system.

A vented attic system refers specifically to having working vents in the attic. The choice of venting or not venting is a design and construction choice not a requirement determined by the physics or by the building code. Vented roofs vented roofs serve a number of different purposes and their roles vary from climate to climate. A vent space clearance of at least 1 must be maintained at the location of the vent and between insulation and roof sheathing.

The model building codes allow both vented and unvented roof assemblies. It has been shown that ventilation has a great effect on the attic air temperature but much less on shingle temperature. Codes for unvented attics. Requirements for unvented attic assemblies are provided in section 0806 4 of the international residential code 2009 irc.

In an unvented assembly anything below the insulation including an attic is considered conditioned space. Researchers have compared the shingle temperature of both vented and un vented roof systems. Basically the term cold roof refers to a traditional roof or vented roof while hot roof refers to a roof that is not ventilated and which has foam insulation attached directly to the roof sheathing. Attics or roofs can be designed and constructed to be either vented or unvented in any hygro thermal zone map 1.

This section outlines the conditions for unvented attic roof assemblies. Unvented may 11 2015 2 26pm deciding to upgrade your attic insulation to include spray foam insulation like icynene is a step toward energy efficiency and a more comfortable home.