2009 irc section r806 4.
Unvented flat roof.
In this case you can learn a lot from foam tech s article vented vs.
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 flat roof assembly.
Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction.
Unvented roofs which provides a detailed explanation of each.
However designers of compact roof assemblies must consider vapor permeance and arrangement of the roofing materials to produce acceptable hygrothermal performance and low.
Condensing surface temperature controlled the thickness of the rigid insulation at both the roof deck and perimeter is determined by a calculation procedure similar to figure 5.
Removing moisture from roof cavities structural members sheathing and insulation.
These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck.
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.
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.
However in many situations the insulation may need to be primarily or entirely below the flat roof membrane and between the roof joists if so what are the best options.
The unvented attic space is completely contained within the building thermal envelope.
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.
There are traditionally four main reasons for venting a roof.
The colder the climate the thicker the rigid insulation required.
Controlling ice damming by keeping the roof cold.
Unvented roofs vented roof.
2012 irc section r806 5 unvented attic assemblies unvented attic assemblies spaces between the ceiling joists of the top story of the roof rafters shall be permitted if all of the following conditions are met.
The higher the interior moisture level the thicker the.
