There is absolutely no room for error in the detailing and installation of roofing and air sealing in these assemblies.
Unvented flat roof assembly.
Figure 6 describes open cell spray foam as air permeable.
Drying of unvented roofing assemblies is by definition only provided to the interior.
By installing spf insulation spray in place insulation in lieu of mineral fiber insulation in the joist cavity of a flat roof or between rafters of a cathedral ceiling the assembly may perform the same as or better than that of a typical one and venting can be shown to be unnecessary.
This document provides a brief description of different types of unvented roof assemblies and the benefits of unvented roof construction.
It s not and so code doesn t require r value ratios.
Unvented flat roof assembly.
An unvented roof assembly is constructed without any ventilation and is fully sealed on all sides and filled with insulation.
Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction.
In some climates it requires a vapor barrier.
Yes unvented roof assemblies can be insulated with fiberglass a wufi post and not just in climate zones 2b amp.
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.
Four options for building an unvented roof assembly.
These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck.
Low slope and steep slope unvented roof systems i e.
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.
The higher the interior moisture level the thicker the rigid insulation required.
Sc historically typical construction of homes in canada and the us have vented attics between the ceiling of the interior space and the roof.
Before constructing a flat roof assembly please refer to the unvented roof assembly comments under 6 2 vented and unvented roof assemblies and if applicable 6 3 parapet walls.
If you don t want to use sips or nailbase there are four basic approaches.
Read all of r806 5 carefully.
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.
This is a mis interpretation of the code.
In unvented flat or low slope roofs with parapets perform a full flood test to ensure leak free installation of roofing membrane.
Martin s post focuses on the marketing of owens corning 039 s propink unvented attic insulation system.