Unvented Shed Roof With Above Deck Installation

Yes they are big thermal holes.

Unvented shed roof with above deck installation.

As it cools it can t hold as much moisture. Martin s post focuses on the marketing of owens corning 039 s propink unvented attic insulation system. But a space needs to be a space or what is the point. Yes skylights went in.

Picture a cloud of moisture floating overhead between the rafters. This roof assembly has no insulating sheathing installed above the roof deck. Drying of unvented roofing assemblies is by definition only provided to the interior. Dallas tx is located in a mixed humid climate region.

That excess moisture ends up as drops of condensation on the roof. Essentially condensation occurs at night when the temperature inside a building is warmer than outside. Another approach is to build a cupola or ventilated doghouse in the middle of the low slope roof an approach championed by joe lstiburek. Polyisocyanurate insulation above the sheathing and approximately 91 4 in.

With three layers of 11 2 in. Warm wet air rises and meets the cold roof and cools. Photograph 1 above left. Simply put unvented roofs get rid of the vents and move the thermal air control and moisture boundaries to the roof deck.

Of cellulose insulation in the rafter cavities the roof shown here has an r value of approximately 63. In unvented flat or low slope roofs with parapets perform a full flood test to ensure leak free installation of roofing membrane. The rigid foam will be fairly thick see sidebar how much insulation. Four options for building an unvented roof assembly.

Unvented roof diagram i know this is a very basic example so if you want to read more on the topic i ve put some additional reading for unvented roofs at the end of this article. The three layers of foam help to seal air leaks but to make this assembly perform well you need to incorporate some unconventional details. With rigid foam above the sheathing and cellulose in the rafter cavities this roof is about r 63. Note that this roof assembly has rigid insulation installed above the roof deck in order to control the condensation potential.

Test roofing membranes for integrity prior to covering from below. Yes unvented roof assemblies can be insulated with fiberglass a wufi post and not just in climate zones 2b amp. Deck for a thick roof rigid foam insulation installed above the roof assembly can create an energy smart roof. Figure 4 shows the potential for condensation of an unvented roof assembly in dallas tx.

Furring straightens out rafter plane for smooth plaster finish. You can install all of the insulation above the roof sheathing but the foam has to be thick enough to meet minimum code requirements for ceiling r value. Rigid foam insulation installed above the roof assembly can create an energy smart roof.