Unvented Shed Roof With Above Deck Installation

With rigid foam above the sheathing and cellulose in the rafter cavities this roof is about r 63.

Unvented shed roof with above deck installation.

Rigid foam insulation installed above the roof assembly can create an energy smart roof. Essentially condensation occurs at night when the temperature inside a building is warmer than outside. Figure 4 shows the potential for condensation of an unvented roof assembly in dallas tx. Yes unvented roof assemblies can be insulated with fiberglass a wufi post and not just in climate zones 2b amp.

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. Polyisocyanurate insulation above the sheathing and approximately 91 4 in. Another approach is to build a cupola or ventilated doghouse in the middle of the low slope roof an approach championed by joe lstiburek. Yes they are big thermal holes.

Deck for a thick roof rigid foam insulation installed above the roof assembly can create an energy smart roof. Simply put unvented roofs get rid of the vents and move the thermal air control and moisture boundaries to the roof deck. Rigid foam above roof sheathing. 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.

Photograph 1 above left. In unvented flat or low slope roofs with parapets perform a full flood test to ensure leak free installation of roofing membrane. But a space needs to be a space or what is the point. Four options for building an unvented roof assembly.

If the upper edge of a low slope shed roof intersects a vertical wall the most logical approach in my opinion is to detail the roof as an unvented roof. Test roofing membranes for integrity prior to covering from below. Drying of unvented roofing assemblies is by definition only provided to the interior. Picture a cloud of moisture floating overhead between the rafters.

That excess moisture ends up as drops of condensation on the roof. With three layers of 11 2 in. Martin s post focuses on the marketing of owens corning 039 s propink unvented attic insulation system. Warm wet air rises and meets the cold roof and cools.

Original roof uninsulated rafter framing with board roof deck. Note that this roof assembly has rigid insulation installed above the roof deck in order to control the condensation potential. Yes skylights went in. The rigid foam will be fairly thick see sidebar how much insulation.

Of cellulose insulation in the rafter cavities the roof shown here has an r value of approximately 63. The three layers of foam help to seal air leaks but to make this assembly perform well you need to incorporate some unconventional details. This roof assembly has no insulating sheathing installed above the roof deck.