This roof assembly has no insulating sheathing installed above the roof deck.
Unvented shed roof with above deck installation.
That excess moisture ends up as drops of condensation on the roof.
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.
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.
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.
Test roofing membranes for integrity prior to covering from below.
Note that this roof assembly has rigid insulation installed above the roof deck in order to control the condensation potential.
Dallas tx is located in a mixed humid climate region.
With rigid foam above the sheathing and cellulose in the rafter cavities this roof is about r 63.
Of cellulose insulation in the rafter cavities the roof shown here has an r value of approximately 63.
Yes skylights went in.
Rigid foam above roof sheathing.
Picture a cloud of moisture floating overhead between the rafters.
Four options for building an unvented roof assembly.
Rigid foam insulation installed above the roof assembly can create an energy smart roof.
The three layers of foam help to seal air leaks but to make this assembly perform well you need to incorporate some unconventional details.
Polyisocyanurate insulation above the sheathing and approximately 91 4 in.
Deck for a thick roof rigid foam insulation installed above the roof assembly can create an energy smart roof.
Martin s post focuses on the marketing of owens corning 039 s propink unvented attic insulation system.
In unvented flat or low slope roofs with parapets perform a full flood test to ensure leak free installation of roofing membrane.
Yes unvented roof assemblies can be insulated with fiberglass a wufi post and not just in climate zones 2b amp.
Furring straightens out rafter plane for smooth plaster finish.
As it cools it can t hold as much moisture.
The rigid foam will be fairly thick see sidebar how much insulation.
Another approach is to build a cupola or ventilated doghouse in the middle of the low slope roof an approach championed by joe lstiburek.
Photograph 1 above left.
Original roof uninsulated rafter framing with board roof deck.
Yes they are big thermal holes.
Figure 4 shows the potential for condensation of an unvented roof assembly in dallas tx.
Drying of unvented roofing assemblies is by definition only provided to the interior.
Warm wet air rises and meets the cold roof and cools.
With three layers of 11 2 in.
