Unvented Porch Roof

In went some skylights on the back side photograph 1 and the rafters got sprayed full of 2 lb ft 3 density spray polyurethane foam spf photograph 2.

Unvented porch roof. Unvented roofs vented roof. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. The attic was turned into living space. Like a wall that is severely out of plumb an unvented roof has insulation packed into the framing cavities aligned with the sheathing.

Rigid foam above roof sheathing. It was a completely uninsulated and unvented roof. 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. Four options for building an unvented roof assembly.

Because porches are often open and unconditioned venting a porch roof for that reason is not usually necessary. The second is an unvented conditioned attic with open cell spray foam insulation under the roof deck and which contains the ductwork. Low slope and steep slope unvented roof systems i e. Foam and the roof assembly foam insulation can play an important role in both vented and un vented roof assemblies.

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. Because the attic space is now inside the thermal envelope blowing a little heat up there is not like throwing twenty dollar bills out the window. 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. In an un vented roof foam can serve as the air barrier and vapor retarder and prevent moisture from getting in to the roof cavities.

I installed collar ties to leave an open space above the finished room along with r 15 insullation and installed a fan on a thermostat at the end of the roof in addition to ridge vent to suck all the hot air that collected between the roof and porch ceiling. If you re willing to invest some more consider an insulated porch roof. The rigid foam will be fairly thick see sidebar how much insulation. A properly functioning un vented roof.

The most common argument in favor of porch roof vents is that venting hot air from. The insulation can go below the roof deck above the roof deck or both. What was the original roof construction. 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.