Spray the foam.
Roof venting with spray foam insulation.
Leave a gap on both sides.
It works great as long as there is no moisture which will significantly decrease r value but when you vault a space and spray in open cell foam rising humidity can really soak that foam over time and holding moisture next to wood is not exactly best practice especially in southern humid environments.
These forms are only 1.
Unvented attic assemblies unvented attics rely on an air impermeable insulation installed to the roof deck s underside i e.
Becoming more affordable significant long term energy savings sealing restricts air movement through the building envelope.
In a vented roof foam can seal the openings and serve as an air barrier and a vapor retarder in addition to its insulating function.
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.
Learn how the need for roof vents are determined.
Foam insulation can play an important role in both vented and un vented roof assemblies.
The movement of air into indirect conditioning of an unvented attic is a slow gradual process that will not be noticeable by occupants and typically will not put any strain on the hvac system.
Spray foam insulation has been increasing in popularity over the last several years due to.
Attic ceiling to stop airborne moisture from reaching a cold surface and condensing inside the building envelope in this design insulation effectively separates the interior and exterior spaces while slowing down moisture flow so the dewpoint is not achieved within.
Not long ago someone even told me that in florida roofing companies won t let their workers go up on roofs with open cell spray foam because the roofs are so spongy the guys fall right through.
An open cell foam low density spray polyurethane is a spray applied to provide continuous insulation and an air sealing barrier.
Air sealing also reduces the natural ventilation rate or air leakage rate further reducing heating and cooling loads.
But spray foam insulation used at the underside of the roof deck would need to be covered by a thermal barrier and intumescent coatings are commonly used.
It rots roofs people have told me.
Build the rafters and secure the 5 8 inch cdx sheathing material.
How to vent a foam insulated roof step 1.
This spray foam is applied as a low or high pressure two component polyurethane spray foam that can be applied onto walls in unvented attics to ducts and ceilings and in vented attics and crawl spaces.
