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.
Attic venting with spray foam.
Install a minimum of 1 inch of spray foam insulation over the attic floor to provide a continuous air control layer.
Spray foam insulation was applied to prevent the warm moist air rising from the interior of the home from condensing on the upper roof structures.
That is why mechanical ventilation has to be introduced to ventilate the spray foam attic.
A lot of builders and homeowners are going with spray foam insulation because of the airtightness benefits.
The most important reason to transform your vented, unconditioned attic into an unvented, conditioned attic is to bring your air handler and ductwork inside your home's conditioned space.
Spray foam insulation performance can offer different ways to address problematic situations:
From a design perspective, attic venting is not provided to address roof leaks.
You're looking to insulate your attic, and are wondering if you need roof vents with spray foam insulation?
It used to be that it was, you know, super hot in the summer and really cold in the winter.
With it, the orientation and type of insulation applied to the top of the building enclosure has changed from the traditional way, and so temperature and moisture conditions experienced by various assembly elements will be impacted.
The simple reason is that spray foam is applied to the attic ceiling and not the attic flooring.
The alternative system is using high density, closed cell spray foam directly to the roof deck eliminating the need to ventilate.
Actually, you should probably get rid of power attic ventilators whether or not you’re sealing the attic, but that’s another article.
Basically, code prohibits venting when you spray foam on the underside of the roof.
There is no need to install any spray foam on your attic floor, since you will be moving your air barrier and your insulation layer to the sloped roof assembly.
Ventilation is not needed in attics with spray foam insulation because sealed attics that have spray foam applied on the underside of the roof sheathing (the attic’s ceiling) should be airtight, ie they are thermally and physically closed off from the.
Only spray polyurethane foam can be used for this application, as batt insulation will end up sagging and blown insulation simply can’t adhere to the roof decking.
The intended purpose was to allow warm air and moisture to escape.