Guest Blog- Atlas Lofts
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Incorrectly installed under-deck spray foam insulation can void the Atlas shingle warranty because spray foam insulation products applied directly to the bottom of the roof deck do not allow for crucial eave-to-ridge airflow.
Atlas does not warranty its shingles when spray foam is applied directly to the underside of the deck.
Asphalt shingle installers or design professionals are responsible for providing adequate ventilation that meets warranty requirements and local codes.
As Paul Casseri, Atlas product manager, shingles and underlayment division, explains:
Atlas Roofing requires that attic ventilation meet or exceed the FHA minimum requirements of at least 1 square foot of net-free unrestricted air flow for each 150 square feet of attic floor space, or 1:300 with a balanced system. While some model codes include an allowance for reduced vent area when the system is properly balanced, an unbalanced system may result in performance and durability issues.
Atlas Roofing does approve and warranty the use of Atlas shingles with spray foam in certain situations:
Atlas Roofing will accept the installation of asphalt roofing shingles and/or self-adhered roof underlayment over highly insulated roof decks insulated with any type of foam insulation when an effective means of providing air flow directly below the nailing surface — such as baffles — is permanently installed.
The best option for a solution for providing under roof decking ventilation would be to install a vented nail base over or a minimum 1-inch baffle system under the original roof decking.
The vent baffles or chutes create a space between the roof deck and the insulation. Installers can also use or construct a ventilated deck sub-assembly, which is applied over or in place of the existing deck.
This solution provides the eave-to-ridge airflow needed to achieve adequate ventilation for shingle performance and warranty requirements.
The provided air flow must be continuous from the eaves through to the highest point of the roof area, available directly below the decking to which the underlayment and shingles are attached.
The best approach is to employ the right amount of vent area, installed as part of a balanced system. Always provide at least 50%, but no more than 60%, of the total required ventilation at the eaves or lowest portion of the roof possible.