If you have spray foam insulation, do you still need attic ventilation, and what does it mean for future roof work?

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It depends on where the foam is. Open or closed cell foam sprayed on the underside of the roof deck creates an unvented, conditioned attic under the code's unvented attic rules, so the old vents are sealed off; foam applied only on the attic floor leaves a normal attic above it that still needs ventilation. Either way, foam on the deck changes how leaks are found and how a future roof replacement goes. Foam on the roof deck The attic becomes part of the conditioned house. Soffit and ridge vents should be closed, because outside air would defeat the foam. The code sets minimum insulation levels and conditions for this assembly, and the installer should follow them. Foam on the attic floor Spraying foam over the ceiling seals air leaks from the house, which is good, but the attic above is still a vented space. It keeps its soffit intake and ridge or box exhaust as before. What deck foam means for the roof Leaks hide longer. Water can travel inside or under foam before it shows on a ceiling, so a small leak can rot decking quietly. Decking is harder to inspect from inside. A roofer may need to probe from above. Replacing decking is more work. Sheets bonded to foam do not pull off cleanly, and the foam has to be patched afterward from inside. Nail placement matters. Roofing nails still need to penetrate the deck; foam does not change that. Shingle warranties Shingle manufacturers have different positions on unvented attics. Ask the roofer to confirm the current policy of the brand going on your roof before installation. Selling the house Home inspectors and some buyers ask about deck

If you have spray foam insulation, do you still need attic ventilation, and what does it mean for future roof work?

Foam on the roof deck

Foam on the attic floor

What deck foam means for the roof

Shingle warranties

Selling the house

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