Hybrid Roof Ratio – Zip Roof Sheathing – Climate Zone 6
Based on this recent article and chart attached: https://www.greenbuildingadvisor.com/article/the-ratio-rule-for-hybrid-roof-insulation
In climate zone 6, if I only use 1/2″ Zip roof sheathing, and roof code is R49, then I should not use any insulated roof deck sheathing at all, because I would not meet the hybrid-ratio minimum R25 suggested for above roof deck and R24 below roof deck.
I thought any amount of exterior insulation would be good, but it seems not. Am I missing something?
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