Über Roof Insulation Retrofit (with an overhang to boot) Adding exterior foam on an old roof is a good idea whenever a reroof is planned. Existing roof sheathing
Because old roofs were often framed with 2x6s, there isn't much room for insulation. Nowadays, energy codes require a lot more.
Peel and Stick membrane
Two layers of rigid foam with seams staggered. Tape seams on second layer.
Cut rafter tails and block the openings. 2x4s screwed into rafters supply backing for roof deck and ventilation channel. Connect roofing membrane to house wrap with peel and stick flashing.
Mortar mesh and insect screen stops bugs.
Soffit blocking, soffit, fascia, and overhang create a solid beam.
Watch the animated drawing on your phone.
Source: David Joyce, Synergy Construction, Lanchaster, MA Illustration: Daniel Morrison
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