Thermal Conductivity of Structural Screws
Climate Zone 5 deep energy remodel on A Frame structure.
There is no attic, structural tongue and groove (roof deck) is attached to the exterior of the internal A-Frame timber structure.
There is no internal insulation “under” the tongue and groove, as the tongue and groove presents as the decorative ceiling within the A frame.
Roof will have air/water barrier at structural deck (T&G), rigid insulation, then insulated and vented Hunter panel (or equivalent). Metal roof underlayment on top of the Hunter panel and then standing seam, hidden fastener, metal roofing as the final layer. When attaching through the Hunter panel and rigid foam (all layers) into the T&G roof structure, long and appropriately rated screws will be used in a resilient roof screw pattern (opposing angles).
There are two (2) concerns:
1. During extended cold periods and/or snow on roof, the top of the screw head under the metal roofing getting cold and transferring the cold into the roof assembly/structure.
2. During extended heating days, the top of screw heads becoming “hot” and transferring that heat into the roof assembly/structure.
1. Is this even something to be concerned about?
2. If so, do the screws needs to be thermally broken?
3. If screws need to be thermally broken, how? Technique or Product recommendations?
1. Counter sinking of the screw heads on the Hunter panel would be difficult.
2. Any thermal break material (fiberglass or foam blocking) on top of the screw heads could show up in as “bumps” under the metal roofing.
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