FLAT Roof - Ice and Water Shield (I&WS)
- Thread starter Bjferri
- Start date
I'm not sure what the advantage of adding I &WS is- they're both vapor-impermeable. There may better materials for providing a slip-surface to minimize strains on the membrane too.
There's a huge advantage to putting down a few inches of rigid foam insulation though- it blocks the thermal bridging of rafters leading to more even temps and less freeze/thaw stresses when there's a snow load, and keeps the roof deck & rafter tops warmer for far less winter moisture accumulation. In summer it blocks the thermal transfer of the short-circuiting rafters to the interior from the hot roof too.
There's a huge advantage to putting down a few inches of rigid foam insulation though- it blocks the thermal bridging of rafters leading to more even temps and less freeze/thaw stresses when there's a snow load, and keeps the roof deck & rafter tops warmer for far less winter moisture accumulation. In summer it blocks the thermal transfer of the short-circuiting rafters to the interior from the hot roof too.
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