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Community and Q&A

Sloped ceiling insulation

IRFL | Posted in Energy Efficiency and Durability on

In climate zone 5 we have renovation of a cape home and a suggested sloped insulated roof design as following:

Soffit to ridge ventilation with baffles the entire way. Blown in fiberglass insulation in 2×8 rafters 16 oc. Underside of rafters covered with 1.5″ Thermax under the entire roof.

Question: Where is my dew point in this assembly and are their any concerns with this type of air barrier and insulation design?

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  1. GBA Editor
    Martin Holladay | | #1

    If you pay attention to airtightness, you are all set. You don't have to calculate the dew point in your assembly, because it is a vented assembly. As long as you don't have any significant air leaks, there won't be any moisture to worry about.

  2. NBABUCKS1 | | #2

    how are you doing your continuous soffit to ridge ventilation? IE what products and how big is your air gap between vent channels and roof?

  3. IRFL | | #3

    I will use the AccuVent Cathedral ceiling vent baffles. They work great to with closed cell foam insulation if venting is to be maintained.

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