Asphalt Shingle Roof — Condensation & Thermal Check

Screening tool (steady-state): estimates temperature and vapor pressure through the roof stack and flags condensation potential where Δp = pv − psat(T) is positive.

Asphalt Shingles OSB / SIP Deck R-60 Blown-In Winter + Summer

Assembly (visual)

Shingles → Felt/WRB → Deck → [Thermal Barrier] → Steel Truss + R-60 blown-in → Gypsum ceiling.

Deck / Sheathing Type

Deck configuration ?

OSB thickness (in) ? 0.563 in

Thermal Barrier (5/8" Type X gypsum below sheathing) ?

Climate

Winter indoor RH (%) ? 40%

Winter outdoor temp (°F) ? 10°F

Summer indoor temp (°F) ? 74°F

Summer outdoor RH (%) ? 80%

Advanced climate

Winter indoor temp (°F) ? 70°F

Winter outdoor RH (%) ? 85%

Summer indoor RH (%) ? 50%

Summer outdoor temp (°F) ? 95°F

Construction quality

Airtightness (ACH50) ? 1.5

Moisture penalty: 8% (ACH50=1.5)

How to read this
Green = vapor pressure stays below saturation at checked planes. Red = condensation probable at that plane.

Screening model only. Does not include bulk water, solar vapor drive, or daily cycling. Use WUFI or similar for full hygrothermal analysis.

Result

Winter risk

CONDENSATION PROBABLE

Summer risk

OKAY

Approx. total R

R-62.8

Worst Δp (Winter)

101 Pa

Worst Δp (Summer)

-1347 Pa

Winter dew point (inside air): 44.6°F
Summer dew point (outside air): 87.9°F

Winter: Deck/CI plane = 101 Pa, Gypsum ceiling = -1365 Pa.
Summer: Deck/CI plane = -1557 Pa, Gypsum ceiling = -1347 Pa.

Δp Across Interfaces (Winter vs Summer)

Blue = Winter · Red = Summer · Dashed = Δp = 0.

Critical planes

Δp at deck and ceiling checkpoints.

Quick table

Checkpoint	Winter Δp	Summer Δp	Worst	Condense?
Deck / sheathing interface	101	-1557	101	YES
Gypsum ceiling (interior)	-1365	-1347	-1347	No

Full table

Layer / interface	Winter Δp	Summer Δp	Worst
Shingles	-39	-1099	-39
Felt	-30	-1127	-30
OSB	101	-1557	101
Therm.Bar.	791	-3899	791
R-60 Blown	-1333	-1349	-1333
Gypsum	-1365	-1347	-1347