We will be replacing our roof soon, and I need to finalize whether or not to use a ridge vent and whether to reinstall gable end vents.

Texas Hill Country house, edge of Climate Zones 2 and 3, just inside the Warm-Humid line on the IECC climate map. We have virtually no snow or accumulation. In the winter attic temperature and dewpoint can be close throughout the day and night, or largely separated from cold front dry air. Summertime dewpoint approaches ambient and attic temperature at night; daytime heating causes large separation.

The house was built in 1978, 2×6 joists and rafters, fiberglass batt insulation in the ceiling – poor detailing – perhaps R 15, heat pump / ductwork in the attic, canned lights, uninsulated/unsealed interior soffit drops, leaky 1970s air sealing, 5/12 pitch gable roof with asphalt shingles with no ridge vent, and a complicated attic reducing air flow through gable vents. Soffit vents were originally installed, but air pathway through the rafter cavities was blocked by insulation. Effectively an unvented attic most of the time.

Note: there is no mildew in the attic, including near the ridge, except around old roof leaks (vent pipe penetrations, etc.)

Air sealing the ceiling will directionally reduce moisture in the attic. New bathroom fans and kitchen vent hood will be ducted through the roof. We plan to upgrade our air HVAC next winter, hopefully reducing supply and return leakage, reducing attic drying on some days. More attic ventilation will directionally wash in more ambient humidity. Moving insulation to the rafter cavities would be difficult, plus they are not deep. Rigid insulation above the roof decking is not practicable.

I installed Hardie soffit Vented Plus and opened up air passageways above the plate in anticipation of using continuous ridge venting.  Gable ends are framed for new gable vents but currently blocked off. On windy days there is more air movement with the upgraded soffit vents / removal of insulation blockage, even without gable end vents.

We will be replacing the roof soon with a double lock, standing seam galvalume metal roof, with peel-and stick-underlayment over the roof decking.

With the new roof I don’t want to create an issue where none currently exists.

I have a science and engineering background and have digested lots info on attic venting on GBA and online by numerous building science experts.

However after looking at the thermodynamics, I wonder whether ridge venting would actually provide benefits?

Same question for gable end vents?

Thanks, Mark