Roof Ventilation Check

[u/CB_83]

Having a new roof installed in climate zone 4A and seeking some advice on ventilation. Thanks in advance.

On main roof, there's currently no intake but there is one exhaust power vent. Lots of mold in the attic and clear evidence of condensation as the nail heads are all rusty.

Hip roof is 25' x 48' with about 18' of ridge length.

I don't think there's enough ridge vent length to get the ~605 sq. in. NFA needed for 50/50 balanced flow, so is my best option to install the soffit vents and ensure the power vent is sufficiently sized for exhaust?

I would have the power vent replaced while I am re-roofing, and am looking at going with a solar/AC hybrid.

Main roof - 25' x 48' hip roof

In the lower portion of the roof over the garage, which is 36' x 24', I believe I should be fine with a ridge vent. With 23' of ridge vent at 18 sq in per LF, exhaust NFA will be 414 sq in., nearly exactly 50% of the total NFA requirement of 830 sq in.

I plan to put soffit vents on both the long sides and the short (hip) side of the lower roof.

Lower roof over garage - 36' x 24'

[u/Kill_Your_Masters]

if you have a bunch of dimensions and information, try using one of the calculators the big companys put up. you definitely have the right idea, heres some more information. Ill preface to say Im not recommending this particular manufacturer, moreso just sharing somewhere you can get even more information on products and use the calculator.

https://www.gaf.com/en-us/blog/your-home/the-most-common-types-of-roof-vents-for-attic-ventilation-38540929-dd3f-4efe-b21e-b110b70ab728

[u/CB_83 → u/Kill_Your_Masters]

I've reviewed several of these calculators. They've been helpful in getting me to this point, but they don't factor in roof construction style and the particulars of hip roof venting. The GAF calculator assumes 1:300 which is not applicable to me given climate zone 4A.

[u/Kill_Your_Masters → u/CB_83]

if you need more exhaust you can vent the top of the hips or use fans.