Venting Multi-Level Hip Roof - Ridge Or Static Vents?

Roofing/Construction Questions
1

Hello, all! I hope the good folks on here can give this avid DIYer some advice and insight. My house does not have adequate attic ventilation. From county appraisal records, mortgage appraisal drawings, and my own measurements, I believe the total attic square-footage (including soffit area) is approx. 3013 sq. ft.

Current attic exhaust ventilation consists of 2 12" turbines. Using the 300 rule (50/50 split between intake/exhaust), and confirming by ventilation calculators on manufacturers’ websites, this is inadequate. On a 100+ day, temps exceed 135 in the attic (that wasn’t even the hottest part of the day, and we get a lot of those in South Texas).

The roof is a series of hips, with the roof over the garage coming to a point (“smaller point”) and the roof over the dining/back-patio making another point (“big point”). Here’s a satellite view from Google maps - the house is oriented slightly to the NE (the turbines are the two spots on the back side of the roof):
http://www.roofing.com/forum/gallery/texasprd-a356/roof-shot-t1255.jpg

Here are two more shots, showing the “smaller point” over the garage and the “big point” over the dining/patio areas:
http://www.roofing.com/forum/gallery/texasprd-a356/ssc-0354-t1257.jpg
http://www.roofing.com/forum/gallery/texasprd-a356/ssc-0349-t1256.jpg
The “points” are not as apparent in the ground-level shots, so you have to match those back up to the overhead shot to really see it.

Given this combination of level ridges and hip-points, am I better off going with ridge vents or low-profile static vents (“turtles”)?

There is enough linear footage on the level ridges, and I know I can get hip-ridge vents for the “points”, but on those hip-points above the garage and bedroom/eating/patio, how many of those ridges should be ventilated? Is there an issue with getting a short-circuit effect from “adjacent” ridges if (for example) both of the south-facing ridges on the “big point” are ventilated? Would it be okay to vent opposite ridges on the “points”?

From the low-profile perspective, I know I could spread “turtles” along the east & west sides and back-/south-side of the central section - but again, how to handle those “points”? The attic area covered by the “big point” is considerable, and I doubt one turtle is enough. So, where should turtles go on these “points”?

Many thanks for any input you can provide!!!

2

Is there anything that would prevent you from replacing your 2 turbine vents with 2 power vents? I believe that would be sufficient for 3000 SF of attic.

3

Thanks for the reply!

I’m really trying to avoid power vents. Reasons:

  1. Have to run power to them (cost of electrician plus ongoing cost of electricity)

  2. Power vents can fail

3)Would need at least three power vents (that starts getting pricey) to exhaust all parts of the attic - notice that there is a point/peak over the garage and one over the back part of the house. As I understand it, each would need a vent because the valley between would prevent the hot air from being pulled from the upper section of the unvented peak/point. That would leave one vent to cover the middle and west ends of the house - would there be a similar issue with getting the heat out of the ridge area of the west end, if the third vent is over the middle (living room) section? What would the best location for the third vent?

Maybe I’m wrong (and if so, please explain why), but it seems like equally spaced static ventilation that lets the heat escape where it wants to go (up!) is the best.

4

Does anyone else have suggestions? I appreciate all input/insight!