Are solar powered vents overkill if you are going to have R55-60 insulation in the attic? Wind powered vents/fans seem extremely weak and ineffective. Thoughts and opinions?

Just collect rainwater and use it to feed an intermittent sprinkler on the roof. I'm kidding - I think.

In general, a hot attic can double the heat loss through the ceiling insulation. But the absolute number isn't that high, so removing that heat might cost more than it's worth. If you do, look at using one fan pulling in and and one blowing out so that you don't depressurize the attic. That is the primary reason that powered attic ventilation isn't cost effective.

jonr has it right- powered or even wind-turbine vents would only serve to depressurize the house, increasing the infiltration losses. Using a CRRC rated "cool roof" material on the exterior cuts into peak cooling loads a bit, but with R55+ in attic insulation actual reduction in cooling load from even that measure would be "in the noise". So long as you have sufficient ventilation cross section to purge wintertime moisture loads (which should be very low, if you air seal the place well) enhanced attic ventilation is of little value.

While SOLAR powered attic ventilators on low pitch low-R roofs in FL can cut the whole house cooling energy use by several percent, in tight high-R houses it's more likely to become a leak-point for rain/snowmelt than provide any real benefit. Even turbine & venturi type ventilators could be counterproductive even in FL, since they continue to pull humid outdoor air in even when the sensible heat loads are low (such as at night), raising the humidity/latent-load of the house, whereas solar ventilators are at least somewhat correlated in time to the sensible load peaks.

Makes me wonder if automatic attic vents (similar to what they use on greenhouses) are economically feasible. Ie, vents that open/close based on temperature, dewpoint, rain and snow cover. On cool sunny days, a warm sealed attic can help you (ie, you don't want vents of any kind).

i figured with a high R attic insulation that the increased venting would be minimal.

i have seen electric vents that open and close once the temp inside the attic reaches a certain point. either way. I'll just stick to my R55+ insulation and call it a day.

thanks.