Do I need to install a gable vent on every gable?

Vent the highest point of the house.
No need to do every gable if the roof is open (attic).
If you ever re-roof then consider ridge vents.
Can’t get any higher than ridge vents.

Thanks

also if you can put some vents in the soffit (back under the gutter. They can be the rectangular type or round 2 – 4” type ( with screens!). Or if no soffit, then a vent on the opposite end of the attic of where highest gable vent is located to get natural convection to “move” air. If your home is not air conditioned and you want to move air through house, then If the is a place to get to the attic, stairs, hatchway etc, consider a whole house fan installation. Amazing what that will do for warm humid still nights. Also, is check on the insulation of the attic “floor” as hot in summer and cold in winter will penetrate to rooms below if not insulated.

I’ve thought about the whole house fan for sure. Problem with my home is it was built in the 50s and has had many additions. The attic areas all have insulation, but are sometimes cut off from each other so cross-gable ventilation won’t happen the way it should. I’d like to vent the soffits someday, but not this year.

Curious, if I install ridge vents and soffit vents, would that be the optimal ventilation system? Would I still need gable and roof vents if I had that?

Soffit to Ridge would be the optimal solution. Air pulled from under the eaves to exit through the ridge. Cross ventilation (gable vents) work really well if you have a powered (fan) that is thermostatically controlled. Check out the options at your local home center or roofing contractor. Business is kinda slow in summer unless the contractor is building new or doing remodels. The economy might be to your advantage getting some decent bids for the project. Usually these guys can do it faster and cheaper the the average home owner. Plus you get a warranty.
Good luck

I was looking at those the other day. They make a solar powered one now, but it is kind of pricey. Maybe I’ll build my own one day.

I get a pro could do it faster, but how could they do it cheaper than me?

How handy are you?
Do you have ALL the necessary tools. Will you need to rent equipment?
Know where to poke those holes?
I’ll bet you could get insulation done cheaper by the pros than doing it yourself. I’m also guessing that the ridge vent material isn’t a stocked item at most home centers.
Get some estimates. You might be surprised. Getting the job done in two or three days beats having the house open for two or three weeks…

Oh, I thought you were just talking about installing an electric gable fan, not installing ridge vents. They do sell ridge vents at Lowe’s though, but I’m not tackling it today. Is there a way to install them w/o reshingling the whole roof?

But yeah, I’m pretty handy. I took the week off to install vinyl siding, and am pulling off all the wood siding first. Found about 15 feet of rotted sill plate and joist I replaced, had to do a real sheating jigsaw puzzle to replace all that rot and get everything flat. Now I’m installing house wrap and proper flashing, then hopefully I’ll get to start putting in some siding later today.

Are you a contractor? If so, I’d like to shoot you questions from time to time.