Any thoughts on the benefit of a motorized attic fan to vent the heat out of the attic?    I have a one story house, I'm looking to get the ceiling (attic) above the attached garage insulated.   I'm then thinking of pumping the hot air out of the attic using a solar powered fan.   Would that help cool the garage at all?   The fan claims to help reduce the amt of A/C you need in the house, help preserve the insulation from breaking down and reduce the wear on the asphalt shingles by reducing the heat beneath them.   

I had an insulation installer give me some strange story about my cellulose insulation and how it was flying through the air of my house through the air conditioning system.   Not once have I seen cellulose flying through the air of my house and I've actually had the A/C inspected 3 times in the past 2 years for unrelated issues and no one has mentioned cellulose in the system.   I also look at my white fluff in the attic and it looks fine, not breaking down, not being sucked into the A/C.  It looks as cloud like as it did when it was installed.    Now I'm scared that other sales folks will try to give me other strange stories and I won't realize it.   

What part of the country are you in?  That's going to make a difference in the advice.

I installed a whole house attic fan in my house, to save on A/C costs at certain times of year.  It does work, and works well, as long as you have sufficient venting in the attic.

In the middle of the afternoon, it won't help you much, as you need to open a window or door for it to draw air, which will be very warm air.

The ideal times for an attic fan to run are morning and evening.  I could never get much breeze coming through my house with all the windows open, so the attic fan forces the air up and draws in cooler air (after it cools outside).

We run an attic fan for summer cooling.  Since they started tracking nighttime low temperatures in Colorado, there have only been three nighttime lows of 70 F or above, so we nearly always dip down into the 60's.  That makes an attic fan very effective at cooling the house down at night, both cooling the house and the attic.  By 5 the next day we might creep up above 80 in the house on a hot day, and on an exceptional 100+ degree day we might get up to 85 F by 7pm or so.  Recently we got a couple of room minisplits for those days, but we really don't use them much.

As mentioned by another, I think the concept of ATTIC fans and whole house fans got mixed up.  They are different.  An attic fan only ventilates the attic.  It has a hole in the roof, or maybe just the ridge vent, and draws air in from the soffit vents.  No connection to the main house space.  It replaces the stale, hot air that builds up in the attic with less hot air from outside.  It would help cool the attic a little because the hot air in the attic is a bit hotter than the moving air outside in the wild.  Not sure about this concept of protecting the insulation.  Fiberglass or cellulose is inert.  It is unaffected by about everything as long as it does not get wet.  And the roof should keep the rain out.  That is a different story.  Fiberglass or cellulose does not care about temperatures.  100, 150, 200 degrees, makes no difference to it.  Its inert.  Does a 2x4 care if its 75 or 100 or 125 degrees?  The ridge vents and soffit vents are a passive way to reduce the heat and ventilate, remove moisture, in the attic.  A electrical powered fan would improve on this.  But not sure it improves much to matter.

Whole house fans are different.  They ventilate the living space in the house.  NOT the attic.  As stated, they draw cool air in through windows, doors and shoot it out through the roof.  Assume you would make a hole in your living room ceiling and in the roof to exhaust the air.  And have ducting that goes directly from the living space through the roof and outside into the open air.  Never touching the attic air itself.  It works the same way as the ridge vents and soffit vents on your roof except applied to the living space.  And most likely always powered by an electrical fan, blower.  And as stated, this works best when it gets cool and nice at night, you turn on the fan, it gets all the hot air out of the house and allows you to sleep nicely.  You turn it off in the morning and throughout the day the house and outside air all heat up so not much point in blowing hot air through the house all day long.  Wait until night time again and then pull in the cool night air and blow out the hot inside air.  Great passive, active cooling system if your environment allows it.  If you live in the Midwest where it gets 98 degrees and 90% humidity in the day and 88 degrees and 89% humidity at night, it does not work well.  Its hot sticky muggy humid.

Sorry, I didn't mean to sidetrack.  I thought one of the posters meant a whole house attic fan and I was clarifying how it wouldn't be what the OP wants.

A powered attic fan (vs a solar one) would help a little, but I'm not sure very much, without having plenty of insulation first.  I've seen powered attic fans that can be controlled by a thermostat, so at least it could turn on automatically at, say, 100F... but it will only get you so far if the temperature that afternoon is 90 or 95F.

Jerry...thanks for your thoughts.   I actually have a cheesy, insulated, west facing garage door.   I won't say that the insulation doesn't help, but ...I wish it helped more!    I need to find someone to blow more insulation in the ceiling of the garage and I definitely think it's a strong first step.    The issue is finding a qualified person to do it.   

The house was built in 2012,  so it has radiant barrier etc.   I added the attic hatch insulation cover where it unzips to allow you to enter the attic and tries to block the heat from coming out of the hatch.   The hatch also appears to have insulation board. 

Part of my issue with a minisplit is having a location to put the outside unit where the HOA won't complain (I'm allowed 1 minisplit system OR a window unit, but it has to be covered up and in that location, it could become difficult to create a covering since it's in an unfenced area between my house and the house next door - I can't fence it off so I might have to add more bushes on the property line to cover it up)

Then...there's the $$$.   I don't do this full time...I'm just a part time hobby person.  My main crafting is weaving, knitting, sewing etc.   I just build tables or custom tools for my crafting!   I would eventually like to convert my garage into a "makerspace", which would have a CNC, 3D printer and such.   But at the rate I'm going, I may only be able to tolerate that garage 50% of the year. 

One step at a time...I'll keep working on getting the insulation in first, since I can't do anything without that.