do you mean a powered attic ventilator (pav) a fan controlled by a tstat & installed in the decking of the roof to pull hot air out of attic? what combination of ventilation do you have? any soffit vents to allow cool air to enter attic? gable end venting? soffit and ridge vents? soffit and pav's? answer depends on these factors. if you have soffit and pav..replace pav with passive ventilators. pav's pull conditioned air from inside living space to cool attic. or do you have a whole house fan that is in the ceiling of the house and pulls house air thru open windows & into attic? hard to tell from your post. best of luck.

no foam mike_home, contractor is proposing blown insulation either fg or cellulose, only OP knows. just google baffles for attic ventilation OP. lots of pics there.baffles are installed on roof at eaves to do two things. one is to keep insulation at low point of eaves/soffits from clogging up air flow. the other is to establish a pathway for air to enter attic at soffit/eaves. attic ventilation that works is one of these three methods. all are stand alone, not strategies to be mixed. gable end vents. soffit/eaves may or may not have vents cut into them. soffit/eaves vents with ridge vent at peak of roof. or lastly soffit/eaves vents with passive vents installed on roof. the idea is to take air from soffits & vent from gable end, ridge vent or passive vents. google attic ventilation for more detailed info. prior to adding insulation minimal air sealing of air barrier (ceiling of living space) from living space to attic is done. for example recessed lights (Insulation contact not IC air tight recessed lights) would be addressed prior to insulation. much harder to dig out each area to be air sealed with newly installed insulation. fortunately, you can do a lot of air sealing from inside the living space. making as tight of an air barrier between living & attic spaces is one of the first steps to efficiency (and better air quality that goes along with it). it is easier to heat/cool a house with minimal air leakage. first area to air seal is house to attic. then floor to crawlspace (now that we have that info) once the air sealing is completed...then insulate. (3" closed cell foam installed on underside of floor, installed from under the house) if you have 8, 12 or 20+ inches of insulation & there is air moving through it...then it isn't performing. keep in mind that there is a diminishing return for more inches of insulation. the first 6" of insulation does most of the thermal barrier work, added insulation above this 6" saves you less & less $$ in utility costs. meeting code minimums is the least you can do. here in La. R0-30 is code, but people often have R-38. not a big jump in price, and not a big savings in utility costs. you make your own call on what to be installed. are you willing to do any work? (ie caulking etc) whats your location? best of luck

Attic ventilation is a science just as much as air conditioning is. In order to vent properly, you need air in to get air out. It's much better to use 'natural ventilation practices'. Powered vents tend to make matters worse, not better. Plus powered vents will burn up in the heat. What is natural ventilation? cold air falls, hot air rises. Follow that principle to cool the attic. You're limited by the design of the home, foolishness of the builder or in some cases the foolishness of the former owner or whoever was last hired to replace the roof and in some cases who insulated the attic (if it was re-insulated). So depending on that you could be looking at major expense to cool (vent) that attic properly. In terms of your air conditioner not cooling below 80F, this may be more of a problem of the air conditioner. Did someone tell you this? I service the Katy, Texas area.

Central Texas - sometimes humid, sometimes dry but always hot in Summers and occasional blast of sustained freezing in Winter I'm really not sure I like the idea of foam in the roof over the un-conditioned garage space. At least not if it effectively 'seals' the attic space over the un-conditioned garage space. Perhaps ensure the foam doesn't close off soffits or ridge vents...? We will have a tankless gas hot water heater off the garage in a closet. We're going with foam insulation in the roof over the living space (with a partition between it and the garage). I think the venting for the hot water heater could easily protrude thru the garage roof and I'd be able to 'see' it. E.g. leaks. I worry about protrusions in roofs with foam insulation because you might not see leaks - at least not for a long time after damage builds up... The roof will be standing seam metal roof. Can they put a cap or whatever it's called for metal roof over the garage portion that allows venting but doesn't look much different from rest of house roof that would not have ridge vent? Blown in loose insulation isn't my favorite either. I just don't like the stuff whenever I get up in current attic... And I do plan on putting 4 or so sheets of plywood up over the garage attic with a pull down ladder for storage of 'stuff' like seasonal decorations, boxes, etc. Some sheets of decking would only allow the blown in up to the rafters and compress it a little. Not ideal. WINTER/COLD: I'm not opposed to insulating the garage as I think it can help take the edge off in the winter months. The water heater and water softener will be in a closet and I think should be OK. But there will be a wash basin against back wall by entry door that could be exposed to freezing. I moved the hose bib from the garage wall - no hose bibs on un-insulated exterior walls. SUMMER/HOT: For this use case - I'm having a hard time seeing much value to insulating an un-conditioned attached garage. To me it seems to mostly 'time shift' hitting 115 or so in the garage - that is it peaks at a high temp a little later in the day and retains that heat a little longer into the evening is all... I do like the concept of a vent in a garage exterior wall that would allow outside air in, and a vent in the garage ceiling to allow hot air to escape up into the attic and out the ridge vents... And soffit vents just at the garage exterior walls, not the living space walls. Still undecided and ambivalent about how to approach insulating the un-conditioned garage - or even whether to do it at all. :)