During an attic ventilation inspection, first of all make sure that all vents are unblocked. In some cases, the homeowners intentionally blocks a vent opening to reduce the cold air entering the attic and reduce the heat loss through that opening, but this is actually causing a problem instead of fixing one.
If the attic is properly insulated, the heat loss through vent openings is minimal. Reducing moisture through those vent openings is more important. You will be able to tell whether the attic is adequately ventilated simply by looking around. Check the roofing nails projecting through the sheathing, and if you do your inspection on a winter day when the temperature is around 20 degrees F you will find frost on the roofing nails if the area is not properly ventilated. The frost that forms on the nails melts and drips onto the floor during the warmer periods of the day, and many droplets of water show up as circular stains on the floorboards and on top of the insulation.
If you conduct your attic ventilation inspection during the warmer months, you will find rust stains and mildew on the sheathing, near the nails. Pay particular attention to the northern slope of the roof, because this begins to delaminate before the southerly slope. If the area is not properly ventilated and plywood is used for the roof sheathing, delamination might be an issue.
If so, the entire roof sheathing and shingles must be replaced. Note that this condition (delamination) can be avoided by keeping a properly ventilated attic. If it is inadequately ventilated, correcting this condition is relatively easy. All you need to do is increase the size of the existing vent openings, if any, or to install additional openings such as roof vents, ridge vents, soffit ventilation, or a power ventilator. A professional will be able to give you precise guidelines for attic ventilation, with the exact number of vent openings needed.
Whole house fans are not fans in the way that you traditionally think of fans. They are not the little things that you put in your living room on hot days. Rather it is a fan that is permanently installed in your attic. It will cool the entire house by drawing cool air in through the windows and ventilating it out through the attic.