If you have a hot space adjacent to a cooler space, heat energy will flow from the hot space to the cooler space until both spaces become the same temperature. Adding insulation between these spaces will slow down, but not prevent, the heat transfer process. So, adding insulation anywhere will not provide any lasting cooling effect. That is why builders do not add insulation to a garage ceiling. Also, blowing 90+ degree air into any space will not cool the space any lower than 90 degrees.
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