Perhaps you need something simplier
You'd have a hard time turning a turbine from the heat in your attic. You'd have to use something with a low boiling point, then have something to cool it back to a liquid. The amount of energy you'd get would almost certainly not be enough to pay for the equipment in any sort of reasonable time frame (say 10-20 years).
Perhaps you need to do something simplier. You could mount a tank in your attic and use that to help provide your family's hot water needs. That would be much cheaper than generating electricity and would still save energy overall.