I came across an interesting concept over the weekend where I read that an American inventor had designed an inflatable shelter for the homeless.
You may think this is a simple tent but it is designed to attach to an external excess heating unit (HVAC) which will heat up the unit to keep the homeless warm in the winter months.
For less than 5$ this seems a sensible way of re-using heat which would simply dissipate into the air.
I’m sure such a concept could take off during the night but I can’t imagine many people wanting these inflatables visible outside their buildings during the day.
Take a look at the paraSITE: http://michaelrakowitz.com/projects/parasite/
and maybe you could think of a less controversial way of re-using this kind of energy ?