We think heat-reuse is a really good idea, and systems level thinking like this is essential for greener server infrastructure.
At present though, we do not have a way to account for this in our own criteria when marking an energy supply as green.
So, if you want a site or service to be marked as green, you still need to provide the required evidence as we describe elsewhere on this website.
How to change this in future
We are members of the Sustainable Digital Infrastructure Alliance, and they have a heat re-use working group. If you’d like to help decide conventions for recognising this kind of innovative resource usage, we encourage you to join us there.
https://sdialliance.org/steering-groups/excess-heat-utilization-from-data-centers
Further reading
If you think this is a good idea, there is already policy support in some parts of the world. In the Netherlands there is funding to support new projects, with a subsidy of 300 EUR per tonne of avoided emissions.
If you want to dive into the literature, this page in the Openmod energy modelling community forum is also good starting point.