DIY

This is actually a really bad idea.

At "best", your server is a resistive heater. Aka "a space heater". Except that your server also has hardware designed to convert power into negative temperature (you know... fans). So you are at a lower efficiency than the space heater in the corner.

Also? Computers aren't meant to run all that hot for all that long. Yes, the safe margin for hardware is a lot higher than people would think. But if you want this to make a meaningful difference you are going to be running REAL hot for extended periods of time. Because you don't need heating when it is warm outside. You need it when it is cold and you are already going to be fighting a low ambient temperature.

The reason this works for larger data centers and specialized installations is that they are designed with this in mind. You generally either have direct water cooling of the racks (plural) or you have "water cooling" of the server room itself. With the water then being recirculated amongst the radiators in the building itself. And... those are quite often borderline "scams" because they don't actually keep the building all that warm in the winter (as discovered during The Pandemic when the lack of body heat from human beings caused issues for a lot of hybrid office/data centers) and they mean more HVAC costs to keep the building cool during the summer.

Which gets to the other aspect. Are you going to change all your fan and cooling settings on a weekly (or even daily) basis? Because maybe you want to get right up to thermal throttling during the winter because the ambient temperature means that heat will "dissipate" fast. But during the summer or even a warm winter day? You are turning your server room into the kind of inferno that even Tom Cruise has someone else deal with.

Don't get me wrong. Having a chonky and inefficient PC is great for late night gaming in the winter when you should have gone to sleep hours ago and your zone is already set for the "nobody but the cat is in there" setting. But, even at the datacenter level, it is not a good replacement for HVAC. And, as a lot of us will attest: Summer is when you grab the Steam Deck or go downstairs and use the xbox.