I suggest making space-heating a synonym of heating.
I find heating a more natural choice and don't think users will look for space-heating. (If they do, they'd be redirected to heating.)
Moreover, Wikipedia writes that
Space heating is generally employed to warm a small space, and is usually held in contrast with central heating, which warms many connected spaces at once. (emphasis mine)
I think that heating, encompassing both space heating and central heating, is the better tag.
(In the sustainability context, heating makes little sense for heating food, but a tag wiki should clarify this. For heating food, food and cooking should be more than enough.)