I would say that heat IS required in order to properly purge.
I don't think you can properly purge without heat. The heat keeps the bho viscous enough to allow the tiny bubbles of butane to travel to the top layer and evap.
if you were going to use a vacuum pump, and let it sit at room temp for a week, you won't be able to get a full purge (ime).
The vacuum pump will increase the surface area a lot, the bho will grow like a soufflé at first, but then it starts to cool down and then the vacuum isn't able to draw out anymore butane.
I prefer to use a pancake griddle set to 110f, an infared thermometer to constantly measure the temp of the oil. If it gets too hot simply lift the parchment paper right off the grill long enough for it to cool down. Make sure to spread it out as much as possible on parchment paper to create the most surface area possible. Cook until no more bubbles.
The griddle allows a faster purge, control over the temp, and ime is much more effective.