I've set thermometers in my apartment in the locations I'm likely to place my Obire bags, and they tend to be about 73F. If memory serves me well, ideal temps for colonization are 85F and fruiting 75F. While I've no intention of trying to reach 85F while the jars of WBS colonize, I'd like to think of ways of getting the best possible temp for the colonizing stage. At the same time, I won't be leaving plug-in heaters unattended!
Sunlight hitting an exterior shell of the box of jars won't work as the windows don't get much sun in winter, and in that section I plan to have the light blinds closed anyway.
My apartment uses baseboard/hot water for heating. It occurs to be I could build a small enclosure next to the line, and set a USB fan on the baseboard to get more heat in that area, and test the result in a cardboard enclosure before committing jars to it.
Would you consider your options in this scenario, or just accept the slower colonization speed of the lower temp?