While I've been figuring what I need to tent off the work area (how much plastic sheeting, lumber, etc), I've been doing a few bits of epoxy work with surprising results.
Temperatures in the barn have been in the mid-50s (outside temperatures in the upper 50s) when I filled a couple of spots between the sheer and adjoining planks. Twenty-four hours later (with an overnight low in the high 30s and outside temperatures again in the upper 50s) the epoxy was soft but not tacky. Eighteen hours after that, the epoxy appears to be cured. I'll let it sit for awhile longer before trying to sand it but I am pleasantly surprised by this result. >br>
The area needs some sort of enclosure and heat but I know work can continue until improvements to the space can be done.