You can only put insulation around those if they are rated for IC (insulation contact). It should say on it, but it may be hard to read or the label may have fallen off over the years. It should only become a problem if it got hot enough to melt the wax on the toilet flange. Otherwise, as long as it has free air movement around it (if not rated for IC), then you should be fine. Just don't exceed the max wattage for the fixture.