They are most comfortable between 18 and 22 degrees and anything below 15 degrees is cold for them.
So, it depends on what night time temperatures are in your area and what temperature your hutch is getting down to, but if your hutch is less than 15 then I’d be adding heatpads and additional insulating measures in.
Mine are in my shed and as it’s warmer in there I’ve not yet had to add any additional measures other than just pulling down the plastic fronted hutch cover. As it gets colder they will get additional hay, blankets on the hutch and the addition of heatpads incrementally. I have four heatpads but add in one at a time so the bedroom area is a warm space they can go to but so that I can still add the others in elsewhere as it gets colder.