I have thermal and water proof hutch covers on my hutches (one hutch in the shed for the piggies but this doesn’t have the waterproof cover as it doesn’t need water protection given it’s inside the shed) , and two hutches outside (for my rabbits).
The thermal covers are thicker and help hold some heat in but you need to have a heat source within the hutch itself. Heat pads provide a warm spot for piggies to sit but don’t really heat the hutch space (I put the pads under their fleece tunnels of under their bendy log arches and then put a blanket over the bendy logs to help keep that area under the log warm). My hutch in my shed (piggies) has the protection from the shed itself, heat pads under their beds, extra hay, and a few layers of blankets and the hutch cover on the hutch. The temperature in the hutch in the shed usually remains 5-10 degrees warmer than outside temperatures - but the majority of this is the protection the shed provides. My hutches outside have the exact same measures taken but they don’t stay as warm as the piggy hutch in the shed does.
