No heat in barn. Should I use bedding or straw for the piglets ? Heat lamps how many ? Other ways to keep them warm?

I make sure there's no draft where they're sleeping. We've got a corner of the stall designated for them with a board that separates their area from Mama's area. I usually use old towels/blankets and hang 2 heat lamps side-by-side. We secure the heat lamps with chains and make sure there's no way Mama can reach them.