Not sure what container you have but buy some actual insulation for houses and suck with a high rating. You could wrap them in a loose garbage bag and pump it full of spray insulation or instead of a bag use a larger container and fill in the gaps with insulation. A blanket is better than nothing. Thats a good temp for the room to be....are you using HID lights? they can warm it up and boost your harvest big time....its well worth it.