It used to be thought that aeration of heaps was very important and heaps were built with good air gaps. Now it is recognised that keeping the heat in is also important, so boxes like the New Zealand box are used where the wooden slats are butted up tight. Insulation - an insulating layer (Old carpet?) is put on top of the top layer of composting material and a waterproof lid used to keep rain from cooling the heap. The core of a good heap should reach 60ÂșC. Commercial green waste temperature varies between 45-90 Centigrade. Weed seeds will be killed off at higher temperatures.