I live in a fairly cold climate (at least during Sukkos, especially this year) and so I am always looking for ways to reduce heat-loss in my Sukkah. There are plenty of options for the walls, but the s'chach is more difficult. In previous years, I have used wood wool (the long thin wood shavings that you typically find in gift baskets) on top of a nylon net suspended under the typical modern reed mat s'chach, but this is tedious to arrange and as far as I understand is not really ideal halachically as the s'chach should not be supported by something not kosher for s'chach. It can also get a bit messy.
I'm looking for ideas for how I can have some kind of kosher s'chach which will act as a good insulator without being too thick (not more than a few centimetres), not too time consuming to arrange and not too expensive (I'm not looking to spend hundreds of British Pounds). The sukkah is about 3x4 metres and I have a sloping frame as I pull a sheet of tarpaulin over the top to protect the sukkah from the rain.
Any suggestions would be appreciated.