A few years back I posted a tip about old swimming pool covers (like industrial strength bubblewrap, available in blue) that you could pick up fro free from pool maintenance companies and use for insulating compost heaps etc. Well this worked well for me for about 3 years but now it's starting to disintegrate, so be aware it's not long lasting - still at least it seems to be biodegradable - but what is it degrading to?