Kollwitz

I have used this recently, it certainly isn't as expensive as it seems. If you buy enough (£15-£20) to add to 5 litres of paint, remembering you only do the outside walls, you only need to use 2 coats to be effective I think, and that makes it quite economical. It was enough for me to do 4 outside walls in two rooms. If you need to do more than this (if you are painting a light colour over a dark for instance) some coats can just be the paint. It definitely makes a difference, which is clear just touching the wall with your hand. I've yet to see the difference it might make with my heating cost, but I already feel the rooms I have used it in are cosier/warmer. I am in total agreement with bjp100 - it's good stuff. Easy to mix in, dries quickly, the slightly sandy texture makes no difference to the application of it and you can't really see a difference between the exterior and interior walls. It's not like that awful textured paint that was so in vogue a while back which scatters gritty bits when you roller it. I used a paintpad, and it went on as normal.