If you have chickens, you might be interested in this. My wife and I live in northern Michigan where the temperatures can reach as low as -25 in the winter. We were having a hard time keeping our chicken coop warm enough without breaking the bank with our electric bills in those kind of temperatures. We were also having to use multiple reflector heaters, you know the ones that use the light bulb. They are so dangerous. Actually a farm caught fire about 10 miles from me two weeks ago due to the use of these heaters. Because of the high electric bills and the danger of the heaters, my wife researched alternative ways to keep the coop warm. For the last two years we have been using the deep litter method. With this method, you allow the straw/wood shavings to break down with the chicken waist like composting. This creates enough heat to keep the coop warm. Instead of cleaning out the bedding you just add to it. When we do clean it out at the end of winter, we use the broken down bedding as fertilizer in the garden. We do still run a couple of IR radiant heaters which are much safer, but between them and the deep litter method the coop stays nice and warm. https://books.google.com/books?id=ZYlqBgAAQBAJ&pg=PT50&dq=deep+litter+method&hl=en&sa=X&ei=oQT_VN-cOMyUNp_mg8AK&ved=0CC0Q6AEwAQ#v=onepage&q=deep%20litter%20method&f=false
https://books.google.com/books?id=ZYlqBgAAQBAJ&pg=PT50&dq=deep+litter+method&hl=en&sa=X&ei=oQT_VN-cOMyUNp_mg8AK&ved=0CC0Q6AEwAQ#v=onepage&q=deep%20litter%20method&f=false