The most common form of biomass energy used inside of homes is wood. Wood stoves and fireplaces are a common feature in colder climate homes, such as in Michigan. In 2002 34% of the renewable energy used in the US came from wood. This accounts for about 2% of all the energy used in the US. Heating homes with wood requires lots of work and attention. Often the wood needs to be protected from the weather and left to dry for months before it can be used.