This Lawns began to appear in city parks and on affluent properties after the Civil War in the 1870s. Lawn mowers and sprinkler technology helped lawns come of age in northern Europe and the United States. Lawns can be made of material other than grass such as the use of plants that include wildflowers, ground covers, low growing herbs and sedges that can all be walked on. Lawns are an important element when it comes to the fight against urban heat as well as providing a number of benefits to the environment. Some of these benefits include oxygen conversion, erosion control, air particle filtering, a place for enjoyment and recreation as well as a surface for air cooling to offset the heat from cement, asphalt and rooftops. -632 Portable radio receivers with a crank are made to reduce battery purchase requirements, see clockwork radio. "home energy audit washington dc " and "green home energy inc ottawa " (include "how solar power works in homes", "how to build a smart house ", "how to make model solar system ", "magnetic field motors ", "five renewable energy sources ", "Home energy grants canada ", 29 Apr 2011 We have several programs for teaching home energy analysis here at Unity College. We teach a basic course in energy efficiency to all & Home network power line )