We have lots of gray days here in Seattle, Washington. So we love having the fireplace roaring in the Fall & Winter months. The most efficient way, is having the fire as hot as it can get, and having it stay warm as long as it can. The solution is having soapstone installed inside your firebox. Here is a photo of a chevron pattern with soapstone firebricks. Another popular design is the herringbone pattern. This is hands down, the best material you can use to retain temperature!