Most people presume that placing a piece of ceramic glass in front of a fire would decrease its efficiency but as we’ve seen it’s the draw that causes heat to be sucked out of the room. High efficient gas fires not only have a glass front, but also a convector box. This is a channel which goes from the front base of the fire to the front top of the fire, wrapping the engine of the fire, this channel will allow cold air to enter underneath the fire and heat-up as it rises around the burner. This then leaves the fire as convected warm air through the convector grill. You also have the glass front which means that the glass holds the heat within the fire box for longer allowing it to escape into the room through the convector channel finally the Glass although ceramic heat proof does allow the radiant heat from the warmed up ceramics to heat also (This is the type of heat you get from a red glow, [infra-red heat]). From a Glass Fronted High Efficiency Gas Fire you can get efficiencies’ of up to 89% meaning wastage is cut right down to only 11% rather than the 70% seen on Open Fronted fires. A specialist in High Efficiency fires is Apex Fires google them!