One easy way to reduce heating (and cooling) costs is to add extra insulation in the attic of a house. Suppose the house already had 15.0 cm of fiberglass (glass wool) insulation in the attic and in all the exterior surfaces (including the floor of the attic room). If you added an extra 7.8100000000000005 cm of fiberglass to the attic ceiling, then by what percentage would the heating cost of the house drop? Take the room to be of dimensions 10 m by 15 m by 3.0 m. Ignore air infiltration and heat loss through windows and doors, and give your answer to one decimal place. Assume the same temperature difference between inside and outside the attic room, and that heat is lost through all six sides of the room. Hint: The cost of heating will be related to the amount of heat that is transferred through the walls, the floor and the ceiling of the attic. If let's say the heat loss is 1000 W in total (walls+floor+ceiling) without insulation, and then 800W in total with insulation, we are decreasing the cost by 20% (just because we are decreasing the amount of heat loss by 20%).

One easy way to reduce heating (and cooling) costs is to add extra insulation in the attic of a house. Suppose the house already had 15.0 cm of fiberglass (glass wool) insulation in the attic and in all the exterior surfaces (including the floor of the attic room). If you added an extra 7.8100000000000005 cm of fiberglass to the attic ceiling, then by what percentage would the heating cost of the house drop? Take the room to be of dimensions 10 m by 15 m by 3.0 m. Ignore air infiltration and heat loss through windows and doors, and give your answer to one decimal place. Assume the same temperature difference between inside and outside the attic room, and that heat is lost through all six sides of the room. Hint: The cost of heating will be related to the amount of heat that is transferred through the walls, the floor and the ceiling of the attic. If let's say the heat loss is 1000 W in total (walls+floor+ceiling) without insulation, and then 800W in total with insulation, we are decreasing the cost by 20% (just because we are decreasing the amount of heat loss by 20%).