EGEE 102
Energy Conservation and Environmental Protection

Lesson 7a: Residential Heat Loss


Houses are heated to keep the temperature inside at about 65°F when the outside temperature is lower. A house requires heat continuously because of the heat loss. Heat can escape from a house through various places; some are well known and some are not noticeable. Heat can escape from the roof, walls, doors, windows, basement walls, chimney, vents, and even the floor.

House with arrows showing heat escaping from windows, floors, roof, etc.
Heat Loss Examples

The more heat the house leaks, the more the furnace has to put out to make up for the loss. For the furnace to generate more heat to compensate the heat loss, more fuel needs to be put into the furnace, hence higher fuel or heating costs.

flow chart: More heat escaping from home = more heat from furnace = more energy used yields more fuel needed = higher heating costs
Heat Loss Flow Chart

As you will recall from Lesson 3, not all energy conversion devices are efficient. Thus, it is important to note that furnaces are not 100 percent efficient. When a furnace’s efficiency is lower, the fuel consumption for the same amount of heat output will be even higher.

Where Does Heat Loss Occur?

Participate in the following activity to find out where the most heat loss occurs.

Click for text description. This will expand to provide more information.

Where Does Heat Loss Occur?

Below are the most common places for heat loss in a typical home.

  1. Heat loss through ceilings.
  2. Heat loss through windows.
  3. Heat loss through doors.
  4. Heat loss through frame walls.
  5. Heat loss through cracks in walls, windows, and doors.
  6. Heat loss through basement walls.
  7. Heat loss through basement floor.

Question: Which one has the most heat loss compared to the others?
Answer: # 5 Heat loss through cracks in walls, windows, and doors
Actual percentages of heat loss for each:
Heat loss through ceilings = 5%
Heat loss through windows = 16%
>Heat loss through doors = 3%
Heat loss through frame walls = 17%
Heat loss through cracks in walls, windows, and doors = 38%
Heat loss through basement walls = 20%
Heat loss through basement floor = 1%