What are the estimated life spans of all the systems in my house?

There is no accurate method to determine exactly how long a particular system or component is going to last. This is due to a number of reasons: the geographic area; the physical location of the units; and the climate and weather. This is similar to asking how long a car lasts. There are too many variables to determine the life span of items that need maintenance and have thousands of integral components. For example, with heating systems, many factors can directly affect the life span of the appliance. If the furnace is located in an unconditioned crawlspace or in the attic, the elevated humidity levels can rapidly cause heat exchangers to prematurely rust. In addition, when furnaces are used in the colder months, the differences between the low air temperature and the high temperature of the heat exchanger can cause expansion/contraction cracking that can lead to leaks in the heat exchanger. Roofs, on the other hand, can be affected by factors like the amount of direct sunlight, adequacy of attic ventilation, number of layers of roofing material, as well as the quality of the roofing material itself. Climate and weather can affect the life of the roof also. For instance, in the West and Southwest parts of the U.S., asphalt composition shingles have a tendency to last no more than 10 to 15 years on average, whereas in the Northeastern states and around the Great Lakes area, the same roofing material can last 18 to 22 years or longer.