Written by Samantha Kearney
Geothermal energy can be used to heat or cool a building by pumping water through tubes that run 100 - 300 feet below the surface, where the earth is constantly around 50 - 60 degrees, and this warm water is pumped through the building to make temperatures more comfortable. Thus, in the winter cold water is passively heated, and in the summer it is passively cooled, and if one wants a temperature higher or lower than the resulting building temperature, the water or building can be heated using a supplemental system.
Geothermal wells save energy, and money, because much of the energy is passive (from the warmth of the earth), not from power plants. The EPA and Department of Energy both find that geothermal is extremely energy and cost efficient.
This interactive map shows all the permits that mention installing or renovating geothermal systems in their descriptions, and cost more than $1. The highest concentration of them is on the north side, but they are present across the city. Data is from 2007 through 2015.
The most expensive projects (deep red) tend to be for large housing projects, often affordable housing. Other building types include single family homes, medical buildings, Chicago Park District buildings, Chicago Public Libraries, and commercial buildings. Programs incentivizing geothermal systems exist, including Chicago's Green Permit program.
Permits that include geothermal projects have decreased since 2011, according to the total estimated costs in these permits per year.
The average estimated cost in these permits per year has fluctuated a bit more, but still shows that costs rose around 2011, then fell in 2015 to practically 2007 levels. It must be noted that these estimated costs include all work for each project, so they may include all new construction costs, or they may simply show costs of installing the geothermal system alone.
Perhaps the surest way to measure the popularity of geothermal systems over time is to show the number of geothermal permits issued each year, which still shows a peaks around 2011 and valleys at 2007 and 2015.
Check out our Solar All Over issue for more information about sustainable building trends.