I’ve been to several homes that are heated and cooled using geothermal technology in the course of my travels for Natural Home, but I’d never actually had the opportunity to watch as the wells were being drilled. So it was great to visit the site of the Boulder home whose construction we’re chronicling and to get the inside scoop on what it takes, sometimes, to make a green dream come true. (Check out the video we just posted to see for yourself.)
The owner of the Boulder home was determined to make geothermal a reality—and that’s a good thing, because his site proved difficult. As project manager Ron Flax of Rodwin Architecture explained to me, Can-America Drilling discovered that the building site is on an old, very deep riverbed consisting of coarse gravel washed down from the Rocky Mountain foothills. As workers attempted to drill the loopfield for the geothermal wells, gravel fell back into the drilled hole as soon as the drill bit was removed. After a week of attempts, no progress had been made. The design and building team was ready to abandon the geothermal system entirely and began considering more conventional, if energy-efficient, systems instead.
But the owner insisted, and the team persisted. The geothermal consultant for the project, Jim Richmond of Radiance Corporation, found they could dig the wells using a top-hammer drill rig designed for water wells, which installs a steel casing while drilling and prevents the sides of the hole from collapsing. This required a collaborative drilling operation between Can-America and James Drilling, a water well driller, as water well drilling companies aren’t usually licensed by the state to drill geothermal wells.
Construction on the rest of the home continued while the drilling team figured out what to do, so some potential drilling locations were built over. To compensate for that, the design team reduced the overall building volume by lowering the interior height slightly and reduced the amount of glass in the house. These changes allowed the team to reduce the required size and number of loopfields to three holes, twice as deep. Can America Drilling was able to remove the steel casings after the loopfield piping and grout were installed, improving the system’s thermal conductivity.
The team pulled it off—the home will now have a much lower carbon footprint and a nice cushion against rising fuel prices. Next step: Insulated Concrete Forms.