project examples

  • Loop Field
    Example of 14T Trench Application for Earth-coupled Geothermal Heat Exchanger, Ashland, WI. Each 90’ X 3’ Slinky Pipe Coil contains 800’ X ¾” HDPE GeoPIPE buried 10’ deep in a (minimum) 42”-wide trench. All fourteen slinkies share common header trench (pictured) and a single 2” reducing reverse-return header which extends to house at 8’-5’ below grade.
  • Loop Field
    Example of 18T Excavated Pit for Earth-coupled Geothermal Heat Exchanger, Saginaw, MN. This High Performance Loop Field contains sixteen 900’ X ¾” HDPE GeoPIPE coils converted to Slinkies, each 100’ long and equivalent to eight straight pipes of application. Half of the Loop Field is already backfilled, economizing on space for placing material (9 visible).
  • Loop Field
    TRENCH SPACING FACT: Responsible loop design will always strive to maximize performance benefit at the most reasonable installation cost. It is simply NOT true that wider trench spacing is necessarily "better" than more closely spaced coils inside a single excavated pit. By using a trench spacing correction factor from the GHEX design tables (pictured), you can increase or decrease pipe length as required for ANY given spacing... and still achieve the SAME desired result!
  • Loop Field
    Northern GroundSource teamed up with McKeever Well Drilling to install the 16 Ton vertical bore field and high-performance S/R header for the geothermal heating & cooling utility at the new Grand Portage Visitors Center (opened Fall 2010).
  • Loop Field
    On vertically bored GHEX applications, drilling is only part of it. Proper vertical GHEX performance begins with a solid design, including critical bore length adjustments for unbalanced ground load (a phenomenon potentially resulting in thermal decline of the entire bore field over time). To better understand local site geology, trade partner, McKeever Well Drilling, goes to the extra effort of taking progressive cutting samples for analysis.
  • Loop Field
    A geothermal pond loop can bring to your project an appealing aesthetic component you might not have originally considered. It can also enhance system performance by delivering "warmer" loop temperatures to the heat pump in the dead of winter. Northern GroundSource is highly specialized and experienced in pond loop design and installation.
  • Clair Nelson Transporation Center
    The Clair Nelson Intermodal Transportation Center is the new community center located in Finland, MN. Northern GroundSource president, Mark Sakry, a fully credentialed AEE Certified GeoExchange Designer (CGD), worked together with Wagner-Zaun Architecture and Foster, Jacobs & Johnson, Inc. (Mechanical Engineers), from Duluth to design an advanced high-efficiency 16 Ton ColdClimate Hydronic GSHP system for the center; it provides 100% geothermal heating (no backup heat needed) for the entire 10,000 sq. ft. radiant slab system. Northern GroundSource installed the high-performance horizontal GHEX, WILO variable-speed loop pump assembly, and 2 X 8 Ton ColdClimate GSHP system. Special state-of-the-art GSHP hydronic assemblies and controls were supplied and installed by specialty trade partner, KP's Heating, Cooling & Refrigeration, Inc., Hermantown, MN.
  • Clair Nelson Transporation Center
    An advanced 7 Ton ColdClimate Hydronic Heat/Cool GSHP application was designed and installed by Northern GroundSource in 2007 for this elegant rural Duluth home. The alternative would have been propane heating w/conventional cooling instead... which made the cost recovery period for this advanced GroundSource system quite short (5 years--even without the 30% Federal Tax Credit at that time).

    Click the photo to see the GSHP cost savings!

  • Clair Nelson Transporation Center
    A 16 Ton vertically bored GHEX drilled through dense Lake Superior rock extracts all the heat necessary for the radiant slab heating system of the new MN-DOT Truck Station in Silver Bay, MN. In addition to conducting the initial GSHP training session for facility personnel, Northern GroundSource president, Mark Sakry, was also invited to prepare and present a special seminar for visiting MN-DOT supervisors from throughout the state, September 2010.
  • Clair Nelson Transporation Center
    Northern GroundSource collaborated with Energy & Air Systems, Inc., Superior, WI, in the design and installation of a 22 Ton geothermal heating and cooling system for the Waters of Life Lutheran Church, which was built north of Duluth in the summer of 2008. A special high-efficiency loop pump station was custom designed and built in Kentucky to perform the task of circulating fluid through the high-performance ground heat exchanger, which contains nearly 3.5 miles of HDPE pipe!


Since 2011, Northern GroundSource president, Mark Sakry, has been a geothermal trainer at the Duluth Energy Design Conference, an annual two-day conference held at the Duluth Entertainment and Convention Center. The training slides from two of the 1.5 hour sessions are available for free viewing from this page (directly below). These workshops were approved for CEU credits by the MN Department of Labor & Industry, WI Department of Commerce, and the Institute of American Architects (AIA). Both courses were highly attended by contractors, architects, and other "building science" professionals from throughout the region.

Geothermal Parameters: What Homeowners, Architects & Contractors Need to Know BEFORE They Plan for Geo'

PowerPoint Presentation

So you're planning to go Geo'. Great!… But did you know that it is considered "low temperature" heating? If you are building new, are your floor trusses spaced widely enough for the required duct system? Did you think you could use radiators or hot water baseboards with geo'…or that you could staple radiant floor tubing up-inside the joist pockets of your basement ceiling? Are you planning a loft…or a bonus room over the garage?

These are just a few of the questions that you need to address BEFORE you plan for geothermal, because neglecting them could prevent you from enjoying its full economic and environmental benefits.


When considering geothermal for new construction, remodeling, or retrofit, there are many limiting factors inherent to heat pump technology itself which can throw a wrench into your plans if not understood from the start:

More careful consideration must generally be given to ductwork and hydronic delivery system designs. Site geology and earth loop options may also be limiting factors. Any number of things can bear directly on building design and cost if not properly addressed.

This course examines how to avoid the most common pitfalls in infrastructure planning around geothermal…and how to achieve its full economic and environmental benefits.




The geothermal ground heat exchanger (GHEX) is the heart and soul of a ground source heat pump (GSHP) system—providing the essential infrastructure necessary for extracting heat from the ground for heating in winter and for rejecting heat to cool in summer.

Does one type of earth loop or installation method work better than another? Is there a single "best way" to do it?

This course examines the different types of geothermal loops and their various cold climate adaptations. Learn how GHEX type, size, and design may be determined by any number of factors—including property size, landscaping, site geology, and relative installation costs.




Mark Sakry [SAH-kree] entered the geothermal industry as an independent building contractor in year 2000 to explore its wider use in the extreme northern climate.

February 2001—Mark and son, Garret, received training and accreditation from the International Ground Source Heat Pump Association (IGSHPA) at Oklahoma State University, and established home-based Northern GroundSource Inc. in Brimson, MN. (Garret, who was only 16 years old in 2001, was considered the world's youngest IGSHPA accredited installer at that time. He is now VP OPS and coordinates all GroundSource field work directly from Duluth.)

Since 2001—Sakry has designed and installed hundreds of residential and commercial geothermal systems throughout northern Minnesota and Wisconsin, specializing in advanced hydronic heat/cool (split) applications; high-efficiency multi-stage/variable-speed forced air…pond loops; vertically rock-bored systems; and advanced horizontal ground heat exchanger designs. Also…

Trained and accredited IGSHPA Certified GEO Inspector (CGI), specializing in forensic system inspections and workable solutions for problem residential geothermal heat pump installations.

Long-standing member of the Association of Energy Engineers and professionally accredited by AEE as a Certified GeoExchange Designer (CGD).

Founding Director (2008) and past President of the Minnesota Geothermal Heat Pump Association.

Fully Licensed MN Residential Building Contractor (20385314) & Certified WI Residential Dwelling Contractor (854032).

Participating member of the Minnesota Department of Health Advisory Committee for establishing new rules specific to "Bored Geothermal Heat Exchangers" (Minnesota Rules, Chapter 4725).