The Steinbach Credit Union built a new 45,000 square foot, 3 story office building in Winnipeg, MB in 2009. The building featured a number of energy efficiency features, including high insulation values, efficient lighting, a green roof and a ground coupled heat pump (GCHP) system that uses the earth under the parking lot as its energy source.

If you’ve been in Winnipeg in January, you’ll have an appreciation for winter. Our winter design temperature is -28 F (-33 C), with extreme temperatures occasionally dropping below -40. This winter, as anyone in North America knows, the Polar Vortex blessed us with the coldest winter on record. We had 25 days when the temperature didn't get above -20 F in December and January.

The last time Winnipeg experienced a winter like this one was in 1898! Water lines to homes and businesses froze even though they were buried 7-8' below ground leaving a few thousand people without water.

So what happens to a horizontal ground heat exchanger (GHX) that's buried only a few feet below that? Can it heat the building in this kind of extreme winter...or does the building freeze up?

Well, because of the extreme cold this winter, the building manager actually bumped up the building temperature a degree. He's been monitoring the temperature of the fluid circulating through the GHX. It had been designed to operate at a minimum temperature of 35 F (1.7 C) in winter and a maximum temperature of 85 F (30 C) by the end of summer during a typical year.

As one of the system designers, I was curious to see how the GHX reacted to the extreme winter. The GHX design was built on a detailed energy model using typical meteorological year (TMY) weather data…but this wasn't a typical winter!