Evergreen introduces a new approach to heating and cooling buildings
An innovative new combined geo and solar thermal heating system will reduce greenhouse gas emissions by 95%.
Published on December 05, 2017
There’s something ground breaking happening below Evergreen Brick Works. Way below. One hundred and eighty metres beneath the earth, we are building a system that will create one of Canada’s first carbon-neutral buildings.
This fall, Evergreen and its construction partner EllisDon, sunk 40 boreholes into the ground beside the historic kiln building. It’s the site of a major redevelopment that will transform the 53,000-sq-ft space into a dynamic, year-round hub to test and drive change in how we create inclusive, low carbon flourishing cities of the future.
These boreholes are the groundwork for a new combined geo-solar thermal heating and cooling system that will be one of the first of its kind in the country. Heat from the ground will heat the large heat-dominant building, and the solar thermal panels will generate heat from the sun to recharge the ground. Combined with improved building insulation, this new approach is set to reduce the building’s energy consumption by up to 75 per cent and substantially decrease its carbon emissions by 95 per cent. Its total output of greenhouse gas emissions will dive from 633 tonnes to just 33, and we have some plans in store to offset those last few tonnes too.
This massive reduction is achieved by rethinking the way we currently rely on conditioning buildings and is specially designed to address the needs of a designated heritage building.
Conventional systems, for example, take air from outside a building, expose it to high heat in a furnace, and then pump that air around through ceiling vents. It’s an inefficient process, especially because heat rises and so is more likely to be warming the rafters than the people on the ground.
The geothermal system takes a different approach. It starts by harnessing the heat trapped far beneath the earth. Each of the 40 boreholes is filled with a transparent liquid called glycol, an organic compound that is excellent at storing heat. In the winter, the glycol travels through each borehole tube, collecting heat that’s stored in the deep bedrock along the way. When it breaches the surface, it’s piping hot and ready to warm up the building.
The glycol will then snake back and forth through the radiant floor tubes embedded under the building’s new sustainable concrete flooring, releasing its heat, which radiates out from the ground up. That way, it heats down low first, where people are, before the hot air rising up to the ceiling. Once it’s travelled around the revived heritage space, the now-cool glycol heads back down underground to repeat the process.
In the summer, the whole process works in reverse. Combining with 600 solar thermal panels that will cover the building’s south-west facing rooftop, the glycol restores heat back underground. The panels collect heat from the sun and push it into the glycol, which then travels down to the bedrock. It heats the bedrock back up, keeping it at a consistent temperature. The process even allows us to get the bedrock a little hotter, making it a better heater when winter rolls around.
The solar thermal panels, however, will do more than just collect heat. They’ll also power the heat exchange pump that pushes the glycol up and down the boreholes, making it a closed loop, energy-neutral system. The leftover electricity will fuel the building’s lights and a large chiller, which will keep it cool in the summer.
This implementation of this combined geo-solar thermal system is the first of its kind in Ontario (a residential model exists in Alberta) and a tremendous latest milestone in Evergreen’s quest to raise the bar for adaptive reuse and carbon neutrality. The next phase – connecting the system to the solar panels – will take place in spring 2018. The redeveloped kiln building is scheduled to be completed in Spring 2019.