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What's the Best Sustainable Investment? Solar, Geothermal, Air to Water Heat Pump, etc...?



The first industrial revolution of 1820-1840 was the transition period in human history toward mass production of goods and services. The Concept of Mass Production as known in Europe and the United States, made available a lot of commodities that needed to be sold. Manufacturers and governments in western countries started looking for new markets to sell their manufactured products and at the same time buying raw materials from foreign countries for their manufacturing processes. 

The massive international trade of the first industrial revolution is the roots of Globalization and Global interconnection. Over the years, people and countries interconnections kept growing and reached an exponential rate during the digital boom at the end of 90s and beginning of 2000s. 

For over a century, despite going through two world wars, many people enjoyed prosperity and abundance of commodities (goods and services). Global Business model was put into questioning after COVID-19 Pandemic. Global Connectedness helped the virus spread into the US and Canada in a very short period of time. Had the COVID-19 pandemic happened in the 18th century in China, People in Canada and the US wouldn't have heard about it.  

The Global Connectedness, which was somehow unconstrained before the COVID-19 pandemic, will be more constrained after it. The anxiety feeling left by the Pandemic will push people to prioritize local production of energy and food. People believe that a similar Pandemic is very possible in the future and being self sustainable is another way of getting ready to cut off connections to global supply chains of goods and services and rely on local resources till the pandemic is over.

Finding the Best Sustainable Investment?

Answering the question of "What is the best sustainable investment" depends on many tangible and non tangible criteria. People could sometimes be driven by perception of Good Investment even though numbers do not support their perception. Also, the status quo (in the case of retrofit projects) or base scenario (minimum building code requirements in the case of a new construction project) varies based on application, geographic location, available energy sources, local grants, etc....

To find the best sustainable investment, this blog will address evaluation criteria for both New Constructions Projects and Retrofit Projects. What makes sense for one might not make sense for the other.

New Construction

NImplementing sustainable design strategies in new construction is way easier than in a retrofit context. Planning for concepts such as underground thermal energy storage (UTES), passive heating or cooling, natural ventilation, etc... does not add a huge extra cost to the overall project cost. The below sub-paragraphs will outline a bunch of feasible, efficient and yet affordable sustainable strategies in newly constructed projects:

Efficient & Smart Building Envelope

Priority number one shall be given to construction an energy efficient envelope, since it contributes to lowering energy demand at the source. Building Envelope components' life span is the higher than any HVAC or Electrical systems components' life spans.

Efficient Home

When conceiving building envelope, we highly recommend that Engineers and Architects do exceed minimum building code requirements. Exceed to a point when marginal benefits of exceeding becomes less or equal to the marginal cost.

Our Blog SMART, EFFICIENT YET AFFORDABLE NET ZERO ENERGY RECIPE FOR SMALL TO LARGE GRID TIED NEW CONSTRUCTION HOMES IN CANADA provide a recipe for designing and efficient and affordable building envelope.

External Walls and Windows shall be properly oriented for passive heating. Overhangs shall be added to windows facing East, West and South. Overhangs should be designed to allow sun to enter to the indoor space in winter and prevent sun form entering in summer. 

Also windows shall be allowed to be opened for natural ventilation in summer and HVAC system shall be design for free cooling in mid-season temperatures (April-May and October-November).

Thermal Energy Storage

In the majority of modern Canadian Homes and Businesses, and with the global warming hitting unprecedented high levels, Cooling in summer is becoming a necessity. The growing trend of designing energy efficient envelope reducing heat loss in winter, have a negative effect in summer. In the absence of Passive Cooling and Free Cooling Strategies (the case of most Residential Constructions), Summer Cooling is becoming a significant portion of the annual energy portfolio in both residential and commercial buildings (Please go through this blog: DESIGNERS NEW CHALLENGE FOR COOLING BUILDINGS WITH HIGHLY INSULATED AIR TIGHT ENVELOPE to better understand the challenge we face in Summer with energy efficient envelope.
Seasonal Underground Sensible Thermal Energy Storage (SUSTES) turns this disadvantage into an opportunity to reduce annual energy consumption and Green House Gases (GHG) emissions (on the short run) and to reverse global warming (on the long run). SUSTES means collecting the heat extracted in the summer (cooling is no more than heat extraction) and storing it below the slab


Locating the thermal Energy Storage Volume below the building, reduces heat losses in winter, since temperature inside the house is steady for 12 months per year and ground temperature below is also steady.

When Designing a smart and an energy efficient envelope, the volume required to store the summer heat plus the extra thermal energy produced by Solar Thermal Panels, can be fit between concrete slab and bottom of foundations. That eliminate the need to do more excavation on top of what's required for the building's foundation, thus limiting the cost of SUSTES to the cost of Soil Storage Medium and HDPE Pipes for circulating heat transfer fluid (Water or Water and Glycol Mix).

Solar Thermal or Solar PV Panels

Vacuum Tube Solar Collectors

In nowadays residential constructions, Heat extracted in the summer, when cooling the indoor spaces, represents between 1/3 to 1/4 of what is required to heat the indoor spaces in winter. So underground thermal energy storage do help a lot for achieving Net Zero Heating Envelopes, yet alone is not enough. Solar Thermal Panels contribute to the supply of the remaining 2/3 to 3/4 of the annual heating demand (Space Heating and Domestic Hot Water Heating).

In most major Canadian Cities such as Toronto and Montreal, we have like 700 sun hours in winter (when heating demand is at its peak) and like 1400 Sun Hours in Summer (when Heating demand is only limited to Domestic Hot Water Heating). The majority of Solar Thermal Systems, designed for winter space heating, end up dumping excess heat in summer.

By having an underground thermal storage system, not only we recycle the heat generated by cooling during summer season but we also reduce the size of the thermal solar system and makes its payback period shorter.

The annual efficiency of PV panels is between 15-17% (when taking into account snow accumulation in winter) compared to 38-42% for Vacuum Tube Solar Collectors. PV Technology is great for generating electricity for plug loads but extremely costly, inefficient and not reliable for application such as space heating or domestic hot water heating.

Geothermal Energy - Closed Loop Geothermal Heat Pump

Closed Loops Geothermal Heat Pumps have an unbeatable annual energy performance and unbeatable reliability and lifespan. Unlike conventional air cooled heat pumps, Closed loops ground coupled geothermal heat pumps works 12 months per year and the annual coefficient of performance of a Liquid to Water Heat Pump varies between 2.5 to 3.2

Geothermal Heat Pump relative high performance comes with a premium that is hard to justify in states and provinces where heating energy sources (such as electricity, gas, propane, wood, etc...) are cheap and widely available. The cost of digging for a vertical geothermal closed loop heat exchangers can vary between 12,000 and 15,000 CAD$. Also connecting the Ground Heat exchanger to the geothermal heat pump (usually installed indoor) requires a lot of excavations, civil and architectural works that deter many homeowners from buying and installing a geothermal heat pump.

Geothermal Energy makes more sense in larger scale new construction projects such as airports, government buildings, schools, universities, etc.... such buildings are built for a lifespan of 70-100 years and it will be easier to justify having a technology that has a payback period of 15-25 years and a life span of 50 years (for the wells).

Also in remote areas, where land is not an issue ( such as farms, remote factories, etc....), going for horizontal closed loops geothermal heat pumps makes sense. Horizontal loops have lower performance than vertical loops, however installation cost is much lower since no specialized equipment are required for horizontal pipes trenches.

Existing Construction or Retrofit Projects

Geothermal, Solar or thermal storage energy efficiency measured direct cost is the same in both new construction projects or retrofitting an existing building project.

Buying a solar panel or a geothermal heat pump is independent of your project type (New construction or Retrofit), however the indirect cost related to the integration of solar geothermal or any other energy efficiency measure, increase the total cost of the project and make payback period too long (not appealing for clients or sometimes does not make any sense for clients especially when payback period is longer than the equipment lifespan).

When retrofitting existing project, the first priority should be the building's envelope thermal properties which lower the peak heating and cooling loads. The second priority should be to enable the envelope for passive heating and Natural Ventilation. Once Building Envelope has been optimized, this is when we attack the HVAC system.

HVAC system components have lifespans ranging from 5 years to 15 years, while building's envelope components have lifespans ranging from 15 to 30 years. Also having an energy efficient envelope means a smaller HVAC system. The opposite is never true.

1 comment

  • Tim MooreMay 25, 2022

    An excellent description of the methods, costs and benefits of alternatives to fossil fuel furnaces.

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