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Roadmap to Net Zero

By The Proulx-Coll Household

Deciding on which retrofit to do is hard!  The Energy Audit report lists all retrofit suggested with associated estimated energy savings (in GJ).  However, there are many factors that come into play when choosing which retrofit to do:

  • Can you do it yourself?  This will likely be the lowest cost option.
  • What is the total cost of retrofit vs. the impact in energy savings
  • What will be the impact on your life in doing the retrofit (being pure energy savings)

The table below lists all the retrofit suggested in order they were given in the energy assessment but with estimated costs.  The final column is a “Cost Per GJ” to evaluate the impact of each retrofit per $ spent.


Energy Saved Estimated Cost Cost Per GJ

Insulate Main Walls

14GJ 40,000$ 2105$ per GJ
Insulate Foundation 19GJ 14,000$ 737$ per GJ
Insulate Attic 2GJ
Upgrade Windows 8GJ more 20,000$ 2500$ per GJ
Upgrade Doors 2GJ 2,000$ 1000$ per GJ
Upgrade Ventilation 1GJ 2,000$ 2000$ per GJ
Perform Air Sealing 7GJ 1,500$ 214$ per GJ
Upgrade Heating System 27GJ 8,000$ 296$ per GJ
Upgrade Hot Water System 9GJ 3,500$ 389$ per GJ
Renewable Energy System 3GJ 1,800$ 600$ per GJ




The amounts are rounded.  They also include the grants available for the retrofits.

Retrofits we completed

Perform Air Sealing✔️

With the lowest cost per GJ, this was the first problem we attacked!  With sealed 3 windows in the basement, improved the caulking around windows and replaced 7 windows (glass only).  We were able to improve the air sealing by 20%!

Upgrade Heating System ✔️

In second place was replacing the heating system.  It was also the single retrofit that could have the largest impact in energy reduction!  We replaced our furnace and heat pump with a low-temperature heat pump/furnace system.

Status Now ✔️

Our house currently uses 117GJ per year in energy.  With the retrofits completed, we are at 83GJ, about 9% away from what a typical new house consumes.  Not bad, but not enough.

Recommendations we will be tackling in the summer ⌛

Insulate Main Walls ⌛

This retrofit is eligible for the Canada Greener Homes Grant.  By the time we received our acceptance letter for the grant, it was too cold to start the work.  And you absolutely can’t start the work until you get the acceptance letter.   The work is therefore planned for the spring/summer 2024.  

Tip: Make sure you plan way in advance since the loan application requires quotes from contractors, which also take time to obtain, especially if you are getting several quotes.

Insulate Foundation ⌛

This retrofit is also eligible for the Canada Greener Homes Grant.  Moreover, the grant also covers “resiliency measures” which are needed in our case to waterproof our foundation walls before we can insulate.  We also opted to insulate the interior of the basement ourselves.  In this case, you do not need a quote from contractors but a detailed list of materials needed.  

By the time we received our acceptance letter for the grant, it was also too cold to start the work for this and therefore this is also planned for the spring/summer 2024.  

Upgrade Doors⌛

We decided to postpone upgrading our doors until next summer.  We can replace our doors ourselves (with the help of my dad the handyman of course).  But at 2GJ and 1000$ per GJ, we decided this was lower priority over other savings.

Expected Status After Summer 2024 ⌛

Our house currently uses 83GJ after initial retrofits.  After the summer, it is expected to use 48GJ!  This is 63% of a typical new house!  But still not net zero…

Recommendations we will not be tackling

Insulate Attic 😐

Although the energy audit came back with this recommendation, it only comes in at a 2GJ savings.  The attic is already insulated as well as it can unless we completely replace the roof.  We’ve decided not to tackle this recommendation.

Upgrade Windows 😐

We did replace 7 windows (glass only).  The other windows aren’t “that bad” and replacing them would be quite costly due to our siding being in asbestos (it strikes again!).   We actually had one of the window contractors refuse to give us a quote saying “I wouldn’t take on this project” 🙁  

Upgrade Ventilation 😐

After some research, we do not have space in our basement to install a heat recovery system 🙁

Upgrade Hot Water System 😐

You can read all about our heat pump water heater adventure here 🙁

Road to net zero 0️⃣

With 48GJ per year of energy needed, we can now look at going net zero using renewable energy sources like solar!  Calculating exactly how many solar panels we need in our area can be tricky, but this very handy tool by Hydro-Quebec makes it much easier to estimate.  It takes into the account the sunlight rate in Montreal and estimates the number of panels needed for 48GJ (which is ~13334KWh).  The market cost of this would be ~31,500$.  This would require 57.3m2 of space, which is about 75% of our roof area.  We would likely need to add a battery bank to account in fluctuations in the sun-light.

Written by The Proulx-Coll Household

Read more of their stories as they vie with the other seven households to reduce their carbon footprint.

Meet the The Proulx-Coll Household
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