Welcome to my adventure in cutting fossil fuels at home! Read the other posts in the series here:
Part 2: Converting Hot Water Tank to Electric
After living car free in a modest apartment for almost 15 years, my wife and I finally had enough savings to brave Toronto’s absurd housing market. We dodged a few bidding wars and finally ended up with a house and a whole new set of energy opportunities. I previously wrote about saving electricity in my apartment here and here but with this house, for the first time in my life I have a gas bill and monthly reminder that I am directly contributing to the climate crisis by burning fossil fuels. To further trick myself into speeding up action on this, I renamed the bill in my online banking to “Climate Crisis” for an added kick in the pants every month. Why is cutting fossil fuels important? See here, here, and here.
As a result of my self mental trickery, I immediately started trying to figure out what it would take to decarbonize the house. There are three gas consuming devices (furnace, gas water heater, gas range) and the eventual goal is to replace all of them with electrical appliances that use relatively clean power from the Ontario electric grid. I am continuing to purchase all my electricity from renewable sources to account for the fact that the grid isn’t 100% clean, and may become less clean. I’m also aiming to not increase utility costs significantly.
The biggest consumer of gas is the furnace, which I am assuming I will eventually be replacing with an air source heat pump. Since the eventual goal is to switch to a more expensive heating fuel (electricity), the first goal will be to reduce the total amount of heat required to heat the house, which is the topic of this post. With a lower demand for heating, the impact of the higher fuel cost will be mitigated.
First of all, I am lucky that the walls are decently insulated and windows had been upgraded by the previous owner. The primary heat saving measures I implemented are temperature setbacks, attic insulation, and draft sealing.
The house was already outfitted with a programmable thermostat, making it extremely easy to implement temperature setbacks. With the house often occupied during the day (parental leave and now work from home) we couldn’t be super aggressive on the low temperatures. Typical setting is 19 or 20C during the day (I don’t believe in wearing a t shirt and shorts inside in winter) and 17 at night when everyone is cozy under a blanket.
This minor temperature tweak yielded so much savings that it caused confusion on my gas bill. Turns out the utility sends someone to read the meter once every two months and they estimate the in between months based on the previous year. In this case, because we were using about 30% less gas than the previous owner (!), we were getting one huge bill (estimated), followed by one tiny bill to make up for it (actual reading). In one case, our consumption for the month was negative to fix their overestimation! Once I realized this was happening I started submitting meter readings myself so that the bills would make more sense.
Temperature setbacks are probably the easiest and cheapest way to cut your greenhouse gas emissions if you have fossil fuel heating. Compared to the previous owners, these setbacks saved about 300 m3 of gas per year, about $100 per year, and about 1.5 tons of CO2 emissions and cost nothing to implement.
The seller’s home inspection report identified that there was about 4-6 inches of loose fiberglass insulation in the attic, equivalent to about R-14. In order to minimize heat loss in winter, current recommendation is for R-60 or higher, meaning more insulation was needed. R-value is a measure of how resistant a material/surface is to transmitting heat.
Before doing your own insulation project, make sure to check with your gas utility to see if there are any rebates available. In my case, the gas company provided a rebate that covered about 80% of the cost of the project (including energy audit, installation).
If you are interested in detailed calculations of savings, I moved that to the bottom of the article. In my case, total gas savings are estimated to be about 73m3 per year, or 7% of total baseline gas consumption. Cost savings from these are not huge (~$25 per year) due to the low price of natural gas, but the key is to reduce total heating demand to make it easier to switch to a heat pump eventually. My house is very narrow and doesn’t have a large attic area, so if your house has a larger footprint, savings would potentially be higher.
There are additional benefits, such as keeping the upper level cooler in summer. Attics tend to get extremely hot in summer and the extra insulation helps to prevent that heat from getting into the upper levels of the house. This makes it easier to cool the upper levels, improving the performance of the air conditioning. You can also take the opportunity to have your attic venting repaired or updated to prevent moisture buildup.
Part of the energy audit funded by the utility rebate included a blower door test. This test involves installing a large fan in the front door of the house and blowing air out to create a negative pressure in the house. As the fan is running, the total leakage of the house can be measured based on how much power is needed to generate a standard negative pressure. A better sealed house will require less fan power to achieve the negative pressure. Additionally, a walk through is conducted while the fan is running to determine where larger leaks are occurring. A smoke pen can be used to make the leaks more obvious.
In my house, there were several locations where leaks were identified, including fireplace flue, unsealed drywall holes, damaged caulking, and a leaky attic hatch. As a result, I installed an easily removable buffer for the fireplace, which we aren’t using, and applied caulking to all the other locations identified. This will be an ongoing process to eliminate leaks.
Images of damaged caulking and leaky attic hatch:
Overall, I would estimate about 3% heating savings from the leak sealing, amounting to 35m3 gas savings for negligible cost. You may have higher or lower savings depending on how leaky the house is. Again, the point is to reduce unnecessary heating to make it easier to eventually switch to a non fossil fuel source of heat.
Overall, it looks like I was able to reduce fossil fuel consumption by 30% (compared to previous owner) by using temperature setbacks, and then a further 10% by insulation and sealing. Stay tuned for future episodes of “Mike at Home” to follow my progress. Let me know about your decarbonization success stories in the comments and let’s kick the fossil fuel habit together!
Look up typical R-value for your material (I used table in the Wikipedia article)
Fiberglass loose fill = 0.44-0.65 m2K/W per inch
Using the average 0.55 multiplied by 5 inches, I have a base case R-value of 2.7 for the existing insulation.
Cellulose loose fill = 0.52-0.67m2K/W per inch
Using the average 0.60 multiplied by 14 inches (final insulation depth was 19 inches), I have added additional R-value of 8.3 on top of the existing 2.7, so the final R-value is 11m2K/W after the install. This is the SI unit for R-value and the equivalent in imperial units is R-62.
In order to calculate energy savings, I used this formula for each hour during heating season:
ΔT is the difference between indoor and outdoor temperature. I used a 30-year average weather file to get the hourly outdoor temperature, assumed 20C constant indoor temperature, and surface area of attic of 26m2.