OUR ENERGY AUDIT RESULTS ARE IN .....

 We have our results of the energy audit back! The analysis states that the energy usage is based on the “average operating conditions” of our home. I asked the auditor what this meant. He said it is a typical use of a house and doesn’t include the temperature we set our thermostat at, hot water usage, where in the country we are, or even the number of people living in the home.  So, it is a pretty generic value that is useful for comparative purposes but doesn’t give an accurate value of our individual circumstances. It predicts that we use 171 GJ of energy per year. The audit compares this value to a “typical new house” (I assume of a similar size) of 84 GJ per year. So they predict we are above a new build which is not surprising. Our usage of 171 GJ, translates to 162 MBTU.

I was curious to compare this to our actual energy usage. Again, thanks to the excellent record keeping of my wife, I know that over the past 10 years, our average energy for heat and hot water has been 100 MBTU. We have averaged 3200 kwh in electricity to power lights etc. which brings the total to 110.9 MBTU (i.e. 1 kwh = 3412 BTU).  So, the energy audit prediction is much higher than our actual use. I assume this comes down to how we operate our house. The thermostat settings, two people, the length of our hot showers, the fact that we run our washing machine with cold water, etc., maybe also the Nova Scotia climate. I’m particularly proud of the fact that my own heat loss calculations of 103 MBTU outlined in my last blog come much closer to our actual energy use than the energy audit does.

The table below summarizes the recommendations for upgrades that the Audit listed to reduce the energy consumption of our house.

Table 1: Audit Recommendations for reducing our energy usage.

	Insulated exterior wall with R 7.5	Insulate Basement walls with R 18	Adding a Heat pump to 1st & 2nd floor	Add an electric heater with heat pump assist	Perform air sealing	Insulate Attic by R 30	Add 10 new windows
Energy reduction	14 GJ	17 GJ	51 GJ	25 GJ	8 GJ	16 GJ	16 GJ
% reduction	8.2%	10%	30%	14.5%	4.5%	9.4%	9.4%

 The audit does mention that the analysis is based on energy reduction only and does not consider a reduction in heating costs or greenhouse gas emissions. So again, a pretty generic result that doesn’t include the local costs of electricity or the %  of fossil fuels used to produce it. This requires a more specific analysis which I will cover in my next blog. I think an energy audit is worth the $200 and provides information that is useful. It is also needed to get government rebates on any you make from their recommendations. I also understand that the analysis is done by a Federal government organization, where it would be difficult to include regional or local conditions. However, it is only one piece of the puzzle.

ALTERNATIVE ENERGY SOURCES FOR HEATING OUR HOUSE

Last week we had our Energy Audit visit but it will take a few weeks to get the detailed report. During the visit, the Auditor used an IR camera to confirm that we do have some blown-in insulation in our exterior walls. He said there was some evidence of insulation settling but that it wasn’t too bad. He estimated the R-value of the walls to be R11 or 12, not far from my assumption of R10. He did say his report would recommend more attic insulation, basement exterior wall insulation, a heat pump, and an electric water heater amongst other things. When he did the fan blower test, he mentioned that our house wasn’t as “leaky” as he thought it would be, so that is good news.

His visit got me thinking more about alternative energies to heat our home, their relative cost and CO₂ emissions. According to https://www.selectaglaze.co.uk/the-benefits-of-retrofitting-houses, the average house in the UK emits at least 5000 kg of CO₂ per year. As the figure indicates, the site suggests that a deep retrofit of a house could reduce CO2 emissions down to 1000 kg of CO₂ .it would be interesting to see how our current house configuration compares to this and what we could do to reduce emissions, could we get down to 1000 kg of CO₂?

, We don’t have natural gas on our street so I won’t consider that possibility. That means we are down to oil, propane, or electricity. One important feature of our old house is that it heats by hot water baseboard. Through some research, I have come to realize that this severally limits our options for alternative energy sources, particularly when considering the switch to electricity. For example, solar panels, wind turbines, and heat pumps cannot be used to produce the 160 to 180 °F hot water needed to feed our baseboard heating system. So the options available that would continue to heat our home through the hot water baseboard system are high-efficiency oil, propane, or electric boilers.

 

Alternative Boilers Energy Costs

As our calculations from the last posting showed, it currently takes about 61 MBTU to heat our old house and an estimated 16 MBTU to provide hot water. The Efficiency Nova Scotia website indicates that modern electric, propane, and oil boilers have efficiencies of 100%, 93 and 95% respectively. Again, according to ENS, we get 36,500 BTU per liter of oil, 24,300 BTU per liter of propane, and 3412 BTU/kwh for electricity. So we can calculate the usage of each energy source as shown in the 3^rd column of Table 1 below. From ENS the cost of electricity is $0.1615/kwh which is close to the current cost of electricity in winter 2023. Oil cost $2 per liter and propane costs around $0.85 per liter. Therefore, the cost comparison is shown in the 4^th column of the table below. The current cost of heating our home assuming a 70% efficient furnace (i.e., 87.6 MBTU or 2400 liters) would be $4800 per year. So all new boilers would result in a cost reduction with the propane furnace giving the lowest cost.

Table 1. Some comparative data for alternative energy

Type of Boiler	Efficiency	Amount of use	Cost of Energy	CO2 emissions	Reduction in CO2 emissions
Electric (100% eff.)	61 MBTU	17878 kwh	$2887	9022 kg	-2566 kg
Oil (100% eff.)	63 MBTU	1726 liters	$3452	4643 kg	1813 kg
Propane (100% eff.)	66 MBTU	2716 liters	$2308	4101 kg	2355 kg

 Alternative Energy CO₂ emissions.

One of the benefits of propane is that it is a cleaner burning fuel. It emits 1.51 kg of CO₂ per liter of propane  https://www.eia.gov/environment/emissions/co2_vol_mass.php . Using the same source for comparison, furnace oil emits 2.69 kg of CO₂ per liter. For our house, this would result in a total CO₂ emission per year of 4643 and 4101 kg for high-efficiency oil and propane respectively. Our current 70% efficiency oil furnace produces 6456 kg of CO₂ for heating, so the new oil or propane furnaces would provide a net reduction in emissions. (see the 5^th and 6^th columns of Table 1 for the details).

Electricity is a harder source to nail in terms of CO₂ emissions. Perhaps the “cleanest” electricity comes from hydroelectric plants. According to https://www.hydropower.org/factsheets/greenhouse-gas-emissions, a hydro plant produces 24 g of CO₂ per kwh. For the situation of our house, this would result in 429 kg of CO₂ per year which is 10 times smaller than that for new oil and propane furnaces. Unfortunately, Nova Scotia Power currently burns fossil fuels (including coal) to produce 70% of it’s electricity, the remainder being from renewable energy sources. One major disadvantage to burning fossil fuels (FF) to produce electricity is that at best it is only 40% efficient. (https://www.mpoweruk.com/fossil_fuels.htm#). This means that for every unit of electrical energy produced, you need to burn 2.5 units of fossil fuel. I will assume that no CO₂ comes from the renewable energies used by NSP. Therefore, of the 17,878 kWh we need to heat our house, 12,514.6 kwh will come from burning fossil fuels which will produce CO₂. Since this FF to electricity conversion is only 40% efficient, providing 12,514.6 kwh of electricity will actually require 31,286.5 kwh of energy from FF. This translates to 106 MBTU which is about 1.7 times more than what we use by directly burning either oil or propane in a boiler to heat the house!

Let’s go to the next step of CO₂ emissions. According to the NSP, 50% of their FF comes from coal and 50% from oil. The site (https://www.eia.gov/environment/emissions/co2_vol_mass.php) lists the CO₂ emissions of various fuels in terms of MBTU. Coal emits 96.1 kg of CO₂ per MBTU while oil emits 74.1 kg of CO₂ per MBTU. IF NSP uses a 50:50 split then on average their FF usage to produce electricity would be 85.1 kg of CO₂ per MBTU.  Therefore, the total CO₂ produced to provide the 106 MBTU of FF used to produce the 12514.6 kwh needed for an electric boiler to heat our home is 9022 kg. An electric boiler would produce about twice as much greenhouse gas as high-efficiency oil and propane boilers. In fact, as shown in the last column it would produce more CO₂ than our current 70% efficient oil furnace. Interestingly, a high-efficiency propane furnace results in the highest reduction in greenhouse gas emissions.

The CO₂ produced by an electric furnace is a crazy calculation, can it be right? I compared these calculations to those provided on the ENS website. For example, they calculate that a house using 80 MBTU’s to heat using an electric boiler, would emit 12,360 kg of CO₂ while the use of a high-efficiency oil and propane furnace would emit 5670 and 4940 kg of CO₂ respectively. Those CO₂ ratios, 2.2 and 2.5 compare very well to the 1.9 and 2.2 from my calculations in Table 1. In fact ENS indicates that the electric boiler performance is even worse than my calculations indicate. So, in the current situation, it makes no sense to switch to an electric boiler, in fact, it would be damaging to the environment to do so.

You might say this is not a fair calculation since NSP is increasing its use of renewable energy all the time. According to NSP, when Muskrat falls reaches its full potential the FF usage to produce electricity will drop to 40%. By 2030 NSP projects that only 20% of its electricity will use FF. We can repeat the above calculation for these cases. At 40% and 20% FF usage, 7151 kwh and 3576 kwh respectively of the of the total 17878 kwh needed to heat our home would come from FF. With the 40% efficiency conversion of FF to electricity, this would climb to 17878 and 8940 kwh for 40 and 20% FF usage respectively. Converting these energies to MBTU results in 61 and 31 MBTU and 5191 and 2638 kg CO₂ emissions respectively. So bringing Muskrat falls online still does not produce less CO₂ than high-efficiency FF furnaces, going to 80% renewables would definitely make an electric boiler more environmentally friendly. According to my calculations, the break-even point when an electric boiler would produce the same CO₂ emissions as a high-efficiency propane furnace would be when NSP uses 68% renewables to produce electricity. In another calculation which I won’t detail here, I compared the total CO₂ emissions if we switched to a propane furnace versus an electric boiler today. From the above calculations, the propane furnace would emit much less CO₂ than the electric furnace due to the high usage of FF by NSP. As NSP migrated to more renewables, this would favor the electric furnace in terms of CO₂ emissions. However, it would take until the year 2042 before the net emissions from the electric furnace were the same as that produced by the propane furnace over those same 20 years. I conclude that there is no scenario where an electric furnace makes sense to heat your home in Nova Scotia from the point of view of CO2 emissions at least at this stage. Maybe it would make sense 10 to 15 years from now when NSP achieves its 80% renewables target.

Thanks for wading through the calculations. Hope you find it useful.

SOME OF OUR DIY RENOVATIONS...

You may notice two distinct voices in this blog. One is my husband, the numbers and equations guy. I'm the one who talks about our renovations and how pretty the houses are after our hard work. 

Our first renovation project in our Old Nova Scotia Home cottage back in 2018 was upstairs. The layout included a little landing as well as three rooms, one large on one side of the house and two small rooms on the other. The two smaller rooms were accessed by one door and were really too small for anything other than just a bed. Also, the rooms have the typical old home slanted walls and old carpets.

Just a bit of our renovation refuse

The first thing we did was to rip down the wall between the two small rooms. Turned out the wall was not original and so it came out easily. Next, we tore off all the existing wall and ceiling coverings on the now two rooms - not so easy! The walls and ceilings were finished with something I think was called beaverboard. It was made of wood fiber pressed into sheets and was commonly used from the early 1900s till the late 1920s. Unlike drywall that you can pull off in big chunks, the beaverboard came off in little pieces - it took us weeks to get it all removed. And the nails ???? Hundreds of nails. My arms ached from pulling those suckers out of the beams. Then we insulated the little attic space, the upstairs walls, and ceilings. Finished up with drywall and did the walls in a relaxing beachy blue color. Very happy how it turned out.

I love how the sun shines in the window through the white gauze curtains 

Lots of room for bureau and seats

Geeking Out on Heat Loss Calculations

Still waiting for our Energy Audit analysis. Ultimately, we hope that this audit will let us decide what steps we should take to reduce our energy usage and CO₂ emissions. As we already mentioned, on average our old house uses 2746 liters of oil which provides 100 MBTU of energy for heating and hot water. According to https://www.carbonindependent.org/15.html, 2.96 kg of CO₂ is produced by burning one liter of furnace oil. Therefore, our home’s current CO₂ footprint is 8,128 kg per year.

I should mention that I am an engineer and love numbers and calculations, hence the equations and tables in the text below. I did some online research and realized I could likely do my own energy audit. Now when the Energy Auditor comes, I can better understand what he is doing and compare the results of his calculations to mine. 

The basic concept is that heat loss through the surfaces of your house must be replaced by the heat source in your home. I’m going to assume that most of the heat loss through the house is by conduction which refers to the heat lost through the walls, windows, attic, etc. I borrowed this great graphic from https://powertoswitch.co.uk/energy-efficiency/where-does-all-the-heat-go/ that illustrates it perfectly.

 To calculate the heat loss, we can use equation 1 below:

Heat Loss =A(T_in-T_out)/R

In imperial units, Heat Loss is BTU/hour, A is the exposed area in ft², T_in and T_out are the inside and outside temperatures in °F and R is the R-value rating for insulation (example R 20) which has units of (hour ft² °F BTU).

I’ve divided my old house up into different zones that have different R values, Table 1 below gives the details. The best R value is in our Attic and the worst is our windows, particularly the old single pane wood windows. The walls represent the largest area by far followed by the attic and basement.

Table 1: Details of the different zones in our old house

Item	Exterior Walls	Old single pane windows	New double pane windows	Attic	Steel Door	Basement
R value	R10	R1.2	R3.1	R20	R1.2	R5
Area	1569 ft2	135.5 ft2	121 ft2	754.75 ft2	18 ft2	754.75 ft2

 We can add up all the A/R values for each zone of the house as shown in the equation below:

Heat Loss = [(A/R)_wall + (A/R)_ow + (A/R)_nw + (A/R)_sd + (A/R)_attic + (A/R)_base](T_in-T_out)

Heat Loss = [1569/10 +135.5/1.2 + 121/3.1 + 18/1.2 + 754.75/20 + 754.75/5] (T_in-T_out)

Heat Loss = [156.9 + 112.9 + 39 + 15 +37.7 +150.9] (T_in-T_out)

If we know the temperature difference between the inside and outside, we can calculate the heat loss in BTU per hour for our old house using the following equation 2.

Heat Loss = 361.55 (T_in-T_out)  + 150.9 (T_in-T_out)                                                                      

The exterior walls, windows, doors and attic all face the outside so their T_out would all be the same. Since the basement is an enclosed space below ground, the T_out would be different. I have measured the temperature in the basement over the last month or so and it seems to stay steady at 50 °F, even when the outside temperature changes. So, I’m going to use that value for T_out for the basement heat loss calculation rather than the actual outside temperature.

We keep our thermostat set at 64 °F during the day and for 8 hours overnight we have it programmed to go down to 58 °F. Of course, the outside temperature varies from day to day and month to month. This may seem a bit obsessive/compulsive, but I managed to find the average temperature for the month of October through April for the years 2013 to 2022 for Halifax. This is approximately the time we have owned our old house. I averaged all this data to get an average temperature for the years we have owned the home for the months of October through April and those values are listed in Table 2 below.

Table 2: Historical average temperatures in Halifax from 2013 to 2022 and resulting heat loss calculation for each month of the heating season.

Heating Month	Oct	Nov	Dec	Jan	Feb	Mar	April
Average outside temperature	50.6 °F	39.1 °F	29.6 °F	23.9 °F	24.3 °F	29.1 °F	40.9 °F
Total Heat Loss in MBTU	4.49	7.26	10.06	11.59	10.38	10.19	7.45

 The heat loss for each month can be calculated by adding the time to equation 2. We have 24 hours in a day, 16 of which the inside temperature is 64°F and 8 of which it is 58°F, and 31 days in the month of October:

Heat loss (for October) = 361.55*[16(T_in-T_out)_day + 8(T_in-T_out)_night]*days + 159.5*[16(T_in-T_out)_day + 8(T_in-T_out)_night]*days                                                                                                                                     
Heat loss (for October) = 361.55*[16(64-50.6) + 8(58-50.6)]*31 + 159.5*[16(64-50) + 8(58-50)]*31

Heat loss (for October) =361.55*[214.4 + 59.2]31 + 159.5*[224 +64]*31

Heat loss (for October) = 3,066,522 + 1,424,016

Heat loss (for October) = 4,490,538 BTU

Repeating this calculation for the other heating months gives the values listed in Table 2.

As expected, the months with the lowest average temperatures, use the most energy to heat the house. Dec., Jan., Feb. and Mar. use the most energy. The total energy for the heating season calculates to be 61.34 MBTU. The furnace needs to provide that energy but is not 100% efficient. Assuming our 27-year-old oil furnace is 70% efficient means we would need to use 61.34/0.7 = 87.62 MBTU.

This value compares well to the actual average energy we have used based on our oil bills of 100 MBTU. Particularly since the 100 MBTU also includes energy we use to provide hot water. Efficiency Nova Scotia indicates that a 4-person 1700 sq. ft. home uses 32.5 MBTU to provide hot water. Since we are only two people, I will estimate our hot water usage to be 16.25 MBTU. Adding that to our above heat loss calculation results in a total energy use prediction of 103.9 MBTU. That is an amazing agreement with our actual use of 100 MBTU.

It is great that the heat loss calculations are pretty accurate and capable of predicting our actual energy used. That puts us in a position to consider different upgrades to the house, particularly in terms of insulation, and to see how much energy and cost savings they would result in. That will be the subject of an upcoming post.

Thanks for sticking with me through the numbers. Hope some of you will find it useful.

BACK IN 2007...

Since the energy audit and insulation consult I mentioned in my last post will take some time, I thought I'd introduce you to our old Nova Scotia home which we lovingly refer to as the Cottage. It's hard to believe it was 15 years ago that we bought on the South Shore.

We were living in Ontario at the time but knew we would be coming back home to Nova Scotia at some point. We had been looking on real estate sites for places but really had not seen anything we liked or could afford. During a trip to Nova Scotia to visit family, we were driving along the Medway River and found a little house for sale. We stopped to look in the front windows and were won over by the sun shining in the side window into the kitchen. We immediately contacted the agent but she said there was already a pending sale. A month later she contacted us to say the deal had fallen through. After a quick trip by one of us back to Nova Scotia in November ahead of a hurricane and the inside sight unseen by the other spouse, we had a new house. This is what it looked like then.

That Christmas, we drove down to investigate our diamond in the rough. We slept on an air mattress on the living room floor and we were so happy LOL. Renovations started in the Spring when we were able to come down for a whole week and still continue. I'll post some before and after pictures another day.

ON THE ROAD TO ENERGY SAVINGS....

One of the things we want to achieve with the old house we live in is to reduce our carbon footprint and reduce fuel costs. Our initial step was to figure out how much energy our 1516 sq. ft. old house has historically used to provide heat and hot water. As you can see from the image below, most of our basement is stone and dirt. Luckily my organized wife had kept all our furnace oil bills since we owned our house. Our average liters of furnace oil consumed per year from 2013 to 2022 was 2,746 L. Using data provided by the Efficiency Nova Scotia website, we know furnace oil generates 36,500 BTU/L. Therefore, on average our old house has used 100,229,000 BTU or 100 MBTU per year to heat our home and provide hot water.

Efficiency Nova Scotia’s (ENS) website gives some great data and examples for home energy usage for a variety of heating methods. For a 1700 sq. ft. home they calculate the average energy consumed to heat the home with furnace oil is 65 MBTU. They do a separate calculation for hot water, which gives an additional energy of 32.5 MBTU for a tankless coil oil furnace which is the kind we have in our house. Combining the two, ENS's prediction of average energy use for heat and hot water would be 97.5 MBTU. Based on this, our old house compares reasonably well to the ENS calculations. Interestingly, ENS does a similar calculation for what they call an “old house” where the energy to heat the home is 80 MBTU, for a total of 112.5 MBTU for heat and hot water. Again, our old house is comparing reasonably well.

This comparison is a bit of a surprise. Our oil furnace is 27 years old and internet sources suggest that an oil furnace this old would have an efficiency in the range of 60 to 75%. A value ENS uses for an old oil furnace that gave the 80 MBTU energy consumption calculated above is 70% efficiency. So is our furnace more efficient than I thought? Not likely. The fact that we keep our thermostat set at 64 °F during the day and 58 °F at night during the cold weather may account for a lower energy usage than the ENS calculations. Our house is also a little smaller (1516 sq. ft.) than the 1700 sq. ft. ENS example which may also factor into the favourable comparison.

I don’t think our house is very well insulated. The basement and crawlspace have no insulation on the walls or ceilings. We think the outside walls of the 1^st and 2^nd floor have some blown-in insulation but it has settled in the wall cavities. Our attic does have some insulation, so it appears there is lots of room for improvement.

Even though our old house seems to compare well with what might be expected, we want to see what we can do to reduce the energy consumption of our old house. Hopefully, this would allow us to reduce the cost of heating and reduce our contribution to greenhouse gases to help mitigate, in our small way, the impact of the climate crisis. Our next steps will be to get an energy audit and have our house assessed by professionals for insulation improvements. Stay tuned for the results of these tests!

IN THE BEGINNING...

While there is some truth to the old saying that the only things working in an old house are the people who live in it, for those of us lucky enough to live in one, it is a labor of love. In our case, we actually own two, both century homes. One in Bedford and one on the South Shore in Queens County. 

Over the last 15 years, we have spent lots of time and money working on the houses and still there is always lots more to do. We hope you will be interested in hearing about the changes and seeing some of our before and afters. Join us as we dig into the pros and cons of more renovation and upgrades while still maintaining the character of the homes we love.

If we have time, we would also like to share a bit about the renovation experiences of other owners of old Nova Scotia homes, so stay tuned.