Tag Archives: energy efficiency project

The Energy Efficiency Project: Month 4

Energy Efficiency Project Month 4March 12th – April 14th, 33 days

This month was pretty boring as far as energy efficiency improvements go. We turned off the heat at the beginning of April and got to start working on the yard a bit. We were still splitting our time between the house and our apartment in the city during this month, so the house was using minimal maintenance energy while we weren’t in it. For example, the furnace was set just high enough to keep our pipes from freezing while out of the house, and really only the fridge was using electricity most of the time. So, again, this month won’t be the best representation of our energy use, but will hopefully serve as a good reminder to put your house into low-energy-use mode when you’re gone for extended periods of time. As far as energy efficiency initiatives went we:

  • Turned off thermostat starting on April 1st!
  • Made sure that all lights and other electricity users aside from the refrigerator were off while we were away.

This month’s upgrade cost: $0

Total upgrade cost to date: $17.64

Over 33 days we used 312 KWH. Which comes out to an average of 9.45 KWH/day. Which is a small decrease from the last billing period average of 10.75 KWH/day. My guess is our decrease came from extended daylight hours, which meant less lightbulb use while we were in the house.

We are part of the Alliant Energy Second Nature renewable energy program, at the 100% level. (In this program you can choose the amount of your energy use that you want to be matched in renewables, and we chose 100%.) So the cost of our electricity is $0.13 per KWH, for a total of $40.85.

We also used 35 Therms of natural gas heat energy. Which averages out to 1.06 Therms/day. We only used the gas furnace for the first half of this billing month, and then of course had some gas use for the hot water heater. Also, we had a pretty warm start to our spring in these parts, so the degree days this month compared to last month: 754 vs. 1383. As you can see, the degree days this month is only a bit more than half of last month, which explains why we were able to turn off our furnace completely for half the month.

The natural gas market fluctuates in Wisconsin, so there is not an easy dollar per Therm number to give you, but during this billing period we paid $32.24 for our gas use.

Our energy bill also provides these numbers for helpful comparison:

Electricity used this month last year: 651 KWH

Gas used this month last year: 41 Therms. Average temperature this month: 43° F. This month last year: 36° F.

Degree Days this month: 754 vs this month last year: 835. Degree days are the number of degrees below 65° F in one day, all added together for the total 33 days of the billing period.

Want to see previous months of the Energy Efficiency Project? Here is Month 1Month 2, and Month 3

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Adding Insulation for Energy Efficiency part 2

The last time we checked in on the topic of insulation and insulating a house to the point where it wouldn’t need a furnace was back in December. Sheesh. The cold has broke here in the northern great lakes region, and while there is still a chill in the air some days, we seem to be headed right into spring. The good news is, insulation is not just a winter topic. Good insulation in your home will help keep it comfortable all year long. And keep your energy bills down. And so we forge ahead with adding insulation for energy efficiency.

Previously, I walked through the calculations to determine the payback period for adding insulation. Today let’s look at a couple of examples of how that might work our in practice.

  • R-value of the initial insulation (Ri)
  • R-value of the final insulation (Rf)
  • Cost of insulation (Ci)
  • Efficiency of the heat system (E)
  • Cost of energy (Ce)
  • Number of Heat Degree Days for the year (HDD)

And the equation looks like this:

P = (Ci * Ri * Rf * E) / (Ce * (Rf – Ri) * HDD * 24)

OK, take a deep breath. We’re about to do some math!

Example 1: Fiberglass Insulation Upgrade

For our first example, we’ll use the following situation: A house in Wisconsin is going to have its insulation upgrades. It currently has fiberglass batting with an R-value of 13, and will be upgraded to fiberglass batting with an R-value of 19. The cost of the new insulation is $0.41 per square foot. The house is heated by a natural gas furnace that is 85% efficient. The cost of natural gas in Wisconsin is $0.82 per therm, and 1 therm is equal to 100,000 Btu (British thermal units). The number of heating degree days for Wisconsin is 7499. We want to find the payback period for the new insulation.

So, breaking down our equation, we have:

Ci = $0.41 per square foot

Ri = 13

Rf = 19

E = 85% = 0.85

Ce = $0.82 per therm = $0.0000082 per Btu

HDD = 7499

P = (0.41 * 13 * 19 * 0.85) / ((0.0000082) * (19 – 13) * 7499 * 24)

P = 9.7 years

Wowza! That’s more time than I was expecting. So what are the key factors here that could cause this to payback period to go down? Well, first of all, with a little more looking, you might be able to find a better price on your insulation than a quick tour through the Home Depot website gave me. Also, natural gas in Wisconsin is pretty dang cheap right now, all things considered. But as more cities and states do things like ban fracking for natural gas, that cost could go up significantly, which would obviously bring the payback period down.

Example 2: Sprayed Foam Insulation – How much can we get?

What if instead of replacing all that R-13 fiberglass insulation with R-19 fiberglass insulation, we wanted to replace it with spray foam insulation?

Spray foam insulation has an R-value per inch of foam thickness. You can increase the total R-value by spraying a thicker layer of foam. There are tons of options available as far as spray foam goes, but for the sake of this example, we will use this Dow Froth Pack as our insulation. This spray foam provides R-6 per inch of thickness, so 1 inch has R-6, 2 inches has R-12, 3 inches has R-18, so on and so forth.

In this example, instead of calculating the payback period for the spray foam insulation, we’re going to see how thick of an insulation layer we can “afford” to apply, given the same payback period as the upgrade from R-13 to R-19 fiberglass. In other words, we are going to solve for Rf.

So, breaking down our equation, we have:

Ci = $1.01 per square foot

Ri = 13

Rf = x

E = 85% = 0.85

Ce = $0.82 per therm = $0.0000082 per Btu

HDD = 7499

P = 9.7 years

Through the magic of algebra, we can rearrange our equation to solve for Rf:

Rf = (P * Ri) – P – ((Ci * Ri * E)/(Ce * HDD * 24))

Which looks gross, but it’s really just a matter of plug and chug at this point:

Rf = (9.7 * 13) – 9.7 – ((1.01 * 13 * 0.85)/(0.82 * 7499 * 24))

Rf = 10.67, or about 1.75 inches thickness of the spray foam insulation.

So, for the same payback period as with the fiberglass insulation, we’d actually be downgrading from R-13 to R-10.67 with the spray foam. If we wanted to increase to the equivalent R-value, our payback period with the spray foam would be nearly twice as long!

But then what’s all the fuss about spray foam insulation? Why would anyone use it if the return on investment is apparently so low? Well, the R-value of the insulation isn’t telling you the whole story here. Remember the walls of your house are not just made out of batts of insulation. There is also the framing, the siding, the sheet rock, and all the other layers to consider. And those layers typically have small cracks and crevices where the heat can leak quite easily. One of the benefits of the spray foam insulation is that it fills in and seals all those leaky spots. So not only do you have the impact of the insulation layer, but you’ve increased the insulation abilities of all those other layers as well. Insulation can be one of those things were whole is greater than the sum of the parts.

Onward, Energy Efficiency Warriors. Next time we visit this topic we’ll get to the big finale: Can you insulate a house enough such that you don’t need a furnace???

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The Energy Efficiency Project: Month 3

energy efficiency project month 3

February 12th – March 11th, 28 days

This month we continued to paint and started building some bookshelves.  We also hosted a first birthday party and started getting ready for our upcoming outdoor projects. We were splitting our time between the house and our apartment in the city during this month, so the house was using minimal maintenance energy while we weren’t in it. For example, the furnace was set just high enough to keep our pipes from freezing while out of the house, and really only the fridge was using electricity most of the time. So this month won’t be the best representation of our energy use, but will hopefully serve as a good reminder to put your house into low-energy-use mode when you’re gone for extended periods of time. As far as energy efficiency initiatives went we:

  • Replaced a frequently used lamp’s CFL light bulb with an LED bulb. (The CFL bulb was still good, so it will be used to replace a bulb down the line when I run out of LED bulbs.)
  • Turned the thermostat down to about 55° while we were out of the house.
  • Made sure that all lights and other electricity users aside from the refrigerator were off while we were away.

This month’s upgrade cost: $8.82

Total upgrade cost to date: $17.64

Over 28 days we used 301 KWH. Which comes out to an average of 10.75 KWH/day. Which is an expected decrease from the last billing period average of 14.2 KWH/day since we spent so much time out of the house.

We are part of the Alliant Energy Second Nature renewable energy program, at the 100% level. (In this program you can choose the amount of your energy use that you want to be matched in renewables, and we chose 100%.) So the cost of our electricity is $0.13 per KWH, for a total of $39.41.

We also used 73 Therms of natural gas heat energy. Which averages out to 2.6 Therms/day. That’s only 0.1 Therm less per day than the previous month! Even though much of the month the furnace was only heating the house to 55°, this month was much colder than the first two months of the year. Looking at this, I’m very glad that we made sure to turn down the thermostat every time we left the house, or we would have had a much higher gas bill. Also, looking at degree days this month compared to last month: 1383 vs. 1286. Our furnace was working hard this month!

The natural gas market fluctuates in Wisconsin, so there is not an easy dollar per Therm number to give you, but during this billing period we paid $60.09 for our gas use.

Our energy bill also provides these numbers for helpful comparison:

Electricity used this month last year: 714 KWH

Gas used this month last year: 73 Therms. Average temperature this month: 16° F. This month last year: 19° F. I’m going to assume that the previous owners lived in the house for the full month last year – rather than just part time like we did – and kept it at a typical 68-72°. So it’s interesting to see how just a few degree change in average temperature really makes the furnace work a lot harder to heat the house.

Degree Days this month: 1383 vs this month last year: 1342. Degree days are the number of degrees below 65° F in one day, all added together for the total 28 days of the billing period.

Want to previous months of the Energy Efficiency Project? Here is Month 1 and Month 2

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Introducing The Energy Efficiency Project

Once upon a time, husby and I thought, what if we bought a house in the small town we’ll be moving to this spring. About a year ago, when I first starting envisioning this whole building earth project, I thought a good progression would be to have a house to demonstrate some of the energy efficiency, green building, and sustainable design ideas that I’ve been writing about. Not to mention we were ready to start investing in our own place inside and out.

One of the projects that I’m super excited about starting in regards to our new house is this series on The Energy Efficiency Project. Each month I’m going to explain what things we’ve done to reduce our houses energy use: upgrades, downgrades, or behavior changes. And then I’ll share the nitty-gritty with you: our monthly energy bill, and the costs, and pros and cons of the changes we’ve implemented. My goal is to be as transparent as possible in how we use energy and how we are attempting to save energy. My hope is to show how small changes can add up to significant energy savings, and maybe you’ll be inspired to adopt some of the same changes yourself.

power lines: the energy efficiency project

So first, let me share some details about our new home to give you the lay of the energy use land.

Size: 1,026 square feet. Single story, with an unfinished basement, rafter attic for insulation.
Energy using appliances: refrigerator, stove, washer, dryer, hot water heater, gas furnace, central air, garage door, coffee grinder, exhaust fan
Electronics: computer, cell phones, alarm clock, seedling starter heating pad
Light fixtures: 21 bulbs worth
Windows: approximately 100 square feet, most of which are fairly new with aluminum sills
Insulation: I’m not sure exactly, since I haven’t looked inside the walls yet, but I’m pretty sure it’s just your basic fiberglass batts. The attic has about 3-4 inches of blown insulation covering the house.
Occupants: 2 adults, one wee tender babe

The Energy Efficiency Project: Month 1

We’ve been living in the new house for about a month now. Long enough to get our first energy bill! So we have a bit of a baseline to start with.

For December 17th through January 13th this is what our energy usage looked like:

Over 27 days we used 379 KWH (kilowatt hours) of electricity. We are part of the Alliant Energy Second Nature renewable energy program, at the 100% level. (In this program you can choose the amount of your energy use that you want to be matched in renewables, and we chose 100%.) So the cost of our electricity is $0.13 per KWH, for a total of $49.62.

We also used 85 Therms of natural gas heat energy. The natural gas market fluctuates in Wisconsin, so there is not an easy dollar per Therm number to give you, but during this billing period we paid $72.90 for our gas use.

Our energy bill also provides these numbers for helpful comparison:

Electricity used this month last year: 834 KWH (!!! what did the former owners have plugged in that sucked more than twice as much electricity as we used?)

Gas used this month last year: 96 Therms. Average temperature this month: 20° F. This month last year: 14° F. So last year was a bit colder than this year which explains the higher gas usage.

Degree Days this month: 1211, vs this month last year: 1698. Degree days are the number of degrees below 65° F in one day, all added together for the total 27 days of the billing period

Now let’s see where we can go from here!

P.S. Interested in seeing a picture tour of our new house? You can check that out over on macnamania.com!