Readers, your patience is commendable. The results are in, and it's good news: my house is unequivocally warmer with the insulation. Warmer, you say. What do you mean? Higher temperature? Less drafty? Fewer blankets on your lap? YES. Lest you doubt the perceptions of this interested and biased observer, let me offer a few testimonials:
My roommate, who is experiencing her second Chicago winter in this apartment, said, "Is it warmer this year? Or maybe I'm just getting used to it . . . "
My friend Elizabeth, who has very high standards for indoor temperatures, said, "It's so nice and cozy in here!"
My sister Marietta, who always gives it to me straight, said, "I can't believe it's actually warm in this apartment."
(Full disclosure: In the You Can't Please Everyone Department, I should acknowledge that my father kept his coat on during Christmas Eve dinner, but that may be partly my fault because I forgot to turn the heat up past 60° until after the guests arrived. It did warm up to 70° soon enough, but I think he'd already caught the chill.)
Here's what I have to say about it: I feel more comfortable almost all of the time. The temperature is more even; I no longer have radically varying warm and cold spots within a single room. Also, once it warms up, it stays warm. That is the biggest difference: previously I would turn up the heat and it would warm up for a very short time, then drop, then warm up again, the furnace running full blast all the while. Now my house is a lot quieter because the furnace goes on once and then it doesn't have to run for awhile again.
And speaking of your furnace, Ange, how's the gas bill?
When you compare gas bills, of course, you can't just take it at face value, because there are many variables: the weather, the price of gas, the amount of time you spend at home with the heat up, etc. Fortunately, much of this information appears on your gas bill, starting with the therms.
A therm is a unit of heat energy equal to 100,000 BTUs (British Thermal Units). It takes about 100 cubic feet of natural gas, depending on the mix, to create one therm of heat. On every gas bill, the gas company tells you how many therms (how much heat) you have used for the month. They also give you your average daily therm usage, right next to the average daily outdoor temperature for that month.
I looked at my November and December gas bills for the last three years. Every year I am home for a week during December, so of course I use more heat during that month. So we'll look at the Novembers together and then the Decembers:
Average daily temperature: 40°
Average daily therms: 3.68
Average daily temperature: 36°
Average daily therms: 4.55
Average daily temperature 34°
Average daily therms: 3.17
In general, there is an inverse relationship between the temperature and the amount of heat you use: the lower the temp, the greater the number of therms. As you can see, November 2006 was, on average, four degrees warmer than November 2007, and I used .87 fewer therms: about 20% less heat. But look! In November 2008 we had a daily average of 34°—almost the same as 2007, but actually a little colder—and I used 30% less heat.
Let's look at Decembers:
Average daily temperature: 36°
Average daily therms: 4.58
Average daily temperature: 28°
Average daily therms: 5.51
Average daily temperature: 22°
Average daily therms: 4.69
This is a little easier to compare because the temperature this winter was dramatically colder than 2006, yet I used only slightly more heat. And it was, on average, six degrees colder than last year, yet I used 15% less heat. A better mathematician than I could give you an overall energy savings that accounts for the difference in temperature, but I'll leave that to any ambitious readers to figure out and post for us.
So there you have it: the qualitative and quantitative comparisons show that, in fact, proper insulation and air sealing make for a warmer, more energy-efficient house.
In a future posting, for anyone who's interested, I will do a cost-benefit analysis to estimate just how many years it will take for these energy savings to pay off the $3100 on the insulation plus the $650 for the energy audit. The environmental benefits are, of course, immediate.
The house is much better. Is it perfect? No. After all, I still have 100-year-old windows and a 25-year old furnace to contend with, not to mention a terribly engineered duct system. The windows I have finally covered with plastic just in time for our cold snap, and the furnace is on the list of things to deal with. My plan is to get several estimates and have the furnace chosen, the new ductwork planned, and then wait for the furnace to break down. Or, if I can come up with the money sooner, I'll be proactive.
More on this to come. Also to come: the raging controversy of thermostat setbacks. In the mean time, stay warm, everybody!