Wonky Math

By Amy Knight

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The House We Live In: A Series on Building the Sustainable Home in Tucson, Arizona


I once had an argument in which I tried (and ultimately failed) to convince someone that the difference between 95% and 100% is more than 5%. The argument had to do with an “I’ll take care of it” type of promise; he did, in fact, take care of most of the bills that needed paying. But not quite all of them, and that last forgotten one mattered. It prevented me from relaxing and trusting that I didn’t need to worry about it. I still had to pay attention to make sure that everything actually was done that month and every month, and that layer of anxiety was the added cost, on top of the 5% that had slipped through the cracks. Sometimes that premium can be worth quite a lot. I’m an anxious person by nature; if my anxiety level is already high, taking something completely out of the realm of worry is really valuable to me.

This kind of math has just turned up again in my design process.

“You said you wanted a gas stove,” Matthew said. (He was right this time; I had said that and I do want that.) “Is that negotiable?”

Oh, no, I thought. This being Thanksgiving weekend I had been spending some time both using and talking about stoves. My dear friend Liz visited my temporary home for the first time and while I complained a little about my rental kitchen (the only part of this house that I really mind), she said, “Well, at least it has a gas stove.” Indeed: that is a feature I have come to love, and when I’ve lacked one, I’ve missed it. I like the control. I like the fact that you can use it even if the power goes out. I like occasionally throwing a whole pepper right on the flame to char it. I like clicking sound of the burner as it lights.

The problem, Matthew explained, was that when you have combustion inside the house (i.e., the flame on the gas stove), it changes the kind of ventilation you need. We might be able to heat and cool more efficiently without it.

“Is that really worth it?” I asked. “A stove doesn’t seem like it would change much.” The suggestion had been put to him by his friend who is a building scientist, and who is also consulting on my project. (Side note: there is such thing as a building scientist.) The gas stove itself doesn’t add a lot of trouble, but going from no combustion to just a little bit of combustion inside the house could make a major change in the systems required. And when temperature regulation is a major source of energy use, being able to create a much more significant seal—which you can’t do if you burn even a little fuel inside the house—can have a major payoff. That 5% is worth a whole lot more than 5%.

My first instinct was to say no, it’s not negotiable. But then I took a deep breath. I’ve written already about the need to make tradeoffs, to build a house that makes sense, not just one that is perfectly convenient and addresses my every desire. I want a gas stove. But do I want it even if there is an alternative that will also work and will make the house more efficient? Maybe I do. Maybe I don’t. This is not an exercise in building the perfect eco-house at the cost of comforts that really matter. It’s about finding a balance. But in so doing, I have to keep myself honest about what drives each choice.

Matthew suggested an induction cooktop, which I know almost nothing about. A little Googling reveals that it’s becoming much more common (and cheaper), and not only does it enable a no-combustion setup for the house, it’s also much more efficient in transferring heat to the food you’re cooking. Of course, you have to use the right kind of pans, but my beloved Le Creuset pans would work. Some real foodies have become serious converts.

This kind of choice feels at first like a sacrifice. But maybe it will lead me to good things I never had any idea about. Maybe I’ll fall in love with induction cooking, which I’d never have learned about if I’d insisted on doing things the way I always have. If the stove was just a stove—if the savings in energy were just the small difference in efficiency between using a flame and using a magnet to directly heat the pan—maybe it wouldn’t be worth it. But like that one last bill, the stove may have the power to improve the situation by more than just its own individual value. It can expand the pie. (Marcy, if you’re reading this, by the way, your Thanksgiving apple pie was delicious.) If this small shift can have a big impact, it may well be worth it.

I am used to making compromises to accommodate missions shared with others but I’m not especially used to making them to accommodate my own competing desires. The concept is starker when I am the only one who shoulders the loss and the only one to feel the benefit. I see now why it was so hard to accept—doing 95% of what was promised was a lot to do. An appliance I really want that uses very little additional energy seems like a small indulgence—until it changes the project’s needs on a scale that actually does matter. I don’t know what I’m going to do yet, but I know the problem will take much more work to solve than simple arithmetic.



Amy Knight is the fiction editor for Terrain.org. In this weekly blog series, she chronicles the process of designing and building an eco-friendly house in Tucson, Arizona. The series will explore both how it’s done and what it means, from the perspective of someone who wants to do the right thing but knows almost nothing about sustainable building. Look for new posts every Monday. You can email Amy at [email protected] or leave a comment here.

Photo credit: Apricot Strawberry Pancake Pie Post Oven via photopin (license)

Terrain.org is the world’s first online journal of place, publishing a rich mix of literature, artwork, case studies, and more since 1997.