More than one person has questioned the ethics of not (or barely) heating my house at this season, based on the fact that I share one wall with a neighbor. People have suggested that I am effectively stealing heat from my neighbor, and should be ashamed of myself. My conscience demanded that I investigate whether they are right.
I do, of course, have some immediate counter-arguments. Firstly, I would point out that my neighbor is well aware of what’s going on over here. In fact I heartily invited her to join me in this experience, and initially she showed enthusiasm. She does have a woodstove, which would make it easier for her. But before long I noticed her furnace was running, so I guess she gave in. In any case the point is that there has been full disclosure and there is nothing sneaky going on.
Second, I will comment that anytime ANY neighbors share a wall, some warmth will flow from one side to the other– unless they agree to maintain exactly the same thermostat settings at all times. Whoever prefers a warmer apartment will inevitably lose a bit of heat to the colder apartment. But I’m not sure you can say that the guy who likes it cold is to be held responsible for that.
Thirdly, a residence sharing a wall with a neighbor is inherently more efficient than a residence with no shared wall– even if the neighbor goes to Aruba for the winter and doesn’t heat his house at all. You still get the benefit of an insulated outside wall, to keep out the great outdoors– but you get the added insulating benefit of 20ft (or however wide your neighbor’s place is) of dead air between your place and that wall. You’re losing less heat to the neighbor’s place than you would lose to outdoors, if the neighbor wasn’t there.
But, all that said– I really like my neighbor, so I still wanted to know how guilty I might be of benefiting from her ill-considered decision not to participate in the Cold House Project. Finding that figure involves the following variables: surface area of our shared wall, insulating R-value of the wall, room temperature difference between our houses, efficiency of neighbor’s furnace, cost of oil, and length of the heating season.
The toughest one to guesstimate is the R-value of the wall, because I’m not sure sure of its construction. (I have been tempted, as you might imagine, to drill some holes through the wall– but have refrained from doing so.) At minimum, let’s say the wall has plywood and wallboard on each side, plus a couple inches of empty air– that gives R of 4.86. However, it does seem the wall is more substantial than that. There is very little sound transmission, so there’s something dense in there. And from poking around, it looks it’s probably cellulose insulation. How thick, hard to say– but there could be, let’s say, 3.5″. Even without a plywood layer, that would give the wall an R of 13.42
The other variables I take two guess at, the first being worst (for neighbor) case, the second, best case:
Surface area of wall: 1000 to 750 sq ft
Difference in room temp: 22 to 16°F
Cost of oil: $4.00 to $1.80/gallon
Efficiency of neighbor’s furnace: 86% to 79%
I’m going to call the heating season is 170 days long.
When I crunch all the numbers for best- and worst-cases, here’s what I come up with:
The heat transfer from Neighbor’s house into mine is equivalent to burning somewhere between 0.15 and 0.92 gallons of oil a day. This works out to somewhere between $45 and $622 of oil per winter. Which is either an amount that is trivial, or an amount that is worrisome. The question is, if it’s worrisome, who should be worried? Me, or neighbor? Would this information induce her to turn her heat down a bit too? Would she consider investing in added insulation to her side of the wall? Or would she report me for being Un-American and try to have get a court injunction ordering me to resume burning foreign oil immediately? Not sure.
One final point, in my defense: Although we own the exterior of our building communally, Neighbor has the entire southern side of the house. Her roof, walls, and windows get almost all of the sun that hits our structure, so her place gets almost all of the heat benefit of solar gain. I lack the expertise to calculate how much energy this amounts to, over the course of the winter– but I feel confident that it saves her at least 0.15 gallons of oil a day, and possibly more than 0.92 gallons. So, as best I can figure– I’m just reclaiming my share of the solar heat from that southern wall that I own half of, but don’t get any direct benefit from.
And Neighbor gets to sit in actual sunshine all winter, while I do not. Hard to put a price on that. Seems unethical.