[Greenbuilding] in praise of small air volumes(?)

[Reuben Deumling]

I've been working on, and supplying firewood to, three different houses over
the past year. We're now experiencing temperatures in the teens at night,
and those of us living in these three wood-heated houses are comparing
notes.

(1) 1870 farmhouse of roughly 1,500 sq ft, 1.5 storey, just insulated with
R-13 cotton batts in walls, R-19 cotton batts under floor, and R-38 double
cotton batts in attic, thermopane windows;

(2) 1987 two-storey 2,300 sq ft house insulated to R-19 fiberglass in walls;
R-38 in attic; I don't remember how many R-s we put under the floor,
thermopane windows;

(3) 1894 single-storey 660 sq ft house in town no insulation (yet) in walls
or under floor, but R-13 fiberglass batts in 3/4 of the attic, original
single pane + Al-frame storm windows;

I live in house # (3), and to my surprise am going through the least
firewood. Though all the heat leaves with alarming speed if I let the fire
go out and it is cold outside (≤1.5 degrees F per hour) I think I also have
the warmest house of the three. With a bunch of blown in insulation I hope
to do much better next winter.

Does anyone know of efforts to model insulation vs house size? I had thought
that reasonably well installed insulation would have a greater effect on the
rate of firewood consumption than house size. Or is the relevant parameter
the exterior surface of the house? If anyone has thought about this I'd be
curious.

Thanks.

Reuben Deumling