This post is by Phil Price, not Andrew.
My wife and I are building a new house, or, rather, paying trained professionals to build one for us. We are trying to make the house as environmentally benign as we reasonably can: ducted mini-split heating, heat pump water heater, solar panels, heat-recovery ventilator, sustainably harvested lumber, yada yada. But there’s one exception: we insisted on a wide expanse of north-facing windows that look out on the creek that runs through the backyard.
All those windows cause a problem because even low-emissivity windows are much less insulating than the insulated walls they replace. We have compensated by making the walls extra-thick, and the ceiling too — indeed we have to extend all of the windowsills and other window trim because the walls are thicker than the thickest pre-fab windows; ditto for door jambs etc. And yet, even with all that extra insulation, we were still not quite compliant with the California Title 24 energy requirements. This is entirely because there is a large penalty for using a heat pump water heater rather than a gas water heater, which makes no sense whatsoever given California’s energy mix and which everyone expects will be revised in the next set of Title 24 requirements, but you go to war with the regulations you have, not the regulations you want.
How does one determine whether one is in compliance with Title 24? One runs approved software that evaluates a computer model of the building: the orientation, the insulation values of the walls, how big are the windows and what kind are they and which direction do they face, and so on. The model said that our original design was just barely non-compliant, even with its heavily insulated walls and ceiling. We could take out some of those precious windows, or reduce them in size, but what other options did we have (besides hooking up to the gas pipeline and using a gas water heater)? The architect noted that we were compliant in all seasons except winter, so even a little bit more solar gain would help. Why not increase the size of the south-facing windows (which face the street), which would get us credit for enough winter heat gain that we would be in compliance? I pointed out that since the south side of the house is in the shade in winter, due to the large house on a hill immediately to the south, increasing the size of the south-facing windows would make the winter energy performance worse, not better. The architect agreed that yes, it would make the energy performance worse, but it would make the predicted energy performance better, and that’s what we need in order to get the permit. The suggestion bothered me some, although I know I shouldn’t find it surprising: most people think of regulations as hurdles to be cleared, and if it’s cheaper or more convenient to honor the letter of the law rather than the spirit, that’s what they’ll do.
I don’t really know what alternative to suggest for enforcing energy efficiency requirements (whose goals I support). Classical and neoclassical economists will say you can just charge more for energy and if you get the cost right people will automatically make the right energy choices, but those economists make their evaluations based on a model world that differs from the real world just as the model of our house differs from the real house. Anyway the whole experience just made me wish — not for the first time, or the last — that people could be counted on to do the right thing so we wouldn’t have to have all these damn rules, especially when they are actually counterproductive in some cases. But they can’t, so we do.
I was going to give two more examples of people confusing the model with reality that have come up in my work as an energy industry consultant, but I think this post is long enough and anyway it’s basically the same story with slightly different characters. The point is that optimizing the performance of the model of your building, or of your electric grid, or of your demand response program, will not optimize the actual performance of your building, or your electric grid, or your demand response program. Sometimes the difference doesn’t matter much but sometimes it matters a whole whole lot. Never forget it.
This post is by Phil Price, not Andrew.