Maximilian Auffhammer is one researcher who tends to have very insightful and challenging posts. In one of his latest posts he discusses recent empirical evidence on whether or not building codes improve the energy efficiency of a house: discuss his thoughts and also talk about why the trends in household electricity use are problematic.

Surprisingly, the most recent and detailed research by Arik Levinson that he reviews suggests that building codes do NOT improve energy efficiency:arik

newly built houses within a construction cohort do consume less electricity. Levinson argues that this is in fact evidence in favor of the point that buildings deteriorate quickly after being built and/or residents turn up the heat/AC once they have more cash. The paper also shows convincing evidence that buildings built under different building code regimes do not have statistically different temperature response profiles

Hence the result that building codes do not affect energy efficiency. So there are two points here. Auffhammer and Levinson suggest that the older a house the more energy is used because houses may become leaky or new houseowners conserve energy. I very much doubt the former argument is true. For example, Figure 3 in the paper shows that a 10-year old house built in the 90s required nearly double as much energy as a newly built house in the 90s. This would suggest that insulation deteriorates very, very fast – too fast. Thus, in my opinion most likely is simply that after a couple of years, house owners have much more money available again in order to buy electronic things that (they hope) make their life more comfortable – like washing machines, bigger TVs, a bigger stereo, etc; they tend to get children, and these help to increase energy consumption; they get older, and the older one gets the more one feels the cold and wants the house to be warmer during the winter.

Now one thing I find worrying from the graph is the evolution of electricity use for houses built during different periods. Taking the average electricity use across each period suggests that, every 20 years, houses increase electricity consumption by 5-10 MBTU. One reason is of course that houses are getting bigger and bigger: For example, in the US, the average house size has doubled in the past 40 years. In contrast, the average number of people per household has decreased from 3 to 2.5 during the same period. However, the US population has increased by 50% since 1975. Thus, we need more houses because of a larger population and the fact that fewer people live in each household. And despite all this, houses grow in size and in energy use. That, to me, is a worrying trend, leading to urban sprawl and higher energy consumption. And this energy consumption is what one may call fixed energy consumption, since the bigger a house and the more technology inside the less easy it is to reduce energy consumption on demand.

Politicians are starting to work against this trend, by e.g. demanding smaller housing units in new construction sites, but is this really enough? The data says unfortunately no. And the problem is that if one’s peer group has a big house, then one would like to have a big house, too. And while some years ago there were often 10-15 people living in the same house, today the same house is occupied by 2-3. We get used to having more personal space, and it is difficult to reverse this trend. The question thus is, where does this trend take us to, and how forceful should regulation address this? In light of the evidence on climate change, it seems reasonable to be more forceful on low energy housing. Also, in light of how mankind replaces nature, it seems evident that we have to reduce urban sprawl significantly.

In my opinion, building codes should very much address this issue and be more forceful on the actual size of the house. Many newly wedded couples construct big houses, then have 1-2 children, then separate (a 50% divorce rate in Europe). Houses need to be sold then, and the bigger the house the more difficult it gets to sell it. Thus, houses should be built in a more flexible way, allowing the house to be potentially broken down into smaller units. This becomes easier if newly built houses are not free-standing. Do we necessarily need to allow new houses to be free-standing? This increases urban sprawl significantly. These are just a couple of quick ideas, I am sure there are many researchers out there who have thought to a large extent on these issues.