The Big Cave

Bill and mansion

by Bill Schlesinger

America is the land of the big—Big Houses, Big Cars, Big Macs, and Big Dreams. The average new house in the U.S. has 1000 square feet (93 m2) per occupant.  Other world citizens get along with a range of 161 to 430 square feet. I suppose our passion for the big house goes back to the Paleolithic, when the recognized leader of society possessed and defended a big cave. Thus, it is perhaps natural that Bill Gates lives in a house of 66,000 square feet.

Of course, big houses require lots of heat and air conditioning. It is not surprising that heating buildings in the U.S. accounts for 13% of our carbon dioxide emissions and almost 40% of our use of electricity. I shake my head every time I pass a McMansion, when it has a Tesla or Prius in the driveway.

The energy used to manufacture and deliver the materials for new house construction amounts to 9% of residential emissions in the U.S.  The choice of construction materials matters; production of cement (0.77 tons CO2/ton) and steel (2.2 tons CO2/ton) result in emissions of CO2 to the atmosphere whereas wood removes and stores it.  Size also matters; apartments are more efficient than single-family homes. To reduce carbon dioxide emissions from the residential sector, one recent study finds that it is much more effective to renovate existing houses than to replace them. Upgrades to insulation and HVAC systems pay off.  Heat pumps are generally preferable to most older furnaces.

The good news is that the trend to larger houses seems to have diminished slightly in recent years. Yet, despite concerns about climate change and environmental impact, the average size of a house in the United States has risen nearly 40% since 1973, while the median household size has dropped from 3.5 to 2.5 people over the same period.  We may focus our attention on transportation, but residential energy makes a huge contribution to energy use.

In our home, we have about 700 square feet per occupant.  Somehow, we get by without stumbling over one another, and it is so much easier to keep a small cave warm and clean.


Berrill, P., E.J.H. Wilson, J.L. Reyna, A.D. Fontanini and E.G. Hertwich. 2022.  Decarbonization pathways for the residential sector in the United States.  Nature Climate Change 12: 712-718.

Ding, G. and X. Ying. 2019.  Embodied and operating energy assessment of existing buildings—demolish or rebuild.  Energy 182: 623-632.

Schlomer, S. et al. 2014.  Technology -specific coast and performance parameters.  Annex III in Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report.  Cambridge University Press.

Bill Schlesinger

Emeritus Director of Cary Institute, Millbrook