Apart from college campuses and cities built before 1940, most cities are decreasing in density. Much of the development taking place after 1940 was built around the proliferation of the automobile and the concept of mortgaging one’s own single-family detached castle. In this way, cities gained land area at a higher rate than population. The only way to cover the greater distances stipulated by this development model was cars. It gave people peace of mind and freedom to roam, but it was expensive to buy and operate this lifestyle.
In the United States, there are approximately 107 million housing units made up of single-family detached homes (SFDH) and multi-family apartment buildings (MF). Three quarters of the housing units are SFDH units, and they use 8.1 quadrillion (that’s 81 with 14 zeros!) British Thermal Units (BTUs) of energy per year. This detached development model uses larger amounts of resources than MF development in every regard: land, money, construction materials and waste, infrastructure, labor, transportation, water, and of course, energy. But how much more?
Looking at the energy alone, a SFDH uses notably more energy versus a MF apartment building. As seen in the Annual Energy Cost chart, the average energy expense for MF living is 30% less per household member and over 50% (over $1,200) less on average per entire household!
How is all that extra energy used in SFDHs? See the Single Family Detached Home vs. Apartment/Multi-Family Home chart.
As shown in the Single Family Detached Home vs. Apartment/Multi-Family Home chart, space heating and air conditioning for SFDH use more than two times as much energy versus MF. An obvious cause for increased space conditioning in SFDH is increased building enclosure area, especially for heating.
The “Other” category includes all other energy-using equipment such as lighting, cooking appliances, clothes washers, dryers, dishwashers, televisions, computers, and electronic devices. In many SFDH’s, all of this equipment can be multiplied by three for extra lighting, extra appliances, extra televisions, extra electronic devices, extra cold storage. It seems like a lot of extras. Not only do these extras consume energy themselves, they add to the cooling load. At the core of this waste are artificially high energy demand, redundant energy usage, and lack of building systems integration. These are concepts that need to be addressed in all building sectors.
Looking to reduce energy costs? Consider the benefits of multi-housing units.
 This can be seen in abundance in places such as Los Angeles, CA, Salt Lake City, UT, and Omaha, NE but this was an interesting paper I found on the topic: http://richmondfed.org/publications/research/economic_quarterly/2007/fall/pdf/bryannintonandsarte.pdf
 Energy Information Administration, Office of Energy Consumption and Efficiency Statistics, Forms EIA-457 A and C-G of the 2009 Residential Energy Consumption Survey
 Multi-family data is “Apartments in 5 or More Unit Buildings” from the EIA residential study.