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Full Story: The End of Affordability Part 1



There are a few good points

There are a few good points in the series but also a number of questionable statistics and faulty conclusions. For example, the claim is made that people in highrises don't use any less water than people in houses. If you don't count water used for landscaping, that might be true.

Water use

Research in Sydney shows that water use in high-rise is about the same as in detached housing. See
"Water Use and the Built Environment: Patterns of Water
Consumption in Sydney", Patrick Troy, Darren Holloway and Bill Randolph, City Futures Research Centre, Research Paper No. 1, December 2005

Water use etc

Centre for Resource Management Studies, New Zealand
We need to be aware that Australia has well advanced water charging regimes to the user generally pays.

Many assumptions about water use in other jurisdictions assume water is free.

Given that Australians pay for their water we should not be surprised if household use does not vary much according to location.

The recent Study "Consuming Australia" generally found that the carbon footprint and energy consumption of the Australian household was typically independent of place and primarily dependent on income.

Not necessarily. Depends on

Not necessarily. Depends on the common areas. In some condo developments the exterior areas are quite extensive; parklike with landscaping, pools, etc.

And some single family homes have very small yards.

I don't think a comparison can be made, given all the variables.

Blame the inhabitants, not the building

Another variable is, the people who can afford to live in highrises can also afford to waste more water.

High rises vs higher density

While a number of their conclusions are based on misleading data, they are right about the high water and energy use by high-rise dwellers in Australia. On this continent, energy consumption per person, per household, and per square foot is also higher for high-rises than for any other form of housing.

High-rise apartment buildings by themselves are not a good environmental or economic solution, but I don't know anyone who claims they are. This is just a straw man argument against any increase in density, like these videos do. Having a range housing choices everywhere, including apartments but not necessarily high-rises seems to be the best solution. It's high-er average density without the extremes.

Is high-density housing really more sustainable?

Thank you for providing these statistics, laplante. A real eye-opener!
John Zeger (

Statistics on High Rises

I don't trust the statistics in these links. Note that he makes a transparently misleading claim at:

His graph shows that people generally drive less as densities go up, and that people in detached houses at higher densities drive even less than people in apartments at the same higher densities. But he doesn't mention that you could not get those high densities unless most people lived in apartments: his claim that people in detached houses drive less at most densities is misleading, because you wouldn't have the higher densities at all if everyone lived in detached houses.

Likewise, I he cites studies of energy use in Australia showing that high-rise dwellers use more energy, but that is because high-rise dwellers in Australia are wealthier and consume more overall. It is their overall consumption that raises their energy, not their living in high-rises.

Those two examples of half-truths meant to support his biases make me suspect anything he says.

Note that I am against high-rises, as I have said in many posts on Planetizen, and I much prefer traditional human-scale cities, but I am still put off by the half-truths in these links.

Charles Siegel

Understandable Skepticism

It's a fair point, these statistics have to be taken in context, the more extreme ones make it into the blog because they are interesting though perhaps exceptional cases. The Australian study has figures and a methodology that I haven't seen repeated on this continent, but the ranking of energy use is the same here: high-rise apartments consume most, followed by detached houses, and townhouses consume least. And in the U.S. high-rise apartment dwellers are not generally wealthier, so that can't be the only explanation, although it might explain part of it in Australia.

Which is not to say that some forms of housing should be built and others not - you can't choose to not house a portion of the population. It's just useful feedback if you can calculate the effect of putting them in different parts of town, and predict the effect of lower or higher density.

If you are suspicious about the data, I will gladly point you to the original sources and tell you more about the methodology.

Your points about not taking statistics in isolation, whether it be the houses that you suspect of being surrounded by apartments or high-consumption apartment dwellers who might consume just as much if they lived elsewhere, are wise. It is in fact possible to achieve quite high densities without high-rise apartments, the highest point on the graph is only 9 housing units per acre, but the data used in the analysis (Federal Highway Administration's National Household Travel Survey) doesn't distinguish between different sources of density, so I don't know. I'm sure you're right, at higher density a larger proportion of housing units are likely to be apartments. Does the surrounding housing type affect how much people drive? Interesting question.

I am not sure what my biases are supposed to be, but in most of the modeling I have done, the CNU recommendations of having a range of housing types with an emphasis on the compact forms is what seems to minimize land and resource use. So my bias is for densities that are not at the high nor the low extremes.

Density without apartments


The highest density on the graph is almost 16,000 units per square kilometer. Let's call it 15,800. A square kilometer is equal to approximately 247 acres ( That comes out to about 64 housing units per acre.

As far as I am aware, single family detached homes have never been built at anything close to 64 units per acre.

High Rises And Energy

My bias is also against highrises and in favor of a traditional urban scale made up of mid-rise apartment buildings (5 or 6 stories) and rowhouses, so I find this discussion very interesting and would like to see some reliable statistics.

Kenworthy and Newman use international comparisons to show that automobile use is inversely proportional to density - greatest in low-density American cities and lowest in high-rise Asian cities. But the inflection point of the curve is right around the density of traditional European cities, so there is not all that much reduction of automobile use above that, and it is possible it could be outweighed by other forms of increased energy use with highrises.

One possibility is heat-island effects, which increase cooling costs. I hear that Arup designed the ecological city of Dongtan outside of Shanghai with an eight-story height limit to conserve energy by avoiding the heat-island effect, but Arup has not made any of its figures about energy conservation public, as far as I know.

Other possibilities are greater energy use for elevators and hvac systems in highrises. I have not heard about any studies of this.

I would appreciate references to any reliable studies about increased energy costs of highrises.

My own reasons for opposing highrises are in my blog post "Why Highrises are Faceless and Impersonal" at, but I would be happy if there were also some arguments about energy conservation to second the obvious human advantages of midrise cities

Charles Siegel

Energy use of different housing forms

Here is one reliable source, the Energy Information Administration.

It seems to vary quite a bit from year to year. It doesn't specifically study high-rises, just buildings with more units. Roughly speaking in the U.S. high-rises use something like 20% more energy than single-family houses. In Canada it's 30%, and in Australia up to 50%.

The articles I've seen name all sorts of different reasons. Yes, there are the elevators, lighting for the common areas, the difficulty in controlling humidity. Some of the physics of HVAC systems are different because of the heights and of the length of ducts, leading to large temperature and pressure differences that need energy to overcome. Even little things like dryer exhaust. In a house you just vent it through the wall, but it's not that simple in high-rises.

Energy use of different housing forms

Great table!

When all nine years of the study are averaged, the ranking comes out like this.

1. Single-Family Attached (87,400 btu/sqft)
2. Single-Family Detached (88,000 btu/sqft)
3. Apt. 2-4 (120,000 btu/sqft)
4. Apt. 5+ (123,400 btu/sqft)
5. Mobile Home (160,200 btu/sqft)

Energy Use Of Houses And Apartments

The problem with these figures is that they give energy use per sq. ft. rather than per person.

People living in apartments generally have less space than people living in houses, so it is possible that there is actually more energy use per person in houses than in apartments, though there is less energy use per sq. ft. in houses.

This is what I would expect, since some forms of energy use are pretty much constant per person (such as hot water use for showers and washing dishes) while others increase as square footage increases (such as heating). Thus, as a person lives in a larger home, that person's overall energy use increases, but not by as much as the size of the home increases.

Of course, it is possible that some or most of the difference depends on lighting of common areas of apartments and the other things you list. But it is also possible that most of the difference depends on the larger square footage per person in houses. Based on these statistics, we just don't know whether there is more energy use per person in houses or apartments.

We really need statistics comparing average per capita building-related energy use in neighborhoods of different densities. It would be interesting to correct the figures for differences in average dwelling unit size in each neighborhood, to see whether someone living in a house would consume more or less energy living in an apartment of equal size. But we should also remember that people who move to denser neighborhoods are often willing to live in smaller units as a trade-off for living where there are more shops and services.

We already have statistics on differences in per capita transportation use at different densities, and it would be easy to derive transportation-related energy use. If we also had figures on differences in per capita home-related energy use at different densities, we could combine that with the figures on transportation and actually come to some conclusion about which urban density is optimum in terms of reducing energy consumption.

Charles Siegel

Energy use and housing types, again

Note that the same website gives statistics on average square footages of the housing types under discussion.

The average single-family detached dwelling is three times as large as the average unit in a building with 5 or more units.

By using these figures, we find that in 2001, single-family attached dwellings used almost 250% as much energy PER UNIT as high-density apartments.

The last figure we would need to get an estimate of per capita energy use would be the average occupancy of the different housing types. Even though SF detached dwellings use the most energy per unit, this would be mitigated because they have more occupants per unit than apartments. However, I suspect they do not average 250% as many occupants, which would be required to relinquish their position as the leading consumers of energy.

Anyone have good stats on average occupancy by housing type that would complete this estimate?

Got Figures on Highrises And Energy

I got this from a local planner:

We researched this fairly extensively. The only metric that we turned up that made a direct comparison between shorter and taller buildings was from the federal Energy Information Administration. In "Consumption and Expenditures in U.S. Households" (1997), the EIA cites the following:

2-5 Floors 68,000 BTU/sf
6-8 Floors 74,000 BTU/sf
8+ Floors 75,000 BTU/sf

Note that a significant part of the energy increase in taller buildings is from having natural ventilation (rather than mechanical ... [so taller buildings can be more energy efficient if they are also designed with natural ventilation].

Since he brought up the possibility of natural ventilation, I mentioned the possibility of shading:

With midrise buildings, you can plant deciduous trees to shade the buildings during the summer and expose them to the sun during the winter, reducing the burden of heating and cooling. This doesn't work for highrises, which are much taller than trees. These figures for existing buildings probably don't take into account the possibility of planting more trees to create more shade.

Charles Siegel

Quote: 2-5 Floors 68,000


2-5 Floors 68,000 BTU/sf
6-8 Floors 74,000 BTU/sf
8+ Floors 75,000 BTU/sf

It looks like the cost increase of building higher is negligible, and worth ignoring when you consider how dramatically it is offset by reduced land consumption, VMT, and infrastructure costs.

Two points:
1) Do you have any idea why these numbers are so much lower than the numbers in the original link?

2) Since we still don't know the average occupancy of different housing forms, we cannot calculate energy use per capita, which is the most important figure.

BTU and building type.

Good points, iso.

Allow me to restate something for a different perspective when considering densifying:

The energy savings of a semi-detached over a single-fam detached is 34% (in KWh). Building rowhouses further reduces consumption 26% (savings are in the shared walls). The reduction in internal and solar heat gain from SFD to rowhouse is only ~9% (fig 5.11). Savings from properly sited vegetation was not calculated.

I would also point out that Charles stated that you could put shutters or shades on high-rises to save energy, and you can also have low e- glass and lined/reflective draperies as well. Trees won't help over about the 4th floor, as usu. they don't live that long to attain such heights or affect the urban boundary layer to reduce wind speeds.

Lastly, average occupancy per dwelling type varies by region, so national averages might be a little misleading (our persons/SFD in my city is almost .5 higher than national average).



Re: 2-5 floors, 68,000

I don't know why there is such a big difference, and I will ask.

About reduced land consumption, VMT and infrastructure costs:

Above traditional European densitites, there is not much of a reduction in land consumption: European cities already are down to 1/100 of an acre per person, so highrises can save less than than that, which is a tiny fraction of each person's total ecological footprint.

There is also not much of reduction of VMT, as Kenworthy and Newman's studies show. In fact, you could ban cars completely in a European density city, and it would be easy to get around by walking and transit.

And there is an increased construction cost above 5 stories, which I am sure outweigh's the savings in infrastructure cost. Below 5 stories, you can use cheap wood-frame construction, and at higher densities, you have to use more expensive forms of construction.

Charles Siegel

Americans In Apartments And Houses

A related question: Does anyone have figures on what percentage of Americans live in apartments and houses?

According to an article on the front page of today's NY Times, "A quarter of American households live in apartment buildings housing 50 or more residents, but 40 percent of households headed by Hispanics and African-Americans live in such buildings."

I had no idea it was that high. If one quarter of households live in apartment buildings with over 50 residents, than I suppose that close to half might live in all multi-unit buildings.

Charles Siegel

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