High density may be a good thing in cities, but tall buildings are not.

It is a standard environmental argument that high densities and tall buildings are greener; it is an excused used in cities like Toronto to approve tall condo towers everywhere. This TreeHugger has tried to make the case that you can have too much of a good thing, and that one should design cities to what I called the Goldilocks Density:

...Dense enough to support vibrant main streets with retail and services for local needs, but not too high that people can't take the stairs in a pinch. Dense enough to support bike and transit infrastructure, but not so dense to need subways and huge underground parking garages. Dense enough to build a sense of community, but not so dense as to have everyone slip into anonymity.

Bisma Naeem/ photo Lloyd Alter/CC BY 2.0

Now, my student Bisma Naeem at Ryerson School of Interior Design points to a number of studies that demonstrate that the higher the building, the more embodied and operating energy required per square unit of measure.

Operating energy low buildings vs high/ Peng Du et al/CC BY 4.0

An article in the 2015 Buildings Journal discusses the difference of energy being used per person, and how much energy one person needs in order to live in a high rise building versus a low rise building. As you can see, high rise buildings need much more operational energy (OE) to function in comparison to low rise buildings (Wood, Stevens & Song, 2015).

Peng Du et al/CC BY 4.0

The embodied energy goes up dramatically with building height as well. And this doesn't even take into account the loss of efficiency in tall buildings, as elevators take up a greater proportion of the floor space.

She found another study from the UK that was also a revelation, looking at office buildings in the UK:

The study set out to answer two questions:

Are high-rise buildings more energy-intensive – all other things being equal – than low-rise buildings?

Is it possible to provide the same floor area on the same site as high-rise buildings, but on a much-reduced number of storeys

The results show conclusively that the answer to both questions is ‘Yes’. It follows that much energy could be saved by discouraging tall buildings and encouraging low-rise in their place.

UCL Energy Institute/CC BY 2.0

The researchers found that "when rising from five storeys and below to 21 storeys and above, the mean intensity of electricity and fossil fuel use increases by 137% and 42% respectively, and mean carbon emissions are more than doubled."

Building height influences energy consumption directly through mechanisms such as changes in external temperature and wind speed with altitude, access to daylight and solar gains, as well as the need for lifts (elevators).

There are also the additional pumps for fire protection and water, larger stairwells, and those tuned mass dampers that they are sticking at the tops of buildings, giant balls of embodied energy.

©. Mike Eliason/ that doesn't look like social housing!

© Mike Eliason/ that doesn't look like social housing!

I have often noted that you can achieve very high densities without building very tall buildings; you just have to

look at Montreal, Paris, Barcelona or Vienna to see how lower buildings have much more efficient plans, and can be packed more closely together. I have also noted that high buildings do not necessarily have a very high population density; just look at all those sliver towers in New York.

The real eye-opener about these studies is that when it comes to energy consumption, lower is better.