What's the Right Way to Build in a Climate Crisis?

In these critical times, it is essential to ask what is the right thing to do and the right choices to make.

Passivhaus townhouses in Goldsmith Street
Walkable affordable Passivhaus townhouses in Goldsmith Street .

Tim Crocker / RIBA

Treehugger recently covered SOM's COP26 presentation of its "Urban Sequoia" concept for a low-carbon building, which demonstrated some imaginative concepts and systems that might exist in the future, but I felt did not reflect the urgency of the situation that we are in today. If we are going to keep global heating under 2.7 degrees Fahrenheit (1.5 degrees Celsius) we have to stop adding carbon dioxide to the atmosphere now, using design strategies and technologies that exist and can be implemented now.

But if one accepts that we are truly in a carbon crisis and have to change the way we build right now, what would be the best way to build? What is the right thing to do? How should we plan our communities? Build our buildings? Get around between them?

It is a subject we have been giving some thought to, most recently in the post "Transport and Building Emissions Are Not Separate—They Are 'Built Environment Emissions'" where I quoted Alex Steffen's wonderful article, "My Other Car is a Bright Green City," written before there were even Teslas on the road. He noted then that "the answer to the problem of the American car is not under the hood, and we’re not going to find a bright green future by looking there."

He continued:

"There is a direct relationship between the kinds of places we live, the transportation choices we have, and how much we drive. The best car-related innovation we have is not to improve the car, but eliminate the need to drive it everywhere we go."

How we get around determines what we build, transportation and urban form are two sides of the same coin, and as Jarrett Walker noted, “Land use and transportation are the same thing described in different languages.” Or as I wrote in my recent book, "Living the 1.5 Degree Lifestyle":

"It is not a chicken-and-egg, a which came first thing. It is a single entity or system that has evolved and expanded over the years through the changes in the form of energy available, and in particular the ever-increasing availability and reduction in the cost of fossil fuels."

So the key is to reverse this, to build at the right density to support low-carbon modes of transportation. Then we have to build at the right height, of the right materials, to the right standards.

Density done right

Density done right graphic

Ryerson City Building Institute

This is why the first thing we have to do is stop piling density into towers and instead, spread it around. Toronto, Seattle, Vancouver—all these booming cities are spiky, with vast areas of low-density detached single-family housing and all new development is piled onto industrial lands, main streets, anywhere where it won't upset the homeowners.

But as the Ryerson City Building Institute noted in their Density Done Right report, density can be gentle and distributed.

"Adding gentle density can help ensure there are enough people in a neighborhood to support local schools, health, and community services and keep shops and restaurants open. It can provide a range of housing types and tenures that support the needs of individuals and families throughout all stages of life and allow for aging in place. It can also support public transit services, providing residents with efficient and affordable transportation options without relying on private automobiles."

I have written before that the single biggest factor in the carbon footprint in our cities isn't the amount of insulation in our walls, it's the zoning.

"We have been talking about the relationship of density and carbon for years, and we have been talking about green building codes, certifications and bylaws. But green building isn't enough; we need green zoning. Any civic government that calls itself green while protecting low density single family housing is just being hypocritical."

A hundred years ago, before restrictive zoning rules stopped this kind of thing, apartment buildings and single-family houses coexisted quite nicely. There is no reason why they can't today.

Ebikes and scooters are drivers of climate Action


E-bikes and other forms of micromobility make getting density right even easier, and they are going to make a big difference, as noted by the Institute for Transportation and Development Policy. Micromobility expert Horace Dediu predicted, "electric, connected bikes will arrive en masse before autonomous, electric cars. Riders will barely have to pedal as they whiz down streets once congested with cars." We should be planning for this now.

 Illustration of the different of urban typologies classified in the present analysis.
Illustration of the different of urban typologies classified in the present analysis.

Francesco Pomponi et al. / CC BY-SA 4.0

Another study by Francesco Pomponi et al. addressed "a growing belief that building taller and denser is better," noting that "urban environmental design often neglects life cycle [greenhouse gas] emissions." It found that high-density low rise housing has half the lifecycle greenhouse gas emissions as high-density high rise, and even less than low-density low rise like we get all over North America. I concluded:

"The lessons of this study are pretty clear. The spiky density that you get in many North American cities, where certain limited areas are zoned for high-rise residential and everything else is very low density detached houses, is actually the worst of all possible worlds. The best form of housing from a life cycle carbon point of view would be mid-rise, what Daniel Parolek called the Missing Middle, and which I called the Goldilocks Density—not too high, not too low, but just right"

Height done right

Small buildings in Munich
Small Buildings with family housing in Munich.

Lloyd Alter

The Urban Sequoia was a tall building, as are most new buildings in cities. But different heights of buildings require different kinds of construction. As architect Piers Taylor noted in The Guardian, “Anything below two storeys and housing isn’t dense enough, anything much over five and it becomes too resource intensive.” Below two stories and we have sprawl, but above five and we have steel and concrete, both of which have massive upfront carbon emissions associated with their manufacture. More recently, mass timber has become popular, but it goes through about four times as many trees as lightweight wood frame construction.

operating energy low buildings vs high

Peng Du et al. / CC BY-SA 4.0

Studies have also shown that costs and embodied carbon per unit of area increase with height, as more sophisticated technologies, are needed for heating, cooling, and even just delivering water. Wind and earthquake bracing mean more structure.

I have always been a huge fan of Mass Timber, and see it as a way of replacing concrete and steel in midrise structures. But if you are looking for material efficiency, we should be listening to Piers Taylor. As I noted earlier in an earlier post, "What's the Best Way to Build in Wood?":

I believe that everything that can be built out of wood should be, but am beginning to think that you can have too much of a wood thing. I am really coming to wonder if CLT has not become too fashionable when there are other, simpler wood solutions that use less material, save more forest, and build more homes.

Design done right

Little Buildings in Aspern Seestadt
Little Buildings in Aspern Seestadt.

Lloyd Alter

In Europe, low buildings can be designed with single open stairs in the middle, allowing for much more efficient small buildings and fewer elevators as more people are comfortable taking the stairs. There are big advantages in cost, speed, and building efficiency in building lower buildings at distributed density.

We need to change our building codes to make it easier to build small buildings. As Mike Eliason noted in his post "The Case for More Single Stair Buildings in the US":

"Personally, I think it is amazing that these kinds of buildings are possible. Many are the smaller, fine-grained urbanisms that make for great cities we talk about so often. They can be family-friendly, with a diversity of unit types, and are both space and energy-efficient. They are also accessible, as buildings in both continents require elevators on projects like this and many in Germany are barrier-free or adaptable."
An image of Montreal urban houses with two white cars in the front.
Montreal Plateau District.

Lloyd Alter

Another design option is to build as they do in Montreal: The Plateau district is one of the most desirable places to live in the city, with its incredibly efficient "plexes" with exterior stairs. The stairs on many are a bit steep, but that is a function of the original setback requirements a hundred years ago. This building form achieves 30,000 people per square mile, pretty much the same as you get with high-rises, and they can be built to modern safety standards.

No More Net-Zero: Upfront and Operating Carbon Done Right

Enterprise Centre image from an angle
As close to zero-carbon as you can get!.

Architype Architects

There were so many promises of net-zero at COP26. But it is time to recognize that net-zero is a COP-out. I have written before that net-zero is a dangerous distraction. When I first discussed this in 2015, readers pushed back and wrote: "What a bunch of nonsense. By definition 'net' means the positive and the negative together when added up becomes zero. This is unsubstantiated drivel."

But it is no longer unsubstantiated. As Emily Partridge of Architype noted, it rarely balances out to zero.

"Building simulation modelling generally considers renewable energy to offset energy demand on a 1:1 basis. In reality, there is a daily, and seasonal difference between most renewable generation and the energy demand of a building. In summer, energy is exported and potentially wasted. In winter, more energy is needed from the grid, which in turn requires high carbon intensity generation to make up the deficit. Seasonal storage is possible, but current technology means some energy losses and costs."
Callaughtons Ash from above
Callaughtons Ash.

Architype Architects

We can get close to zero carbon operating emissions by building to the Passivhaus standard of energy efficiency and filling in the tiny gap with renewables. It helps if you design like Architype did here at Callaughton Ash, an affordable housing project, with simple forms, careful orientation, watching the windows, and as architect Bronwyn Barry notes on Twitter with her hashtag #BBB, or Boxy But Beautiful.

Material Palette
Material Palette, Enterprise Centre.

Architype Architects

We can get close to zero carbon upfront emissions the way Partridge does at Architype: "by using materials which use less energy to produce and are made from natural materials, such as timber and recycled newspaper insulation, instead of steel, concrete and plastic insulations."

We can (and have to) do this right now

At about the same time as I was stewing about the Urban Sequoia, the roads and rails that tie Canada together were being washed away in an unprecedented flood caused by an atmospheric river. This is serious, and it is happening now. Climate change is not waiting for 2050 or even 2030.

But almost nobody is taking this seriously. In the United Kingdom, activists who are actually protesting to get governments to Insulate Britain get arrested for blocking roads. They are serious about better buildings–blocking traffic in support of insulation sounds extreme, but this is our future.

This is why I have no stomach for future fantasies. We can do all this now. We can do zero carbon without a net. We know how to plan it, we know how to build it, and we know how to get around in it. And we have run out of time.