Speaking to architecture students at Carnegie Mellon University Monday night, urban planner Leon Krier said he had long thought that sustainable cities and buildings would be a matter of choice. But reading James Kuntsler's new book, "The Long Emergency," convinced him otherwise.

"Most materials [that] architecture is made from, we'll no longer be able to produce because they waste too much energy," Krier told a receptive audience.

He is the master planner for Poundbury, the new town commissioned by Prince Charles for his own land in Dorset, and an outspoken proponent of traditional building forms and technologies. Born in Luxembourg, he now lives in France and works in Europe and America.

Here are excerpts from a telephone interview yesterday:

You say, "We already are living in the long emergency." How so?

This problem of energy supply is probably deciding all the major conflicts in the last century. The United States and Europe have built this planetary system on which it is dependent. We are living way over our means.

James Kunstler says each citizen is living as though he has 100 slaves that he cannot see. We should start shrinking populations in our cities to live in the capacity of our ecology. If we don't do that, we will collapse in a terrible and dramatic and tragic way.

Past disasters will be of no comparison. New Orleans is almost like a warning. It has been building most of that town in areas that should not have been built.

When is it predicted that we will expend the Earth's fossil fuels?

The question is not when it will run out but when we will reach the peak of exploitation. That is approximately now. What will happen after that peak? [The decline] won't be symmetrical but full of crises.

[After the peak, about half of the world's oil will be left, Kunstler wrote in Rolling Stone in March, but "it's the half that is much more difficult to extract, far more costly to get, of much poorer quality and located mostly in places where the people hate us."]

You talked about retrofitting cities by filling them in to increase density, but what do you think will happen to all the buildings that were designed in the age of fossil fuels?

That is why I am a mortal enemy of excessively high buildings ["vertical cul-de-sacs," he calls them]. When electricity is no longer assured, what do you do with high buildings in which you can no longer walk up and down? They will just be abandoned.

How will we heat and illuminate existing homes?

There is now a lot of effort and laws to ensure houses against cold or heat. But that is not the main problem. The problem is where they're located. [Many people who live in the suburbs] have to drive to reach their work or [public transit]. You must be able to do it on foot. ...

We need to shrink our needs. The whole house is overheated, and often for one person. At 3 o'clock in the morning, the entire country is illuminated while we sleep. People say more light at night increases security, but the crime rate has increased parallel to the increase of light. Why light an enormous parking structure when nobody is using it but rats and cats?

How should Pittsburgh begin preparing for the long emergency?

(Quiet laughter) I don't know. ... We drove through the North Side last night and saw all the restored old buildings, these beautiful old facades. You really feel like you want to live there.

I am on the 11th floor [of the Renaissance Pittsburgh Hotel] overlooking the old hospital [Allegheny General], which is absolutely beautiful, but what they built behind it is awful. ... When people who have three cars can no longer afford three cars, they will come back to the city.

Do Poundbury buildings use passive or active solar heating or any other green technologies?

We have all the fashionable green technologies. ... Our buildings don't look like solar houses. We have buildings that are two or three stories high, with a small garden exposed to the sun. They have good insulation and don't have excessively large windows. ... We are dependent on fossil fuel, but they have relatively high performance compared to houses on the market.

The high-tech products are 100 percent dependent on fossil fuel construction. What is the real savings in the long term? All these beautiful [wind] turbines are high-tech instruments. ... They are not things that are done with low tech. It's to calm people's minds that we are doing something good about the planet.