Mixed-mode Building Design Combines Old and New Ideas

09/24/2007 by Paul Price

As we devote more and more thought to the concept of sustainability, I sometimes wonder why it took us so long.

Mankind has a history of doing things mostly because we can, then trying to convince ourselves that it’s progress, a concept that is often badly skewed.

Technological advances, and an apparently unlimited amount of cheap energy let us design and construct buildings that really weren’t in synch with their environments. Then, when an energy crunch hit, we responded with ever-tighter buildings and mechanical systems that allowed operators virtually complete control over every breath of air that wafted through the structures. The downside was that building occupants began to suffer more often from scratchy, sore throats, watery, irritated eyes, dry skin, all sorts of maladies that resulted in unhappy staff and increased sick time with the resulting loss of productivity.

It gave rise to what was popularly called sick-building syndrome, and set off a whole round of research projects dealing with various aspects of indoor air quality.

Somewhere along the way, a Montreal developer who specialized in renewing old office buildings, did one project in which he replaced old operable windows with . . . new operable windows. If tenants wanted a breath of fresh air, they could crack open a nearby window. They loved it. Some architects and engineers — hung up as they were on energy efficiency — treated the idea as heresy.

So it was interesting to read recently of increasing interest in North America in mixed-mode buildings, in which passive ventilation and natural cooling are combined with mechanical systems to create healthier indoor environments and even better energy efficiency.

In this, our designers are learning from their European counterparts, who have been at the forefront of the sustainability movement. When I was doing graduate work at York University more than 30 years ago, the concept of interdisciplinary or multidisciplinary studies was still considered novel, and even a little crackpot. Now the concept is everywhere, including the design of mixed-mode buildings.

That’s a job that requires a fully integrated multidisciplinary team from the start. As the first step, the team must come to understand weather patterns in the region where the building is to be built, as well as the microclimate right at the site. Atmospheric conditions, solar orientation, prevailing winds throughout the year — all must be thoroughly understood.

Then the team must understand what is going to be done in the building, and the comfort criteria to be applied to each function. And from all that it can plan for the various ventilation and cooling needs.

The orientation of the building on the site, the building mass, even the detailing, must all come together to minimize unwanted heat gain and maximize opportunities for passive ventilation. Mechanical equipment must be specified to handle any heating or cooling needs that are over and above the capacity of passive strategies, and electronic controls planned to operate at the interface between passive and mechanical systems. And the building occupants have to be kept in the loop.

Gail Brager, of the Center for the Built Environment at the University of California, Berkeley, says that “education of the occupants about the performance of the building and operable windows is . . . critical to ensure that the building achieves its potential for optimizing both energy conservation and thermal comfort.”

All of this is a roundabout way of saying that we are going to have to stop designing and building self-contained monoliths that are supposed to function as independent units, and begin paying more attention to the environment in which we place those buildings. Or, put another way, we’ve begun to realize the need for paying more attention to the world around us when we plan buildings, much as our forefathers did five, or six or seven generations ago. And perhaps that’s what progress should always have been about.

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