Windows Are Hard

I was recently honored to be a guest critic of five student projects at the New York School of Interior Design, in a mouthful of a course called "Master of Professional Studies in Sustainable Interior Environments", taught by David Bergman and  Seema Lisa Pandya. The projects were an interesting mix of cohousing, multigenerational housing, even tiny houses that weren't very tiny. I found them fascinating because although I teach sustainable design at Ryerson School of Interior Design in Toronto, it is not a studio course and I do not often see students' design work. During this review, I became preoccupied with the different approaches to windows.

I smiled when Jamie Jensen and Hilary Tate presented their classic "mass and glass" approach, combining the carefully calculated roof overhang that keeps the sun out in summer and lets it in during winter, with a high-mass floor with radiant heating. This was almost a religious doctrine in the seventies, but it never quite worked, because the heat loss through the glass was generally greater than the gain. As Martin Holladay wrote in Green Building Advisor,

"While large expanses of south-facing glass help heat up a home on a sunny day, the solar heat gain doesn’t come when heat is needed. Most of the time, a passive solar home has either too much or too little solar heat gain, so much of the solar heat gain is wasted. At night and on cloudy days, large expanses of south-facing glass lose significantly more heat than an insulated wall."

When Frank Lloyd Wright did it in the Jacobs Hemicycle House, he didn't have double glazing and the house would lose all its heat at night, even after the owners installed heavy curtains. Tony Denzer writes in "The Solar House" that the family would all get dressed in the bathroom, the only room with a radiator.

Now, of course, we have much better glass, and far better insulation and the problem we have is generally too much heat gain. Martin Holladay concludes that high thermal mass floors are not particularly comfortable, that south-facing windows as an energy source are counterproductive and “should be limited to that necessary to meet the functional and aesthetic needs of the building.”

I put Martin Holladay's last sentence in boldface because this is so important. In many buildings and houses, the windows are designed from the outside in, because they look good on the facade, or they are as big as possible, because people believe they want those big views. And it is really dramatic, as shown above in Rainey Charbonnet and Maha Dahroug's Manhattan Penthouse. But can you sit comfortably on that sofa in the depths of winter or the heat of summer (although there is an exterior roller blind)? In many buildings with floor-to-ceiling glass, the first four feet of room in front of the windows is barely habitable in summer or winter.

Lindsey Draves and Paula Francisco dealt with big walls of glass by using photochromic smart glass, where you can dial up a tint to cut solar gain. But it is very expensive stuff. They also have motorized blinds over the big existing windows in the residential units.

Windows are hard.

When I started writing this post, it was going to be titled "In Praise of the Dumb Window" as a reaction to all the high-tech smart glass and smart blinds that were being shown. I was going to quote Douglas Rushkoff's brilliant title "Technologies Don't Solve Problems – They Just Disguise Them." But then I realized that windows used to be very smart, and really hard to do. In 1810 glass was really expensive, so even though there was not much artificial light, they made them as small as they could and still get enough light to see. They were double-hung so that you could tune them for maximum ventilation. They had shutters for security and privacy while maintaining ventilation, and interior sheer blinds to cut glare. There is an overhanging cornice to keep the rain off so that they would last longer. There would be two in every room for cross-ventilation, and heavy drapes in for keeping the heat in during winter. This was a hard-working, carefully thought-out piece of climate control. There is not a motor to be seen and 200 years later, it still works.

Compare that Jessup House window to the worst windows I have ever seen, by Le Corbusier in La Tourette from the 1950s. Single-glazed, full walls of them, set in concrete window frames. You can love Le Corbusier (and I do, he also designed some of the most beautiful windows in the world, some of which are in the same building) but he, like so many other modern architects, just forgot what windows are supposed to do and how they are supposed to work.

Windows are particularly hard to do well in really efficient and affordable buildings like Architype Architects' affordable Passive house project, Callaughton Ash. It has a simple form, what I have called a dumb box, which makes it more economical and thermally efficient. But the windows are relatively small. In my post on this project I quoted Nick Grant of Elemental Solutions:

"Windows are much more expensive than walls and are lovely things, but truly a case of where you can have too much of a good thing, causing "overheating in summer, heat loss in winter, reduced privacy, less space for storage and furniture and more glass to clean." Windows are such an important architectural and aesthetic element, and hard to do when you are limited by cost and the math of Passivhaus, especially when you are starting with a box; it takes a good eye to pull it off. But instead of treating a window as a wall, as so many modernists do, think of it as a picture frame around a carefully chosen view. Or, as Nick suggests, "size and position are dictated by views and daylight."

In no way do I mean to be critical of those talented students at the New York School of Interior Design; as I noted, windows are hard. They have to do so much and they have to look good too, being one of the key design elements in a building facade. As the ugliest building I have ever seen demonstrates, design is much harder when you do not have big windows or any talent.

A few blocks away in Munich, another architect with a bit more skill shows how one can still have simple forms, not too many or too big windows, and can still do something really interesting with it.

The rules haven't changed in 500 years:

Keep the windows as small as you can get away with and still let in the light and views that you want, with an eye for proportion and scale. And keep it simple.