There's much more to SmartDwelling I than the things I wrote about two years ago when it was published in the Wall Street Journal's Green House of the Future story. Really cool stuff is afoot with Project:SmartDwelling, so this will be the first of several new posts looking at SmartDwelling elements.
There are two Breeze Chimneys on SmartDwelling I, which was designed for the US Gulf Coast region. Because it's a land by the sea, I decided to use seafaring materials for the Breeze Chimneys. As we'll see in a moment, Breeze Chimneys in other parts of the country could be made out of other materials like sheet metal. The framework is built of small spars, like those which frame sails on sailboats. The spars could either be made of wood or fiberglass. The shroud is sail cloth stretched over the spars. This assembly is attached to a ring at the top of the chimney that rotates freely. Here's how it works:
The Breeze Chimney is designed to turn into the wind, like a weathervane. The open end of the Breeze Chimney is always leeward as a result. There's a phenomenon in physics known as the Venturi Effect, and it works like this: air moving past an opening tends to pull gases or liquids out of the opening. If you're old enough to remember cars before fuel injection, then it was the Venturi Effect that made the carburetors work.
Breeze chimneys behave the same way. They have another thing working for them as well: the Thermal Chimney Effect. Because hot air rises when given the opportunity, hot air in a tube like a chimney flue will rise out of the tube, pulling other air in behind it from the room below. To start a breeze chimney, all you need to do is to open a window somewhere in the house.
Pulling in air almost as warm as the air exhausted by the Breeze Chimney wouldn't do much good, so you need to find a window around the house or shop where the air is coolest.
The best place would be under a grove of trees or big shrubs. Not only do the leaves shade the area around the window, but they also cool the air even further by giving off water vapor. It can easily be 10-15 degrees cooler under a shady grove or in a thicket.
A louvered verandah like the ones found throughout the Bahamas would be good because the louvers prevent the sun from getting into the porch and warming it up. A porch on the shady side of the house would work equally well.
A breeze chimney works best in late afternoon or early evening, when the air has cooled a bit from the heat of the day. Porches on the eastern side of the building would be coolest at this time of day. There's no reason you have to use the same window, however… you could experiment to see what works best for you. But in any case, it's the act of opening the window that starts the Breeze Chimney's operation because without replacement air pulling into the house, the Breeze Chimney can't pull air out. So think of it as an attic fan that doesn't require any electricity.
What about storms? Wouldn't the sail cloth tear in high winds, flooding the house? Clearly, there needs to be some way of shutting the Breeze Chimney in a storm, or when you're going to be away from home for awhile. See the heavy black line on the right side of this drawing? It's meant to represent a spring metal arc that holds the spars up. There would be two cords coming down the chimney. Pull one of the cords, and that pulls the spring metal arc over to the left, collapsing the shroud. Pull the other one, and it pops back up. I haven't yet built a Breeze Chimney, so I'm sure it would require a bit of tinkering, but that's the general idea of how it should work.
The house above was designed for a competition we never expected to win. It was intended as a critique of the Gizmo Green competition program and, just as I expected, the jurors didn't view it very kindly. I'll blog more about it later… my point of showing it here is to illustrate how differently Breeze Chimneys can be designed.
This house was designed for Dallas. A century ago, you could find pivoting sheet metal roof vents all over the Midwest and Southwest. So I designed this Breeze Chimney to be built of the same material. There are only two differences between this Breeze Chimney and the old pivoting roof vents. First, it's a good bit larger than the old ones so it can ventilate the whole house. Second, the old pivoting roof vents usually vented the attic. In this design, there's a chimney (concealed by the roof) that connects the cap to the living spaces below.
More on SmartDwelling I:
Score one for Schooner Bay! The eye of Hurricane Irene came right across DPZ's new town of Schooner Bay in the Bahamas late last week, and except for a few outdoor ceiling fans, the buildings sustained no damage at all. Sustained winds were 125 miles per hour, with gusts up to 130. This is all the more remarkable because of the way Schooner Bay is being built… it's following patterns of ancient wisdom that are illegal in every hurricane zone in the United States.
Years ago, when Seaside was hit by its first hurricane (Opal) and sustainaed almost no damage, hurricane experts called it the "Seaside Miracle," and studied it for several years thereafter. Opal's winds were probably 100 miles per hour at Seaside. It'll be obvious shortly why, beyond just Irene's higher wind speed, this should be considered the Schooner Bay Miracle and studied as well.
All of the photos in this blog post were taken by Schooner Bay staff less than 24 hours after the hurricane passed through. You can still see Irene's angry waves breaking against the ironshore in the image above.
For a bit of perspective, Irene brought great devastation to other parts of the Bahamas, including this image taken just a few miles away from Schooner Bay at Elbow Cay. As you can see, two of the houses have been completely destroyed and washed out to sea. The cause of destruction here was due to a very common error of oceanfront construction: building on the dunes. Schooner Bay took a completely different approach, heavily planting the first dune with native dune vegetation to strengthen it, then building a secondary dune with material dredged from the harbor. No houses have been built above this second dune yet, but it wouldn't have mattered, because the second dune was completely untouched by Irene. The seawall at the harbour handled the storm surge in textbook fashion with no damage whatsoever.
Schooner Bay's architecture is an important part of the story as well, as much for what they're not doing as for what they are doing.
What's the first thing you think of when people talk about hurricane construction? Probably the Miami-Dade hurricane code windows, right? Guess what? Schooner Bay isn't using them. Quite the opposite: because of high Bahamian import duties, they're making all their own windows onsite!
So how did these homemade windows manage to withstand Irene's fury with not one broken pane? The same way homemade Bahamian windows have withstood countless storms before her for centuries: the homeowners simply shut their shutters. Schooner Bay shutters are typically solid instead of louvered, so they can take a serious lick from wind-borne debris, protecting the windows behind them, which remain untouched by the storm.
The windows are only the beginning. All houses built to date at Schooner Bay have been built of poured concrete. You can see several under construction in this photo, most with the concrete structure still exposed because the stucco work hasn't been done yet. Reinforced concrete is quite simply the strongest way to build. And many buildings in the Bahamas have been built of concrete or masonry for a very long time, for this same reason. But there are wood cottages in the Bahamas as well that have survived countless storms, so Town Founder Orjan Lindroth is looking into the best ways of building strong wood cottages to complement the predominant concrete construction.
Take a look at the roofs in the image above. See how most of them are hipped, and how they're built at a simlar pitch? Hurricane experts now tell us that hips are the strongest roof forms because each roof plane supports its neighbors. And pitches between 8:12 and 9:12 strike a balance between shallower roofs that fail in uplift and steeper roofs that fail in overturning. Gables are permitted, but only where the house is built of concrete or the roof span is very short.
It's interesting to note that Bahamians knew all these things long before "hurricane experts" ever existed. Their system was very simple: when you crawl out of a house that's been destroyed and see your neighbor's house that's still standing, you say "I'm going to rebuild like that!" And so the best ways of building emerge naturally in a place from centuries of testing into something I call a "living tradition."
Well before construction began at Schooner Bay, Orjan commissioned a new kind of pattern book to guide the architecture. Until then, pattern books had focused on random collections of historical styles. In short, they were necessarily more about fashion than function. But A Living Tradition [Architecture of the Bahamas] begins each pattern by telling homeowners and builders not only what to do, but also "We do this because…" In doing so, it opens up the rationale behind each pattern, allowing everyone to think again… and allowing architecture to live again. And crafting an entire language of architecture around what works best for this people, and in this place, creates an architecture with far more meaning than mere style and fashion, and one imprinted indelibly with the region of the world it inhabits.
The benefits of living traditions are legion. For example, many of the construction workers at Schooner Bay were fishermen just one year ago. But because they weren't just told what to do but also why to do it ("We do this because…") they caught on quickly and now perform better than many long-time construction workers that would have to have been untrained and then retrained in this new living tradition.
All of this sounded like really cool (possibly even Utopian) theory: building a highly sustainable place with fishermen based on ancient wisdom; using homemade windows in a hurricane zone. But now, the theory has passed the test of a strong Category 3 storm. What can be more sustainable than keeping things going in a healthy way, long into an uncertain future? This is real sustainability.