Sunday, March 15, 2009

--"What is new about this?"

The Wikipedia articles on Passive Solar Heating and Passive Cooling make clear that New Regionalism is by no means a novel idea nor a breakthrough technology. Quite on the contrary, New Regionalism is a way of integrating an understanding of how energy is gained and lost in a home with an appreciation for the methods of solving that problem that were common in earliest vernacular architecture.

Let's take a closer look. To start, I googled images of "Southern House" and found this house on the front page:
Most people would relatively quickly recognize this as a Southern-style house. Quintessential elements include the wrap-around porch, the galvanized metal (or "tin") roof, the gargantuan windows, and the setting among countless pine trees. But why are those elements quintessentially Southern? Did Southern homebuilders meet together before Europeans colonized the area and set design standards, as neighborhood planners do today? Certainly not. The elements that have come to be considered quintessentially Southern are the product of a type of evolution: the houses best suited to their environment became models for future houses, and the houses poorly suited to their environments were not replicated. With time, the replicated models exhibited increasingly more of those characteristics that observers would regard as exemplary of a given region.

Determining, in hindsight, why a given architectural feature would prove advantageous requires a little forensic science. Most commentators and writers, for instance, have considered the front porch of a Southern house to be a primarily social space: everyone sits on the front porch and greets the neighbors, and conversations and relationships arise accordingly. But why were people congregating on the porch? Likely because the porch was cooler than the house. But did you know the porch also serves to cool the house interior!

Let's revisit the photograph above. The tin roof over the porch reflects the sunlight and therefore prevents the radiant heat from warming the air on the porch. In the summer, the windows around the porch can be opened. Because the air in the house will be warmed by the enclosure during the day, the inside of the house can at times be hotter than the outside. Everyone remembers from high school that hot air rises. By opening the windows in the second story, the heated air inside can flow up and out of those windows. Where will the replacement air in the house come from? It will be drawn in from the first floor windows--the cooled air from under the porch.

This is a passive version of precisely what an air conditioning unit does: pump out the hot air and pump in air that has been cooled. But a passive cooling technique offers this benefit for free. The house has the additional cooling benefit of a pine forest surrounding it. The shade of the trees naturally blocks heat and thereby cools the house.

Now compare that house to this block of houses:
No large trees shade the houses. Small windows on two elevations prevent cross-breezes. No porches mean no cooled air to draw inside. Black asphalt shingles absorb heat and make the whole house an oven. Without an HVAC system, this house cannot breath and neither can the people who live in it!

Now look at this house from Mother Earth News, a design even better than the one above:
The tin roof covers the entire house, reflecting solar energy away and preventing the house from warming during the summer. (The roof is also a barrier to heat loss from the house during the winter). Notice the wrap-around porch extending to the hidden exposure. Also notice the extended eaves on all gables: the sun is shaded from entering the windows and more free heat-shielding occurs even where there is no porch. The traditional (as opposed to poured slab) foundation allows air to circulate under the house. The windows and doors allow for better circulation and thereby free air conditioning.

The proximity to water does raise interesting questions about how one might construct a commercial subdivision: water has cooling effects on nearby houses, but unless that water circulates well, it can promote mosquitoes.

The next post will consider how an entire subdivision might be constructed using these principles.

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