North American houses turn to mush in a flood. What can we do about it?

Flooded houses in Conway, South Carolina, September 17
© Sean Rayford/Getty Images/ Flooded houses in Conway, South Carolina, September 17

TreeHugger asked two experts, Alex Wilson and Steve Mouzon, for their thoughts.

The typical North American house is not designed to get wet. In fact, if you read How water damages a flooded house — and what can be saved in the Washington Post, you have to wonder what they were thinking when they allowed houses to be built out of chipboard, drywall and fiberglass. It all just turns into mush. Everything except, hey,

Here’s some good news: Most homes are framed with solid wood lumber, which usually withstands flooding quite well unless it sits in water for weeks or was already damaged. Even if the wood soaks up some water and swells, it should return to shape and maintain its structural integrity. All framing has to be cleaned thoroughly and dried quickly to prevent mold, which flourishes in warm, moist areas.

Everything else is landfill. Claudette Hanks Reichel of Louisiana State University’s Agricultural Center tells the Post:

The deeper the water, the more extensive and expensive the restoration project. It’s not just the cost, it’s the ordeal, and the time and competing for contractors and materials. It’s a horrendous, stressful situation.

I thought this was deeply troubling. Why would we build this way, especially in areas that are prone to hurricanes and flooding? I sent a note to two experts asking what they thought about it. Both responded with comments that I am publishing in full here.

Alex Wilson house© Alex Wilson's resilient house

Alex Wilson is the founder of BuildingGreen, the definitive source of green building information and the basis of many TreeHugger posts, the most recent being Why embodied carbon is so important and what designers can do about it. He is also founder of the Resilient Design Institute, which "creates solutions that enable buildings and communities to survive and thrive in the face of climate change, natural disasters and other disruptions."

Clearly, we need to start building smarter. That means, among other priorities, building with materials that can get wet and dry out without creating mold or losing structural performance. I like mineral wool insulation rather than cellulose in any situation where flooding might be possible—and that’s a lot more places than most of us tend to think are at risk. I also like polished concrete floors—in which a concrete floor slab is turned into an attractive, decorative finished floor surface.

We need to stop putting mechanical and electrical equipment in basements. Even if the building isn’t in a floodplain, plumbing leaks can cause basement flooding. Don’t put the furnace and electrical panel down there!

We need to design houses using knowledge about building science—that means understanding how moisture moves through buildings, whether during storm events or normally as water vapor. We know how to design building envelope assemblies that can dry out. We know how to shed water away from buildings using deep overhangs. We know how to install drainage that carries water away from buildings. Often, our grandparents knew this stuff as good common sense building practices. We need to re-learn some of this and get common sense back into building.

And, my favorite argument: we need to be creating or renovating houses with “passive survivability” in mind. Storms will happen—and probably much stronger storms due to climate change—and these storms (and other events) will cause power outages. Our houses, apartment buildings, schools, and any other buildings designated to function as emergency shelters should be designed to maintain habitable temperatures in the event of an extended power outage or shortage of heating fuel. This can be achieved with such features as high levels of insulation, passive solar design, cooling-load-avoidance measures, natural ventilation, intelligent building orientation. My own 1820s farmhouse in Vermont, which my wife and I did a major renovation of five years ago, would go for days before dropping to 50°F in the middle of winter.

Mahogany bay© Mahogany Bay, Belize/ Steve Mouzon

Steve Mouzon has been a profound influence on my thinking about design, with his thoughts about the Original Green, "which is that originally, before the Thermostat Age, the places we made and the buildings we built had no choice but to be green." Steve’s Katrina Cottage VIII, which is the first design of the next generation of Katrina Cottages, was awarded a 2007 Charter Award by the Congress for the New Urbanism.

I have long advocated for drywall-free houses, and we’ve built a bunch of them now in the tropics and sub-tropics, with excellent results. Hurricane Katrina in 2005 made abundantly clear the difference between building as we have in recent decades with multi-ply components that can delaminate when wet, and old houses built of studs and boards that can simply be toweled off after getting wet, like a fish camp cabin. Drywall remains a wall only so long as you keep it dry. Let it get wet, and it turns into moldy, mildewy mush. No other product this fragile is used in greater quantities in modern construction. Drywall alone kills any chance at cross-ventilation because people rightly reason that if they leave the windows open and a rainstorm blows up, it’ll ruin everything… especially the drywall.

I started experimenting with open walls in the wake of Katrina, and Katrina Cottage VIII -- which I designed and which won a Charter Award from CNU -- got most of the way there. Because it was designed for the DC area to raise lawmakers’ awareness, outside walls had to be insulated, but interior walls were left open and shelves were built between studs so that each interior wall became a shelving unit. Every cavity that can be left open to air circulation is one less place mold and mildew can grow easily and where bugs can hide undetected. Unbeknownst to me, Eric Moser had been working on the same ideas since the Coastal Living Idea House at Habersham in 2002. We joined together with Julie Sanford to create Studio Sky in 2012, and have built over a hundred completely drywall-free cottages at Mahogany Bay Village in Belize. Incidentally, these units almost completely condition themselves, even when days get as hot as 100° because they’re designed to open up and breathe at night, then close up mid-morning when it starts to get warm. The reflective metal roofing reflects most of the radiant heat of the sun back to the sky, and ceiling fans make for a comfortable day.

Thanks to Steve and Alex. Perhaps it is time to look again at how we build in the first place, instead of throwing everything out every time there is a storm.

North American houses turn to mush in a flood. What can we do about it?
TreeHugger asked two experts, Alex Wilson and Steve Mouzon, for their thoughts.

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