7/1/2009 6:00:00 AM Straw adds twist to home design
Architect Lou Host-Jablonski used the “light straw” method of construction in a day care center in Madison.
Unfinished straw-clay walls.
Straw bale house
Don't tell Cindy and Doug Johnson that straw bale construction isn't feasible. After six years of sweat equity, the residents of rural Blue Mounds have almost completed their dream house - and it's a beauty.
Aside from plumbing and the septic system, they constructed the house themselves, with help from about 50 friends and relatives.
Doug said he outlined the footprint. "The rest put itself together," he said. The structural timbers and boards came from an old barn in the area, and they salvaged doors and windows from a house that was being torn down. The thick walls have an R value of about 40 and that of the super-insulated ceiling is about 45.
The purchased windows from a house being torn down. The windows were originally from Sweden and also very energy-efficient, Doug said.
The concrete floor is slab on grade with radiant tubing. The 1,200-square-foot house includes a garage and a greenhouse, which shield the house from winter winds. They heat the house with a wood stove, and use 3-4 cords of wood during the winter.
Straw bales were stored in a barn so they remained dry. Doug said moisture wasn't that great a hazard. Before bales were covered with a special plaster, they dried out if they become wet. He said the plaster is also semipermeable to avoid trapping moisture.
"In hindsight, I probably wouldn't have built as large," Doug said.
For three years, they lived in a camping trailer on the site, which quickly grew old, especially since they weren't connected to a septic system and had to collect excrement in buckets and haul it elsewhere for proper disposal.
Doug estimated the house cost about $65,000, which includes about $15,000 for the septic system and about $10,000 for roof insulation. They borrowed no money for the house and thus have no mortgage.
Straw bale construction is efficient, cheap and, well, relatively easy, Doug said. The beams dictated the height. of the house. They had planned on dividing the main living space into several rooms, but later decided they liked the appearance of the exposed roof, which is sheathed in old-growth lumber from the barn.
Ryan Dostalek ConnectFitchburg.com
Finally, you can have a house that's really green, sustainable and energy efficient.
Cheaper? Probably not, but it's likely to be around for several hundred years.
It's a long way from becoming a standard - or even a trend. But Lou Host-Jablonski, an architect with a Madison firm, the Design Coalition, thinks he has a handle on the future, a sturdy house with thick walls of local clay and straw, an earth-friendly alternative to the, well, spindly, disposable housing of the last few decades.
It borrows liberally from modern construction techniques and amenities, so it certainly isn't a reversion to a previous, more primitive era.
And save for the use of straw, construction bears only a faint resemblance to straw bale houses that are often do-it-yourself projects and a relative arriviste on the housing scene, often involving generous amounts of what Host-Jablonski calls "folk-engineering."
Before you start sniggering about clay-straw walls, look at your mortgage and seep in the realization that even the best house probably won't last 40 or 50 years. Oh, and look over your heating and cooling costs, because, unfortunately, they aren't going anywhere but up.
Host-Jablonski means business, although he doesn't think the housing industry will sit up and take notice until they have to, which might not be that far away after all.
He has been studying and refining the system, which he calls "light clay," for a decade, carefully honing manufacturing and construction techniques.
An important milestone was determining the optimal mix of straw and clay, which he describes as "little clay and lots of straw." He's found that describing the optimal combination is only partially effective. It's far better to provide hands-on experience, which he offers in workshops, attended by everyone from adolescents to grandmothers.
It also takes a very fine clay, which has to be carefully processed to break it up and emulsify. He has modified some off-the-shelf equipment for this purpose and invented other devices, such as a paddle mixer.
Lowly clay's strong affinity for water molecules makes it remarkably adhesive. As water evaporates from the exterior walls, the clay particles pull water from the walls, thus avoiding the need for moisture impervious membranes.
Host-Jablonski said this is a major advantage, avoiding contemporary construction methods that he said are like "living in a plastic bag" and, if moisture enters the wall, creating ideal conditions for rot and mold.
"We're fooling ourselves if we think we can keep insulation entirely moisture-free for 50 years," he said.
The beefy clay-straw walls essentially temper the moisture content from the outside, avoiding extreme fluctuations in humidity. The 12-inch thick walls have an R-value of 20 to 22. He would like to increase the width to 12 or 15 inches, creating walls with an R-value of 25-28. (The R-value of a house framed with 2 by 4s and conventional insulation is about 12.)
The clay-straw walls nearly eliminate the need for air-conditioning or to add moisture to interior air during the heating season.
"It's like a humidity flywheel, which prevents humidity from rapidly spiking up and down," he said.
But Host-Jablonski emphasizes the clay-straw walls are part of a system that involves factors such as site selection for optimum solar orientation, placement of energy efficient windows and eaves to maximize heat gain in the winter and provide shade during the summer, coupled with the appropriate thermal mass.
He cites well known building scientist Joe Lstbrurek's contention that the types of homes built today have a tenth of the moisture handling capability of those built in the early 1900s.
He built a small house employing the walls and several other features, such as channels in the earthen floor to recirculate air and a system of roof ventilation that prevents ice dams.
The architect has built three similar homes in Madison for clients. He worked closely with building inspectors to make sure every aspect of construction was transparent, and there was no problem with passing inspection.
Host-Jablonski questions why Americans tend to build houses with a relatively short lifespan versus those in several European countries.
Germans, for example, prefer the durability of masonry and don't skimp on windows, doors, fixtures and other amenities. Host-Jablonski tried to find why this was acceptable there - Higher wages? Better health insurance? - and finally concluded that sturdy houses were the norm simply because that's what everyone expected.
Of course, masonry isn't a very good insulator, but Holst-Jablonski said Germans have quickly altered construction techniques to compensate for this deficiency.
The use of local resources in house construction is one reason why he favors straw-clay construction - the raw materials are certainly readily available - but there are several others, including durability, aesthetics and sustainability.
It is an alternative to the current system, which involves the manufacture and shipping of materials thousands of miles, many involving plastics and other materials that release harmful gases.
"Although people tend to fixate on the walls, I call it an evolution. There are still roofs, windows and other elements to consider," he said.
Current methods involve constructing "boxes powered by machines" instead of "building structures that can do a lot of the work for us," Host-Jablonski said.
He is teaching the method to several Native American tribes in the state. They understand and accept the principles underlying the construction technique, but lack the resources to construct more than a few houses at a time.
Framing two six-inch walls on 24-inch centers (instead of the conventional 16-inch centers) and placing windows between studs reduces lumber requirements by one-third.
The panels used to surround walls while the straw-clay mix dries can later be used for flooring.
Although the method used to tamp down straw-clay in the walls is singularly low-tech (workers stomp it down with their feet so every crack and cranny is filled), Host-Jablonski said construction still requires skilled craftsmen, albeit with some slightly different skills.
During a recent visit to Germany, Host-Jablonski visited an intact straw-clay structure built more than 700 years ago, plenty of time to pay off any mortgage.
