Next meeting:

Ecological Building Presentation: Measures of Sustainability & Super-Insulation Strategies. In this program, ecological builder Robert Riversong introduces seven tools for understanding the impacts of our building choices—Embodied Energy, Operating Energy, Exergy, Durability, Life-cycle Costs, Externalities, & Ecological Footprint—and presents the pros & cons of several super-insulation systems.

Over the past 30 years, Robert Riversong�s work has extended from geodesic domes to rural homesteads. He has been a project manager, trainer, and consultant for non-profit building programs from inner-city Boston to the hollers of Tennessee. His has developed a native lumber / hybrid timber frame / modified Larsen Truss / healthy house system that can be heated for less than $200 per year. One of his design-build projects received a Citation for Excellence in a national energy efficient design competition, and another included the first Massachusetts-approved indoor site-built composting toilet.

5 pm on Sunday, July 2nd in room 2 East of the Marlboro Tech Center—on the edge of downtown Brattleboro (next to the Brattleboro Museum & Art Center, which is across the street from the co-op). The door will be open shortly before 5, but locks automatically shortly before 6. There�s a big, free parking lot there.

The program will last a couple hours, and will include Q&A. A freewill donation will be taken to help cover Robert�s travel expenses and to thank him for coming to see us.

Download a flyer.

---

We'll have a second presentation in July—same time, same place, a week later.

Sustainable & Natural Building: An International Perspective... a conversation with Derek Roff, director of Builders Without Borders (BWB), a grassroots network of activists promoting sustainability and natural building internationally as an option in housing, small-group, and community buildings. BWB undertakes small building projects world-wide, and works to make informational and educational resources available to those who can benefit from them.


Derek will share photos of bamboo buildings that he was involved in building in Costa Rica recently, and participate in what will be a fascinating and freewheeling open discussion about cultural issues, natural building and sustainability domestic and abroad, appropriate materials, the challenges of international collaboration, and more.

Your questions, comments, and experiences are very welcome.

5 p.m. on Sunday, July 9th in room 2 East of the Marlboro Tech Center... on the edge of downtown Brattleboro (next to the Brattleboro Museum & Art Center, which is across the street from the co-op). The dialog will last pretty much as long as people want it to, or until Derek goes hoarse. The door will be open shortly before 5, and will automatically lock shortly before 6. There�s a big, free parking lot there.

A freewill donation will be taken to help cover Derek�s travel expenses and to thank him for coming to see us.

Download a flyer.

---

A couple dozen of us turned out for the June meeting / tour of Juliet & David's 10-year-old, off-grid, lime-plastered strawbale house. Good stuff!

---

From: Juliet Cuming <earthswt@sover.net>
Subject: [BANG] Straw Bale Demolition and Analysis

Sunday June 25th 10:30 am-2:30pm. For anyone interested in seeing inside a 10 year old straw bale wall, we will be demolishing our straw bale mud-room in preparation for our new bigger straw bale mud-room and while demolishing we will be analysing how well our 10 year old mud-room has fared on the windy wet north side of our house. Come join us and BANG founders Mark Piepkorn and Sarah Machtey as we probe for moisture levels, analyse how plaster has survived, and find out other fascinating things.

We would like only really interested people- this is not a straw bale house tour. Bring work gloves and be prepared to get dirty. Free Straw for Mulching!

Email your RSVP and we'll send you directions.
Juliet and David

---

At 07:36 PM 6/25/2006, Juliet Cuming wrote:

Thanks to all of you who helped us this Sunday demolish our straw bale mudroom. I think we're all more convinced than ever that Straw ( along with lime and mud and a few other ingredients) can be an incredible and forgiving building material which survives really well even in our harsh climate. We're so happy with what we saw while demolishing that we'll be using all the same techniques we used 10 years ago to build our new mudroom and also to build our new cottage next year. Oh, and it's fun that all our building debris can be thrown in our compost pile or directly on the garden! Thanks again- Juliet and David

At 09:35 AM 6/26/2006, Mark Piepkorn wrote:

There are a small few before, during, and after photos at http://www.flickr.com/photos/duckchow/

We'll put together something more comprehensive about it all later, but in short: I concur with Julia's synopsis - it was pretty impressive.

This was in many respects a "worst-case" situation. The weather-receiving, windward north wall of the unheated mudroom (added to the design in afterthought) had almost no roof overhang; received splashback accumulated from the gutterless main roof and porch roof (average annual rainfall, 41"); was exposed to significant snow drifting every winter; and perhaps most debilitating, had dense foliage directly against the wall. The mudroom was also an unconditioned space, so any drying value that might be given by winter heating and pressure differences was largely absent.

This had been going on for ten years. This year has been wetter than normal.

The mudroom was built on a deck on a pier foundation. Using a forage probe, we recorded moisture-content levels at various depths in the lower three feet of the wall on an approximately-six-inch grid of holes punched through the lime plaster with a piece of rebar and a three-pound sledge. The general pattern was no surprise, mirroring previous findings by Kim Thompson, Shawna Henderson, Clark Sanders, Bob Platts, Rob Jolly, and others (much of that data resulting from studies undertaken for CMHC, something like the Canadian version of HUD in the US). Moisture accumulations were highest at the outside face of the straw at the bottom of the wall, diminishing as height and depth were gained.

Moisture content at the face of the bales in most of the probe-holes of the lower 18" of the wall was high, averaging above 30% (ranging from 20.2 to >40), with diminishing moisture content in the middle of the wall (averaging about 24%, ranging from 15.7 to 37.6). Farther up the wall, moisture content at the straw face averaged just below 20%, with a range from 14.3 to 24.2. The mudroom sidewalls, well-protected from the weather by roofing, yielded excellent readings averaging about 10%.

We punched probe-holes through the lime plaster at some other potential trouble spots on other parts of the north side of the house, and the readings were all less than 15% at the outside of the straw. These areas have bigger overhangs (though the overhangs are two stories up, rather than one), no foliage to impede drying regimes, less splashback due to having less roof area above them, and (I think) more height above grade than the mudroom had.

When we took off the plaster, there was no evidence of mold - though the straw at the intersection of plaster-to-bale in the wet areas of the lower wall was degraded and friable after a decade of these adverse conditions. The degradation diminished rapidly toward the interior of the bale, and the straw at an inch or two in was bright, sound, and strong. The wall system wasn't in any kind of immanent danger of failure.

A larger overhang, less foliage, and gutters would probably have been enough to keep moisture content below 20%. A rainscreen system (basically, siding with an air gap over the plastered bales) would have prevented the moisture loading of this wall, but wouldn't have fit the character of the rest of the house.

The new mudroom will have two-foot overhangs and foliage issues will be avoided. I feel confident that the rest of the house is in fine shape. Improving the situation, the current building project will add a covered porch around much of the house, including the entire north side.

On a separate note, I've never been impressed with bale pinning using rebar or small-diameter saplings/bamboo. (And I'm not alone; exterior pinning has gained significant favor in the last few years, and eliminating pinning altogether is increasingly common.) However, after banging apart the walls David and Juliet put together, I'm impressed with the method they devised, which involved square oak pins cinched together with poly twine.

Mark

---