Thermal Performance Data on an Earthbag Dome

Awhile ago, I wrote to you asking if you had any recommendations for stabilizing our 14′ (inner diameter) scoria dome tank house which had started to fail as a result of the bags breaking down. I wanted to give you an update.

Beldar
We paid a crew last November to shotcrete it inside and out, and it is performing very well. I just wish I knew whether it was the mass of concrete or the insulation of the bags. Probably a combo. I am interested to see how it performs once the mass has heated up a bit this summer.

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Does Insulating Paint Really Work?

For many years I have wondered about the effectiveness of various products that advertise that they can insulate roofs and walls by simply painting them! The technology is said to stem from the science (developed by NASA) of protecting space vehicles by coating them with tiny ceramic spheres that reflect heat, so that they don’t burn up when re-entering the atmosphere. Some products consist of an additive for paint, while others are specially formulated paint.

When I realized that I wanted to insulate the 1940’s adobe house I had bought, I began to wonder whether this might be a simple solution to accomplish this. In researching this possibility I discovered that there were conflicting opinions about whether such a paint could work. The manufacturers claimed that many tests have proven their effectiveness and there were some testimonials from individuals or businesses that made similar claims. But I couldn’t find any independent studies that I considered actual validation of the concept.

Not being willing to proceed blindly with painting my entire house with expensive paint on the assumption that it would improve the thermal dynamics of my completely thermal mass walls, I decided to conduct an experiment that would accurately inform me exactly how effective the paint might be. I conceived of a situation that would simulate the thermal mass walls that were left open to the ambient atmosphere over several days. There would be one setup painted as prescribed with the insulating paint and then a second control setup that was identical, except without the insulating additive. Embedded within each of these would be a wireless thermometer probe to keep track of the separate interior temperatures.

painting

I found some perfectly uniform 16’X16″X3.5″ concrete blocks for sale at my local building supply store quite cheaply, so I bought ten of these. Next I acquired the insulating additive (Insuladd was the brand name) and used some exterior latex paint that I already had on hand. I thoroughly mixed the additive to some of the paint and kept some of it in its original form for the control. Then I painted half of the concrete blocks with the insulating paint and half with the control paint, applying two coats of each.

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The Eco-Home Design Guide

ecohomedesign

Christopher Day is a veteran of the world of architecture in Britain. In his new book, The Eco-Home Design Guide: Principles and practice for new-build and retrofit, he has condensed his considerable experience of both designing and hands-on building into a set of guiding principles for how to go about your own ecological building project.

The book is well organized into primary divisions that deal with the major issues that confront anyone who undertakes such a journey. These what, where, how and when issues are each examined in turn, so that by the time you complete the book, you should have a good understanding of all of the issues that need to be addressed. Each chapter is summarized at the end with a listing of the key points covered and a chart of the main choices that need to be made. With this approach, you can quickly thumb through the book to review the basic information presented.

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Hands-On Workshops at the NBC

In addition to the tree house and rocket stove projects already described, there were quite a few other hands-on demonstration projects happening at the Natural Building Colloquium (NBC), and I’ll describe a few of these.

sb2

A simple straw bale wall was erected on a prepared concrete foundation; this was directed by Bill Steen with the assistance of Matts Myhrman and many others. This L-shaped wall would immediately serve as a kind of performance stage and could eventually be enclosed for a building.

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