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Re: GSBN:Ask the Experts



--On Tuesday, June 24, 2003 12:45 PM -0500 Chris Magwood TLSEditor@... wrote:

Hello All,

Here's a question that arrived in the TLS mailbox.
[snip]
Do I use straw bale because of the insulation
abilities, or adobe earth for thermal mass, or a combination
thereof?  The more I read the more I get confused and the longer it
takes for me to begin the actual project.
Does Last Straw have any writers that can help answer this question
with my region in mind, with explanations of why?

Sincere Regards,
Dave Adams

Here's my perspective on this question: Natural builders have discovered, over the millennia, adequate, and sometimes elegant solutions to housing in different climates. However, in current times, our standards and available options have changed, in both good and bad ways. Options which were sustainable when practiced by millions, are often unsustainable when practiced by billions of humans. Our minimum standards for space and comfort have increased dramatically in the last fifty years, increasing our energy consumption disproportionately. We now have effective insulation options that didn't exist before the last century. For these reasons, few of us natural builders want to build a typical 2003 house, nor a typical 1803 house.

In most climates, a comfortable, energy-efficient home needs lots of insulation and thermal mass. High mass materials, like adobe, cob, and rammed earth, do not have significant insulative value. Their great mass can average out the daily temperature swings. If your daily average is 70 degrees Fahrenheit (overly-simplified, a daily high of 90 and low of 50), mass could be all that you need. In Baja Norte, I would guess that during different parts of the year, the daily average temperatures would be too high or two low to be comfortable in a mass-only home. Adding insulation outside of high-mass materials can be done, but it presents some challenges.

I am excited by strawbale, because it offers both mass and insulation in an affordable, renewable material. Most people are aware that straw bale houses have outstanding thermal insulation. Fewer people recognize that a strawbale also contains significant mass. A strawbale wall covered with a thick mud plaster, as many of us favor, has about the same mass per square foot of wall surface as a standard adobe wall. But the SB wall's effective thermal mass is higher than an equal mass of adobe wall, due to the efficiency gained in insulating the thermal mass.

A strawbale house with thick plasters and a high-mass floor offers superior levels of thermal mass and insulation. No other sustainable, affordable building method, as usually built, provides an equivalent combination of these essential building elements. For this reason, strawbale construction is a useful approach to energy-efficient housing in many climates (assuming good design and construction, including a well-insulated roof).

Derek Roff
Language Learning Center, MSC03-2100
Ortega Hall Rm 129, 1 University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek@...