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GSBN: Digest for 6/30/03

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-> Re: GSBN:Ask the Experts
     by Derek Roff derek@...


Date: 30 Jun 2003 17:51:39 -0500
From: Derek Roff derek@...
Subject: 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.
> 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@...


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