[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: GSBN:Ask the Experts



<x-html><!x-stuff-for-pete base="" src="" id="0" charset=""><html>
<blockquote type=cite class=cite cite><font size=3>Dear
Dave,</blockquote> 
Thermal mass vs. Insulation... The "best" approach depends on
many factors: 
 
<b>Climate:</b> temperature, relative humidity and wind 
(since I know this is a hot-dry climate, I won't even get into the
discussion of relative humidity...) 
Thermal mass (un-insulated for exterior walls) works best in area with a
high diurnal temperature swing. Thermal mass doesn't prevent the flow of
heat, it just slows it down. This can be good if the temperature is swing
back and forth daily. For cooling, you need cool nights with plenty of
ventilation (natural or mechanical) to cool the thermal mass down so it
can radiate "coolth" during the day. You also need windows that
you can open at night (for ventilation) and then close down during the
day. For heating with thermal mass, you  need sunny daytime weather
and a passive solar orientation. (Heating doesn't seem to be the issue
for this climate though.) In hot dry climates, one can also use
evaporative cooling to make the house more comfortable. When temperatures
are high and relative humidity is low, a fountain in a courtyard, a stand
of trees or a swamp cooler can bring be delightful. 
 
Insulation is well suited for climates without a large diurnal swing. The
heat flow is all in one direction (not swinging) and you want to stop it.
For example, climates that get cold and stay cold - Minneapolis would not
be a great climate for adobe - or climates that get hot and stay hot -
Miami wouldn't be great for adobe either because the thermal mass would
heat up and never cool down.  
 
In truth, most climates are mixed. Some parts of the year you want
thermal mass, other times, insulation performs better. I personally like
a combo of insulation and thermal mass - straw-bale with thick earth
plasters and cob built-in furniture with a passive solar orientation
(with good summer shading of course). That way, you get the benefits of
high thermal mass and insulation, both.  
 
But wait... there are many other factors to consider: 
 
<b>Microclimate: 
</b>Are there particular elements on the site that change the more
general climate - proximity to a body of water, winds, vegetation, lots
of exposed thermal mass (rock, sand, etc)? Is it in a seismic zone?
Termites to be careful of? Slope? Drainage paths? 
 
<b>What materials are available locally: 
</b>Is there straw available? Are there good soils for adobe or cob? Is
there wood for a structural system? Concrete? etc? 
 
<b>Who will build it and what skills do they have? 
</b>If you're depending on local labor, you better find out what skills
they have.  
 
<b>What's your budget and your time line? 
</b>If you need to build fast, pick a system that will allow you to do
that. If you have budget constraints, you'd better start by costing out
each system. 
 
<b>What's the weather like during the building season? 
</b>Is it rainy? How will you protect your building while under
construction? Straw is especially susceptible to water damage, adobe less
so. With straw, you might want to put the roof up first, then the
bales. 
 
<b>What kind of design do you want? 
</b>Straw-bale needs a roof with large overhangs. If you want a flat
roofed building with parapet walls, better to go with adobe. 
 
<b>What do you love? What calls to you? 
</b>Building a house is a huge commitment of both time and resources.
When it's done, you'll live in it for a long time. In a hot-dry climate
both thermal mass and insulation can perform well. Do what you love. Of
course, you'll need to get some hands-on experience to see which
materials you like best. A workshop or two or three and helping out with
a friend's house will tell you which materials you feel best working
with. 
 
 
 
 
<blockquote type=cite class=cite cite>---------------------------------------------------------------------- 
 
Dear Editor, 
In February of 2001, after thinking about building a natural building
for 
several years, I ordered 20 past subscriptions to the Last Straw as well
as 
a new membership which I continue to receive.  I read them all and
was 
totally sold on building a load bearing straw bale home.  Then I
decided to 
read about other types of natural construction and have since read 20
plus, 
(every) book on the subject, including stone houses, adobe, rammed 
earth,cob, earthship, etc.etc. 
PS.   The best book I've read most recently, "The Natural
Plaster Book" by 
Cedar Rose Guelberth &amp; Dan Chiras is a detailed description on how
to 
finish any and all of the above natural homes which brings me to
this 
e-mail today.  Because of my extensive reading, I feel that I could
build 
any of these style homes or even a combination thereof (in my
sleep).  The 
problem is, which one or combination there of would be best for me? 
I live 
in Southern Arizona but am looking to build in Mexico's Baja Norte which
is 
of similar climate.  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  
 
 
<smaller>Dear Editor, 
 
In February of 2001, after thinking about building a natural
building 
for several years, I ordered 20 past subscriptions to the Last Straw
as 
well as a new membership which I continue to receive.  I read them
all 
and was totally sold on building a load bearing straw bale home. 
Then 
I decided to read about other types of natural construction and 
have 
since read 20 plus, (every) book on the subject, including stone 
houses, adobe, rammed earth,cob, earthship, etc.etc. 
 
PS.   The best book I've read most recently, "The Natural
Plaster Book" 
by Cedar Rose Guelberth &amp; Dan Chiras is a detailed description on
how 
to finish any and all of the above natural homes which brings me to 
this e-mail today.  Because of my extensive reading, I feel that
I 
could build any of these style homes or even a combination thereof
(in 
my sleep).  The problem is, which one or combination there of would
be 
best for me?  I live in Southern Arizona but am looking to build
in 
Mexico's Baja Norte which is of similar climate.  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  
</blockquote>

Kelly Lerner, Architect 
One World Design 
<a href="http://www.one-world-design.com/"; eudora="autourl">http://</a>www<a href="http://www.one-world-design.com/"; eudora="autourl">.one-world-design.com</a> 
510-525-8582</font></html>

</x-html>