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<div class="moz-cite-prefix">On 4/23/2013 3:44 PM, Alan Abrams
wrote:<br>
<blockquote
cite="mid:CADj3_s6pNfek_CC+NvuFSjb8DaHemmcNH7mGp1dz7=Q9fHujEA@mail.gmail.com"
type="cite">
<div>f'r'instance, a claim was made that a 12" AAC wall has a
functional R-value of over 20, much greater than its "steady
state" value of something like R-12... </div>
<br>
</blockquote>
<br>
In the high mass building I did energy analysis for, I used the
Minnesota data for a Maine climate, and the final results differed
from my predictions by about 15% (with large error bars on a
number of things, of course). Certainly even in my climate there
is a benefit from high mass walls, IMO. The results would have
been far more divergent if no benefit was evident. The occupants
are very happy with the house, if that is any indication.<br>
<br>
I would view with <i>profound</i> skepticism any claim such as
the one you quote, which lacks climate reference.<br>
<br>
The trouble with peak load is that it is generally used to size
HVAC equipment. As such, I would NOT recommend ignoring the
affect of high mass. The 'time to heat' a high mass house can be
an order of magnitude longer than a light house, and its return to
ambient is similarly long. At this point, I want to know the
owner's occupancy patterns, and tolerance for temperature swings.
If they are present for much of the day and prefer a stable
temperature, one can size HVAC equipment based on an average heat
loss (i.e. no considerations of mass). If occupancy is varied, or
temperature is expected or desired to vary, HVAC equipment will
need to be reassessed and probably increased in size.<br>
<br>
Thank You Kindly,<br>
<br>
Corwyn<br>
<br>
</div>
<pre class="moz-signature" cols="72">--
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
<a class="moz-txt-link-freetext" href="http://www.GreenFret.com/">http://www.GreenFret.com/</a>
<a class="moz-txt-link-abbreviated" href="mailto:topher@greenfret.com">topher@greenfret.com</a>
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