<div dir="ltr">Glad there is someone intelligent checking these things, Derek. The GBA article, and I think the research, as well, are centered around looking at buildings with heavy mass in exterior walls, particularly in direct contact with the sun, so the expected performance of the mass is contingent upon the thermal lag of the wall system and the solar glazing. Our plastered straw bale presents a different case. <div>
<br></div><div>I would consider the plaster on bales to be essentially interior walls, because they're backed by so much insulation. So then the question becomes, what is the effect of high interior mass, the flywheel effect, on energy usage. The flywheel is more effective in buildings that experience a greater diurnal temperature swing, whether because of direct solar gain or conduction through walls and windows. Few climates don't have temperature swings, though, and so, if I understand correctly, that would account for the dynamic insulation effect of mass in a variety of climates.</div>
<div><br></div><div style>John "Daily Swing" Swearingen</div><div style><br></div><div><br></div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sun, May 12, 2013 at 6:58 PM, Derek Stearns Roff <span dir="ltr"><<a href="mailto:derek@unm.edu" target="_blank">derek@unm.edu</a>></span> wrote:<br>
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Certainly worth reading, but the primary information source for the Green Building Advisor (GBA) article doesn't fully support the conclusions that the article presents. GBA references an earlier paper written by researchers at Oak Ridge National Laboratory
(ORNL), and most of the other references also use the ORNL data. <a href="http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/dyn_perf/index.html" target="_blank">
http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/dyn_perf/index.html</a> The ORNL data says that even the worst case location, Minneapolis, showed a dynamic insulation effect of almost 1.5 times, such that insulation of R-14 plus internal mass
would function like insulation like R-21 in a building lacking significant internal thermal mass. The best case was location was Phoenix, which, in one of the examples, attained a dynamic thermal performance of 2.58 times.
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<div>Both of these locations are the least likely, of the six analyzed locations, to have the diurnal temperature swing above and below the desired indoor temperature, for most of the year. Denver, which I judge most likely to have those daily temperature
swings, was only the third best, and closer in performance to Minneapolis than to Phoenix, with top ratings of 1.88. In order from best to worst, the six cities analyzed were Phoenix, Atlanta, Denver, Miami, Washington, and Minneapolis. <br>
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<div>Unfortunately, the ORNL article doesn't break anything down by season or daily temperature variations, so no data is available to say whether the advantages of interior mass are more pronounced in the summer, winter, or spring/fall. Several of the articles
referenced in this GBA article make statements similar to the one the John quoted for us, but none of them offer any data to support the idea. </div>
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<div>Derek</div>
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<div>On May 11, 2013, at 9:25 PM, John Swearingen wrote:</div>
<br>
<blockquote type="cite"><span style="border-collapse:separate;font-family:Helvetica;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;font-size:medium">Martin
Holladay, as if he were listening to our discussion, just published an excellent summary<span> </span><a href="http://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-thermal-mass?utm_source=email&utm_medium=eletter&utm_content=gba_eletter&utm_campaign=green-building-advisor-eletter" target="_blank">"All
About Thermal Mass"<span> </span></a> at Green Building<a href="http://Advisor.com/" target="_blank">Advisor.com</a>, with references to several studies that have been done.
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<div>Most of this has been covered in this discussion. One thing he makes explicit is that mass is most effective in lowering energy usage when the diurnal temperature swing is above and below the indoor temperature (ie: warm days, cool nights). He also points
out that mass is most effective in reducing energy usage in cooling environments because the thermal lag will shift air conditioning usage to the cool night hours, when air conditioners are more efficient. </div>
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<div>It's a good read.</div>
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<div><span style="text-indent:0px;letter-spacing:normal;font-variant:normal;text-align:-webkit-auto;font-style:normal;font-weight:normal;line-height:normal;border-collapse:separate;text-transform:none;font-size:medium;white-space:normal;font-family:Helvetica;word-spacing:0px">Derek
Roff<br>
<a href="mailto:derek@unm.edu" target="_blank">derek@unm.edu</a><br>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><font face="'trebuchet ms', sans-serif"><span style="font-size:x-small"><font color="#666666">John Swearingen<br>Skillful Means Design & Construction<br>
2550 9th Street Suite 209A<br>Berkeley, CA 94710<br>510.849.1800 phone<br>510.849.1900 fax<br><br>Web Site: <a href="http://www.skillful-means.com" target="_blank">http://www.skillful-means.com</a><br>Blog: <a href="https://skillfulmeansdesign.wordpress.com" target="_blank">https://skillfulmeansdesign.wordpress.com</a></font></span></font>
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