Concerning my previous post, ofcourse that the final result for a thermal confort depends on the combination between thermal mass and insulation (also ventilation, sun exposure, humidity, etc).<div><br></div><div>Thanks</div>
<div><br></div><div>JVK<br><br><div class="gmail_quote">On Mon, May 13, 2013 at 4:17 PM, Van Krieken <span dir="ltr"><<a href="mailto:vankrieken@gmail.com" target="_blank">vankrieken@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Thermal mass, like insulation, its a general expression, but in fact "thermal mass depends on the type of material we use.<div>
<br><div>It is important to know what are the properties and thermal performances of the materials we want to use, because each of them have their own thermal characteristics. Due to their structure and their mass they manage the heat in different ways:</div>
<div><br></div><div>a) Statics: conductivity or thermal capacity. How does the material reacts to a thermal flow, independently of the reaction time?</div><div>b) Dynamics: diffusivity and effusivity. At what speed the material manages the thermal flow?</div>
<div><br></div><div>Because the exterior conditions are going to determine the interior changes, its essential to know how the materials react. Iron and clay, both thermal mass, react in a very, very different way.</div>
<div>
<br></div><div>1. The thermal conductivity (lambda) gives us the information concerning the amount of insulation a material can achieve (air passage of calories).</div><div><br></div><div>2. The thermal capacity, measures its aptitude to stock the heat. This is the key element to stock the heat in winter, as well as to absorb the heat in summer. They are not only heavy materials (like clay or stone, or cement). Straw, a much more light material, has also a thermal capacity, and therefore thermal mass.</div>
<div><br></div><div>3. The thermal diffusivity <span style="line-height:19.1875px;font-size:13px;font-family:sans-serif">is the measure of thermal inertia and it </span>increases with the conductivity and decreases with the thermal capacity. <span style="line-height:19.1875px;font-size:13px;font-family:sans-serif">In a substance with high thermal diffusivity, heat moves rapidly through it (m2/hour). </span></div>
<div><span style="line-height:19.1875px;font-size:13px;font-family:sans-serif"><br></span></div><div><span style="line-height:19.1875px;font-size:13px;font-family:sans-serif">4. The thermal effusivity measures its capacity to exchange its thermal energy with the environment. The more the effusivity is high, the more the material absorbs energy without </span><font face="sans-serif"><span style="line-height:19.1875px">warming up significantly. In contrary, the more the effusivity is low, the faster the material warms up.</span></font></div>
<div><font face="sans-serif"><span style="line-height:19.1875px"><br></span></font></div><div><font face="sans-serif"><span style="line-height:19.1875px">Obviously, the thermal mass importance of a material depends on these characteristics, but we can help the final result with some technology. If in a hot climate I do not have a significant difference of temperature at night, then I can get 11 or 12º C of fresh air from the soil (foundations), colling the thermal mass; or I also can run 19ºC water in radiant walls made of clay. The same we can do on winter, stocking the heat on the clay walls.</span></font></div>
<div><br></div><div><span style="line-height:19.1875px;font-family:sans-serif">What is the best material for thermal mass? I do not have a scientific knowledge to tell it, but I like to think that "clay" -- this thermally lazy natural and beatifull material -- is the answer. </span></div>
<div><span style="line-height:19.1875px;font-family:sans-serif"><br></span></div><div><span style="line-height:19.1875px;font-family:sans-serif">The simple issue -- my karma its to arrive allways to a easy conclusion... -- it's how to use it to keep the heat in cold seasons, and what to do, to cool it in hot seasons. That's it.</span></div>
<div><font face="sans-serif"><span style="line-height:19.1875px"><br></span></font></div><div><font face="sans-serif"><span style="line-height:19.1875px">All the best</span></font></div><div><font face="sans-serif"><span style="line-height:19.1875px"><br>
</span></font></div><div><font face="sans-serif"><span style="line-height:19.1875px">Jorge Van Krieken</span></font></div><div><font face="sans-serif"><span style="line-height:19.1875px">Portugal</span></font></div><div>
<br>
</div><div><br></div><div><div><br><div><br></div><div><br><div class="gmail_quote"><div><div class="h5">On Mon, May 13, 2013 at 2:58 AM, Derek Stearns Roff <span dir="ltr"><<a href="mailto:derek@unm.edu" target="_blank">derek@unm.edu</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5">
<div style="word-wrap:break-word">
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.
<div><br>
</div>
<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>
<div><br>
</div>
<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>
<div><br>
</div>
<div>Derek</div>
<div><br>
</div>
<div><br>
<div>
<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.
<div><div><br>
</div>
<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>
<div><br>
</div>
<div>It's a good read.</div>
<div><br>
</div>
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<br>
<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>
<br>
</span></div>
<br>
</div>
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