[GSBN] Fwd: Modeling or measuring mass effect of interior plaster

[Van Krieken]

Thermal mass, like insulation, its a general expression, but in fact
"thermal mass depends on the type of material we use.

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:

a) Statics: conductivity or thermal capacity. How does the material reacts
to a thermal flow, independently of the reaction time?
b) Dynamics: diffusivity and effusivity. At what speed the material manages
the thermal flow?

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.

1. The thermal conductivity (lambda) gives us the information concerning
the amount of insulation a material can achieve (air passage of calories).

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.

3. The thermal diffusivity is the measure of thermal inertia and it increases
with the conductivity and decreases with the thermal capacity. In a
substance with high thermal diffusivity, heat moves rapidly through it
(m2/hour).

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 warming up significantly. In contrary, the
more the effusivity is low, the faster the material warms up.

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.

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.

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.

All the best

Jorge Van Krieken
Portugal





On Mon, May 13, 2013 at 2:58 AM, Derek Stearns Roff <derek at unm.edu> wrote:

>  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.
> http://www.ornl.gov/sci/roofs+walls/research/detailed_papers/dyn_perf/index.html 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.
>
>  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.
>
>  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.
>
>  Derek
>
>
>  On May 11, 2013, at 9:25 PM, John Swearingen wrote:
>
> Martin Holladay, as if he were listening to our discussion, just published
> an excellent summary "All About Thermal Mass" <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> at
> Green BuildingAdvisor.com, with references to several studies that have
> been done.
>
>  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.
>
>  It's a good read.
>
>
>
> Derek Roff
> derek at unm.edu
>
>
>
> _______________________________________________
> GSBN mailing list
> GSBN at sustainablesources.com
> http://sustainablesources.com/mailman/listinfo.cgi/GSBN
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.sustainablesources.com/pipermail/gsbn/attachments/20130513/2b2594a0/attachment.htm>