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

Mon May 13 16:25:39 UTC 2013

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).

Thanks

JVK

On Mon, May 13, 2013 at 4:17 PM, Van Krieken <vankrieken at gmail.com> wrote:

> 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
>>
>>
>>
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>>
>>
>
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