[GSBN] Fwd: Decrement factor of SB walls

Tue Dec 6 12:52:35 UTC 2011

John,

As I wrote before, the best source of information (I have) about this issue
it is the book writen by Jean-Pierre Oliva and Samuel Courgey ( L'Isolation
Thermique Ecologique).

Jean-Pierre Oliva is perhaps the best known french bio climatic architect,
and since many years a great enthusiast of straw bale building. His books
(also La Architecture Bioclimatique) can be found at Amazon.

Unfortunately, this book is only in FRENCH. I am sorry if my translation
was not well done, so I include here the original text in french.

Citing their book, page 175, concerning a wall with wood structure and
straw bales with medium density (80 to 110 Kg/m3, strawbale section
34x46cm. Vented façade (or rainscreen claddind) in exterior, and interior
with clay render.

Note.: I attach to this discussion a paper wrote by Jim Carfrae, attached
 to this forum last January, 22, where you may have more information about
the benefits on using of a rainscreen clading in a straw bale building,
specially on humid climates.

The  rainscreen cladding is  included in the calculation of JeanPierre
Oliva for this next example:

Wall:

1. Bardage bois (2cm)
2. lattes support et contre-latte (6cm minimum)
3. Panneaux pare-plui contreventans (16mm)
4. Poteaux bois massif (4x20 tous les 60cm)
5. Liteau de maintien des bottes (toutes les 2 bottes)
6. Botte de paille posé sur champ (36cm)
7. enduit terre (30mm)

Caracteristiques Thermiques et environnementales:

Coeficient de déperdition thermique U (W/m2K) / R (m2K/W)
.................................. 0,13 / 7,76
Pertes dues aux points thermiques
intégrés....................................................................
4%
Capacité thermique intérieure
quotidiennekWh/m2K)..................................................
15 (forte)
Capacité thermique intérieure séquentielle
....................................................................25
(moyenne)
Déphasage (heure) / Atténuation du flux de chaleur
(%)..............................................16h / 13%
Epaisseur supplementaire pour atteindre le niveau
"passif"....................................... 0
Bilan "CO2" du m2 de
paroi.............................................................................................
-83 kg CO2 eq
Bilan "energie grise" du m2 de
paroi..............................................................................
62 kWh

Translation (?):

1. Thermal loss U (W/m2K) / R (m2K/W) ..................................
0,13 / 7,76
2. Losses due to thermal
bridges............................................... 4%
3. Daily indoor heat capacity (kWh/m2K)................................ 15
(strong)
4. Sequential indoor heat capacity (kWh/m2K).......................25
(medium)
5. Phase shift (hour) / mitigation of the heat flux (%)............... 16h
/ 13%

All the best

Jorge VK

---------- Forwarded message ----------
From: John Swearingen <jswearingen at skillful-means.com>
Date: Tue, Nov 29, 2011 at 1:35 AM
Subject: Re: [GSBN] Decrement factor of SB walls
To: Global Straw Building Network <GSBN at sustainablesources.com>

This is very interesting, and fortunately in English.  Unfortunately, I
don't really know what it means.  Can you explain more?

   - U-value I know.
   - Thermal bridges to nowhere, I know, but what is a "vented facade"
   (above).
   - What are daily indoor heat capacities and sequential head capacities,
   and what does "strong" and "medium" mean?
   - Phase shift mitigation?

Thanks!

On Mon, Nov 28, 2011 at 3:40 PM, Van Krieken <vankrieken at gmail.com> wrote:

> Hi
>
> The best source of information about this issue (and many others
> concerning insulation, thermal mass, etc) it is the book writen by
> Jean-Pierre Oliva and Samuel Courgey ( L'Isolation Thermique Ecologique).
>
> Citing their book, page 175, concerning a wall with wood structure and
> straw bales with medium density (80 to 110 Kg/m3, strawbale section
> 34x46cm. Vented façade in exterior, and interior with clay render.
>
>
> Thermal loss U (W/m2K) / R (m2K/W) .................................. 0,13
> / 7,76
> Losses due to thermal
> bridges............................................... 4%
> Daily indoor heat capacity (kWh/m2K)................................ 15
> (strong)
> Sequential indoor heat capacity (kWh/m2K).......................25
> (medium)
> Phase shift (hour) / mitigation of the heat flux (%)............... 16h /
> 13%
>
> Unfortunately, this book is only in English. Jean-Pierre Oliva, is one of
> the best known french bio climatic architects, and since many years a great
> enthusiast of straw bale building. His books (also La Architectire
> Bioclimatique) can be found at Amazon.
>
>
> All the best
>
> Jorge VK
> Portugal
>
>
> On Mon, Nov 28, 2011 at 10:55 PM, <strawnet at aol.com> wrote:
>
>>  Ken, Polly Cooper and Jennifer Rennick's chapter that John mention's in
>> that Wiley book - Alternative Construction: Contemporary Natural Building
>> Methods, has a lot of information on this though they don't use the term
>> "decrement." They talk about this issue with straw and other types of wall
>> systems and go into considerable detail. I would get in touch with them and
>> see what they have to say.
>>
>> David Eisenberg
>>
>>
>>  -----Original Message-----
>> From: Laura Bartels <laura at greenweaverinc.com>
>> To: Global Straw Building Network <GSBN at sustainablesources.com>
>> Sent: Mon, Nov 28, 2011 3:40 pm
>> Subject: Re: [GSBN] Decrement factor of SB walls
>>
>>  Hi Martin,
>> Without going back to the details, I could be mistaken, but it seems that
>> a study by Ken Haggard a while back addressed this or similar properties. I
>> found reference in a GSBN email from '07- see below. Is this the same
>> metric?
>>
>>  Laura
>>
>>
>>  John,
>>
>> There is that chapter from Ken Haggard and Polly Cooper on Natural
>> Conditioning in the book Alternative Construction where they look at
>> this. I was looking at it just recently for some curriculum development.
>>
>> Laura
>>
>> John Swearingen wrote:
>>
>> Very interesting paper, and well written.  Some time ago I remember
>> hearing
>>
>> someone toss out some similar observations about thermal storage, that on
>> a
>>
>> diurnal cycle, plaster is activated to a depth of about 2-3 inches
>>
>> (5cm -7.5cm).  I have always figured that the exceptional thermal
>>
>> performance of
>>
>> straw bale buildings is not due solely to the high R-value.  The broad
>>
>> thermal mass of the plastered walls, readily available to indoor air for
>>
>> heat exchange, modulates temperatures like my pink Cadillac modulates
>> bumps
>>
>> in the road.
>>
>>
>> Does anyone know of research and measurements of short and medium thermal
>>
>> storage in walls?
>>
>>
>> John "Diurnally Yours" Swearingen
>>
>>
>>    * *
>> *
>>
>>
>>  Laura Bartels
>> GreenWeaver Inc.
>> 520 S. Third St., Suite 5
>> Carbondale, CO 81623
>> 970-379-6779
>> www.greenweaverinc.com
>>
>> *
>>
>>
>>
>>  *
>>  We've moved to the Third St. Center
>> http://thirdstreetcenter.net/
>> A community place promoting inspiration, sustainability and creative
>> exchange
>>  *
>>
>>
>>
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-- 
John Swearingen
Skillful Means Design & Construction
2550 9th Street   Suite 209A
Berkeley, CA   94710
510.849.1800 phone
510.849.1900 fax

Web Site:  http://www.skillful-means.com
Blog:         https://skillfulmeansdesign.wordpress.com

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