[GSBN] Fwd: Decrement factor of SB walls

Tue Dec 6 14:34:41 UTC 2011

Thank you, Jorge, for greater details on the French research.  It appears to me that the construction describes a wall with earthen plaster/render on the inside, and no plaster/render on the outside.  Is this correct?  If so, the lack of an exterior plaster/render layer would have a significant effect on the thermal characteristics, I would think.  As well as fire resistance, structural rigidity, moisture buffering, and perhaps a bit of insect and rodent deterrence.  I know that some people build this way, but it seems imprudent to me.  Have I misunderstood the nature of the wall that Jean-Pierre Oliva and Samuel Courgey are describing/testing?  

Thank you,
Derelict
Derek Roff
derek at unm.edu

On Dec 6, 2011, at 5:52 AM, Van Krieken wrote:
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

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