[GSBN] Fwd: Decrement factor of SB walls

Tue Dec 6 22:26:41 UTC 2011

Are there any tests on the R-value of rendered strawbales?

In my research (over 12 years as an architect of strawbale houses  and other
buildings) I’ve never been able to find a true tested value.

Would appreciate any help here.

Bohdan Dorniak

AUSBALE

From: GSBN-bounces at sustainablesources.com
[mailto:GSBN-bounces at sustainablesources.com] On Behalf Of Danny Buck
Sent: Wednesday, 7 December 2011 8:24 AM
To: Global Straw Building Network
Subject: Re: [GSBN] Fwd: Decrement factor of SB walls

I side with Dereck in general and in particular on impact of the thermal
characteristics with no exterior render. There is the potential for air
infiltration through the joints between bales and accompanying convective
currents that can be set up with the delta T across the thickness of the
bale. I believe a significant component of a bale wall's thermal performance
comes from the interstices being closed off from the outside atmosphere on
both sides of the wall. 

I do not remember the particulars, but as I recall, there have been tests
done on bale walls where the R-value was dramatically lower than in other
tests and one of the differences was the lack of render on both sides of the
wall.

Thanks,

Danny Buck

----- Original Message ----- 

From: Van Krieken <mailto:vankrieken at gmail.com>  

To: Global Straw Building Network <mailto:GSBN at sustainablesources.com>  

Sent: Tuesday, December 06, 2011 9:21 AM

Subject: Re: [GSBN] Fwd: Decrement factor of SB walls

Yes, Dereck, you're right. In this example there is no exterior
plaster/render. Instead, there is a 16mm rainscreen panel (could be
fiberwood). 

I attach here a picture of the example presented in the book.

Thanks

Jorge VK

On Tue, Dec 6, 2011 at 2:34 PM, Derek Roff <derek at unm.edu> wrote:

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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