Dear Henryk,
I did not experiment, I have my informtion from
several presentations I've seen in the US.
What I understood is:
When you add 5cm of insulation to a non
insulated building it will make a big difference.
However, when you add 5 cm to a building that
allready has 100cm of insulation it will hardly make a difference.
That is how the diagonal (increased
insulation) becomes a curve.
This argument was expressed in relation to the
discussion about the R value of SB. Some tests show better results than
other, but all agree that the insulation is 'Good enough!' since they
surpassed the angle in the above mentioned curve. I could contact 'them' in America, but they use an other R
value than we do in Europe. They state about R 40 for SB where in Europe it
seems to be R 6. I don't know how to convert
from the American R to the European R.
I agree that the decision on what is good enough
depends on "prices of buildig materials and labour and on the cost of
energy for heating (cooling) you would find acceptable" However, in one
building system the optimum could be much lower than in an other building
system.
So, if we take the price of the insulation
and heating out of the calculation (since some insulation materials are
extreemly cheap like straw or sheep wool, and energy prices might sky rocket
some day), at what point is it 'enough'? I do realize that defining
'enough' ('reasonable optimum') will probably be difficult.
I want to know this because it can give a scale
to judge the effectiveness of a certain solution relative to the 'reasonable
optimum'.
Rather than giving just an R value (which I feel
is only a number as long as we don't have a frame to place it in)
I hope this clarifies my question,
Greetings,
Andre
Hi Andre
and Coralie,
Could you explain how did you get the
curve of thermal resistance R vs thickness of straw layer x? Can you send me
the data obtained in your experiment?
You suggest that R
value is not proportional to x. Possible reasons : 1)not uniform properties of
straw, ( for example higher moisture content in the exterior part of bale), 2)
error in experimental procedure. That why I ask you for additional
data.
I guess that the
answer at the question At what point (R value) do we reach 'enough'
insulation? depends on Amities Henryk Czachor
-----Original Message-----
From:
Coralie & Andre de Bouter <m.ep@laposte...>
To: ESBN
<strawbale@amper....muni.cz>
Date:
Monday, June 24, 2002 10:27 AM
Subject: [Strawbale] At what
point (R value) do we reach 'enough' insulation?
a question :
When we draw the relation between insulation in cm and the thermal
resistance obtained we obtain a curve.
For example:
0 cm insulation > 0 thermal resistance
5 cm insulation > x thermal resistance
10cm insulation > 3x thermal resistance
curve starts to slow down...
50 cm insulation > 30x thermal resistance
100 cm insulation >
40x thermal resistance
So at some point it is as good as useless to increase the insulation
because it hardly adds up to increased performance.
***The the million dollar question is: At what point (R value) do we
reach 'enough' insulation?***
I guess this is relative to the climate, is there any objective way of
calculating this?
I ask this because other ecological/natural building systems do not
offer R6 (R=m².C/W), but I would like to form an idea on at what point we
can say it is well enough insulated. rather that bluntly stating that SB has
the best R value. (a bit like saying a Ferrari can do 300km an hour, when
100 km an hour is enough)
I know that some other building systems fonction in a different way
(storing the heat or cold in thick high mass walls for instance) but I'm
only looking to the insulation approach here.
Greetings,
André