[Stoves] Sand as Insulation

Xavier Brandao xvr.brandao at gmail.com
Sat Aug 27 03:29:22 CDT 2011


Crispin,

I was wondering also how good/bad an insulator it was. I couldn't find
figures about its thermal conductivity. On forums, one or two persons were
wondering the same and couldn't find info on the web. There seemed to be a
consensus from house builders about sand thermal inertia, and about the fact
is was a bad insulator. It can be used in the walls of house next to an
insulator, to keep warmth inside.
Here is a insulation for wooden houses, with recycled glass and sand:
http://www.maison-bois-passive.net/isolation-sable-verre-recycle-pure-one.ht
ml

It is said on Wikipedia quartz is the main material to be found in sand, and
it has a conductivity of 6,8-12 W/(m·K) for a temperature of 20 °C:
http://fr.wikipedia.org/wiki/Conductivit%C3%A9_thermique 

Sandstone has a high conductivity also:
http://en.wikipedia.org/wiki/Thermal_conductivity
http://en.wikipedia.org/wiki/Sandstone

I read in another study that sand conductivity decreased as its size
increased.

If you find more info about that, I'm interested.

Regards,

Xavier


-----Message d'origine-----
------------------------------

Message: 7
Date: Wed, 24 Aug 2011 23:09:28 -0400
From: "Crispin Pemberton-Pigott" <crispinpigott at gmail.com>
To: "Stoves" <stoves at lists.bioenergylists.org>
Subject: [Stoves] Sand as Insulation
Message-ID: <0b2b01cc62d4$67a35d10$36ea1730$@gmail.com>
Content-Type: text/plain; charset="us-ascii"

Dear Friends

You know how I like to look up the numbers to see what the truth looks
like..

So I was looking up some heat conduction values for materials for a stove
and came across the following:

Heat conduction constants (k). The value is expressed as 

Watts/m.K which is derived from Watts/m2/m/K and reads as Watts conducted
per square meter of area, per metre of thickness, per degree Kelvin. The
first formula has the m2/m reduced to m.

So here goes: values for these materials at 225 C:

 

Sand                                      0.06 Watts/m.K

Sawdust                               0.06 

Rock wool                           0.045 

Polystyrene expanded 0.03

Wood                                    0.13

Brick dense                         1.6

Brick work                           0.5

Cement                                1.01

Cotton Wool insulation 0.029

Felt insulation                    0.04

Magnesia insulation        0.07

Paper                                    0.05

PVC                                        0.19

Straw insulation                0.09

 

So the big surprise is sand. We are often asked if sand can be used as
insulation and the answer is 'yes', apparently. In fact it is better than
magnesia insulation.

Maybe this is a typographical error. Confirmations, anyone?

 

Regards

Crispin

 

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