[Strawbale] Concrete Base - foundations question??

[Brand J.H.J.]

Hi Kurt,
 
yes indeed the short waves of cellphones and similar stuff does need a much
finer mesh. in fact you can see the mesh in the door of a microwave to get a
good indication of the size needed for such frequencies. i think cellphones
operate on quite similar wavelenths as microwaves. i guess the normal rebar
mesh does give a nice shielding for the 50hz noise.
About the magnetism yes the sources you mention are right. I'm curious 2
hear more of what the effects of it would be. Roughly my gutfeeling tells me
that its an order less of a problem then all the EM waves we're dealing with
on a daily basis. But of course its never wrong to minimise the amount of
steel. if for the energy that was needed for the production. 
 
Bye
 
Joost
 

 
  _____  

From: strawbale-bounces at amper....muni.cz
[mailto:strawbale-bounces at amper....muni.cz] On Behalf Of Kurt Splittdorf
Sent: dinsdag 3 april 2007 15:47
To: European strawbale building discussions
Subject: Re: [Strawbale] Concrete Base - foundations question??



Hi Joost, 

it is part of my job, so i know some about the "E-smog", that is the way we
call it in germany. 

you can demagnetise iron, but it is complicatet and expensiv! 

The iron is like a permant magnet, the magnetismen will be there for a very
long time. it gets usaly magnetised during the production process or when
you weld the iron. 

It does shield off electro magnetic radiation, but this effect depends on
the mesh width. And the way we use the steel in concrete it has no efect at
all!!! It only keeps the very long waves out of the house. I just want to
name the Schumann-Frequenz, it is about 8 Hz. If we talk about mobiles than
it is totaly worthless! the waves are to small. the higher the frequence is
that you want to shield off, the smaller the mesh width need to be. 

The good results in reduction of EMF is because of the mass of the concrete.


But you dont need a lot of iron for a strawbale house, only in the
foundations we use a lot of it. 

i suppose: 

minimize the iron 

if you habe a problem.... demagnetise or keep distance 

kurt 




Hi Kurt, 

what i know is that if a steel ship is moored for a long time (a year or so)
in the same direction it gets magnetised in the same direction as the earth
magnetic field. To let the compasses work well the ships then need to be
demagnetised. So parallel i guess that the steel in concrete will also adapt
to the local magnetic fields and over time, like a cameleon, have the same
properties as the land beneath. 

The good thing of steel is that it does shield off lots of electro magnetic
radiation. so for that reason i might rather use some steel in my straw
walls rather then to be afraid of magnetic disturbances. However i'm not
very experienced with devining and i'm sure a sourcer can tell you more
about this 

bye 

Joost Brand 

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