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RE: [Strawbale] Concrete Base - foundations question??



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@amper....muni.cz [mailto:strawbale-bounces@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