Cob Chimney?

[Frank Duffy]

In message <Pine.SUN.3.95.980430085804.11386A-100000 at tincan.tincan.org>,
Don Stephens <dsteph at tincan.tincan.org> writes
>
>Chuck Learned <clearned at bminet.com> writes:..."Mike I am currious why you
>have two flue's. Also I am wondering how high above the roof the chimney 
>needs to be?"  

It is very common to have two flues in one chimney stack.  In the UK
there must be a minimum of 100mm (4") of solid noncombustible material
between them.  With the comments in some posts recently - would cob be
classed as solid noncombustible?

About how high the chimney needs to go, this depends upon the building
itself.  A common mistake in attempts to coomply with the UK regs is
that most people think that the requirement is for 1m higher than the
roof.  This is true but there is also a requirement for 2.3m (about 7ft
6in) horrizontally from the roof to the top of the chimney.  So if you
have a steep roof then you will need to go well over the 1m high to
comply with the horizontal requirement.  The aim is to lift the flue
outlet out of the areas arround the building that are affected by the
wind pressure.  There will be local regulations about chimney heights
with different wording, but I bet they produce a chimney that is close
to this shape anyway.
>
>Frank-what part of UK?  

Glasgow, Scotland - Though my job takes me all over UK.

Don's suggestion of using fibreglass mat insulation back by chicken wire
might not work.  The temperatures involved may be too high for the
resins that bond the fibreglass.  Has anyone looked at mixing one of the
light weight concrete aggregates with cob, vermiculite, micafil, LECA,
or perlite?  This would produce a far more insulating mix for arround
the flue.  If not then fill arround the liner with one of these
materials  - or check out www.isokern.co.uk   :-)


-- 
Frank Duffy