Re: [strawbale] Progress and questions

["Rene Dalmeijer" <rened@cistron...>]

Martin, Attila,

Just a small correction and some background info.

> * How do one crosses a chimney and a strawbale wall or a strawbale
>   insulated ceiling or roof. According to the hungarian regulation
>   no flammable material (wood eg.) can be placed closer then 12 cm
>   to the surface of the chimney. Does mineral fiber work?

The air space as required in the US between the insulation and any
inflammable material is to insure that due to convection it is really cooler
then potentially dangerous temperatures. If you burn wood you could have a
chimney fire due to creosote buildup. If you do experience such a fire the
temperature buildup can be quite high, worst case 1000 C. Even higher is
possible but that would be extreme. If the insulation is tightly packed
between the chimney and the flammable material can reach dangerous levels.
This is due to the fact that the thermal gradient between the hot chimney
and free circulating air is distributed through the different structural
materials in direct proportion to their thermal conductance. If the whole
construction is chimney> mineral wool> wood> free air  and the wood has a
total resistence about 1/10 of the insulation then the inside surface of the
wood would experience about 100 C. This is only so if the air is able to
circulate freely every restriction to circulate will cause a marked increase
in temperature experienced by the wood.

>Yes glasswool has the best insulating performance, 4-5 times better than
>rockwool (stones in pizza ovens can transfer a lovely heat and if you blow

Normal glass wool insulation has a comparable insulation value to mineral
wool of comparable density ie. about 0.035 W/mK. Due to sensitivity problems
with regard to glasswool (like asbestos but not so bad) mineral wool has a
small edge in my opinion. (mineral wool also has this problem but to lesser
degree). Anybody who has worked with both materials knows the difference.
There are specific insulation materials for fireplaces, ovens and chimenys.
I suggest you consult an experienced tradesmen ask him for advice and pay
him to have a look at your chimeny before you cover everything up.
Disregarding insurance and other aspects it will give you peace of mind.

Rene Dalmeijer
>From the reclaimed swamp at the mouth of the Rhine.

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