Re: [GBlist] Keeping the Insulation On

[Speireag Alden <Joshua.M.Alden.91@alum.dartmouth.org>]

Sgrìobh michael:

>why do you not use the mineral wool as insulation on the roof/under 
>the organic layer?

     Mineral wool is nifty stuff, but it's not all created alike. 
This stuff is mineral wool batts, not intended to support much 
weight.  If I slopped a bunch of earth on top of it and let water 
soak down into it and freeze, it would eventually have the insulating 
value of soggy earth.

>  why foam in stead?

     It will hold up to being walked on and compressed by soggy earth 
and a snow load of 70 pounds per square foot.

>  i take it that it freezes in your neck of the woods which is why 
>you want the added synthetic insulation to the earth insulation?

     Earth is not insulation, especially wet earth.  It's thermal 
mass.  Thermal mass works well all by itself in some climates, but 
not in a climate where the temperature drops well below the comfort 
zone and stays there for months.  I do get some benefit from having 
it up there on the roof, because it moderates the temperature 
difference for the insulation, but at the end of the day it's not 
insulation.

>  maybe this is where i could use all the corks i have saved? do you 
>think a 6" layer of corks would act as well as your foam insulation?

     Not for the purpose I intend, no.  Cork absorbs water, and any 
absorbed water will degrade the R-value of the material.  On the 
other hand, it might work under a second layer of waterproofing, one 
which sheds some or all of the water.  Eventually, though, I think 
that it would degrade.  Although cork has some remarkable properties, 
it is organic in the end, and if you let it stay a little damp it 
will probably, eventually, become mulch.

-Speireag.
-- 
I feel most emphatically that we should not turn into shingles a tree 
which was old when the first Egyptian conqueror penetrated to the 
valley of the Euphrates.  -- Theodore Roosevelt 

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