The Natural Philosopher wrote:
wrote:
The Natural Philosopher wrote:
o Careful insulation required, otherwise heating bills will skyrocket
as you try to heat up the surrounding earth.
The earth does have large thermal inertia, so to start of with,
moisture will condense on the walls like crazy, unless ventilation is
adequate. After lots of heat input, the walls (and floor, and roof)
will have heated up to a comfortable temperature. The problem then is
to avoid overheating (like the underground, as you say). A lot of this
is climate dependant - in a hot, dry, climate massive walls and sunken
homes are an advantage. In a cold, wet, climate, a layer of sodden
earth at between zero and 10 degrees centigrade against the walls of
your dwelling makes it No Fun At All. Hence, decent
isolation/insulation is required, otherwise you will be trying to heat
the groundwater. You'll be looking at needing cavity walls, floor and
ceiling - not a bad idea for drainage anyway - increasing construction
costs. You'll need to ensure the drainage does not get blocked,
otherwise the cavity will become a nice cold water jacket. Allowing for
reasonable access for this will start to get expensive. Most of the
water in the UK is hard water, so the drainage cavity will start to
fill up with limescale deposits - even more fun to get rid of.
You don't understand about insulation do you?
Apparently not. What specifically do you think I'm not grasping? I'm
willing to learn.
That once upo to temperautire, 4 foot of wet earth or 8 foot of masonry
is as good an insulator as 50mm of celotex.
And in fact its a damned sight better as a thermal store.
Aah! I see. Thank-you.
I agree completely that a 4 foot thickness of wet earth can potentially
be a good thermal store. How good it is as an insulator, I'm not sure.
I'm pretty certain a 4 foot thickness of dry earth would be better.
I'm sure someone (possibly even you) may have tables that include the
numbers comparing celotex, wet earth, dry earth, straw, concrete, you
name it. A quick Google gives:
"Dry materials are better insulators since water is a good conductor -
so dry insulation is better than wet insulation. That's especially
important with earth-insulated buildings.
Here are some very rough approximate r-values of materials per inch of
thickness:
Dry earth: 0.33 per inch
Wet earth: 0.05 per inch
Wood: 1.25 per inch (assume the same for cardboard - not the corrugated
kind but solid cardboard)
Fiberglass insulation: 3.5 per inch
Styrofoam: 5.0 per inch (use packing material or cut up a Styrofoam
cup)
So in order to compare a house wall with 3 inches of fiberglass
insulation and 1/2 inch of plywood siding (total r-value of 11.125) to
the same r-value of earth-sheltering, you'd need about 36 inches of dry
earth. Once the earth wet, you'd need 222 inches (18 feet) to get the
same effect."
The problem is that water tends to move through wet earth - having
heated the water up, it's difficult to guarantee that it will stay in
the same place, unless you take measures like enclosing the wet earth
in a water-tight membrane of some type. If it is not enclosed at the
top, heating it above ambient will mean you increase the evaporation
rate. Ground-water movement also means it will be replaced by cooler
water at varying rates depending on the environment. I'm not saying
you can't make it work, the point I was alluding to about needing
'decent isolation/insulation' was simply that you will have to take
special measures.
As an afterthought, here's a page from CSIRO, admittedly talking about
rammed earth
URL:http://www.csiro.au/files/mediaRelease/mr2000/RammedEarth.htm
My, tentative, conclusion is that you would want to use something other
than just plain in-situ earth as an insulator in a subterranean home -
possibly your 50mm of Celotex.
Regards,
Sid