Cob Re: Carpet/cement per Pat

[Laurie Flood]

Don Stephens wrote:

> The common confusion with earth is between INSULATION and MODERATION.
> as
> I indicated above, earth has a very poor ability to insulate - prevent
> the
> transfer (escape/intrusion) of heat.  On the other hand it has a high
> mass
> which very effectively moderates temperatures - it takes a lot of heat
> to
> warm it up, a lot of cold to cool it down.  This means if your day
> temperature is ~ 20 F. but it drops to - 10 F. overnight, the soil
> surface
> in the morning will have dropped down almost to the - 10, but even
> just 3"
> down the soil will remain an AVERAGE of all the temperatures of the
> past
> week - say ~ 15.  So the underlying roof won't "see" those short-term
> overnight drops.  Likewise, in summer, if you have two or three
> blazing
> days of + 105 F., under even three inches of dirt your roof will never
>
> "see"  it, instead remaining the several week day/night average of say
> ~
> 75 F.!
>
> Also the PLANT LIFE on top will reduce windchill and increase air film
>
> insulation factors in winter and the shading and transpiration cooling
> it
> provides will help in summer.
>
> So plants/dirt on top shield against short-term weather extremes, but
> to
> prevent the slow penitration of outdoors summer heat or the slow
> escape of
> indoors winter warmth, you want INSULATION, and at R-.2/inch, it's
> just
> too expensive to suport the R-40 (almost 17 feet!) you would
> theoretically
> need in some northern climates,
>
> I say "theoretically"  because the soil's thermal flywheel effect is
> such
> that it takes (in dry soil) about a month for heat to travel 18", so
> in 6
> months (9' of soil)  your winter heat would be escaping but it
> wouldn't
> matter because you'd enjoy that cooling 'cause it would be summer!
> They
> use that principle in Australia (See AUSTRALIAN EARTH-COVERED BUILDING
> by
> Baggs - Rog, have you seen that one?) to let summer sun arrive in
> winter
> and winter cool arrive in summer, but it means holding up hellacious
> amounts of dirt with "hell-fer-stout" concrete roofs and walls.  They
> should discover subsurface insulation as a way to hugely deminish
> those
> loads. (As I've indicated before, I'm into minimizing concrete for
> eco-reasons.)
>
>

Don,

I am interested in this, because it is my situation.  What would you
recommend in a very cold and wet winter climate (heavy snow and rain) in
terms of a balance of insulation and moderation?  I notice that you say
that dry soil has the best thermal flywheel effect.  That is not the
winter reality here.  How could I best get the insulation and
moderation, or is the moderation only possible with dry soil i.e. how
much subsurface insulation and how much soil on top?

Thanks in advance,

Laurie Flood
4,500' level in N. Sierra (Thinking of trying to move to 6,000'+)