Cob verify?

[Speireag Alden]

Sgrìobh Michael Saunby:

>Sgrìobh Speireag Alden:
>>     I invite any who has actually lived in a cob building (and understands
>> the difference between insulation and thermal mass) to tell me differently,
>> and why.

> I've spent time in various buildings but never studied any of them with a
> great deal of scientific rigour but here are some observations and
> thoughts.
>
> I've never lived in a cardboard box or an expanded polystyrene container
> but it's obvious to anyone that a small very well insulated container is
> easy and cheap to heat.  However if you want ventilation and a reasonable
> degree of temperature stability then just going for insulation isn't going
> to make for a comfortable living space.  In fact you've created a huge
> problem that can probably only be solved with a lot of technology - some
> sort of life support system is going to be needed for your plastic bubble.
>
> The modern lightweight buildings with lots of insulation that I've lived in
> have required very responsive heating systems and have been unpleasant in
> warm weather - air conditioning is uncommon in the UK. Why are well
[snip]
> A cob building doesn't suffer huge temperature changes every time the doors
> or windows are opened because the walls are constantly taking heat from and
[snip]
> B.T.W. buildings are not only subject to conductive heating and cooling,
> when skies are clear radiative heating and cooling plays a big part.  A
[snip]

Michael -

    I agree with everything you say here.  I like the idea of cob for 
exactly the reasons you cite, and certainly any building can be improved by 
proper siting and orientation, both of which take radiative cooling into 
account.  I especially like the point that summer nights are longer if 
you're closer to the equator, which is obvious when you think about it, but 
which I had never thought of explicitly.

    These are excellent points in the larger discussion, and perhaps you 
meant them in that context, expanding the previous conversation rather than 
simply replying to it.  However, none of what you wrote addresses my point 
to the other Mike (nernka at home.com).  He wrote the following:

Sgrìobh Mike:
> Perhaps the comparison of a cave was not a good one, but the concept is the
> same. To really discuss this, we have to talk about the composition of cob.
> For it is not merely mud. The clay and straw have certain insulative
> qualities that surpass alot of modern-day building materials.

    My point in reply was that cob doesn't insulate any better than any dry 
earth (rammed earth, adobe, and whatnot).  It moderates temperatures 
because it has thermal mass.  In many situations, thermal mass by itself is 
perfectly adequate and comfortable.  In a much wider variety of situations, 
thermal mass with an outer layer of insulation is perfectly adequate and 
comfortable.  (This is why I'm building for my family a small straw bale 
house with lots of interior thermal mass.)

    There are even situations insulation and little thermal mass is good 
(for instance, intermittently occupied buildings in harsh climates, where 
you want a fast response, but don't want to waste energy in heating or 
cooling mass which will only give off the heat or coolness after you've 
left).  These are few and far between, in my opinion.

    So, cob, adobe and rammed earth work well in many situations.  But I 
think that if someone builds a cob house in Minnesota, without additional 
exterior insulation, they're going to be very cold in the winter, or much 
poorer come spring, after they pay for the heating bills (or both).  Cob 
isn't insulation; it's thermal mass.  Insulation and thermal mass behave in 
different ways and must be separately understood before you can use them 
properly in *any* climate.  That's my point.

-Speireag.

P.S.  I notice that there is a verb for "insulation":  "insulate". 
However, I can't think of an equivalent for "thermal mass".  Does anyone 
have any suggestions?  "Masses", perhaps, if we might stretch an existing 
verb a little?

0>>>>>>(---------------------
Speireag Alden, aka Joshua Macdonald Alden
Joshua.M.Alden.91 at alum.dartmouth.org
Usually found somewhere in the wilds of New Hampshire.
Nach sgrìobhaidh thugam 'sa Gàidhlig?