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Re: Trombe wall efficiency



Leo Hendry  <leo@unixsoft.demon.co.uk> wrote:
>Nick Pine <nick@vu-vlsi.ee.vill.edu> wrote:
>>The formula for radiation loss is
>>Ur = 0.174 x 10^-8 A e ((Tw+460)^4 - (Ta+460)^4), where U is in Btu/hr...

>>     (I may be doing this wrong, and I would be pleased if someone were to
>>     post better calculations, vs. posting talk about better calculations.) 
 
>Are American R values something other than the m2K/W we use, or are you
>mixing units in a near-masochistic manner?

There's actually no mixing above, just pure infernal English units, as
Norman Saunders, PE, says. He uses MKS in this country, and perhaps this
is one reason so few people know of his work. Our colonial R-values are in
hr-ft^2-F/Btu, about 6 times bigger than the R-values in the rest of the
world. We are thinking of exporting them, which will reduce world energy
consumption by 83%, if we don't export the rest of the units. 

>What's the matter with metres, degrees Kelvin and watts?

They are nice for electrical engineering, but it seems to me that people who
build things in this country are already confused or ignorant enough about
passive solar heating mathematics and performance, that it isn't a good idea
to go switching the system of units around as well, yet. (Or perhaps it would
be a good idea (?), to help people get a fresh perspective, and unlearn what
they think they know, but I think it would just further isolate the solar
ranters who use numbers from the builders and spenders who use numbers.)

One basic grounding is that our R-values are what you see stenciled on big
rolls of insulation for sale in stores in this country. Most people here
think R-19 is pretty good, vs R-3, and superinsulated houses with R-40 walls
are pretty good, and 68 is a good house temperature. People here still measure
things in feet, too.

And most people don't give much of a hoot about energy conservation anymore.
It would be nice if passive solar house heating were to aquire the same hobby
status as sailing, something a body does that a body is not obliged to do, a
capital-intensive sport where performance matters. I've seen lots of passive
solar palaces that use 70% or more of the yearly backup heat of a conventional
home the same size. Would that for every million dollar earthship of such ilk,
there were 10 slick $200K houses with smiling owners enjoying close to 100%
solar space and hot water heating. 

I'm used to this system right now. I know a lot of the numbers by heart, and
it's easy to look at new numbers and recognize patterns right away. This would
take a while to relearn in a new system, just for me, ignoring the additional
problem of communicating with others via a new language barrier. To me, a
kitchen match has 1 Btu, and a gallon of oil and a ccf of natural gas contain
about 100K Btu, a therm, and a cord of wood is a hundred gallons of oil. And
windows and still air films have an R-value of 1, and a pound of water needs
1 Btu to warm up 1 degree, as do 50 ft^3 of air. 

>(Posting talk about better calculations)

We are not amused...

Nick


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