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R-value conversions (was: Solar Heating, Empirical Measu(r)ements & Experience)



nick@vu-vlsi.ee.vill.edu (Nick Pine) writes:

>William R Stewart  <wstewart@patriot.net> wrote:
>>I would recommend talking to a number of different energy consultants.

>Me too. I usually start by asking "Are you familiar with Ohm's law?"
>That filters out more than half of the "energy consultants" I've met,
>but asking this question is sometimes embarrassing all around...

>Here's another litmus test for an energy expert: what will the average water
>temperature be inside a 4' cube full of water surrounded by 5 R20 foam walls,
>sitting outside in December, when the air has an average 24 hour temperature
>of 36 F and the sun puts 1,000 Btu/ft^2/day of heat into the R1 glazed side
>of the box? And how will that change over time if we shade the sunny wall?
>Anyone care to answer that question? I'll offer a $10 reward to the first
>person who answers it correctly.

This brings me to another point (thus the change of topic title). When I
first started reading these groups I was rather taken aback by the high
R-values people mention. Here in Australia, they are generally in the
range R-1.5 to R-3 or 4 for (say) fibreglass insulation. The units are,
naturally, degC.m^2/W. I was surprised to find that American ones are
expressed in British Thermal Units (which I had thought went out with the 
ark), feet, and fahrenheit, but at least it explained the difference. So I
tried to work out a conversion factor. Can someone confirm it for me? i.e.

  Is it true that 1 watt = 3.412 BTU/hr?  If so, have I got it right that
  R-1 (International) degC.m^2/W = R-5.678 (US) degF.hr.ft^2/BTU?

Thanks,
David.

--
----------------------------------------------------------------------------- 
David Hoadley                        Internet: s840157@minyos.its.rmit.edu.au
Electrical Engineering, RMIT
Melbourne, Australia                Ph: +61 3 9660-4847, Fax: +61 3 9660-2007



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