[BLDG-SIM] passive solar, round 2: Energy-10

Lee Elson lee.elson at jpl.nasa.gov
Fri May 13 16:06:58 PDT 2005


In an earlier email, I wrote:

I'm designing a 3500 sq foot residence at a 5000' desert-like elevation 
(Nevada).
The site has good sun exposure and the climate is generally dry. Typical
temperatures in Feb are 20-40 F. The building is mostly oriented 
east-west and has
a 2' deep insulated rock floor (for thermal mass) with active air 
recirculation.
ICF's will be used as well as tile over concrete (above rock floor) in 
south
facing rooms.

I received many very useful responses regarding how to simulate this 
building. As a result, I've acquired and tried to master Energy-10 (I 
was using eQuest, but that's another story). I've done 2 simulations of 
the building where the only difference is that I use either clear double 
glazing or double low-e glazing *on the south side*. All other sides use 
double low-e glazing. The reason for doing this is that many sources 
strongly suggest that using low-e glass on the south side will inhibit 
much of the solar gain. The results show that the low-e case requires 
about 1/2 the heating as the clear case. Thinking that this might be due 
to thermal mass, I increased the thermal mass and that helped reduce the 
heating needs of the clear case by about 15%.

My thinking is that for the clear glass case, I'm loosing more heat when 
there is no sun than I'm gaining when there is sun, relative to the 
low-e case. In reality, this can be helped by covering the windows when 
there is no sun, but I don't know how to simulate this in Energy-10. Is 
there a way to change the U-value at night?

Any suggestions?

Lee Elson

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