RE: [GBlist] Roof angle for active solar?

["Ralph Bicknese" <ralph.bicknese@christnerinc.com>]

Bob:

The best angle for year round solar collection is equal to your latitude or
40.5 degrees.  The best angle for water heating is considered to be equal to
your latitude plus 15 degrees.  A difference of 5 to 10 degrees is not
usually considered to be overly significant.  For instance a variance of 20
degrees only causes a reduction of gain of about 10%.

The answer to your shading question is quite a bit more complicated and I do
not have time to get into it all now.  The short answer is that to maximize
heating with a fixed overhang you will have to admit some summer sun.  The
optimal length and height above the window of your overhang will be
different for different height windows even for a due south orientation in
your climate and latitude.  For instance a pretty good all around overhang
length is 2 feet with distance above window at 1 foot for a 6-foot high
window in St. Louis, MO.  This strikes a good balance between letting sun in
for winter heating and minimizing summer sun.  The most effective approach
would be to utilize movable shading or a combination of fixed and movable
shading.

Cheers,
Ralph Bicknese

-----Original Message-----
From: Robert Jordan [mailto:rwjordan@charter.net]
Sent: Thursday, December 27, 2001 11:39 AM
To: greenbuilding@crest.org
Subject: [GBlist] Roof angle for active solar?

I am designing a house West of Boston, Latitude approximately 40.5 degrees,
that I hope to some day have passive solar on.  The rear of the house faces
directly true south.  The house will be well insulated and tight.  I gather
that DHW is viable.  Is it worth trying to collect enough hot water to
satisfy at least part of the heat load?  I also hope to have a masonry
heater.  Further down the road is PV.  I would like to design the roof at a
pitch such that the panels can lie flat on the roof.  Can anyone offer
advice as to the best roof pitch for this program?
Thanks in advance,
Bob Jordan




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This greenbuilding dialogue is sponsored by REPP/CREST, creator of
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______________________________________________________________________


______________________________________________________________________
This greenbuilding dialogue is sponsored by REPP/CREST, creator of
Solstice http://www.crest.org, and BuildingGreen, Inc., publisher of
Environmental Building News and GreenSpec http://www.BuildingGreen.com
______________________________________________________________________