[Greenbuilding] Passive solar in hot, humid climate

[Bruce Donelson]

Even if the sun hits the glass, if it hits at a steep angle, most of the
enrgy will be reflected down to the ground. West facing glass gets hit by
rays that are closer to perpendicular to the glass (later in afternoon), so
will mostly penetrate. In winter, the sun has a lower angle above the
horizon, so you will have more heat gain in winter.
Bruce Donelson
A Better Builder

-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org]On Behalf Of Ian Remmler
Sent: Monday, November 06, 2006 8:32 AM
To: greenbuilding at listserv.repp.org
Subject: [Greenbuilding] Passive solar in hot, humid climate


Hi,

I'm planning to build a house in the Austin, Texas area, and I
want to incorporate passive solar heating and cooling into the
design.  Common wisdom around here is that a 2 foot overhang on
the south wall is enough to block the sun in the summer.

But this is based on the sun's path around solstice time.  If my
calculations are correct, in late August at a bit after 1:00
(solar time), the sun will hit about half of the south wall at a
45 degree azimuth.  We had 24 100+ days this August.

I've thought about putting an 8 foot deep porch along the entire
south wall.  Yes, this will prevent much direct gain in the
winter, but I'm wondering if it would be worth it to keep cool
in late summer / early fall (and spring sometimes).  I've only
found a couple of references that recommend this approach, but
before air conditioning it was a common feature of the local
architecture.  So does it make sense to block all direct gain
when it's hot at the expense of some winter heating (which is
really only needed for about two months around here)?

Please share your thoughts and experiences.

Thanks,
    - Ian.

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