On Fri, 04 Jul 2014 06:28:33 -0700, RobertMacy
wrote:
On Thu, 03 Jul 2014 21:28:13 -0700, Jeff Liebermann
wrote:
...snip...
In some areas, white rocks and white roofs are required by code to
reduce air conditioning requirements. It's suppose to reflect the
sunlight instead of absorbing it. Now, you're telling me that the
collective wisdom of the local planning department might be wrong? Are
you sure?
Now you understand why I discount 'experts'
Trust, but verify is how I operate. That usually means figuring out
how things work before making a judgment. I'm not sure I'm ready to
accept your observations quite yet. Color me undecided.
I do not know where the code is located but it is my understanding that in
AZ it is AGAINST the law in every municipality around these desert
communities to paint WHITE, too blinding, just not allowed. Instead, there
are a series of slightly darker/offwhite, desert colors, many named for
the city of origin trying to obtain some semblance of uniformity, each
contiaininng their own city name.
Ok, that makes sense for AZ. However, they still specify a presumably
reflective light color, not a dark black asphalt surface that would
absorb heat.
The US Dept of Energy version:
http://energy.gov/energysaver/articles/cool-roofs
http://web.ornl.gov/sci/roofs+walls/facts/CoolCalcEnergy.htm
Yes direct sunlight onto a surface is reflected or absorbed, but walls are
not direct sunlight, if done properly. They're under eaves in mid day. I
even found that our garage interior at mid day was noticeably cooler with
the darker color than it was before. I assume radiation of heat OUTWARDS
became more dominant a heat transfer. What made me think of it was
thinking about how frost used to form on lawns at 38F degrees, night sky
radiation sucked the heat right out,
It's not the radiation into the night sky. It's the lack of clouds to
trap the hot air between the ground and the cloud layer that makes a
clear night sky rather cold.
In regions of Sahara many desert
populations wear a preference of dark clothing too.
Not quite. White is worn outside in the summer, with gray or black in
the winter. While dark clothes do get hotter on the surface, they are
somewhat cooler on the inside. The clothes are worn loosely where the
vertical temperature differential sets up a convective vertical air
flow. The inner layer traps much of the sweat against the skin, which
is cooled by the convective air flow. Much of the sweat remains
trapped against the skin, thus reducing overall water loss. The outer
layers provide air pockets, which offer some insulation value. If the
clothes are worn tightly, it doesn't work. Dark clothes also loose
heat faster than light clothes and are therefore worn indoors.
http://www.traderscity.com/abcg/pic1.htm
so thought I'd give it
a try. Now, during the transitional seasons, when neither run AIR nor
HEAT; the temperature range has narrowed to around 3 degrees, which is
very reasonable, before it varied 5-6 degrees. Wake up house cool, during
day heats to some temp, with the narrower range we don't even turn on the
Heat Pump System, irritating our utilities suppliers to no end, but saving
the US overall energy costs.
I do much the same thing. At night, I leave the house partly open so
that it cools down. In the morning, I close all the doors and windows
to trap in the cold air. At about noon, the house warms up to the
same as outside temperature, so I open with windows.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558