| Mac the Nice 2007-08-11, 1:25 pm |
| From: "Mac the Nice" <mac_the_nice@bigstring.com>
Subject: Mint Green: a study in the architecture of a roof
Date: Friday, August 10, 2007 4:37 PM
Two weeks ago, the LP tank in the RV suddenly dropped to empty and we were
out of hot water for the evening showers. The thought of burning up at least
twenty bucks (at 6 mpg) in gasoline plus three or four working hours out of
the day for that drive down the mountain caused me to think again about how
maybe we could put that trip off for a few days by a resort to some sort of
primitive technology closer to hand. When the sight of a pair of five gallon
buckets, one white, the other black came to my eye out there under the sun,
I figured that maybe we were suddenly, and for a first time most fortunately
in the gas-free hot-water business. After filling both with water from the
well, I set them out in direct sunlight to stand all day while we went back
to work getting those rotten old shingles off the roof of the 1,200 sq. ft.
log home we just bought (with some wooded acreage) and are in process of
restoring to a livable condition.
Long about midday, upon my first check of the water temperature in those
buckets, I found that science was not to be insulted in one of its most
basic principles of physics concerning heat absorption and light
reflectivity, in what would be otherwise known as the LRV or *light
reflectivity value* when it comes to a variance of temperature pertaining to
color.
The water in the black bucket was already risen to a comfortable bath
temperature, whereas in the white bucket, the water was still cool to the
touch. There are few things more satisfying in life than to see theory
substantiated by experiment in fact and reality. I almost got a kind of
'rush' out of it, as they say in the crack house or out on the Rainbow
Family Farm--and I continued to get off on it, as they say, the rest of that
day as I slaved on under the hot sun scraping those black shingles off the
roof.
This remarkable contrast between the black bucket water and the white had me
thinking long and deep (and not a little angrily) about what was striking me
more and more as the abjectly stubborn stupidity of roofing a building with
a color of material that turns out to be lowest of all on the LRV scale,
where white is 86.64 and black is 4.16!
"What manner of thick-headedness is this?" I had to wonder, as I went on
hoeing those nasty, smelly black tiles off the roof and pushing them over
the edge of the eaves on to a clear plastic sheet I had laid out over the
grass below--such a horrible mistake as that, by the end of the day, would
turn out to be. When we took up the sheet to empty all the detritus of
asphalt and black roofing granules, we found that the lawn beneath had been
burned to a beautiful shade of light, golden brown.
I gasped, staring aghast not so much at the fried grass as at the reality of
what the sheathing on most people's roof-tops is being subjected to, at
brunt of the same destructive cause: dark roofing materials cooking that
roof, every day the sun is up there beating down on it.
I decided to try an experiment, now that I had seen first hand that my
physics teachers hadn't just been whistling "Afternoon Delight", as to all
the difference a color of material can make, and I was bound and determined
to see might happen if someone were to be so confident in these principles
as to actually break with some old dirty roofing habits and try a new thing.
I took a one foot square of Dow-Corning 3/4" sky blue Styrofoam panel and
nailed it down to the now bare plywood surface of the roof, and left it
there. Now of course you can read up on all the dope of do's and don'ts
from Dow itself as to the specifications for this material when it is used
strictly to a purpose of roof insulation . . .
http://files.buildsite.com/dbderive...derived7344.pdf
Clearly, what I had in mind was not unprecedented--for insulation. So, you
can imagine the sense of satisfaction that came by the touch of a hand, to
feel the contrast in heat between the light brown surface of the bare
plywood, and that of the light blue Styrofoam. It was totally, "Wow!" The
plywood was hot to the touch while the Styro was cool by comparison, just
perhaps around air temperature or that of a lukewarm bath.
Then, just to be on the safe side of a greater certainty, I decided to leave
that square of Styro up there under full sun, through peak daytime temps of
+92 degrees for two more days. Yesterday morning, as I climbed down the
ladder from the roof, just before taking off for our house in town, I was
happy to jump behind the wheel in the Blazer and announce to my Baby that
there had been absolutely no visible deterioration to the Styro--none
whatsoever.
I have long been a firm believer in the proposition that modern mankind gets
stuck, more often than not in stubborn old habits that we get mistaken for
the 'state of the art'. We keep using heavy, expensive, smelly old
materials from a bygone era that technology has since made obsolete--if only
we could know that by suddenly recognizing the new material and method that
is here to replace the old.
Here is the idea . . .
You are hardly going to find a membrane less permeable to moisture than
Styrofoam--whether by direct penetration or osmosis. The stuff is just flat
out water-tight, as I have been able to observe, once again by experiment,
putting water over its surface and waiting long hours to see if any gets
through. None does.
But Styrofoam is soft and highly subject to damage by impact of whatever
might come flying through the air; hail, sticks, bird-beaks and claws, name
your favorite fine-feathered or furry varmint, like your wife's most beloved
cat. Because of that, Styro must be covered by something to protect its
highly vulnerable surface. Even so, the fact remains that those Styro panels
can be caulked along every edge, peak and valley, to make of the entire roof
one water-impermeable surface. Now that *is* the roof, and all it needs is
something to shield it which theoretically need not even be water-tight. Had
you a mind to get all wild and wicked, you could strap a bunch of bare
wooden lattice up there over the Styro covered by a layer of window screen
*(to keep the leaves and crap out of the gaps) and paint . . .
By damn! Even as I sit here rethinking all this (as first written yesterday)
I begin to realize how wildly, wickedly ventilated such a roof would be, all
aerated by a lattice-work of treated wood the color of wooden shakes like
that, and if you were to ask me, I'd say that it would look damned nice!
In any case, here's the rest of what I had (yesterday) before this
Satori-like thought came to sit on my mind like a fat, but feather-light
outrageously laughing Buddha . . .
In a manner of speaking it almost doesn't matter what you put over the Styro
for a shell so long as it does not defeat the other primary purpose aside
from shedding water--that of reflecting heat. In any case, the Styro would
have to be painted for protection against UV radiation, as according to
considerations revealed by a fine study done in Florida on the feasibility
of working with something developed by NASA for the Space Shuttle in the
form of the "elastomeric" ceramic micro-sphere technology--as a paint
additive.
http://www.fsec.ucf.edu/en/publicat...93-95/index.htm
Such products e.g. "Kool Seal" are on the market already mixed, and the LRV
of the white, rubberized coating, for the first year or so before dirt,
mildew and staining had a chance at it, was high enough to result in so much
as a 60% reduction in air conditioning costs--according to that study backed
by some pretty fancy looking science.
But as some people have cause to complain about the eye-strain impact of a
bright roof, a few communities as e.g. in Arizona have outlawed the
stuff--and I don't know that I blame them--as I think about that red metal
roof lately installed across the street from my house in town, the way that
sucker reflects heat and light. While storm clouds are rising, I have been
known, a time or two, to get out on the lawn for a few quick rain dance
Boogaloo steps, in conjuration of a thunderstorm with golf-ball or better
sized hail, just to serve that neighbor right. And, upon wishing not to be
like that tin-roof lodger over there, I have had much thought toward a
better, kinder more neighborly idea.
There is a fairly informative article entitled "Paint it Green" on the
"green technology" of LRV factors and that NASA micro-sphere technology when
it comes to such an additive in the various colors and shades of paint . . .
http://www.metrosantacruz.com/metro...paint-0717.html
And you can access a list giving the precise value for nearly every color
and shade in the rainbow . . .
http://www.apcosigns.com/techpdf/lrv.pdf
What led me to that Santa Cruz site was a search on the keywords "green" and
"LRV", going on the hunch that the color green, in its lighter shades might
prove to have a higher LRV than most any other. The above-linked list bears
the hunch true, as it turns out that e.g. "Mint Green" is higher on the
scale even than the lightest shade of yellow.
Well! it only stands to reason that trees and most all plant life with the
kind of sun exposure they get, would evolve with a color scheme for their
foliage which would be least susceptible to burning from UV sunlight
radiation. Most plants do not have blue leaves, so I figure that we should
not have a blue roof, but a Mint Green one for that log cabin.
Here's the plan . . .
We invest in some of that unpigmented translucent fiber-glass corrugated
roof sheeting to serve as the shell over the Styro and we paint the Styro
the color we like, namely Mint Green--and maybe we'll even go so far as to
paint the underside of the shell Mint Green, too. As shown by the list . . .
http://www.apcosigns.com/techpdf/lrv.pdf
.. . . of all colors, short of the various shades of white, Mint Green is
highest on the LRV scale at 75.80, higher than Sky Blue at 65.80 (no wonder
the Styro was so cool to the touch out in that sun), the Satin Silver at 52,
the Chrome Yellow at 42, and the Buff at 53.40.
Back to the Styro: Two more advantages are these: since it is soft and
compressible like a sponge, you can buy the 'ship-lap' sheets, fit them
together with no necessity of allowing for contraction and expansion as with
all other forms of sheathing. And yet, so spongy as that stuff may seem, as
the weight of anything put down over it gets distributed, it is remarkably
capable of sustaining its depth without being depressed even to the extent
that we were able to underlay the air-conditioners on the roof of our RV (to
stop leaks) with Styro sheets at the beginning of this season with as yet,
no visible change in 3/4" depth of the material. You can crawl on it with
your knees (while cutting) or even walk on it--carefully--with minimal
effect to the surface.
The stuff holds up, and due to this virtue, our plan continues as follows .
.. .
We'll lay down the adhesive, the Styro and caulk it. Either we'll paint
that or simply undercoat the fiberglass corrugated sheets--maybe both. The
fiberglass sheets will be pre-drilled for the screws, and we'll use the
neoprene washers. Finally, although we might fully trust that the screws
through the Styro would be self-sealing--for peace of mind, we'll dip every
screw in silicone just to be on the safe side.
Any objections? If so, I want to hear them before I wind up sitting up
there drenched to the drawers under that roof with nothing to show for it
but a cold shower and a bunch of Mint Green paint chips offering a fine
contrast to a cherry red face so wet that you could not tell the teardrops
from the rain.
--
Mackie
http://whosenose.blogspot.com
http://doo-dads.blogspot.com/
http://www.mackiemesser.zoomshare.com/0.html
http://vignettes-mackie.blogspot.com/
--
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