Subject: Re: black 80%-solar-absorbing shadecloth, Was: AC Short Cycling

From: [email-masked] (Meir Laker)
Date: 11 Jun 96 17:42:58

From: [email-masked] (Nick Pine)
   Date: 8 Jun 1996 07:16:22 -0400
   
   PS: Lent 700 ft^2 of 13.9 cent/ft^2 black 80%-solar-absorbing shadecloth to
   the local newspaper, . . .  so they could see how their
   comfort and AC bills change when they hang it over their barn red south wall
   with R11 insulation and 84 ft^2 of double pane windows. 

Why black, solar absorbing cloth?  Wouldn't white reflective cloth
keep the sun "away" and therefore keep the building cooler?

--
Meir Laker 

IBM Thomas J. Watson Research Center      
P.O. Box 218, Yorktown Heights, NY 10598    
Phone: 914-945-2699  
Tieline: 862-2699

[email-masked]

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From: [email-masked] (Nick Pine)
Date: 12 Jun 1996 00:28:23 -0400

Meir Laker <[email-masked]> wrote:
    
> the local newspaper... so they could see how their comfort and AC bills
> change when they hang it over their barn red south wall with R11 insulation
> and 84 ft^2 of double pane windows. 
 
>keep the sun "away" and therefore keep the building cooler?
 
Yes, but that black is what I happened to have around... And they plan to put
some transparent polycarbonate siding over their shadecloth in the fall, to
make a huge inexpensive solar air heater. For that, a dark color is better.

For summer shading, black is cool, as long as there is an air gap behind it
and at the top. They would like red, eventually. Shadecloth comes in black,
red, green, gunmetal gray, white, aluminized, sandlewood, etc. Home Depot
sells a nice ~100% black furry polypropylene shadecloth ("landscape fabric") 
that is still fairly porous to air, made by DeWitt (800) 888-9609, for $78
for a 4' wide x 250' long roll, with no hems or grommets, but it would not
let much light in through windows, unlike 80%, which looks like a window
screen from the inside, or makes a moire pattern if there is already a
window screen in place..

Nick

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From: Jason Mansfield Roth <[email-masked]>
Date: Tue, 11 Jun 1996 20:18:26 -0400

>keep the sun "away" and therefore keep the building cooler?

As I understand it, you want deep shade -- which black provides (Bedouin
tents are black, if I recall correctly. Also tightly woven to keep out
sand). This is providing you have: a) ventilation beneath the shade and
b) a surface between you and the shade (like a glass wall) so that the
absorbed heat of the black shade does not radiate to you directly. At
any rate, the point of the shade is to prevent solar radiation from
penetrating to you, while a white shade only reflects some visible
light, end lets in all sorts of radiation (blackout curtains are black
for a reason).

If I'm missing something on this, please let me know, as I've actually
just been thinking about this concept a lot, and it sure is
counter-intuitive.

JMR

93 SL2, blue-green

The foul stench of death is upon us!!! Mmmm...burger....

"What's the use of a good house if you don't have a decent planet to put
it on?"

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From: [email-masked] (Nick Pine)
Date: 12 Jun 1996 00:28:23 -0400

Nick

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From: Jason Mansfield Roth <[email-masked]>
Date: Tue, 11 Jun 1996 20:18:26 -0400

JMR

93 SL2, blue-green

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From: [email-masked] (Alan Horowitz)
Date: 12 Jun 1996 19:15:11 -0400

I bet if the beduin had facilities to silverize their tents, they'd do it.
You're going to have a hard time convinc