Subject: Re: Energy conservation

From: [email-masked] (Nick Pine)
Date: 15 Sep 1997 06:41:02 -0400

Elaine Gallegos  <[email-masked]> wrote:
 
> Think trees...

Or maybe grapes, runner beans, trumpet vines, clematis,
or greenhouse shadecloth...

> Your solar heat collector should be on the south side of the building. An
>entire wall if possible.

Sounds nice.

>Like a big greenhouse on the south/west side.

Mine is 32' long x 16' tall x 12' deep, made from standard commercial plastic
film greenhouse parts, mainly 9 $35 curved galvanized pipes each 24' long, 4'
apart, running from the ground to the eave. They slip/bolt over some 5' pipes
pounded into the ground, and there's a pressure treated board bolted on edge
around the perimeter. After this winter, it will be covered with a single
800 ft^2 $40 piece of 4-year cloudy private polyethylene greenhouse film, to
collect solar heat equivalent to about 500 gallons of oil, and add about
400 ft^2 of floorspace to my house. The building inspector said "It's nice
you called it an air heater instead of a 400 ft^2 2-story addition." I think
I'll cover the ground with more poly film and Astroturf, or a collection of
worn-out carpets, and put a picnic table, umbrella and chairs out there. 

>Line the solar collector with thick concrete tiles on the floor, and
>stone masondry along the wall. The stones will collect heat and radiate
>this heat all night long in winter.

This would work as a more efficient house heater if most of the thermal mass
were in the house, vs in the greenhouse, radiating heat all night... Let warm
air circulate through the house during the day, then turn off the window fan
(in series with a $6 greenhouse cooling thermostat and a $16 house heating
thermostat) or close the windows and doors between house and greenhouse at
night, and let the greenhouse/collector get cold quickly, so it loses very
little heat to the outdoors through the solar glazing at night. 

If the greenhouse contains plants, the fan might also have a parallel 35 F
greenhouse heating thermostat. Greenhouses containing freeze-tolerant plants
like cactus, or no plants at all, make more efficient house heaters, since
they can be colder at night and dryer during the day, with less condensation. 

> The thickly planted trees will cool your house in summer. Plan it so that
>the trees prevent any direct sunlight from hitting your roof, ESPECIALLY
>your sun collector in summer. That would be bad. 

I have found it difficult to shade my house roof from high summer sun with big
trees, without having 1' diameter branches fall on the (steep, transparent)
south roof. Exterior shadecloth, venting and attic floor insulation help.

> If necessary, cover the sun collector in summer with silver tarp until
>your trees are tall enough to block all sunlight.

I hung a $75 16x32' piece of 80% black greenhouse shadecloth over my south
wall this summer. It looks solid black from the outside, but like a window
screen from the inside, through the house windows. Shadecloth comes from
greenhouse suppliers like Stuppy (800) 733-5025, made to order, with hems
and grommets around the edges. Delivery time is about 2 weeks. It comes in
various colors.

I hung a $140 20x32' piece of 57% red shadecloth a few inches away from the
flat south wall of the local newspaper's red barn/office building this summer,
to help them save money on air conditioning by keeping about 60K Btu/day of
sun (eg 2 window ACs running 6 hours per day) from shining into 120 ft^2 of
south windows. We hope to cover it with $32 worth of poly film and a few nylon
ropes to keep it from flapping much in the wind, and use it as a 640 ft^2
solar air heater this winter. Building air would exit a lower window, rise up
between the shadecloth and poly film, travel sideways from south to north
through the warm shadecloth, and re-enter the building through 1 or 2 upper
windows with 1 or 2 $12 window fans. This might collect 580K Btu of heat on
an average December day, and lose about 6h(100F-30F)640ft^2/R1 = 270K, a net
gain of about 310K Btu/day, slightly more than the heat in 2 gallons of oil.  

The newspaper building seems so old and large that this air heater will
probably only let the oil burner run less often. It's unlikely that storing
this comparatively small amount of heat would be economical. 

Nick

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From: [email-masked] (John D. Muccigrosso)
Date: Tue, 16 Sep 1997 01:18:53 -0400

> and grommets around the edges. Delivery time is about 2 weeks. It comes in

How did you attach the cloth to the house?

> south windows.

How did this go?

-- 
John D. Muccigrosso                         Department of Classical Studies
[email-masked]  <-- remove the .nowhere from my address         University of Michigan