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My bioshelter project, design through building  RSS feed

 
Gilbert Fritz
Posts: 1300
Location: Denver, CO
22
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I want a small bioshelter greenhouse in my yard project. Here is a link to the main thread, to show where it fits into my other projects and background.

http://www.permies.com/t/39202/projects/pics-models-project-advice-criticism

The design ideas so far: It will be 120 square feet, probably eight by fifteen, since that is the biggest I can build without a permit. It will be freestanding, and the site is decided for me by the property. Only one location in the back yard has sun year around. I built a handy solar angle finder from Rimstar.org to verify this. Thanks to Dave Burton for this tip.

I want it to: maintain a warm temperature year around; provide salads in the winter; house an aquaponics tank; filter greywater; contain a climate battery; grow tropical plants, especially an some dwarf avocados and a bannana; raise seedlings for my home garden and for my community farm project; and enable me to raise peppers as the perennials they are. With our short climate here, the frost comes just as peppers are about to turn red. For those who don't know, a climate battery consists of pumping warm air into a gravel bed, where moisture condenses, thus storing heat in the bed for recovery at night, and reducing the need to vent the greenhouse, wasting heat to the sky. Greywater is currently illegal here, but I want to be ready, as things are changing.

I want backup heating to be a rocket heater.

The greenhouse will be heavily massed, with the equivalent (in gravel and masonry) of five gallons of water per square foot of glazing. I am hoping to massively damp temperature swings.

The back wall will be rammed earth and cinder block (A way to use up the tons of dirt from my wicking bed project!) Foundation will be a rubble trench, glass will be salvaged. However, I don't want to see what happens to overhead salvaged glass in a Colorado hailstorm, so the roof will have to be polycarbonate or some other plastic.

So, as I develop my design from this sketchy beginning, I will post ideas, plans, and questions here. Comments and suggestions are welcome!
 
Gilbert Fritz
Posts: 1300
Location: Denver, CO
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Greenhouse design thoughts.

So here are my second round of design thoughts.

The greenhouse will be framed with salvaged wood, and the front face, which will be vertical, and the east and west facing sides,
will be clad with salvaged glass windows, with an inner layer of some sort of greenhouse film stapled to the wood. Insulation
panels will be stored elsewhere, and fitted to the east and west sides in the winter, when they would become a disadvantage if
left clear. The rear wall will be cinder block for thermal mass part way up, maybe to three feet, at which point it becomes framed.
The south roof is covered with polycarbonate, while the north roof is insulated. To reflect light back to the plants, from the top of
the cinder block wall an inner reflective wall slopes up to meet the ridgepole. Any ideas as to using the hidden space behind this,
besides its insulating dead air value? Any walls which are not thermal mass or glazed have reflective white plaster on them, and
will be insulated with strawclay.

Around the northeast, north, and northwest sides will be an arch of small fruit trees. In front of
the house the earth mounding, which wrapped around the foundation of the structure, will be extended into suntrap arms,
within which will be sited a pond to reflect light to the greenhouse, and will receive cleaned greywater from it. The foundation will
be a rubble trench with a poured concrete top, and cinderblocks on top of this. The North roof will have a second layer lying on it,
which can be flipped over to lay on the South side on cold nights, for more insulation. The main path of the greenhouse will be
sand, with will double as a rocket stove thermal mass. There will be a fish tank with an aquaponics media be on top of it. Tall plants
and objects will be to the back: the tropic "jungle," the reedbed for the greywater, the raised aquaponics tank. In the front will be
an inground bed, with shelving above it for seedling starting. Some of the beds will be equipped with a climate battery system.
This will be a simplification of John Cruickshank's version. A local gardener simply built a raised bed three feet high, ran pipes
through it, and filled it with a deep sheet mulch of wood chips and horse manure. A small fan pushes air through it. On a cold
but clear winter day, he can raise the temperature in the bed by four degrees, and then it drops by the same amount that night,
as the pipes return warm air to the greenhouse. By rebuilding this bed fairly often, some of the advantages of a compost pile
will be gained. Rabbits may be kept in the building to raise the CO2.

Greywater will come from showers and a washing machine, which together will produce 700 gallons of water in a week. The reed beds will be forty square feet, two feet deep, filled with gravel,
and planted with common reeds (as far as I know, they can take the year around heat) and various tropic bog plants. Maybe the dwarf
bananas, too. Then the water will overflow to the pond, and from there to the gravel storage underground. From there, a small
solar operated pump will move it to an elevated barrel, where gravity can feed it to soaker lines in the gardens.
 
allen lumley
pollinator
Posts: 4154
Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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books fungi hugelkultur solar wofati woodworking
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Gilbert Fritz : Instead of a reflective surface that will radiate some of the light/heat energy back outside you want a black surface to trap as much of the visible
light and heat, and also the UV and infrared, other than that I see nothing wrong with your plan ! Big AL !
 
Gilbert Fritz
Posts: 1300
Location: Denver, CO
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Hello Allen,

I don't think I was very clear. Basically, the north roof will be reflective, while the north wall will be thermal massed and black.

Here is an image.

http://www.attra.org/images/solar-gh/shed2.gif

Or do you think that a reflective north roof will send too much light back out? It will have the same angle as the altitude of the sun at the summer solstice. (72 degrees here.)

Thanks for your input!
 
allen lumley
pollinator
Posts: 4154
Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
58
books fungi hugelkultur solar wofati woodworking
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- O.K., I understand what you are trying to do With a low on the horizon late winter, early spring sun the light will be reflected down on to plants and the floor !

Mid summer with its high sun at mid day you will have some shading, with some sunlight still reaching the plants along the north wall by diffusion ! Should work
a treat ! Go for it! Big AL
 
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