Tuesday, February 8, 2011
Passive Solar Design – Improving the Passive Solar House — Earth Sheltered Homes | Passive Annual Heat Storage
Passive Solar Design – Improving the Passive Solar House — Earth Sheltered Homes | Passive Annual Heat Storage
August 13, 2010 By EarthShelters.com
A Proper Understanding of Convection Improves Passive Solar Design
* Make the heat move itself to where you want it, when you need it.
* Power a fresh air system to keep you comfortable.
* Make that fresh air warm in the winter and cool in the summer.
Convective Heat Flow in the Passive Solar Home
Radiant sunshine comes into the passive solar home, with the home itself being the solar collector. But much of this heat will not go directly into the heat saving earth. It must be carried there by convective heat flow.
“Hot air rises,” is the way most people put it. To be more precise, it floats. If all of the air in a passive solar house is heated to the same temperature, it simply gets hot and goes nowhere. The hot air that rises is actually any air that is warmer than the surrounding air and the cool air which descends must only be cooler than the warm air which displaces it. Convection takes place within what we would normally call hot air or cold air. In fact, air masses of different temperatures will tend to seek their own levels, hot air on top, warm air in the middle and cool air at the bottom.
If the cool air is not allowed to descend, then the hot air cannot rise to replace it. A close examination of many passive solar plans for homes will reveal that a proper place has been made for hot air to go, but no provision has been made for the cool air. The usual result is stagnation with places that are too hot or too cold to be pleasant. Many passive solar homes have been built with the expectation of passive solar energy storage by convection which, in fact, run cool air into the storage bins.
Conventional Passive Solar Architecture
An improperly designed passive solar envelope house, whether underground or not, will fail to store more passive solar energy than it would with a correct layout of windows and envelope.
Figure 40 An IMPROPERLY DESIGNED, but popular convective envelope home. In spite of the claims, very little heat will actually be stored in the earth underneath the house.
Here (above) is a typical double envelope passive solar design that has appeared in a number of magazines, basic passive solar architecture that has often been applied to underground houses. The claim is made that the passive solar energy is stored in the crawl space underneath the passive solar house. Is it? Look closely at its convective loop. Where is the cold air going? Isn’t the so called storage area actually the coolest part of the loop? How effective can such an arrangement be?
The convective loop requires a heat input and a heat output in order to keep working. To force such an arrangement to work at least a little bit, fans are used to make happen what would have happened via passive solar energy if it had been designed right in the first place. Even with fans, the entire body of air, must be heated up warmer than the storage zone by an appreciable amount before any heat will be stored at all.
When the sun goes down and the outdoor temperature cools off, the windows become the heat sink (a cool place for heat to go). So the interior and the crawl space (if there is any heat stored at all), become the source. Now the convective loop reverses direction, pumping the heat back out. This reverse flow, unless prevented by closing off the air flow passages, or insulating the glass at night, is worsened by the addition of, what would ordinarily be considered a good idea, a super insulated north wall.
Why would a super insulated north wall make it work even worse? Because the convective loop requires both an input and an output in order to keep working. If the daytime output is shut off by super insulating the back wall, the loop will stop. When the loop stops, so does the storing of what little heat was moving into the crawl space. However, this occurs only during the daytime when the sun is shining. At night an output path is readily available and, because the sink is now above, or at the very least, level with the new source, what stored passive solar energy there is, is pumped outside much more rapidly than it was pumped in. It is, in effect, a reverse thermal siphon.
Notice why these actual problems have not been so obvious. A great number of things are usually included in each design that clouds the basics of convective heat flow. Insulation on the windows at night, fans, conduction and the sun shining all the way inside, and overall super insulation makes them work better than many conventional homes. But so called conventional above ground homes are really a poor standard. The only viable standard is one that requires no commercial energy at all.
A well thought out convective loop should be the first consideration in designing any passive solar home and the concept of using a double envelope should not be discarded off hand. Convection is very efficient. However, it may be working for you or against you.
Figure 41 A properly designed Envelope home will store gigantic amounts of heat. Here an insulation/watershed umbrella is used along with an INSULATED COLD SUMP to prevent conduction from canceling the effect of a property designed convective loop.
These passive solar plans (above) have a heat input and a heat storage sink (a heat output when the sun is shining). There is a place for the hot air to go and a place for the cold air to go. Everywhere we want heat to move in and out of storage is located in the warm parts of the loop. The cold part of the loop is in the “cold sump” and it must be large enough to contain the expected amount of cold air that will be gathered there. Also, it must be insulated from the warm conductive surroundings. With this arrangement we will actually be storing heat under the floor.
The interior of the passive solar home would have very little effect on the loop during the daytime, summertime or whenever you are collecting those golden rays. Therefore, at input time, the internal envelope is really of little value unless the air temperature is made uncomfortably high.
At night however, if any of the basic principles that make a convective loop work are removed, the passive solar energy flow will stop. Cold air will settle into the cold sump and prevent reverse flow. However, extreme cold can over power this and turn the loop on anyway. The passive solar energy output may be prevented by covering the windows with insulation or by having the air flow stopped and then the loop will be broken. There is, however, some heat loss that will be sustained by the interior. Therefore, heat must be allowed to enter it. Also, the windows may be placed below the level of storage. The sinking cold air will then fill these collectors and trap all the heat above it as with a thermal siphon.
Since these methods of preventing night and cloudy day losses work even without the interior envelope, good air circulation can accomplish the same job much more cheaply and easily. However, the raised floor has additional comfort advantages so you may wish to retain it.
These particular passive solar plans (above, left) also give us an idea of how the passive solar energy storage principles discussed earlier may be applied to passive solar architecture, and are by no means confined to the full earth shelter.
Passive Solar Design with an Open Convection Loop
Figure 42 An OPEN convective loop requires its parts (source, sink, and storage) to be SEPARATE like the confined loop of Fig. 38. Plus it uses a counterflow heat exchanger to allow the stale air to be replaced with nice fresh air.
Consider what can be done if the convective loop is modified as in this diagram (above). This is called the open loop. Note that it requires the source, sink and connecting pipes to be separate. An open loop system will not work in a big open room or if a door or window is open. As before, the heat input (sunshine) heats the air on the left and the heat sink removes the heat allowing the cool air to fall through the right hand pipe. Rather than recycling the same old air through the system, the open loop takes a new breath of air as long as heat is moving in the loop, either into or out of storage. If part of the loop is a living space, then we will have a continuous supply of fresh air whenever heat is moving into or out of the passive solar house. Now we have a passive solar powered ventilation system that works even when the sun isn’t shining, since it is also powered by stored solar heat.
In order to isolate the system from the outdoor weather the heat exchanger will warm the winter air, cool the summer air and allow the convective loop to function at any temperature we like. The operating temperatures naturally will be in the range where we feel comfortable.
Adapted from chapter 6, “What Goes Up,” Passive Annual Heat Storage Improving the Design of Earth Shelters, by John Hait.
August 13, 2010 By EarthShelters.com
A Proper Understanding of Convection Improves Passive Solar Design
* Make the heat move itself to where you want it, when you need it.
* Power a fresh air system to keep you comfortable.
* Make that fresh air warm in the winter and cool in the summer.
Convective Heat Flow in the Passive Solar Home
Radiant sunshine comes into the passive solar home, with the home itself being the solar collector. But much of this heat will not go directly into the heat saving earth. It must be carried there by convective heat flow.
“Hot air rises,” is the way most people put it. To be more precise, it floats. If all of the air in a passive solar house is heated to the same temperature, it simply gets hot and goes nowhere. The hot air that rises is actually any air that is warmer than the surrounding air and the cool air which descends must only be cooler than the warm air which displaces it. Convection takes place within what we would normally call hot air or cold air. In fact, air masses of different temperatures will tend to seek their own levels, hot air on top, warm air in the middle and cool air at the bottom.
If the cool air is not allowed to descend, then the hot air cannot rise to replace it. A close examination of many passive solar plans for homes will reveal that a proper place has been made for hot air to go, but no provision has been made for the cool air. The usual result is stagnation with places that are too hot or too cold to be pleasant. Many passive solar homes have been built with the expectation of passive solar energy storage by convection which, in fact, run cool air into the storage bins.
Conventional Passive Solar Architecture
An improperly designed passive solar envelope house, whether underground or not, will fail to store more passive solar energy than it would with a correct layout of windows and envelope.
Figure 40 An IMPROPERLY DESIGNED, but popular convective envelope home. In spite of the claims, very little heat will actually be stored in the earth underneath the house.
Here (above) is a typical double envelope passive solar design that has appeared in a number of magazines, basic passive solar architecture that has often been applied to underground houses. The claim is made that the passive solar energy is stored in the crawl space underneath the passive solar house. Is it? Look closely at its convective loop. Where is the cold air going? Isn’t the so called storage area actually the coolest part of the loop? How effective can such an arrangement be?
The convective loop requires a heat input and a heat output in order to keep working. To force such an arrangement to work at least a little bit, fans are used to make happen what would have happened via passive solar energy if it had been designed right in the first place. Even with fans, the entire body of air, must be heated up warmer than the storage zone by an appreciable amount before any heat will be stored at all.
When the sun goes down and the outdoor temperature cools off, the windows become the heat sink (a cool place for heat to go). So the interior and the crawl space (if there is any heat stored at all), become the source. Now the convective loop reverses direction, pumping the heat back out. This reverse flow, unless prevented by closing off the air flow passages, or insulating the glass at night, is worsened by the addition of, what would ordinarily be considered a good idea, a super insulated north wall.
Why would a super insulated north wall make it work even worse? Because the convective loop requires both an input and an output in order to keep working. If the daytime output is shut off by super insulating the back wall, the loop will stop. When the loop stops, so does the storing of what little heat was moving into the crawl space. However, this occurs only during the daytime when the sun is shining. At night an output path is readily available and, because the sink is now above, or at the very least, level with the new source, what stored passive solar energy there is, is pumped outside much more rapidly than it was pumped in. It is, in effect, a reverse thermal siphon.
Notice why these actual problems have not been so obvious. A great number of things are usually included in each design that clouds the basics of convective heat flow. Insulation on the windows at night, fans, conduction and the sun shining all the way inside, and overall super insulation makes them work better than many conventional homes. But so called conventional above ground homes are really a poor standard. The only viable standard is one that requires no commercial energy at all.
A well thought out convective loop should be the first consideration in designing any passive solar home and the concept of using a double envelope should not be discarded off hand. Convection is very efficient. However, it may be working for you or against you.
Figure 41 A properly designed Envelope home will store gigantic amounts of heat. Here an insulation/watershed umbrella is used along with an INSULATED COLD SUMP to prevent conduction from canceling the effect of a property designed convective loop.
These passive solar plans (above) have a heat input and a heat storage sink (a heat output when the sun is shining). There is a place for the hot air to go and a place for the cold air to go. Everywhere we want heat to move in and out of storage is located in the warm parts of the loop. The cold part of the loop is in the “cold sump” and it must be large enough to contain the expected amount of cold air that will be gathered there. Also, it must be insulated from the warm conductive surroundings. With this arrangement we will actually be storing heat under the floor.
The interior of the passive solar home would have very little effect on the loop during the daytime, summertime or whenever you are collecting those golden rays. Therefore, at input time, the internal envelope is really of little value unless the air temperature is made uncomfortably high.
At night however, if any of the basic principles that make a convective loop work are removed, the passive solar energy flow will stop. Cold air will settle into the cold sump and prevent reverse flow. However, extreme cold can over power this and turn the loop on anyway. The passive solar energy output may be prevented by covering the windows with insulation or by having the air flow stopped and then the loop will be broken. There is, however, some heat loss that will be sustained by the interior. Therefore, heat must be allowed to enter it. Also, the windows may be placed below the level of storage. The sinking cold air will then fill these collectors and trap all the heat above it as with a thermal siphon.
Since these methods of preventing night and cloudy day losses work even without the interior envelope, good air circulation can accomplish the same job much more cheaply and easily. However, the raised floor has additional comfort advantages so you may wish to retain it.
These particular passive solar plans (above, left) also give us an idea of how the passive solar energy storage principles discussed earlier may be applied to passive solar architecture, and are by no means confined to the full earth shelter.
Passive Solar Design with an Open Convection Loop
Figure 42 An OPEN convective loop requires its parts (source, sink, and storage) to be SEPARATE like the confined loop of Fig. 38. Plus it uses a counterflow heat exchanger to allow the stale air to be replaced with nice fresh air.
Consider what can be done if the convective loop is modified as in this diagram (above). This is called the open loop. Note that it requires the source, sink and connecting pipes to be separate. An open loop system will not work in a big open room or if a door or window is open. As before, the heat input (sunshine) heats the air on the left and the heat sink removes the heat allowing the cool air to fall through the right hand pipe. Rather than recycling the same old air through the system, the open loop takes a new breath of air as long as heat is moving in the loop, either into or out of storage. If part of the loop is a living space, then we will have a continuous supply of fresh air whenever heat is moving into or out of the passive solar house. Now we have a passive solar powered ventilation system that works even when the sun isn’t shining, since it is also powered by stored solar heat.
In order to isolate the system from the outdoor weather the heat exchanger will warm the winter air, cool the summer air and allow the convective loop to function at any temperature we like. The operating temperatures naturally will be in the range where we feel comfortable.
Adapted from chapter 6, “What Goes Up,” Passive Annual Heat Storage Improving the Design of Earth Shelters, by John Hait.
"passive annual heat storage," by john hait SOLAR.KnowledgePublications.com
"passive annual heat storage," by john hait SOLAR.KnowledgePublications.com
9 sep 1997
i just interlibrary-borrowed and finished reading the first edition, second
printing of john hait's 152 page out-of-print (?) 1983 "passive annual heat
storage" book, which references and seems to take off where mike oehler's
"$50 and up underground house" book leaves off, thermally-speaking.
hait is/has/had a non-profit organization called the rocky mountain research
center/pobox 4694/missoula mt 59806, not to be confused with amory lovins'
rocky mountain institute. hait seems less well-funded and sure of himself than
lovins, and less survivalist and outspoken than oehler. i wonder what he's
doing these days. he studied mazria's book and the underground space center's
earth sheltered housing books and built an underground "geodome" home in
missoula with 48 temp sensors and 5 moisture sensors to try out his ideas.
he's done a lot of good basic thinking. the book has novel and interesting
concepts, and some very clear explanations, eg this one on page 83:
figure 43 shows two types of heat exchangers, parallel flow and counterflow.
in the parallel flow, as the name suggests, the air is moving in the same
direction in both pipes. heat will pass through the walls of the interior
pipe from the hot air to the cold air. the cold air is warmed up, and the
hot air is cooled off, and their temperatures meet in the middle coming out
the other end, warm.
the counterflow heat exchanger, on the other hand, has its fluids (gas or
liquid in either or both tubes) traveling in opposite directions. once again,
the hot one cools, and the cold one warms up. but, when the cold one reaches
the other end of the pipe it sees, not a warm fluid that has already been
cooled off, but a hot one that hasn't had a chance to cool yet, and the hot
one sees a cold fluid at its other end... when the fluid which is supplying
heat is hot, the one receiving heat can get hot. but if the source fluid
were to lose its temperature in the process, as with the parallel flow heat
exchanger, how could it make the destination fluid anything but warm?
this way, the hot one comes out cold, and the cold one comes out hot.
hait may have been the first person to suggest making earth tubes into
counterflow heat exchangers. he goes on to describe the camel's nose :-)
a heat exchanger with flow that periodically reverses direction.
the book is short on arithmetic: at one point hait carefully explains how to
calculate the area of a circle. on the other hand the book seems full of good
physical insights, experience, and numerical clues, like "it takes six months
to conduct heat 20 feet through the earth." he says "plain old dirt is the
ideal heat storage medium," and suggests covering the dirt around and over
an underground house with an insulating "umbrella/watershed" made with several
layers of foamboard and plastic film, to keep rain from washing stored heat
down and out of the dirt. the umbrella slopes downward to shed water and
extends some 20' outwards from the house, about 2' underground, and it
contains about 4" of foamboard at the thickest point.
deep earth normally has a temperature close to the average annual air temp, but
in this case, the house with uninsulated underground walls is used as a central
heater to slowly warm ("it takes three years to fully climatize the soil around
the home") and bias the earth to a higher temperature (eg from 45 to 68 f)
under the umbrella. passive solar heat is one way to do this, allowing sun to
shine into the house through windows ("whatever you wish the average indoor
temperature to be, adjust the inside temperature to be about 3 or 4 f (1.5-2 c)
higher in the summertime. the whole structure should swing only about 6 to 8 f
(3.3-4.4 c) all year.") another way is to make use of seasonal air temperature
differences. he describes a possible origin of his system:
baked dry in august... frozen stiff all winter, a montana sodbuster and his
neighbors battled the elements. they shivered through the frigid northern
winters, gathering buffalo chips for fuel, to ward off the frostbite.
our field farming friend noticed that the vegetables in his root cellar
never got hot and never got cold. they were always comfortable. he wasn't!
so he installed a window in this root cellar and moved in.
within the first year, the unheated indoor temperature rose from its natural
45 f (7 c) to 55 (13 c), all by itself. this drastically reduced the amount
of fuel he needed, but his neighbors just laughed at him and continued
gathering buffalo chips.
this rise in temperature was a surprise improvement, since everyone had
told him that it would always be 45 (7 c) no matter what. mulling this over
in his mind he tohought: "if i could only raise the termperature another
10 or 15 degrees (6-8 c)... i wouldn't need any buffalo chips at all."
but how can you intentionally raise the constant temperature that occurs
naturally in the earth? well, he had already raised that average temperature
about ten degrees by installing the window. he reasoned, "it must be like
raising the natural level of a lake. you let more water in and less water
out. that's it!"
he grabbed his hat and dashed into town. soon he returned with a pickup load
of styrofoam insulation and several rolls of plastic sheeting. he put the
insulation and plastic over the top of his home, dirt and all, and covered
the whole thing with another layer of earth.
all summer long, the heat which collected inside soaked into the ground to
keep his home cool and comfortable. just as he had suspected, the newly
insulated earth began warming up from 55 to 65 (13-18 c) and, finally by
fall, all the way up to 71 degrees (22 c.) when cold weather arrived, the
earth remained warm and kept his new earth sheltered abode cozy all winter.
our subterranean sodbuster was at last _continuously comfortable._ he had
invented passive annual heat storage!
and his neighbors? well, times have changed. now a big monopoly collects
and distributes all the buffalo chips... and goes to the public service
commission each month to ask for a rate hike.
hait says the us r-value of earth is often assumed to be about 0.08 per inch
(about r1 per foot) vs 3 to 7 per inch for many commercial insulations. hence,
we have something like an r20 wall with lots of thermal mass (20 btu/f-ft^3
would make rc roughly 4,000 hours, ie 6 months, with the capacitor in the
center of the r20 resistor and both ends of it at a low-impedance) if heat
has to travel 20' horizontally before escaping upwards. hait also points out
that a wall thicker than 20' doesn't add much effective thermal mass, since
the winter cold front that travels into the wall becomes a warm front after
6 months, and heatflow reverses. i guess most people would say it's easier
to build a wall with 6" of fiberglass insulation than to arrange this sort
of earth umbrella. we might cover a house with polyethylene film and surround
it with a gigantic earth berm, with a ring of tires to make the outer walls
steeper, and 2' of some sort of fluffy compost on top, over plastic film...
hait has an interesting way of providing fresh air and conducting and storing
heat in the earth around the house, like this:
earth earth earth earth
uuuuuuuuuuuuuuuuuuuuuumbrella
solar gain --------------------- <-> uuuuuuuuuuuuuuuuuuu
uu \ | | \ upper earth tube uuu
uu | house | \ uu
lower earth tube<-->| | \
---------------------
the lower earth tube slopes up to the house (to make an igloo-like heat trap)
and enters the living space at floor level. the upper earth tube enters at
ceiling level, and slopes down to exit at the same outdoor level as the lower.
if the house becomes slightly warmer than the surrounding earth, outside air
naturally enters the lower earth tube and warm air flows out of the upper one.
if the house becomes cooler than the surrounding earth, flow reverses. in
either case, heat is exchanged between earth tube air and surrounding earth,
storing excess house heat in the earth or removing it to heat the house.
he suggests eliminating the windows and turning all this upside down, with
upward sloping earth tubes (making a cold trap), to make this into a permanent
cold storage place in a cold climate.
the book ends with design guidelines:
insulation/watershed umbrella:
1. extend umbrella out and around the entire home and above also, if
the home is fully earth sheltered.
2. extend out 20 feet (6 m) wherever possible.
3. taper insulation from 4 inches (10 cm) down to one (the first inch
is the most important.)
4. insulate the backs of retaining walls and other items that will be
backfilled before the main umbrella goes into place.
5. plastic: (0.006 inch (0.15 mm), largest sheets practical.)
a. 3 layers min.
b. separate layers with soft insulation or dirt that will drain well.
c. provide adequate drainage out the end of the umbrella.
d. do not stretch, but allow for settling with folds and slipping overlaps.
e. lay like shingles.
f. prevent future ponding after settling by allowing sufficient
drainage angles.
g. pay particular attention to possible extreme settling and the problems
that might occur given its new confuguration.
h. make underground gutters to guide water off the front and away from
the building.
i. cover it with flashing if it exits the ground.
earth tubes:
1. size... 4 to 18 inches (4-46 cm) in diameter.
2. length...60 feet (18 m) min. more like 100-200 ft.
3. must go downhill from the house at least a foot plus the tube diameter.
4. must be kept relatively level (1/4 inch to the foot for drainage in
those places where heat exchange is to be minimized.
5. the greatest angle of grade must be in those areas where heat
exchange is preferred.
6. at least two tubes must be used.
a. one enters the home at the highest point where air can be taken.
b. the other enters the home at the lowest point where air can enter.
7. provide for condensation removal.
8. provide for backfill settling so that the tubes will not be sheared off.
(backfull with gravel under the tubes.)
9. provide bug screens.
10. a small umbrella should be provided over the tube if it is not
under the main umbrella (about 8' wide, full length.)
11. do not "short out" the storage zone of an earth tube by placing it
too close to an interior wall so that conduction becomes a more
prominent factor than the convection through the tube.
12. plastic tubes should work quite well; their r-factor is small (given their
thickness) and they can withstand the earth environment for a long time.
internal design:
1. light colored walls and ceilings to spread the heat around.
2. medium colored floors so they will be slightly warmer than the ceiling,
to help avoid stagnation.
3. carpet should make little difference [hait likes mike oehler's carpet
over poly film over earth.]
4. allow for free flow of air between places where sun comes into the home and
conductive surfaces near storage, so heat can be transferred by convection.
5. provide a place for the warm air to go.
6. provide a place for the cool air to go.
window layout:
1. use moderately sized windows. greater than the 10% required by law [?],
and less than the usual passive solar recommendation. probably about
25 to 30% of the equivalent floor area in glazing.
2. do not localize the windows all on the south, as if it were a regular
passive solar building. spread the windows out so the heat input is
spread over the whole day.
3. at the same time (be careful) do not severely reduce the conductive
surface area, and thus the storage mass accessibility.
adjustments:
1. external shading devices that are adjustable!
2. earth tube shut-offs and one way doors.
3. windows, floor vents, skylights.
4. provide for cross ventilation and high and low vents also with earth tubes.
monitoring:
at least, monitor critical temperatures inside, outside, and in the
storage mass.
waterproofing:
insulation/watershed umbrella.
gravity drainage.
do not allow hydrostatic pressure from water table.
at least one layer of plastic as a vapor barrier.
use the complete water control program.
nick
9 sep 1997
i just interlibrary-borrowed and finished reading the first edition, second
printing of john hait's 152 page out-of-print (?) 1983 "passive annual heat
storage" book, which references and seems to take off where mike oehler's
"$50 and up underground house" book leaves off, thermally-speaking.
hait is/has/had a non-profit organization called the rocky mountain research
center/pobox 4694/missoula mt 59806, not to be confused with amory lovins'
rocky mountain institute. hait seems less well-funded and sure of himself than
lovins, and less survivalist and outspoken than oehler. i wonder what he's
doing these days. he studied mazria's book and the underground space center's
earth sheltered housing books and built an underground "geodome" home in
missoula with 48 temp sensors and 5 moisture sensors to try out his ideas.
he's done a lot of good basic thinking. the book has novel and interesting
concepts, and some very clear explanations, eg this one on page 83:
figure 43 shows two types of heat exchangers, parallel flow and counterflow.
in the parallel flow, as the name suggests, the air is moving in the same
direction in both pipes. heat will pass through the walls of the interior
pipe from the hot air to the cold air. the cold air is warmed up, and the
hot air is cooled off, and their temperatures meet in the middle coming out
the other end, warm.
the counterflow heat exchanger, on the other hand, has its fluids (gas or
liquid in either or both tubes) traveling in opposite directions. once again,
the hot one cools, and the cold one warms up. but, when the cold one reaches
the other end of the pipe it sees, not a warm fluid that has already been
cooled off, but a hot one that hasn't had a chance to cool yet, and the hot
one sees a cold fluid at its other end... when the fluid which is supplying
heat is hot, the one receiving heat can get hot. but if the source fluid
were to lose its temperature in the process, as with the parallel flow heat
exchanger, how could it make the destination fluid anything but warm?
this way, the hot one comes out cold, and the cold one comes out hot.
hait may have been the first person to suggest making earth tubes into
counterflow heat exchangers. he goes on to describe the camel's nose :-)
a heat exchanger with flow that periodically reverses direction.
the book is short on arithmetic: at one point hait carefully explains how to
calculate the area of a circle. on the other hand the book seems full of good
physical insights, experience, and numerical clues, like "it takes six months
to conduct heat 20 feet through the earth." he says "plain old dirt is the
ideal heat storage medium," and suggests covering the dirt around and over
an underground house with an insulating "umbrella/watershed" made with several
layers of foamboard and plastic film, to keep rain from washing stored heat
down and out of the dirt. the umbrella slopes downward to shed water and
extends some 20' outwards from the house, about 2' underground, and it
contains about 4" of foamboard at the thickest point.
deep earth normally has a temperature close to the average annual air temp, but
in this case, the house with uninsulated underground walls is used as a central
heater to slowly warm ("it takes three years to fully climatize the soil around
the home") and bias the earth to a higher temperature (eg from 45 to 68 f)
under the umbrella. passive solar heat is one way to do this, allowing sun to
shine into the house through windows ("whatever you wish the average indoor
temperature to be, adjust the inside temperature to be about 3 or 4 f (1.5-2 c)
higher in the summertime. the whole structure should swing only about 6 to 8 f
(3.3-4.4 c) all year.") another way is to make use of seasonal air temperature
differences. he describes a possible origin of his system:
baked dry in august... frozen stiff all winter, a montana sodbuster and his
neighbors battled the elements. they shivered through the frigid northern
winters, gathering buffalo chips for fuel, to ward off the frostbite.
our field farming friend noticed that the vegetables in his root cellar
never got hot and never got cold. they were always comfortable. he wasn't!
so he installed a window in this root cellar and moved in.
within the first year, the unheated indoor temperature rose from its natural
45 f (7 c) to 55 (13 c), all by itself. this drastically reduced the amount
of fuel he needed, but his neighbors just laughed at him and continued
gathering buffalo chips.
this rise in temperature was a surprise improvement, since everyone had
told him that it would always be 45 (7 c) no matter what. mulling this over
in his mind he tohought: "if i could only raise the termperature another
10 or 15 degrees (6-8 c)... i wouldn't need any buffalo chips at all."
but how can you intentionally raise the constant temperature that occurs
naturally in the earth? well, he had already raised that average temperature
about ten degrees by installing the window. he reasoned, "it must be like
raising the natural level of a lake. you let more water in and less water
out. that's it!"
he grabbed his hat and dashed into town. soon he returned with a pickup load
of styrofoam insulation and several rolls of plastic sheeting. he put the
insulation and plastic over the top of his home, dirt and all, and covered
the whole thing with another layer of earth.
all summer long, the heat which collected inside soaked into the ground to
keep his home cool and comfortable. just as he had suspected, the newly
insulated earth began warming up from 55 to 65 (13-18 c) and, finally by
fall, all the way up to 71 degrees (22 c.) when cold weather arrived, the
earth remained warm and kept his new earth sheltered abode cozy all winter.
our subterranean sodbuster was at last _continuously comfortable._ he had
invented passive annual heat storage!
and his neighbors? well, times have changed. now a big monopoly collects
and distributes all the buffalo chips... and goes to the public service
commission each month to ask for a rate hike.
hait says the us r-value of earth is often assumed to be about 0.08 per inch
(about r1 per foot) vs 3 to 7 per inch for many commercial insulations. hence,
we have something like an r20 wall with lots of thermal mass (20 btu/f-ft^3
would make rc roughly 4,000 hours, ie 6 months, with the capacitor in the
center of the r20 resistor and both ends of it at a low-impedance) if heat
has to travel 20' horizontally before escaping upwards. hait also points out
that a wall thicker than 20' doesn't add much effective thermal mass, since
the winter cold front that travels into the wall becomes a warm front after
6 months, and heatflow reverses. i guess most people would say it's easier
to build a wall with 6" of fiberglass insulation than to arrange this sort
of earth umbrella. we might cover a house with polyethylene film and surround
it with a gigantic earth berm, with a ring of tires to make the outer walls
steeper, and 2' of some sort of fluffy compost on top, over plastic film...
hait has an interesting way of providing fresh air and conducting and storing
heat in the earth around the house, like this:
earth earth earth earth
uuuuuuuuuuuuuuuuuuuuuumbrella
solar gain --------------------- <-> uuuuuuuuuuuuuuuuuuu
uu \ | | \ upper earth tube uuu
uu | house | \ uu
lower earth tube<-->| | \
---------------------
the lower earth tube slopes up to the house (to make an igloo-like heat trap)
and enters the living space at floor level. the upper earth tube enters at
ceiling level, and slopes down to exit at the same outdoor level as the lower.
if the house becomes slightly warmer than the surrounding earth, outside air
naturally enters the lower earth tube and warm air flows out of the upper one.
if the house becomes cooler than the surrounding earth, flow reverses. in
either case, heat is exchanged between earth tube air and surrounding earth,
storing excess house heat in the earth or removing it to heat the house.
he suggests eliminating the windows and turning all this upside down, with
upward sloping earth tubes (making a cold trap), to make this into a permanent
cold storage place in a cold climate.
the book ends with design guidelines:
insulation/watershed umbrella:
1. extend umbrella out and around the entire home and above also, if
the home is fully earth sheltered.
2. extend out 20 feet (6 m) wherever possible.
3. taper insulation from 4 inches (10 cm) down to one (the first inch
is the most important.)
4. insulate the backs of retaining walls and other items that will be
backfilled before the main umbrella goes into place.
5. plastic: (0.006 inch (0.15 mm), largest sheets practical.)
a. 3 layers min.
b. separate layers with soft insulation or dirt that will drain well.
c. provide adequate drainage out the end of the umbrella.
d. do not stretch, but allow for settling with folds and slipping overlaps.
e. lay like shingles.
f. prevent future ponding after settling by allowing sufficient
drainage angles.
g. pay particular attention to possible extreme settling and the problems
that might occur given its new confuguration.
h. make underground gutters to guide water off the front and away from
the building.
i. cover it with flashing if it exits the ground.
earth tubes:
1. size... 4 to 18 inches (4-46 cm) in diameter.
2. length...60 feet (18 m) min. more like 100-200 ft.
3. must go downhill from the house at least a foot plus the tube diameter.
4. must be kept relatively level (1/4 inch to the foot for drainage in
those places where heat exchange is to be minimized.
5. the greatest angle of grade must be in those areas where heat
exchange is preferred.
6. at least two tubes must be used.
a. one enters the home at the highest point where air can be taken.
b. the other enters the home at the lowest point where air can enter.
7. provide for condensation removal.
8. provide for backfill settling so that the tubes will not be sheared off.
(backfull with gravel under the tubes.)
9. provide bug screens.
10. a small umbrella should be provided over the tube if it is not
under the main umbrella (about 8' wide, full length.)
11. do not "short out" the storage zone of an earth tube by placing it
too close to an interior wall so that conduction becomes a more
prominent factor than the convection through the tube.
12. plastic tubes should work quite well; their r-factor is small (given their
thickness) and they can withstand the earth environment for a long time.
internal design:
1. light colored walls and ceilings to spread the heat around.
2. medium colored floors so they will be slightly warmer than the ceiling,
to help avoid stagnation.
3. carpet should make little difference [hait likes mike oehler's carpet
over poly film over earth.]
4. allow for free flow of air between places where sun comes into the home and
conductive surfaces near storage, so heat can be transferred by convection.
5. provide a place for the warm air to go.
6. provide a place for the cool air to go.
window layout:
1. use moderately sized windows. greater than the 10% required by law [?],
and less than the usual passive solar recommendation. probably about
25 to 30% of the equivalent floor area in glazing.
2. do not localize the windows all on the south, as if it were a regular
passive solar building. spread the windows out so the heat input is
spread over the whole day.
3. at the same time (be careful) do not severely reduce the conductive
surface area, and thus the storage mass accessibility.
adjustments:
1. external shading devices that are adjustable!
2. earth tube shut-offs and one way doors.
3. windows, floor vents, skylights.
4. provide for cross ventilation and high and low vents also with earth tubes.
monitoring:
at least, monitor critical temperatures inside, outside, and in the
storage mass.
waterproofing:
insulation/watershed umbrella.
gravity drainage.
do not allow hydrostatic pressure from water table.
at least one layer of plastic as a vapor barrier.
use the complete water control program.
nick
Passive Annual Heat Storage: Improving the Design of Earth Sheltered Homes – Mother Earth News — Earth Sheltered Homes | Passive Annual Heat Storage
Passive Annual Heat Storage: Improving the Design of Earth Sheltered Homes – Mother Earth News — Earth Sheltered Homes | Passive Annual Heat Storage
Are you pooped out from paying the power people to pump heat into your home all winter, only to pay them again to pump it back out all summer? If so, maybe it’s time to open a special sort of back-to-the-land savings account—one that will let you make energy deposits all summer and withdrawals in the winter. And just where do you put six months of intense seasonal sunshine for safekeeping? To find the answer, you only have to look down, because you’re standing on the bank!
As you know, the earth exchanges heat constantly, soaking it up from the sun all summer and giving it up to the atmosphere in the winter. In most areas, this annual flux doesn’t level off until a depth of about 20 feet is reached—where the year-round temperature hovers near the average annual air temperature. A 20-foot depth of earth, then, can be a mighty big savings account, and it’s dirt cheap. However, to open such an account, you’ve got to figure out how to make deposits and withdrawals, and you ought to find a way to keep the vault secure from robbers.
The technique calls for a specially designed cap, known as an insulation/watershed umbrella, that’s placed a few feet above an underground building’s roof (not against it), extending outward to isolate the earth around the structure from the temperature fluctuations of surface layers.
Windows on the south side of the dwelling let sunshine in to heat all the mass within the insulating umbrella. Slowly—ever so slowly over the whole year—a balance is achieved between the warmth of the summer sun and winter heat loss. Thus, an artificial average annual air temperature is established at the junction of the house’s walls and the earth. Prevailing temperatures inside the building will be transmitted through the walls and into the earth, extending to a radius of at least 20 feet from the structure. By controlling the amount of sunshine let into the house and the amount of heat rejected (by shading and ventilation), it’s possible to adjust the temperature of the surrounding soil with some precision.
Because of the tremendous mass of the building and surrounding soil—a volume of about 45,000 cubic feet (1,800 tons) for the 20 feet beside and below a 30-foot-diameter home—the interior temperature will vary only a few degrees throughout the year. And unless a major change is made in the annual heat-flow balance, it will typically float between about 76°F in the summer and about 70°F in the winter . . . without any additional form of heating or cooling required!
Nonetheless, fine homes have been built that capitalize on winter sunshine to offset a major portion of their heating bills. And some use can be made of solar gain even in the most frigid locales. However, in order to prevent overheating, these conventional active and passive solar homes are forced to discard (by shading) most of the summer’s lavish supply of energy. And in a majority of climates, early attempts to use earth sheltering for storage have been thwarted by the need to insulate walls, thus crippling (or eliminating) a dwelling’s thermal link with the earth’s mass.
Still, these precursors to the passive annual heat-storage system have paved the way by demonstrating the principles of a more efficient form of construction. It’s been obvious for years that the earth around an underground structure—even when it’s separated by insulation—soaks up heat from the building when the interior temperature rises above that of the soil . . . and that, given the right circumstances, the earth will return heat to the building when the interior temperature drops below that of the soil. Earth-sheltered homes have long been known to have slowly changing temperatures that are largely controlled by the earth around them. The average of this annual flux is often referred to as the floating temperature by people who design and live in such buildings. If the auxiliary heat is kept off, the temperature will assume a certain level that is related to the climate of the area. In the late winter in Montana, for example, a conventional earth shelter might have a floating temperature of around 50-55°F. But oddly enough, the average annual air temperature (and thus the deep-earth temperature) in Montana is only 43-1/2°F!
Many designers at first assumed that an earth-sheltered house would take on the natural soil temperature, but experience has shown that this just isn’t the case. Even an “old-fashioned” underground building modifies the temperature of the earth around its walls, because the owners add heat to the building (and therefore to the dirt around it) for comfort. The result is an adjusted floating temperature, and passive annual heat storage’s trick is to get that temperature into the comfort zone.
Geodome needs to have only 6% of its 3,000 square feet of floor space in windows, which is a lower percentage than either passive solar or conventional construction employs, because the building obtains most of its solar heating during the summer months.
By the end of the first summer after Geodome’s completion, an array of 48 sensors buried in the dirt indicated that temperatures 12 feet out from the north wall had risen to 64°F . . . 20°F higher than normal. In fact, the sensor array indicated that the entire ball of earth within the umbrella had very slowly been heated by the solar-heated home that sat at its core.
The following summer, shades were used on the most directly solar-exposed windows, and—naturally—the interior and earth temperatures dropped slightly, so that the late-winter floating temperature hit a low of about 63°F. But, like all good earth shelters, the home was still very energy-efficient: It actually used less energy for space heating than was consumed in warming water for domestic use! And the experiment has proved that the floating temperature of a passive annual heat-storage building is adjustable.
An umbrella extending 20 feet from the walls is only sufficient, however, if the earth under the umbrella is dry. Though damp dirt has greater heat capacity than dry earth, the greater thermal conductivity of water allows too much heat to escape the confines of the insulated cap. It’s inadvisable to build any earth-sheltered home where there’s a high water table, and that same restriction applies to a passive annual heat-storage dwelling. But it’s also important to protect the earth within the insulating umbrella from surface water; hence, the layers of insulation in the cap are interspersed with water barriers to shunt liquid down the upper surface of the umbrella to a drainage system.
The insulation/watershed umbrella we use in Montana consists of a four-inch-thick (at the center) sandwich of two layers of insulation and three sheets of plastic, which tapers down to one inch in thickness at the outer edge. In addition, we superinsulate (above R-30) the exposed surface of a PAHS building to reduce losses to the air. A good thermal connection between the house and the earth around it is important, so we don’t insulate the backfilled portions of the building at all. Doing so would merely force us to overheat the house during summer to drive heat into the earth. As it is, Geodome varies only 6-10°F through the seasons. (Still, we have found that it’s a good idea to have shades to adjust the summertime interior temperature.)
Now, not only can homes be situated in a constant-temperature environment that will never need auxiliary heating, but the same principles can also be applied to help keep houses cool in hot climates. Or, if a separate 40-to-60-foot ball of earth were insulated and heated with high temperature collectors during the summer, it could provide a year-round—and free —supply of solar-heated domestic hot water. At higher temperatures—say, the 300°F levels possible from parabolic solar collectors—a source of steam for power generation could even be contained in an insulated heat-storage “ball.” And, at the other end of the scale, heat could be spilled in the winter from an insulated mass to form a year-round passive refrigerator.
In short, it now is evident that solar technology no longer need be hamstrung by the earth’s 22-1/2° tilt: Passive annual heat storage truly takes solar energy out of the dark seasons… and probably out of the dark ages, as well!
Article first appeared in Mother Earth News, January/February 1985. Click here to view article at their
Are you pooped out from paying the power people to pump heat into your home all winter, only to pay them again to pump it back out all summer? If so, maybe it’s time to open a special sort of back-to-the-land savings account—one that will let you make energy deposits all summer and withdrawals in the winter. And just where do you put six months of intense seasonal sunshine for safekeeping? To find the answer, you only have to look down, because you’re standing on the bank!
As you know, the earth exchanges heat constantly, soaking it up from the sun all summer and giving it up to the atmosphere in the winter. In most areas, this annual flux doesn’t level off until a depth of about 20 feet is reached—where the year-round temperature hovers near the average annual air temperature. A 20-foot depth of earth, then, can be a mighty big savings account, and it’s dirt cheap. However, to open such an account, you’ve got to figure out how to make deposits and withdrawals, and you ought to find a way to keep the vault secure from robbers.
PASSIVE ANNUAL HEAT STORAGE (PAHS)
What I’m talking about, of course, is passive solar earth sheltering, but not just any old rendition of those now-familiar concepts of energy-efficient construction. Passive annual heat storage is a new approach to using the earth to store solar heat—one that treats dirt surrounding a dwelling as a part of the structure’s thermal mass by insulating it from the elements . . . but not from the walls.The technique calls for a specially designed cap, known as an insulation/watershed umbrella, that’s placed a few feet above an underground building’s roof (not against it), extending outward to isolate the earth around the structure from the temperature fluctuations of surface layers.
Windows on the south side of the dwelling let sunshine in to heat all the mass within the insulating umbrella. Slowly—ever so slowly over the whole year—a balance is achieved between the warmth of the summer sun and winter heat loss. Thus, an artificial average annual air temperature is established at the junction of the house’s walls and the earth. Prevailing temperatures inside the building will be transmitted through the walls and into the earth, extending to a radius of at least 20 feet from the structure. By controlling the amount of sunshine let into the house and the amount of heat rejected (by shading and ventilation), it’s possible to adjust the temperature of the surrounding soil with some precision.
Because of the tremendous mass of the building and surrounding soil—a volume of about 45,000 cubic feet (1,800 tons) for the 20 feet beside and below a 30-foot-diameter home—the interior temperature will vary only a few degrees throughout the year. And unless a major change is made in the annual heat-flow balance, it will typically float between about 76°F in the summer and about 70°F in the winter . . . without any additional form of heating or cooling required!
THE NEED FOR BETTER DESIGNS FOR PASSIVE SOLAR HOMES
In the past, solar homes haven’t been universally practical simply because in many areas the sun doesn’t shine enough in the winter. In some areas, such as upstate New York, cloud cover blocks direct radiation on at least two-thirds of the winter days. And farther north—in much of Canada, for example—the few hours between dawn and dusk in January just don’t have much heat to offer.Nonetheless, fine homes have been built that capitalize on winter sunshine to offset a major portion of their heating bills. And some use can be made of solar gain even in the most frigid locales. However, in order to prevent overheating, these conventional active and passive solar homes are forced to discard (by shading) most of the summer’s lavish supply of energy. And in a majority of climates, early attempts to use earth sheltering for storage have been thwarted by the need to insulate walls, thus crippling (or eliminating) a dwelling’s thermal link with the earth’s mass.
Still, these precursors to the passive annual heat-storage system have paved the way by demonstrating the principles of a more efficient form of construction. It’s been obvious for years that the earth around an underground structure—even when it’s separated by insulation—soaks up heat from the building when the interior temperature rises above that of the soil . . . and that, given the right circumstances, the earth will return heat to the building when the interior temperature drops below that of the soil. Earth-sheltered homes have long been known to have slowly changing temperatures that are largely controlled by the earth around them. The average of this annual flux is often referred to as the floating temperature by people who design and live in such buildings. If the auxiliary heat is kept off, the temperature will assume a certain level that is related to the climate of the area. In the late winter in Montana, for example, a conventional earth shelter might have a floating temperature of around 50-55°F. But oddly enough, the average annual air temperature (and thus the deep-earth temperature) in Montana is only 43-1/2°F!
Many designers at first assumed that an earth-sheltered house would take on the natural soil temperature, but experience has shown that this just isn’t the case. Even an “old-fashioned” underground building modifies the temperature of the earth around its walls, because the owners add heat to the building (and therefore to the dirt around it) for comfort. The result is an adjusted floating temperature, and passive annual heat storage’s trick is to get that temperature into the comfort zone.
THE FIRST EXAMPLE: AN EARTH SHELTERED GEODESIC DOME
The world’s first earth sheltered geodesic dome has achieved that goal! Built in 1981, the Geodome has a polystyrene/polyethylene (insulation/watershed) umbrella that’s roughly half the size that we now know to be needed for optimum performance. Despite the minimal size of the protective cap, after its first summer of soaking up sunlight, the Geodome’s late-winter floating temperature was 66°F!Geodome needs to have only 6% of its 3,000 square feet of floor space in windows, which is a lower percentage than either passive solar or conventional construction employs, because the building obtains most of its solar heating during the summer months.
By the end of the first summer after Geodome’s completion, an array of 48 sensors buried in the dirt indicated that temperatures 12 feet out from the north wall had risen to 64°F . . . 20°F higher than normal. In fact, the sensor array indicated that the entire ball of earth within the umbrella had very slowly been heated by the solar-heated home that sat at its core.
The following summer, shades were used on the most directly solar-exposed windows, and—naturally—the interior and earth temperatures dropped slightly, so that the late-winter floating temperature hit a low of about 63°F. But, like all good earth shelters, the home was still very energy-efficient: It actually used less energy for space heating than was consumed in warming water for domestic use! And the experiment has proved that the floating temperature of a passive annual heat-storage building is adjustable.
WHAT’S NEEDED FOR THIS PASSIVE SOLAR DESIGN?
An entire year’s worth of heating and cooling (three to five million BTU) can be contained in an area that extends outward about 20 feet from the walls of a house. Furthermore, over this distance the accumulated resistance to heat flow (R-factor) is sufficient to block 90% of the loss.An umbrella extending 20 feet from the walls is only sufficient, however, if the earth under the umbrella is dry. Though damp dirt has greater heat capacity than dry earth, the greater thermal conductivity of water allows too much heat to escape the confines of the insulated cap. It’s inadvisable to build any earth-sheltered home where there’s a high water table, and that same restriction applies to a passive annual heat-storage dwelling. But it’s also important to protect the earth within the insulating umbrella from surface water; hence, the layers of insulation in the cap are interspersed with water barriers to shunt liquid down the upper surface of the umbrella to a drainage system.
The insulation/watershed umbrella we use in Montana consists of a four-inch-thick (at the center) sandwich of two layers of insulation and three sheets of plastic, which tapers down to one inch in thickness at the outer edge. In addition, we superinsulate (above R-30) the exposed surface of a PAHS building to reduce losses to the air. A good thermal connection between the house and the earth around it is important, so we don’t insulate the backfilled portions of the building at all. Doing so would merely force us to overheat the house during summer to drive heat into the earth. As it is, Geodome varies only 6-10°F through the seasons. (Still, we have found that it’s a good idea to have shades to adjust the summertime interior temperature.)
BACK-TO-BASICS: UNDERSTANDING HEAT FLOW
Passive annual heat storage leads us to reexamine our basic thinking on heat flow and on the use of earth as a practical thermal storage medium. At the same time, it dramatically widens the horizons of passive solar energy, which for centuries has been hobbled by the fact that the sun wasn’t out when work needed to be done.Now, not only can homes be situated in a constant-temperature environment that will never need auxiliary heating, but the same principles can also be applied to help keep houses cool in hot climates. Or, if a separate 40-to-60-foot ball of earth were insulated and heated with high temperature collectors during the summer, it could provide a year-round—and free —supply of solar-heated domestic hot water. At higher temperatures—say, the 300°F levels possible from parabolic solar collectors—a source of steam for power generation could even be contained in an insulated heat-storage “ball.” And, at the other end of the scale, heat could be spilled in the winter from an insulated mass to form a year-round passive refrigerator.
In short, it now is evident that solar technology no longer need be hamstrung by the earth’s 22-1/2° tilt: Passive annual heat storage truly takes solar energy out of the dark seasons… and probably out of the dark ages, as well!
Article first appeared in Mother Earth News, January/February 1985. Click here to view article at their
Monday, February 7, 2011
stony run farm
stony run farm
Supposedly, she's editing Book II of her post-apoc for print publication, but she's distracted by the goings-on in the Middle East and the possible link between those and food shortages and between food shortages and what Stony Run's all about. So she's been fantasizing about how she thinks everyone's yard should look -- drawing on her touchpad again (crudely) with Paint. If you want to see how this sort of thing looks when drawn by an expert, see Aaron Newton's blog. Better yet, take the class he's offering with Sharon Astyk (see same post).
The diagram echoes similar images in books with "self-sufficient" in the title. No, she doesn't think self-sufficiency is all that possible, and thinks resilience is a better term. Other things being equal, the more you can take care of yourself sustainably, the more everybody else doesn't have to decide whether to take care of you. She likes this concept at any scale: personal, family, extended family, peer group, neighborhood, community, region, nation, continent -- and recognizes that minerals and mineral-based products have their place in the scheme of things -- but thinks the main thing to be more resilient in is access to food and water.
To which end, she's always recommending rural or small town over urban, ownership over rental, free and clear over debt: your own patch of arable land, with enough water, and scaled to get by without oil-intensive machinery if necessary. On a foundation of working-class subsistence farming, any locality is much more resistant to the Four Horsemen than it might otherwise be. Large urban centers, dependent upon massive transportation networks carrying the produce of industrial-scale farming, fishing, mining, and production worldwide, are more vulnerable.
In the drawing above, she's visualizing a half-acre's worth of resiliency. She'd say something about Permaculture at this point, but has noticed that when she says "permaculture," those to whom she's speaking think "hippie" -- and that's where the conversation grinds to a halt. This happens in her head, too, alas. So instead, she'll just say that the activities on this site are "diversified." If you do like the word "permaculture," just re-draw Risa's diagram with lots of really curvy lines instead of straight ones and you're all set.
Yes, it's aimed at a suburban "western" readership and of little use to people in "developing" nations. Yes, it all comes to naught if things happen fast. She's aware it's an interim fantasy. Etc. But for the sake of discussion, bear with us a bit here, please.
![The Encyclopedia of Country Living [Book]](http://books.google.com/books?id=cw9JKgAACAAJ&printsec=frontcover&img=1&zoom=1&l=90)
For futher information, you could do worse than to start with Carla. ==>
Here are the labels for the image:
a -- house. Consider energy audit, retrofit, passive solar, wood, composting toilet, greywater. Points if the house emphasizes access to visiting, music-making, board games, reading and such over having a 60-inch flat screen TV. Extra points for access to non-electric lighting, just in case. Double points if there's something you can do in here for a living. Be able to cook. Be able to cook solar. Be able to cook on wood. Be able to preserve foods -- especially without a freezer.
b. -- garage. (Roofs, and walls, are white here for a reason. You might not have air conditioning. If you can, develop water catchment from these as well.) Practice a skill here, such as candlemaking or ironmongering. Big points for being a doctor, veterinarian, or dentist.
c. -- well house. If they don't allow wells where you are, move. Otherwise, perhaps, be surreptitious. If possible put it on its own separate circuit, with a freeze-proof hydrant nearby, in case of house fire. Add supplementary non-electric pump.
d. -- Potting shed/toolshed. Cold frames, hoophouses or greenhouse in this vicinity a plus.
e. -- barn. A little shed will do. This one is for two milk goats plus poultry. YMMV.
f. -- garden beds, polycultural. Tomatoes and lettuce are nice, but think beans, potatoes, squash, corn, kale. Things to live on.
g. -- orchard. Semi-dwarf fruits, nuts. Start now; nuts are a long time coming.
h. -- "chicken moat." Poultry live in the orchard and mostly not in the garden or your play space. They eat bugs that like your orchard and bugs that are migrating toward your garden. Points if you run vining crops along the fences.
i. -- goats. Fence well; they love young fruit and nut trees.
j. -- vehicle access. A pickup will be necessary in the near term; if you live to see the return of horse carts, you'll still want to get things to your barn and potting shed.
k. -- path to potting shed and barn should withstand heavy rains; if you slip and break a leg, well there you are.
l. -- shade trees to hang out under on breaks in summer, reading a book maybe. Remember books? Bonus if the trees are "standard" size fruit/nut trees.
m. -- your play space. Toss an old Frisbee; they don't need batteries and will be with us forever. Add a garden swing.
![The Concise Guide to Self-Sufficiency [Book]](http://books.google.com/books?id=h1yRAAAACAAJ&printsec=frontcover&img=1&zoom=1&l=90)
If you're young and ambitious, and have room, put in a vineyard, a cross-fenced pasture, assorted fields, fish pond, and woodlot. Bees are nice, too. Here's some discussion of managing a larger place ==>
If you're old like Risa, don't bother; you can only do so much, and after sixty, what you can do diminishes steadily, like the orchestral chord at the end of Tchaikovsky's 6th symphony. And that's if you're healthy. So then convert some of the raised beds into berry patches and grape arbors accordingly, reduce the flocks, spend more time sitting in the swing at point "l" (shade trees), and tell stories to the grandkids. Then try for a graceful exit, leaving the place better than you found it -- for descendants if they're interested. If they're not, don't trouble yourself about it; the stars will continue to shine.
Supposedly, she's editing Book II of her post-apoc for print publication, but she's distracted by the goings-on in the Middle East and the possible link between those and food shortages and between food shortages and what Stony Run's all about. So she's been fantasizing about how she thinks everyone's yard should look -- drawing on her touchpad again (crudely) with Paint. If you want to see how this sort of thing looks when drawn by an expert, see Aaron Newton's blog. Better yet, take the class he's offering with Sharon Astyk (see same post).
The diagram echoes similar images in books with "self-sufficient" in the title. No, she doesn't think self-sufficiency is all that possible, and thinks resilience is a better term. Other things being equal, the more you can take care of yourself sustainably, the more everybody else doesn't have to decide whether to take care of you. She likes this concept at any scale: personal, family, extended family, peer group, neighborhood, community, region, nation, continent -- and recognizes that minerals and mineral-based products have their place in the scheme of things -- but thinks the main thing to be more resilient in is access to food and water.
To which end, she's always recommending rural or small town over urban, ownership over rental, free and clear over debt: your own patch of arable land, with enough water, and scaled to get by without oil-intensive machinery if necessary. On a foundation of working-class subsistence farming, any locality is much more resistant to the Four Horsemen than it might otherwise be. Large urban centers, dependent upon massive transportation networks carrying the produce of industrial-scale farming, fishing, mining, and production worldwide, are more vulnerable.
In the drawing above, she's visualizing a half-acre's worth of resiliency. She'd say something about Permaculture at this point, but has noticed that when she says "permaculture," those to whom she's speaking think "hippie" -- and that's where the conversation grinds to a halt. This happens in her head, too, alas. So instead, she'll just say that the activities on this site are "diversified." If you do like the word "permaculture," just re-draw Risa's diagram with lots of really curvy lines instead of straight ones and you're all set.
Yes, it's aimed at a suburban "western" readership and of little use to people in "developing" nations. Yes, it all comes to naught if things happen fast. She's aware it's an interim fantasy. Etc. But for the sake of discussion, bear with us a bit here, please.
For futher information, you could do worse than to start with Carla. ==>
Here are the labels for the image:
a -- house. Consider energy audit, retrofit, passive solar, wood, composting toilet, greywater. Points if the house emphasizes access to visiting, music-making, board games, reading and such over having a 60-inch flat screen TV. Extra points for access to non-electric lighting, just in case. Double points if there's something you can do in here for a living. Be able to cook. Be able to cook solar. Be able to cook on wood. Be able to preserve foods -- especially without a freezer.
b. -- garage. (Roofs, and walls, are white here for a reason. You might not have air conditioning. If you can, develop water catchment from these as well.) Practice a skill here, such as candlemaking or ironmongering. Big points for being a doctor, veterinarian, or dentist.
c. -- well house. If they don't allow wells where you are, move. Otherwise, perhaps, be surreptitious. If possible put it on its own separate circuit, with a freeze-proof hydrant nearby, in case of house fire. Add supplementary non-electric pump.
d. -- Potting shed/toolshed. Cold frames, hoophouses or greenhouse in this vicinity a plus.
e. -- barn. A little shed will do. This one is for two milk goats plus poultry. YMMV.
f. -- garden beds, polycultural. Tomatoes and lettuce are nice, but think beans, potatoes, squash, corn, kale. Things to live on.
g. -- orchard. Semi-dwarf fruits, nuts. Start now; nuts are a long time coming.
h. -- "chicken moat." Poultry live in the orchard and mostly not in the garden or your play space. They eat bugs that like your orchard and bugs that are migrating toward your garden. Points if you run vining crops along the fences.
i. -- goats. Fence well; they love young fruit and nut trees.
j. -- vehicle access. A pickup will be necessary in the near term; if you live to see the return of horse carts, you'll still want to get things to your barn and potting shed.
k. -- path to potting shed and barn should withstand heavy rains; if you slip and break a leg, well there you are.
l. -- shade trees to hang out under on breaks in summer, reading a book maybe. Remember books? Bonus if the trees are "standard" size fruit/nut trees.
m. -- your play space. Toss an old Frisbee; they don't need batteries and will be with us forever. Add a garden swing.
If you're old like Risa, don't bother; you can only do so much, and after sixty, what you can do diminishes steadily, like the orchestral chord at the end of Tchaikovsky's 6th symphony. And that's if you're healthy. So then convert some of the raised beds into berry patches and grape arbors accordingly, reduce the flocks, spend more time sitting in the swing at point "l" (shade trees), and tell stories to the grandkids. Then try for a graceful exit, leaving the place better than you found it -- for descendants if they're interested. If they're not, don't trouble yourself about it; the stars will continue to shine.
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