Here is a promised, periodic update on the solar greenhouse experiment we are conducting in our Concord household. To review: it's a 21' x 48' greenhouse. We are trying to use as few technological and electric-driven inputs as possible.
A "solar greenhouse" means that no additional heat sources are used beyond those that are naturally occurring. These include the sun, geothermal heat from the ground, and any heat that can be generated from the exothermic processes of decomposition (such as composting). (We have not been using decomposition heat until the past couple of weeks... and have no idea how much it is contributing to the total heat in the greenhouse.)
January was cool-to-cold in the greenhouse -- even on sunny days. Nights were so cold that we used our only non-natural source of heat under the cover of the mushroom logs: a single 40 watt light bulb. We had inoculated the logs with shitake spawn in a too-cold part of the season for good colonization by the mycelium. It would be fine if the logs experienced freezing temperatures, but not all the time. December and January just weren't warm enough to leave them outside unprotected. Starting sometime in April, the logs will spend the rest of their lives (which could be several years) outside under our spruce trees.
Things Start Heating Up in February, March
Early February saw a string of bright, sunny days, and the strength of the sun was such that it was simply heaven in the greenhouse: 70-80 degrees, humid, and smelling of living plants and fragrant earth. Friends and neighbors who wandered into the greenhouse would sit in a daze muttering, "Ohmygoodness... it's so amazing in here. I can't believe it," staying for hours in a tranced out state of bliss. Using a typical 18" oscillating household fan on a stand, we were able to mix the warmer air at the top with the cooler air near the ground quite effectively. The below-the surface soil temperature remained in the upper 30's... not warm, but warmer than outside air temperatures.
We finally dared to plant out the winter-hardy vegetable plants we had started in the house in the Fall. They did fine under a layer floating row cover, and even started putting on growth. We also experimented successfully with pieces of reflective insulation ("Reflectix") made into rounded cloches. By late February, we were having to open the 4-foot exterior door in the mid-afternoons for a couple of hours to vent out the excess heat, lest it be 90 degrees at the top. We started enjoying light harvests of greens such as broccoli raab, arugala, turnip greens, red mustard, and a variety of Asian vegetables such as bok choy and tatsoy.
In early March, it started to become hot in the greenhouse -- 100 degrees or more at peek. We would vent the hot air earlier and earlier in the day as the calendar "Marched" on, needing to put that fan in the open doorway to facilitate cool outside air intake. We use a gallon jug of water to prop open this northwest-facing door. One noon in early March, I noticed as I put it in place to vent some 105 degree air, that the water inside the jug was partly frozen. This represented an approximately 70 degree difference between inside/upper air and outside, in-the-shade temperatures!
By mid-March, we were enjoying several-servings-weekly of fresh vegetables from the greenhouse. And we had to cut a window in the end without the door for cross-ventilation. We cut out the upper triangle at the peak, using a long piano hinge to form the window. We are now temporarily shutting it with tape at night while we wait for a temperature-sensitive automatic opener/closer arm to arrive in the snailmail. The piston on this arm starts to open at around 70 degrees, and will become fully extended around 90 degrees; and visa versa as it cools. It is run by wax inside that expands/melts and contracts/congeals in response to changing temperatures.
Attack of the Killer Tomatoes?
And then the Tomato Plant Crisis began. Tomato seeds we had planted in our own house on February 1 for three indeterminant varieties got so large by the time they were 5 and 6 weeks old, they started to set buds. Now, they were not strangled because their were in tiny pots -- they had been planted up to 2-3 quart containers because they were growing so fast. Seeing that the below-the-surface ground temperature had risen to 50 degrees, and not knowing what else to do, on the last day of winter I planted six in the greenhouse to see how they'd do, protecting them at night. They did fine! This past weekend I planted six more... and still we have at least 20 more giant plants of equal size and maturity waiting for a home in 2-3 quart containers.
Clearly. Something. Must. Be. Done.
But having a greenhouse filled ONLY with tomato plants was not what we had in mind. We are examining a variety of alternatives, including hanging bags where our (still small) determinate variety will grow, making more bedding room for their bigger, more mature cousins. This is a case where we''re being stymied by too much success.
Not that I am truly complaining. The strong scent of the tomato foliage is to me an integral part of the real smell of summer. Sometimes after working with them, I then brush the leaves of our still-small green, purple, and lemon basil seedlings, mixing their frangrances, anticipating the supreme pleasure of eating them together sometime in the close in the near future.
A "solar greenhouse" means that no additional heat sources are used beyond those that are naturally occurring. These include the sun, geothermal heat from the ground, and any heat that can be generated from the exothermic processes of decomposition (such as composting). (We have not been using decomposition heat until the past couple of weeks... and have no idea how much it is contributing to the total heat in the greenhouse.)January was cool-to-cold in the greenhouse -- even on sunny days. Nights were so cold that we used our only non-natural source of heat under the cover of the mushroom logs: a single 40 watt light bulb. We had inoculated the logs with shitake spawn in a too-cold part of the season for good colonization by the mycelium. It would be fine if the logs experienced freezing temperatures, but not all the time. December and January just weren't warm enough to leave them outside unprotected. Starting sometime in April, the logs will spend the rest of their lives (which could be several years) outside under our spruce trees.
Things Start Heating Up in February, March
Early February saw a string of bright, sunny days, and the strength of the sun was such that it was simply heaven in the greenhouse: 70-80 degrees, humid, and smelling of living plants and fragrant earth. Friends and neighbors who wandered into the greenhouse would sit in a daze muttering, "Ohmygoodness... it's so amazing in here. I can't believe it," staying for hours in a tranced out state of bliss. Using a typical 18" oscillating household fan on a stand, we were able to mix the warmer air at the top with the cooler air near the ground quite effectively. The below-the surface soil temperature remained in the upper 30's... not warm, but warmer than outside air temperatures.
We finally dared to plant out the winter-hardy vegetable plants we had started in the house in the Fall. They did fine under a layer floating row cover, and even started putting on growth. We also experimented successfully with pieces of reflective insulation ("Reflectix") made into rounded cloches. By late February, we were having to open the 4-foot exterior door in the mid-afternoons for a couple of hours to vent out the excess heat, lest it be 90 degrees at the top. We started enjoying light harvests of greens such as broccoli raab, arugala, turnip greens, red mustard, and a variety of Asian vegetables such as bok choy and tatsoy.
In early March, it started to become hot in the greenhouse -- 100 degrees or more at peek. We would vent the hot air earlier and earlier in the day as the calendar "Marched" on, needing to put that fan in the open doorway to facilitate cool outside air intake. We use a gallon jug of water to prop open this northwest-facing door. One noon in early March, I noticed as I put it in place to vent some 105 degree air, that the water inside the jug was partly frozen. This represented an approximately 70 degree difference between inside/upper air and outside, in-the-shade temperatures!By mid-March, we were enjoying several-servings-weekly of fresh vegetables from the greenhouse. And we had to cut a window in the end without the door for cross-ventilation. We cut out the upper triangle at the peak, using a long piano hinge to form the window. We are now temporarily shutting it with tape at night while we wait for a temperature-sensitive automatic opener/closer arm to arrive in the snailmail. The piston on this arm starts to open at around 70 degrees, and will become fully extended around 90 degrees; and visa versa as it cools. It is run by wax inside that expands/melts and contracts/congeals in response to changing temperatures.
Attack of the Killer Tomatoes?
And then the Tomato Plant Crisis began. Tomato seeds we had planted in our own house on February 1 for three indeterminant varieties got so large by the time they were 5 and 6 weeks old, they started to set buds. Now, they were not strangled because their were in tiny pots -- they had been planted up to 2-3 quart containers because they were growing so fast. Seeing that the below-the-surface ground temperature had risen to 50 degrees, and not knowing what else to do, on the last day of winter I planted six in the greenhouse to see how they'd do, protecting them at night. They did fine! This past weekend I planted six more... and still we have at least 20 more giant plants of equal size and maturity waiting for a home in 2-3 quart containers. Clearly. Something. Must. Be. Done.
But having a greenhouse filled ONLY with tomato plants was not what we had in mind. We are examining a variety of alternatives, including hanging bags where our (still small) determinate variety will grow, making more bedding room for their bigger, more mature cousins. This is a case where we''re being stymied by too much success.
Not that I am truly complaining. The strong scent of the tomato foliage is to me an integral part of the real smell of summer. Sometimes after working with them, I then brush the leaves of our still-small green, purple, and lemon basil seedlings, mixing their frangrances, anticipating the supreme pleasure of eating them together sometime in the close in the near future.
