Imagine on a frigid winter eve coming home after a long days work and opening the your door onto a warm verdant garden room filled with sun and scented geraniums. In the background is the sound of falling water and zebra finches rustling in the foliage of a lemon tree. You pick some dill and a ripe lemon and net a thick Tilapia fish for supper. The last rays of sun glance off the insulation shutters as they close over the glass super insulating the garden from the Arctic night...
I'd expect you'd say they've tried this in the seventies and it doesn't work that well and besides its too expensive. Let me reassure you solar greenhouses work extremely well, are more affordable than your furnace and your thousand dollar annual heating bills.
The dream of a garden home is very real. Solar greenhouses can work a synergy of savings for homes, businesses, schools, family farms, animal husbandry, factories and of course greenhouse operators. Solar greenhouses attached to these buildings could produce clean solar heated air, wash water becomes fertilizer for the gardens. Potentially a home grown family farm industry could arise in the year round cultivation of local produce, promising fresher fruits and vegetables shipped tens of miles verses today's thousands.
Like many people, I was an initial skeptic of the potential of solar greenhouses : the glazing allowed too much heat to escape to the winter night and blocked too much of the sun to be a net heat source; when there was too much heat it was difficult to store it for cloudy days; summer heat made the greenhouse into an oven; and the greenhouse humidity was often too high. I thought there must be a way to control the incoming and outgoing radiation, and a better way to store the heat without filling the greenhouse up with jugs of water. I had just the opportunity to try and improve on some of these common shortcomings.
I designed a cold climate solar greenhouse for Badgersett Research Farm ,near Canton, MN. It would be used to grow seedling trees. The result was a hybrid of passive and active systems in a super insulated envelope. Seven operable insulation shutters automatically closed over the glazing at night providing an R27 or more than a magnitude of improvement over the double paned windows. At sunrise the shutters open providing up to 50% more light inside by reflecting the light off the snow and glass. This exciting development meant not only more heat but more lumens for crops starved of light in the winter months. The shutters alternately shade the greenhouse during hot summer weather reducing the need for venting. The greenhouse is often cooler then outside summer temperatures. Another innovation came with storing heat for cloudy days. Here I designed a thermal envelope around the soil beneath the greenhouse and riddled it with a system of plastic drainage piping. Two fans blow hot air through the pipes, up through the soil, heating and aerating the plants roots. The result is a 100 tons (a ton for every ten square feet) of thermal mass which consumes no additional space in the greenhouse. This exceeds by more then a magnitude the thermal mass of earlier designs. There are indications that the plants may be growing faster as a result of warmer roots. I also designed a system of underground pipes to the outside as a natural thermal siphon and dehumidifier. In summer hot air rising to the ceiling of the greenhouse is drawn outside through ventilators pulling in air through the underground pipes. Since the ground stays around 50 degrees year round this dehumidifies and cools the incoming air. In the winter this cycle is slowed by closing vents and the incoming air is preheated to ground temperature and is, as we know, extremely dry providing wonderful dehumidification. The results of these innovations worked better then anyone had expected.
After three months of design and four months of construction I walked into this contrivance on a frigid January day. My glasses fogged as I passed though the vestibule from ten below to eighty degrees above. I had arrived in Miami without leaving Minnesota. Inside the proud owners, Philip and Mary Rutter were wearing sunglasses and shorts tending their prize hybrid Hazel and Chestnut seedlings for an insatiable customer demand. When their three crop production peaks they will be able to grow over 150,000 seedlings worth over half a million dollars. Granted few of us have such a golden nut growing tree, but with all these bells and whistles at $20 a square foot all of us can afford to bring the this technology home to save real green on our heating bills to say nothing of the health and quality of life issues. The Rutters insisted on being off the utility grid to run fans, lights, pumps and shutters so we integrated a photo voltaic solar array and a wind power generator. Since the normal operation of the greenhouse used only 500 watt hours of electricity (3¢ to 5¢) a day they were now leaving the lights on. Soon each crop in the Rutter's greenhouse will be worth more then the greenhouse.
After a year of favorable test results at Badgersett, including the fourth coldest January on record where the average daytime greenhouse high was in the upper seventies, I was convinced this solar greenhouse stuff was worth taking a closer look. I've since moved back to Wisconsin from Arizona to pursue the symbiotic application of greenhouses to dwellings, and beyond that, the year round production of local produce.
Upon completion of our super insulated straw bale 'A' frame house this summer we will begin the second in a series of prototype greenhouses. This next one will attach to our house via in ground tubes through which fresh solar heated air from the greenhouse will be exchanged for our stale CO2 rich air. Every time we wash a load of clothes or take a shower we'll be sending nutrients to our garden in the form of good old phosphates, and fatty acids. Other household wastes, such as food scrapes and wood stove ashes, will be plowed back into the greenhouse to enrich the soil. This second prototype greenhouse we hope to demonstrate a wider variety of high end winter crops and integrated pest managers. The current construction estimates are between $5 and $10 per square foot depending on material selections such as glass verses polyethylene glazing, and fiberglass verses straw insulation. Our goal is to develop prototypes which are cost effective planet friendly, and easily adaptable to local conditions or specific design applications. We have a long row to hoe (our greenhouse will be 14' by 120' long) before we will be able to claim success at this multifaceted endeavor, but we know evolution and ecology are on our side. We need plants and soils more than they need use!
The symbiosis of billions of years have made animals for plants for microbes; an animals waste is a plants meal. For industrially contrived and unnatural reasons we, particularly in the west (or better north), have "segregated" our corporal remains to the sterile existence of buildings and away from our native habitat. As an architect I am too painfully aware that I, along with my fellow Americans and including Floridians, will spend over 90% or 65 years of our lives inside of these poor-excuses-for-a-life buildings. With the energy crisis of the seventies the further tightening of building envelopes have resulted in sick buildings. It is quite likely we all suffer the effects of sick buildings as evidenced in the increased rate of respiratory illness during the indoor months of winter or conversely summer months in the Sun Belt. Besides, we haven't studied a large control group of people not living in buildings of the high off gassing sort to compare our health with.
Plants and the microbes found in soils have been shown to be effective at cleaning air of noxious volatile organic compounds(VOCs) common to a wide variety of processed building materials. In a series of studies for NASA Dr. B. C. Wolverton has demonstrated a significant abatement of household VOCs such as Phenol Formaldehyde by common house plants. By augmenting the flow of air from the house through and active soil (not sterile potting soil) one could accelerate significantly the consumption and breakdown of the VOCs. While much work needs to be done on qualifying and quantifying the results the basic fact remains that soils in concert with plants is effective at cleaning VOCs in indoor air. So if we integrate greens into our buildings we can make our buildings tighter, polluting the outdoors less, while saving money on energy bills. Chances are we might be healthier, happier, and more productive -all without the aid of Prosaic.
Of course if you're in the position of building a home or office soon you can do it right from the start and use clean or low off gassing building materials and integrate a solar garden room from the start. Many of the glues, binders, coatings and fibers used in our building materials contain high levels of these VOCs. Products like Dacron carpeting, wall paneling, chip boards, acoustic tiles, upholstery foams, vinyl flooring, and wood stains contain many long lived VOCs which keep on giving and off gassing for years. Curiously, as with processed foods, processed building materials are more likely to contain high levels of VOCs then less processed building materials such as wood, ceramic tile, wool carpeting, or straw (for insulation). And likewise in their production are likely to do more damage to our environment then less processed materials.
Living healthier and more planet friendly in buildings for less money is nice but it is only half of the holy grail of the solar garden. The other half is intensive sustainable year round organic food production. In the future the new family farmer will live near cities on as little as a few acre farms with a half acre in solar greenhouse. They will grow year round high end produce, herbs, and flowers while running small animal husbandry operations. By eliminating most or all of the energy required to grow crops year round a solar grower can reduce as much as 15 to 25% of the operating cost (around one dollar per square foot per year). Why then is the state of the art greenhouse a gas guzzeler?
Short sightedness and linear thinking contribute to the gluttonous state of greenhouse design. First, we can blame the interest rate pressures on growers to build cheap, energy inefficient greenhouses. At a buck or two a square foot many kit greenhouses look cheap. That is until you start adding the furnace, huge fans, and the annual heating fuel bill, and ventilating bill, and the emergency backup heaters. Over a period of three to five years that cheap greenhouse will have cost two to three times what it cost to begin with, and with more bills coming every season. Solar greenhouses, on the other hand, are often more expensive up front, but will often pay for themselves in three to five years incurring savings beyond. But why bother with locally grown produce in the middle of winter, which seems quite unnatural anyway,, why not just import it from the sun belt or Mexico? This is where freshness and our food production and distribution system come to shed light on the real gold of the solar greenhouse.
Freshness, whether in flowers, milk, eggs, or herbs, is the mantra of good marketing. It is also the promise of solar greenhouse crops grown near their markets. Ironically we Americans have never been further from our food, and never before has a successful species risks such a distance from sustenance. In 1979, after the Iranian oil embargo, the Department of defense conducted a study of the average distance food traveled in the US from the field to the dining tables of Americans. At that time it was over 1300 miles. Today, with expanded world trade; winter grapes from Chile; apples from New Zealand; the average particle of food travels well over two thousand miles before it reaches our mouths.
It is certainly a wonder we can achieve these common delights at a reasonable shelf price. But have you wondered at the hidden price. What of the costs to tax payers to build and repair roads, bridges, airports, harbors. What of the costs to tax payers for the elimination of living space that 2% of the lower 48 are now paved or in right aways as sighted by the Department of Interior's inventories. What of the cost to the quality of life and medical bills from pollution to the air, water and soil caused by the fuels used to move food faster and further around the globe. What of the cost to the millions of road killed animals and birds. What of the costs to tax payers, all of us and our conscience, for the need of such a military to be interested in making sure those fuels are supplied to move food. And the fuels to move ourselves to catch a bit of fast food - the most energy intensive and least fresh kind. The round trip ticket to Iraq was over $40 billion and a couple hundred thousand lives, but the military technology and equipment cost for that outing was in the hundreds of billions of dollars. Next time you bite into a delicious Braeburn Apple from New Zealand you will also pay for it at tax season. So complain, to your legislators about this fiscal and environmental imbalance, then build yourself a solar garden to begin the slow moss decay of this burdensome old oak of a food delivery system mulching the way towards freshness and sustainable food security.
How did we get so far away from our food? Ironically, partly our desire for freshness and partly our desire for diversity drove us further afield of canned, dried, or even frozen foods. We in the industrialized temperate climes took special favor to that once rare orange and apple which appeared in our stockings at Christmas as a succulent teaser of freshness. Fresh food, food which has recently been alive or indeed as with produce, is still alive, has more nutritional value. If one orange could be brought why not more, and a multitude of fresh produce heretofore only available seasonally. We have come to the point where the Northern Hemisphere swaps seasonally with the Southern Hemisphere (although the trade is substantially imported to the wealthier North). While a large program of year round solar greenhouses producing fresh crops near their markets will undoubtedly hurt the exporters of these crops from California, to Florida, to Mexico, and Chile, this technology can be adapted the developing world to many regions where growing conditions are extreme both too hot as well as too cold. The development of "Low Input" agriculture and animal husbandry, where the requirements for water, energy and nutrient for growing crops is at a minimum for a maximum yield of crop, could be a harbinger of sustainability for many ravaged lands and peoples.
The promise of solar greenhouses is as great as our willingness to invite a variety of life into our dwellings, to share the fruits of their existence in exchange for a more sustainable way of living. Each of us can evolve our collective and personal ecologies, with differing characters of culture as our economies of living turn green.
Home