Facebook  YouTube

Small Farmer's Journal
PO Box 1627
Sisters, Oregon 97759
800-876-2893
541-549-2064
agrarian@smallfarmersjournal.com
Mon - Thu, 8am - 4pm PST

The Woodfired Bottom-heated Greenhouse Bench

The Woodfired Bottom-heated Greenhouse Bench

Cultivating Questions Concerning the Bio-Extensive Market Garden

The Woodfired Bottom-heated Greenhouse Bench

by Anne and Eric Nordell of Trout Run, PA
illustrations by Ed Ochsner of Hohenwald, TN

Hi Anne and Eric,

This is Sam and Rich Wickham writing to you. We have been living and working on farms in the Finger Lakes for the past few seasons and, by way of our Amish neighbors and all the talented draft powered farmers in the area, we have been inspired to pursue farming with horses.

We have been passively gleaning knowledge from you through the SFJ, the world wide web, and your wonderful DVD and booklet which we got for Christmas this year. Your in depth, thoughtful coverage has been, far and away, the most valuable resource to us in our fledgling farming career. At first, we were just excited to find another couple who wanted to keep their farm a two person operation and how they went about that. However, it quickly became apparent that that knowledge was the very least we would stand to get out of poring over your old SFJ articles.

Anyway, we think we have exhausted our google search capacity in trying to find out more about your farm so we figured we had better sit down and write a letter to you both. We are quite curious about your wood stove greenhouse seedling set up. It has been difficult for us to determine the possible dimensions and arrangement of the system. Any insight into this would be much appreciated. Also, are you only heating up the stove at night or is it continuous throughout the day?

We are not prone to pestering but we are so intrigued by this idea that we just can’t help ourselves in this instance. We have been wanting to drop a line your way anyway to let you know that your work has elevated our understanding of farming (and appreciation of the craft) by leaps and bounds. Thank you for your generosity!

Take Care,
Sam and Rich
Caseville, MI

Before launching into the construction details of the bottom heated bench, we should explain why we chose this unusual method of heating the greenhouse in the first place. Looking for a low tech, low cost heat system which did not require electricity, we were intrigued with the nineteenth century greenhouse design in Peter Henderson’s Gardening for Profit. [see below – ed.] The flue from the wood stove of this renowned market gardener’s greenhouse ran underneath the length of the central bench and back again before joining the chimney built directly on top of the firebox. The heat from the stove created enough draft in the stack to pull smoke and heat through the long horizontal flue, warming the 20′ by 60′ greenhouse and providing bottom heat to most of the plants.

As much as this innovative heating system appealed to our minimalist outlook, we were concerned that this setup would be overkill for the 10′ by 16′ structure we intended to build in time for the 1988 greenhouse season. It seemed to us that a clean burning fire would make the small greenhouse too hot for the health of the plants and that moderating the greenhouse temperature with a smoldering fire would quickly lead to creosote buildup in the horizontal flue, a sure recipe for a chimney fire. We decided a safer, less polluting alternative would require thermal mass directly under the plants to capture the intense heat from a clean burning fire and release the warmth slowly for twelve or more hours.

The Woodfired Bottom-heated Greenhouse Bench

It took several incarnations to come up with a satisfactory design for the bottom heated greenhouse bench. In the final version we used two 55 gallon drums welded end-to-end for the firebox and a salvaged piece of 12” stainless steel chimney for the horizontal flue. (Metal culvert pipe or gasline casing might work just as well.) We learned the hard way that a large firebox and flue are necessary to dissipate the intense heat into the surrounding air chamber and to minimize heat stress on these components.

To shield the wooden greenhouse structure from the heat, we built the end walls of the bench with 4′ by 4′ pieces of sheet metal, cutting a large enough hole in one end for the door of the barrel stove and a smaller hole at the other end for the horizontal flue to exit and join the chimney outside of the greenhouse. A farmer that copied our design but neglected this safety feature had to call the fire department when the heat from the stove caught the greenhouse on fire.

The Woodfired Bottom-heated Greenhouse Bench

For the same reason, we built the side walls of the bench with concrete blocks. We placed salvaged grating from a sidewalk heat vent across the top of the block walls to support an 8″ layer of field stone and gravel, doubling the depth of this thermal mass over the barrel stove where the most heat is radiated. The weight of the stone on the grate keeps the side walls in place so mortar is not needed when laying the block.

The stove and flue rest on a bed of gravel sloped so that the pipe rises 12″ over the 16′ length of the bench. This modest slope along with the warmth retained by the thermal mass surrounding the flue produces a strong and dependable draft. When heat waves replace the smoke coming out of the chimney, we close the damper installed in the horizontal flue just outside of the greenhouse to hold as much heat inside the bench as possible. Managed this way, there is no creosote or ash buildup in the flue or chimney.

Since our goal is a brief, clean burning fire, we load the barrel stove with a couple of armloads of very dry wood. Scrap wood, tree trimmings, small pieces of seasoned hard wood all work well. For a number of years we used hemlock slabwood from a local sawmill. A half cord of slabwood was more than sufficient for the typical greenhouse heating season running from mid-March to mid-May.

The Woodfired Bottom-heated Greenhouse Bench

Normally, one firing around six in the evening is all that is needed to heat the bench overnight. (We fire up the stove a couple of times at the start of the greenhouse season to warm up the thermal mass.) If the thermometer dips into the twenties or lower, then we load the stove twice a day, morning and evening. We have never had to get up in the middle of the night to heat the greenhouse. Firing the stove a couple of times in a row, on the other hand, can get the stones so hot that they will fry the plants resting on top. Keep in mind that heat released from the bench keeps the greenhouse just 20-30 degrees above the outside temperature. That is fine with us because the combination of warm potting soil and cool air produces plants with the stocky topgrowth and large root system necessary for trans- planting without irrigation. Dryland planting also benefits from larger plugs than normal. For example, we use 72 cell flats for lettuce and 50’s for the brassicas.

Only one of the two greenhouse benches is heated. This arrangement is adequate for space heating because we insulated all four sides of the small structure with foam board sticking at least 18″ in to the ground. By contrast, a grower who tried a single wood heated bench in the middle of a larger, uninsulated hoop structure found the results unsatisfactory.

The only reason this small heated structure meets our needs is our business is based on successive plantings of cool season vegetables and we move the flats through three growing areas: our wood heated house with enclosed front porch for germination (beginning mid-February); the bottom heated greenhouse for early growth of the vegetables; and an adjacent unheated 12′ by 28′ hoophouse for the later stages of growth and hardening off.

The Woodfired Bottom-heated Greenhouse Bench

So far, this low cost, multi-stage system has reliably produced enough plants for our small market garden. Over the course of the 2014 growing season we transplanted 15-1/2 of our 380′ rows to lettuce set 9″ apart (grossing $10,436), 7 rows of onions @ 7-8″ ($2,748), 5-1/4 rows of broccoli spaced 20″ ($2,704), 3 rows of kale ($2,532), 3 rows of leeks ($1,200), 1 row of peppers ($685), 1 row of cabbage ($519), 4-1/4 rows of miscellaneous vegetables ($2,789), 4,360 sq. ft. of transplanted hoophouse crops ($11,188) and bedding plants for sale ($2,713). A much larger heated greenhouse would be necessary if we grew lots of warm season crops, like tomatoes, melons and peppers.

Also in 2014, our first summer intern replaced the rusted out grates in the bottom heated bench. The refurbished greenhouse attracted a lot of attention at the Columbus Day tour, probably because it was the only spot on the farm that looked somewhat warm on that raw, chilly day.

In closing we should point out that our make-do growing system requires moving every flat between three different buildings and an intimate understanding of which part of the heated bench is best suited for each crop. There is a reason why most growers eventually put up a single structure for all the stages of plug growth. Although the initial investment and annual fuel costs are significantly higher than the woodfired bottom heated greenhouse, one large hoop structure with automated heating is much more labor efficient and straightforward to manage.


Heating By Flues

from Gardening for Profit by Peter Henderson (1890)

When personal attention can be given to the fires, by heating greenhouses with flues a great saving in cost can be made; in fact, nearly half the cost of construction; for we find that the hot-water heating apparatus is usually half the cost of building greenhouses, while, if heated by flues, the cost would be no more than ten percent of the whole. A new method of constructing flues (or rather a revived method, for it originated in 1822,) has been in use for the past few years, which has such manifest advantages that many now use it who would no doubt otherwise have used hot water heating. Its peculiarity consists in running the flue back to the furnace from which it starts and into the chimney, which is built on top of the furnace. As soon as the fire is lighted in the furnace, the brick-work forming the arch gets heated, and at once starts an upward draft, driving the cold air from the chimney, which puts the smoke flue into immediate action and maintains it; hence there is never any trouble about draft, as in ordinary flues having the chimney at the most distant point from the furnace. It will be understood that the chimney into which the flue is returned is placed on top of the arch of the furnace, and not in it, as some might suppose.

By this plan we not only get rid of the violent heat given out by the furnace, but at the same time it insures a complete draft, so that the heated air from the furnace is so rapidly carried through the entire length of the flue, that it is nearly as hot when it enters the chimney as when it left the furnace. This perfect draft also does away with all danger of the escape of gas from the flues into the greenhouse, which often happens when the draft is not active. Although no system of heating by smoke flues is so satisfactory as by hot water or steam, yet there are many who do want to go to the expense of hot-water heating, and to such this revived method is one that will, to a great extent, simplify and cheapen the erection of greenhouses.

The Woodfired Bottom-heated Greenhouse Bench

The flue will always “draw” better if slightly on the ascent throughout its entire length. It should be elevated in all cases from the ground, on flags or bricks, so that its heat may be given out on all sides. The inside measure of the brick flue should not be less than eight by fourteen inches.

After the flue has been built of brick to twenty-five or thirty feet from the furnace, cement or vitrified drain pipe, eight or nine inches in diameter, should be used, as they are not only cheaper, but radiate the heat quicker than the bricks; they are also much easier constructed and cleaned. Care should be taken that no wood work is in contact with the flue at any place. It should be taken as a safe rule, that wood work should in no case be nearer the flue or furnace than eight inches. In constructing, do not be influenced by what the mechanics will tell you as few of them have any experience in such matter, and are not able to judge of the dangers resulting from wood work being in close contact with the heated bricks. There are scores of greenhouses burned every year owing to carelessness or ignorance in allowing the brick work to be too close to the wood. The cost of such a greenhouse, at present prices, heated by flue, would be about six hundred dollars, or about sixty cents per square foot covered by the greenhouse.

Spotlight On: Livestock

Expanding the Use of the Heavy Draught Horse in Europe

Expanding the Use of the Heavy Draught Horse in Europe

“La Route du Poisson”, or “The Fish Run,” is a 24 hour long relay which starts from Boulogne on the coast at 9 am on Saturday and runs through the night to the outskirts of Paris with relays of heavy horse pairs until 9 am Sunday with associated events on the way. The relay “baton” is an approved cross country competition vehicle carrying a set amount of fresh fish.

Horseshoeing Part 1B

Horseshoeing Part 1B

Since the horse is useful to man only by reason of his movements, his foot deserves the most careful attention. The horse-shoer should be familiar with all its parts. Fig. 3 shows the osseous framework of the foot, consisting of the lower end of the cannon bone, the long pastern, the two sesamoid bones, the short pastern, and the pedal bone.

Ask A Teamster Round Pen Training

Ask A Teamster: Round Pen Training

When we ask a horse to follow us in the round pen we can help him succeed by varying things a bit – changing direction and speed frequently, stopping periodically to reward him with a rub (“a rub” or two, not 100), picking up a foot, playing with his tail/ears/mouth, etc. In other words, working at desensitizing or sensitizing him by simulating things he will experience in the future (trimming and shoeing, crupper, bridle over the ears, bit, etc.).

Hand Plucking Poultry

Hand Plucking Poultry

by:
from issue:

I confess that I am cold-hearted and cheap. Though I love raising poultry, I hate spending time and money anywhere but on my little farm. So I process at home. If you are only raising a few birds for yourself, say 25 or 30 at a time, I recommend having a party and doing it all by hand. My journey backward from machines to hands started with a chance encounter with a Kenyan chicken grower visiting the United States. He finishes 15,000 broilers each year.

The Milk and Human Kindness: Making Cheese

The Milk and Human Kindness: Making Cheese

by:
from issue:

Yogurt making is the perfect introduction into the world of cultured dairy products and cheese-making. You are handling milk properly, becoming proficient at sanitizing pots and utensils, and learning the principles of culturing milk. Doing these things regularly, perfecting your methods, sets you up for cheese-making very well. Cheese-making involves the addition of a few more steps beyond the culturing.

The Mule Part 1

The Mule – Part 1

by:
from issue:

There is no more useful or willing animal than the Mule. And perhaps there is no other animal so much abused, or so little cared for. Popular opinion of his nature has not been favorable; and he has had to plod and work through life against the prejudices of the ignorant. Still, he has been the great friend of man, in war and in peace serving him well and faithfully. If he could tell man what he most needed it would be kind treatment.

A Gathering of Comtois in France

A Gathering of Comtois in France

by:
from issue:

I was soon planning for a stop in the town of Pontelier, the main hub in one corner of the country I had never been to and was bent on exploring: the Franche-Compte. As luck would have it, this region has its very own breed of draft horse, the Comtois. It was to an “exhibition” of this horse that I was heading, although thanks to my lousy French, I was not sure exactly what kind of “exhibition” I was heading to.

Plant Poisoning in Horses & Cattle

Plant Poisoning in Horses & Cattle

by:
from issue:

There are hundreds of plants that can be toxic to livestock. Some grow in specific regions while others are more widespread. Some are always a serious danger and others only under certain conditions. Poisoning of livestock depends on several factors, including palatability of the plant, stage of development, conditions in which they grew, moisture content of the plant and the part eaten.

Hay Making with a Single Horse Part 3

by:
from issue:

In parallel with making hay on the ground, nearly every year I have also made some hay on tripods. The attraction of this method is that it only needs one day of good weather to dry the grass sufficiently before it is put on the tripods, and then the hay takes very little harm no matter what the weather, usually coming out green, dry and smelling of hay two weeks later when it can be baled or stacked.

Step Ahead Horse Progress Days 2016

Step Ahead: 23rd Annual Horse Progress Days 2016

by:
from issue:

I had only been to Horse Progress Days once before, at Mount Hope, Ohio in 2008. It had been an eye-opener, showing how strong and in touch with sustainable farming values the Amish are, and how innovative and sensible their efforts could be. So at the 23rd annual event in Howe, Indiana, I was there partly looking for signs of continuity, and partly for signs of change. Right off I spotted an Amish man with a Blue Tooth in his ear, talking as he walked along.

Chicken

The Best Chicken Pie Ever

by:
from issue:

She has one more gift to give: Chicken Pie.

Chicken

How To Cure Chicken Roup: Then and Now

How To Cure The Common (Chicken) Cold

Horseshoeing Part 3A

Horseshoeing Part 3A

An examination should be made while the animal is at rest, and afterwards while in motion. The object of the examination is to gain accurate knowledge of the direction and movements of the limbs, of the form and character of the feet and hoofs, of the manner in which the foot reaches and leaves the ground, of the form, length, position, and wear of the shoe, and distribution of the nail-holes, in order that at the next and subsequent shoeings all ascertained peculiarities of hoof-form may be kept in mind and all discovered faults of shoeing corrected.

Littlefield Notes Making Your Horses Work For You

LittleField Notes: Making Your Horses Work For You Part 1

by:
from issue:

The practical everyday working of horses and mules in harness has always been at the heart of what the Small Farmer’s Journal is about. And like the Journal, a good horse powered farm keeps the horses at the center: the working nucleus of the farm. All the tractive effort for the pulling of machines, hauling in of crops, hauling out of manures, harvesting and planting is done as much as is practicable with the horses.

Fjordworks Horse Powered Potatoes Part 2

Fjordworks: Horse Powered Potatoes Part Two

These types of team implements for digging potatoes were the first big innovation in horse powered potato harvesting in the mid-19th century. Prior to the horse drawn digger the limitation on how many potatoes a farmer could plant was how many the farm crew could dig by hand. The basic design of these early diggers works so well that new models of this type of digger are once again being manufactured by contemporary horse drawn equipment suppliers.

The Milk and Human Kindness Caring For The Pregnant Cow

The Milk and Human Kindness: Caring for the Pregnant Cow

by:
from issue:

Good cheese comes from happy milk and happy milk comes from contented cows. So for goodness sake, for the sake of goodness in our farming ways we need to keep contentment, happiness and harmony as primary principles of animal husbandry. The practical manifestations of our love and appreciation are what make a small farm. Above and beyond the significant requirements of housing, feed and water is the care of your cow’s emotional life, provide for her own fulfillment. Let her raise her calf!

Livestock Guardians

Introducing Your Guard Dog To New Livestock And Other Dogs

When you introduce new animals to an established herd or flock, you should observe your dog’s reactions and behavior for a few days. Since he will be curious anyway, it is a good idea to introduce him to the new animals while he is leashed or to place the new animals in a nearby area.

Hay Making with a Single Horse Part 2

Hay Making with a Single Horse Part 2

by:
from issue:

From reading the Small Farmers Journal, I knew that some people are equally happy with either model, but because McCormick Deering had gone to the trouble of developing the No. 9, it suggests they could see that there were improvements to be made on the No. 7. Even if the improvement was small, with a single horse any improvement was likely to increase my chance of success.

Small Farmer's Journal

Small Farmer's Journal
PO Box 1627
Sisters, Oregon 97759
800-876-2893
541-549-2064
agrarian@smallfarmersjournal.com
Mon - Thu, 8am - 4pm PDT