Greenhouse In Use – Stocking Density

South Field Plateau Greenhouse – The Ark

Ten days ago we pulled the tarp up and and over the south field greenhouse. The greenhouse doesn’t look green yet since it has the initial winter tarp rather than the clear plastic we’ll put on later but the pigs are enjoying it.

Old South Herd Nest and New South Field Plateau Greenhouse

The weather had gotten too cold to pull the clear plastic so this year we put on a billboard tarp ( That will get us through the winter until we can put on the clear plastic in the warm summer months when the plastic won’t be damaged by handling in the cold. Someday we’ll replace that clear plastic. By the time that happens I hope to have the money to do it with either kalwall fiberglass or twin-wall polycarbonate. The FarmTek frame can handle all of these different cover types.

Pigs Walking Winter Paddock Trail from Greenhouse to Whey

When Kimsa and I went out to check the pigs this morning most of them had already left their nest in the greenhouse and were headed north along their roughly 1,000′ long trail to the water and whey. Spitzon, the southern boar, was walking along the line checking each of his sows as they went by.

Open South End of Greenhouse for Ventilation

The north end wall blocks the cold winter wind, a pretty continuous thing here on the mountain. You’ll note that at the east and west corners of the wall we’ve left openings for cross ventilation – a necessary element even in our cold climate to make sure there is fresh air throughout the greenhouse. If need be I would also open a window up at the peak in the north wall. For now I’m observing to see if that is needed. We’ll fine tune the system over time.

Pigs in Communal Nest

The floor of the greenhouse is covered with a two foot thick pack of wood chips which composts to create heat rising up from their deep bedding pack. The communal nest is about 80°F. Nice and cozy even with our deeply negative winter weather.

Hoar Frost Snow on Rope

The moisture rises up in clouds from the bedding when the pigs rise in the morning. The 21′ ridge line lets this rise clear of the animals so they are getting fresh air throughout the greenhouse and the bedding is staying well dry. I am seeing some condensation on the tarp in the top two panels by the ridge line along the entire length of the greenhouse but it is not excessive and there are very few drips. It seems to mostly condense, freeze and then sublimate away rather than building up. A problem we had with smaller greenhouses was that the moisture condensed on the plastic and rained down on the bedding from the short height. In those smaller structures the cloud was low to the ground and couldn’t escape as easily. The height of this greenhouse seems to solve that problem as I had hoped it would.

I put the black side outward on the tarp to increase solar gain and snow shedding which let me put the white side inside for increased light. On the exterior we are not getting a build up of snow. The greenhouse has a heavy duty center ridge pole with seven supporting posts so that it should hold up to any snow load we would get. My math says the center posts should hold up to 300 lbs per sq-ft in addition to the strength of the arch made of 2.375″ metal pipes. The reality is the wind and sun seem to be keeping it clear. The center posts may be overkill but I like them their for the confidence factor.

End to End View Inside South Field Plateau Greenhouse

Ten days is long enough to let them settle into their new home so I now have some data from this morning’s observations:

They don’t seem to be avoiding or clustering around the east and west vents at the north end. In other words the vents weren’t a big positive or a negative to where the pigs chose to sleep. I had wondered if the vents would create drafts the pigs would not like but this doesn’t seem to be an issue.

The pigs were fairly evenly spread out. There was no piling and there was some empty space. They weren’t clustered in the middle or against walls. It is normal for pigs to lie right up next to each other. As a rule of thumb, they should not be piled more than about 1.25 pigs high on average. That would be a pig having it’s head on another. 2.0 high would be bad, that’s when pigs are sleeping on top of other pigs for warmth and can cause prolapsing and crushing. A little one on top of bigger pigs is not a problem, unless it falls down in the crack between larger ones and can’t get out. What I saw this morning was as stacking depth of about 1.0 which is great. This means the pigs were very comfortable with the temperatures.

I counted 77 pigs still laying down and snoozing in the north most 20′ of the greenhouse. Their total nest was about twice that – mostly vacated by the pigs that had already headed out to breakfast. That comes to 77 pigs / (38’x20′) or 9.8 sq-ft per pig for the area still occupied. This was a mix of sizes from 600 lb sows down to 50 lb grower pigs. I would estimate that they were using up around 50% of the floor area which left plenty of space for walking. Other pigs had been lying in that area before I arrived – Remember that most of the pigs had already left for the morning. But some of the bedding area clearly had not been laid on this past night so they were not using it all.

What makes this interesting is they have more room to spread out but that is the ‘stocking density’ they are choosing to use for their sleeping space. This is just sleeping nest space since they spend much time outdoors on the winter paddocks. If I assume that is their natural stocking level then they need about 9.8 sq-ft x 50% or about 5 sq-ft per pig. Do keep in mind that this is across many sizes of pigs and a rough figure but perhaps a good guide – I’m often asked by people how much space pigs need for shelter. Five square feet per pig is probably a good rule of thumb to what pigs think they need – I would allow a bit of extra space in building out.

Hot Wire Along Foundation Top to Keep Pigs Off the Tarp

Thus for a herd of 400 if all of them were in this space, which they’re not since we have other spaces, then they would need about 2,000 sq-ft of space for sleeping which is about half of the greenhouse’s 3,648 sq-ft. In reality, I would rather allow them to spread out a bit more than that and divide the greenhouse up into sections. Eventually each section will have its own entrance so the pigs will have a minimal walk to the outdoors and the larger world. The setup will allow auto-sorting by size using the creeps into the spaces.

Sidewall Snow Buildup & More Hot Wires

One of my concerns is how high the snow will build up along the sides of the greenhouse. This year is not a good test as we had already gotten most of our snow for the year by the time we got the tarp on. But we do have the east vs west sides to compare.

Sidewall Snow Buildup on East Side for Comparison

The top of the greenhouse foundation is nearly perfectly level but the ground slopes by about two feet from the north west corner down to the south east corner in order to provide drainage for the interior. There is also a berm around the uphill sides to prevent ground water from flowing into the bedding. The result is the east foundation is higher than the west foundation which does give a good comparison of what snow dump might be like.

One of the things we’re hoping to see is a reduction of our hay usage during the spring and fall mud seasons due to having more covered space. That extra hay is never ‘wasted’ as it goes to compost that feeds our soil. But it’s expensive compost. If we can cut the hay usage that goes to bedding that will help pay for the greenhouse. In a year or two we’ll know more how that pans out.

Thermometer measurements 4′ up at center of North End of Greenhouse

Update 20150306 of Greenhouse Data:

Outdoor = 15°F
Indoor = 45°F
Bedding = 75°F to 100°F

Search pattern for more on the Greenhouse Ark.

Outdoors: 34°F/10°F Mostly Sunny
Tiny Cottage: 64°F/61°F

Daily Spark: Mother Nature invented pork. Man improved it with salt, sugar and smoke to make bacon. Meat candy. -Adam & Eva Lution’s Smokehouse

About Walter Jeffries

Tinker, Tailor...
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17 Responses to Greenhouse In Use – Stocking Density

  1. Adam DeGraff says:

    Awesome Walter. Hey, how do you keep them from tearing the structure? Plastic/Tarp? Center supports? Did I miss something? Ours would.

  2. Edmund Brown says:

    That is awesome. It looks just like a giant version of my pig house. I have billboard tarps over a 12 x 28 ft hoop right now.

    Interesting you put in 2 ft of wood chips – That’s about what I did when 1st moved my pigs in. At this point I think it was overkill, and I could have gotten away with half that for starters. But better a little too much and dry beds than too little and gooey.

  3. Glenn Warren says:

    Years ago when first following you blog, long before the butcher shop, you started a foundation structure which I think you called the greenhouse, and in which you provided bedding for the pigs. Did this larger structure leapfrog that earlier effort, or is it’s topsides still in the long range plan?

    • The older greenhouse is also called the south field shed and is north of the newer south plateau greenhouse. The roof of the older one is mostly scavenged materials, some of which are translucent glazing, some opaque. The pigs prefer the translucent areas. This is one of the places we learned about their preferences. Another is the house end shed which has a mostly translucent glazing roof. All of the previous structures are much smaller than the new greenhouse. Someday we’ll replace the entire south field shed greenhouse with a translucent roof too. For now we needed to keep using it so don’t have the luxury of pulling the roof off. Baby steps.

  4. Bill Beaman says:

    Do you anticipate problems with the pigs depositing their waste in the excess space within the greenhouse on their way out in the morning? And could this problem spread back into the sleeping area causing damp bedding problems?

    • No, there isn’t any problem with it. They manure and urinate along the entire 1,000′ trail north to their whey feeding area just as in the summer months they spread their manure out over the pastures. In confinement situations apparently pigs pick a corner and just use that but with our open setup they spread it instead so that it naturally fertilizes the soils over a large area. This has resulted in the gradual improvement of our land over the years. One more advantage of extensive farming.

  5. Nicola says:

    Thanks for all your details! We are hoping to get into breeding pasture pigs and this will greatly help with the budget and planning!

  6. Janice says:

    I really like the photos detailing how you’ve built out this grand project of yours — and all your projects. Were thinking of doing something similar and have been looking at farm tek and other kits. Your observations and numbers are helpful as alaways.

  7. am in the pm says:

    Nice pictures of indoors of greenhouse and details of hot wiring. Interesting the former nest is now vacated but with 15 degrees outside vs 45 inside with no wind and dry,warm bedding ,it’s a no brainer.

  8. Nicola says:

    I’m assuming the wood chips are under the snow in the greenhouse. Did you try and remove snow when the pigs were ready to use it? Do you know when you will be clearing out the bedding (by the end of June?)?

    • The wood chips went in in the fall but then the greenhouse got delayed in it’s arrival which then happened at a time that further delayed the setup. At this point there is snow on the southern portion of the wood chip bed which is about 2′ thick. In the northern portion we cleared the snow off with the tractor and put down a hay top layer. All of the bedding is composting and generating heat, both what is under the snow and what is under the nesting area in the north. Thus what remains of the snow will probably melt out and drain away soon. I can see it already happening. This will be accelerated since it is warmer in the greenhouse than outdoors. It was above freezing inside this morning while it was in the teens and windy outside.

      With other bedding packs we have used them for multiple years, adding layers. This creates a ongoing deep bedding pack that is composting and generating heat. This will be the largest one at 96’x38′ which we have done so we’ll see if we make adjustments in technique. One of those things where time will tell.

  9. michael says:

    Hi Walter, I just ordered a smaller farmtek (clearspan) tunnel (36×48) to get my sows and 30 0dd feeders through the winter. I am starting ground work next week, and couldn’t be more excited. Have you had issues with snow loading on your tunnel?

    • No, but being cautious I put in a central beam just incase. My first observation is the center beam never became loaded so that means the structure wasn’t bending downward. My second observation is the wind blows the snow off our greenhouse. Ours is 21′ high and we get a lot of wind.

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