The Chinese Greenhouse by Dan Chiras

That's really interesting. I really want a passive solar greenhouse. However I struggle with the need. I'd like to start seedlings earlier and grow tropicals. Haha

Thanks for sharing. Loved the video of mongolia. What a beautiful place. Such winters.

This likely is a good solution for cold weather places. I look forward to hearing more.

Thank you

Has anyone thought the smallest practical greenhouse for people who live on small lots? At least something you can walk in and that is functional and passive. Thanks.

Stewart

I give this book 8 out of 10 acorns

The book starts with Dan Chiras' experiences when initially exposed to the Chinese Greenhouse concept, followed by a look at the typical North American greenhouse and the large energy footprint associated with them.

He goes on to describe what makes the Chinese Greenhouse concept special - unglazed areas have thermal mass inside an insulated envelope with earth berming outside that, to help moderate extremes in temperatures by absorbing heat when there's too much and gradually releasing that heat when it's needed. Glazed areas have curtains designed to reduce the heat loss at night during cold weather.

Chapter 4 discusses several approaches - A)building into the side of a hill: this decreases the amount of earth needing moving, but increases the risk of water infiltration.
B)build it into a rise: dig the foundation and dump the subsoil on top of the "back" side of the greenhouse.
C)build it flat: dig the foundation to get some of the berming dirt, but get dirt from elsewhere to make up the deficit.
All of these options require good foundations and various degrees of earth moving and water management. He goes into a fair bit of detail about the efforts needed to keep things dry, mentioning French drains, swales up-slope, roof run-off management etc.

He then expands on how thermal mass is a "key element to the success of a Chinese greenhouse". He bases much of his experience on studying, building and living in passive solar homes. This is important as it includes information such as how thermal mass thickness affects absorption by a greater degree just up to 4 inches after which the storage capacity drops off. He discusses thermal mass options with some concern about the embodied energy involved, but not without even more concern shown for the risk of the back wall collapsing if not engineered properly.He states that many of the more natural materials other than concrete, he considers unsafe in an underground, high humidity environment. He then moves on to framing options, and from there to glazing. He acknowledges that the cheapest option in the short term is not the most environmentally sound in the long term, but even the longer term options are mostly plastic based. He considers glass the least desirable option due to its cost and risk from hail. Certainly there are locations where hail risk is quite high, the option of designing the green house to divert glass from the landfill for locations such as mine where hail risk is low, seems to me to be a more responsible, long term solution. However, if Mr Chiras' goal is to change the "agro-industry's" approach to greenhouse growing, where they will need much larger greenhouses with uniformity, I can see his point. Let me just admit that I've had bad luck with plastic greenhouse covers that I've been exposed to!

He moves on to an overview of insulation. He recommends super-insulating the east, west and north walls and any part of the roof which isn't glazed, and provides a chart and reference for the environmental costs and efficacy of common options. What he doesn't mention is the resistance to various insects of the options he mentions, or how he ensures they're kept out of it, so I would consider my area's risk factors when choosing.

He then discusses glazing insulation - this can be important both in summer when overheating is problematic, and winter when conservation of heat is an issue, along with the need for  easy management.

He then moves on to various approaches to daytime internal heat banking. He describes small solar panels to run DC fans to move air from the hot ceiling to underground storage in soil or rock. His suggestions are focused on keeping it simple and long lasting.

Chapter 7 goes into solar hot air systems in considerable detail. With minimal power and resources, he suggests they are a good way to super-charge the ground to hold heat for the cooler seasons, or to help keep the greenhouse warmer in winter. The downside is that he doesn't feel they are easy to adjust the slope for different times of the year. I was hoping he had some suggestions for that.

He continues from there to describe a number of versions of heat banking under the structure and in the berms using a variety of systems with varying degrees of complexity and cost. He describes enough different systems which can be used alone or in combination, that I think most people would find one that fit their situation.

Plants need light as much as warmth, and in Chapter 12 he explains about the spectrum of light that plants need and specifically discusses the use of LED lights to help where needed.

Lastly, he has a "Pictorial Documentary" of his own greenhouse build.

He lost a couple of acorns because he is more comfortable than I am with pressure treated lumber and particle type board (and here in BC, pressure-treated materials aren't allowed under "organic" standards) but I suspect that he's aiming at the larger audience and if most of the greenhouse growers around here did even 1/2 of what Mr. Chiras suggests, the saving on fossil fuel from heating greenhouses would make up for some of the material choices most people make. There is *huge* local pressure to "just build a hoop house and cover it with plastic", and I've seen very few with a solid north wall, let alone a solid insulated north wall with thermal mass on the inside, and none that are earth bermed. Let's hope that changes!

It sounds really interesting.   I wonder if you could use this concept and just use an alternative material for the pressure treated wood? I think it is worth looking into

Saralee Couchoud wrote:It sounds really interesting.   I wonder if you could use this concept and just use an alternative material for the pressure treated wood? I think it is worth looking into

Absolutely - pressure treated wood is simply "accepted" by many people because it lasts a long time in a wet environment and is far cheaper than naturally weather resistant woods like cedar. Unfortunately, although they have made it somewhat safer than the original treatment was, it's still incredibly damaging to the neighborhood where it's produced.

They are currently building an earth bermed greenhouse at Wheaton Labs and just using big logs and intelligent design to keep it as dry as possible. I'm looking forward to the results.

Jay Angler wrote:

Saralee Couchoud wrote:It sounds really interesting.   I wonder if you could use this concept and just use an alternative material for the pressure treated wood? I think it is worth looking into

Absolutely - pressure treated wood is simply "accepted" by many people because it lasts a long time in a wet environment and is far cheaper than naturally weather resistant woods like cedar. Unfortunately, although they have made it somewhat safer than the original treatment was, it's still incredibly damaging to the neighborhood where it's produced.

They are currently building an earth bermed greenhouse at Wheaton Labs and just using big logs and intelligent design to keep it as dry as possible. I'm looking forward to the results.

You can definitely use other wood, but it may dramatically cut longevity if it is not carefully chosen... there are very robust sorts of wood, the problem is finding and paying for quality!

For example, western red cedar is known for rot and pest resistance.. but this applies primarily to the dense heartwood of mature, healthy trees. Young trees and unhealthy trees have far less protection; sapwood and quickly grown trees are inherently more vulnerable. Combine several of those factors and prepare to be dismayed...

The red cedar at lumberyards these days is mostly remarkably poor. I've milled.some of my own that is no better; rapidly grown second-growth that is failing from drought...



I have been wondering if regular exterior plywood plus heavy applications of oil based stain is any less bad than treated ply... hard to quantify all the aspects...

D Nikolls wrote:

I have been wondering if regular exterior plywood plus heavy applications of oil based stain is any less bad than treated ply... hard to quantify all the aspects...

This is an area I wish I knew a lot more about. I believe the biggest issue is with the types of glues used to make the ply - how toxic they are in the making and how toxic they are in the "off-gassing" afterward".

Similarly, a commercial oil based stain could have nasty stuff in it and it can be difficult to determine that. My friend swears by just plain old "Boiled Linseed" oil - however the commercial stuff has been accused of being " ...heated and treated with chemicals that make it toxic for humans" (from https://www.cuttingboard.com/blog/what-type-of-oils-are-safe-to-use-on-your-cutting-board/ ) I use straight canola oil on my chicken's perches, renewing it yearly or more often as a method of helping with mite control. I'm not worried about oxidation as the chickens are not "eating off" their perch, but I don't want something toxic. The problem is that if I oil a perch that isn't in active use, it goes moldy. I think the difference is simply air flow - the chickens tend to jump up and down off the perches as they feel like it all day. So if I was tackling this situation, my approach would be to research home-made versions and if time allows, do some tests in my eco-system to see what seems to work.  Try searching here for some options: https://permies.com/f/154/Finishes .

There's some Japanese system used which seems to be about "charring" the outside layer of wood. The two places I saw it being used, they were using a hand-held propane torch - think of the embodied energy there! Those small canisters are almost all single use. We've tried to restrict use of them in our life - if we need similar, we use our long hose that runs to a re-fillable tank - it's still propane, but at least its not all the "disposable single use" issue.
(OT - you can't recycle the disposable propane cans because they're an explosion hazard. However, Hubby has put them in a water bath on the drill press bench and drilled holes in them to remove that issue. Water gets in and it's a crappy explosive!)

Those are some interesting things to think about.   Question, if I did use cedar how long would you think it would last.   I ask this as I have a lot of standing/ growing cedar on my property.   It's been here a long time.   The property has been selectively cut many times in the last hundred years or so, but for some reason they have never cut the cedar