Mike's passive solar greenhouse design/build

Thanks mike,
You are giving me hope for a multi-use compost pile of practical size.

I've had a few sunny days to work out there in the last two weeks.  The siding is up on the East wall.  White stained pine is a lot prettier than insulation

The water tower is built and the IBC tote is in place atop it.  I got a bunch of IBC totes and one was the extra tall style.  That's the one that is the water tower tank.  I miscalculated and struggled to install it.  I wanted the tank as high as possible but I forgot that it would put the tank between the trusses.  Thus I couldn't build the tower and then put the tank on it.  Instead I had to block and tackle the tank up there and build the tower under it.  My local OSHA rep wouldn't have approved.  The structure it's sitting on is about 12' off the ground so I should have decent water pressure.  The missus just finished staining it today (involving much swearing and moving of ladders).

I got the catwalk partially in place.  It's there for several reasons.  The primary reason is for easy access to the vents, moveable insulation chamber and water tower.  Secondary reason is to have a cool canopy tour walkway.  Tertiary reason is to have more places to hang pots.  Quaternary reason is a place to route drip irrigation header pipes down the length of the greenhouse.

The catwalk is two 2x8's on-the-flat with a 2x4 vertically between them and at each edge.  It's pleasantly sturdy despite the 8' span.  The middle 2x4 is for stiffness, the edge ones will give extra stiffness and act as toe kick safety rails.  It's about 6" higher than I wanted but it will work.

Next is to connect the catwalk to the yoga platform atop the compost bin.  Then I'll either work on the West wall siding, start into electrical or begin a shallow climate battery.

In other news, we've received over 30" of snow in the past three weeks and the greenhouse is still standing.  We dug out the snow from the south side to give more room for sheeting snow twice now.  Since the two poly layers aren't inflated, the snow sitting on the top of the greenhouse has kind of pressed the layers together.  The R value is still fine due to the foot of snow.  The snow is melting/sheeting off anywhere the glazing is exposed, the only accumulation is on the topmost foot.  In the exterior picture of the base of the greenhouse, you can see where we removed snow prior to the latest 12" snowfall.  The pile against the greenhouse comes just over the patio door vents (as evidenced by the shadows in the first picture).  So the snow is about 5' high up the greenhouse.  We'll probably dig it out tomorrow if we get a chance.

Enjoyed reading your adventure in building your greenhouse. I'm also designing a greenhouse for zone 4 and have been studying the various ways to keep low temps above 50f with sub zero winter temps.
It seems from studying the available info on the web  a lot of effort  and thinking goes into finding ways to store or add heat during night time lows and not much thought goes into addressing the elephant in the room ,the huge heat loss thru the glazing at night. I was glad to see you at least have attempted to minimize this.
I'm assuming since the snow is pushing the poly layers together it's not easy to get the rolled insulation to fall down. I had a similar idea but instead of poly id use two layers of polycarbonate with a high r  value rollup blanket in between them. Have you tested to see if your insulation has an effect on inside temps when it's deployed? I'm assuming it has an r value around 4. Is that about close?

Thanks Glee, it has been an adventure!  Welcome to Permies by the way :)  I agree, the heat loss through the glazing is the biggest challenge.  You need to do plenty of insulating elsewhere (foundation, North side, etc) to make a greenhouse work well here, but the glazing kinda blows all those heat losses out of the water.

Yes, the snow pressure is keeping the insulation from moving currently.  I've kind of given up on it for this winter since I need to trim the edges on some pieces to allow them to slide down nicely anyway.  I'd think a more rigid glazing would work better.  I'm not sure if polycarbonate can span 4' or not at my uppermost roof slope.  I might have to upgrade to that but it will be a real pain to install without tearing the inner layer of poly in the process.

Yes, the insulation does help.  I did get it halfway deployed on our coldest night and it helped.  -22F on our second coldest night with no insulation and the inside temp in the morning was 16F.  The next night I had the insulation 50-60% deployed and it got down to -29 and the temp in the morning was 20F.  So 11 degree larger temperature difference with the insulation and it wasn't fully down.  I don't know how to calculate the R value with and without but I suspect it's 3-4 when deployed.  

Thanks for the reply mike. I've been working on all kinds of methods to cover the glazing at night and I'm finding out why there isn't any real info about how to do it, because it's not an easy thing to have something moveable with a high r value.  When you think about insulating the north, east, west walls to an average r value of say 24  then have half the structure (the glazing) at r2 the high r walls are not saving all that much. Increasing there r value is not cost effective above a minimum without also addressing the glazing heat loss. Now if we could get that glazing to r24  at night then  storing solar heat in the floor, or water ,or even heating the greenhouse become a real asset for cold winter growing in our zone.

I haven't come up with any way to do that yet, at least not if I want a conventional looking greenhouse but I'll continue  thinking it thru.

I Wasn't suggesting you put polycarbonate on your greenhouse just that I had thought of a similar idea but had thought about the polycarbonate because I live where its windy all the time and plastic just wont hold up. I do think though it might help to allow your insulation to endure the rigors of repeated opening and closings. Maybe one day when you have to change it for some other reason

Ill keep following this thread and see how it turns out for you and if I come up with a way to get that r24 glazing covered at night ill share it.

One way to cover a smaller greenhouse could be an automated grain cart cover.  Here's one example: Carolina tarps.  It could be done externally with some higher R value material.  Normally exterior moveable glazing insulation is a challenge due to wind and snow but these systems are ok for highway use so they're probably pretty tough.

Mike, I'm so excited. You're doing fine

Hi Mike,
A few days ago you reacted to my post on coldsinks. I didn't realise you've got such an amazing extensive post on your design, with inputs from so many knowlegable people... Great! I'm going to read all of it!
Thanks a lot for your thumbs up, by the way.
Greetings,
Michiel

Mike Jay wrote:Hi Daren, welcome to the party!  So I take it you will do two curved 20' pieces of pipe, joining at the peak?  I built my curved trusses a bit beefier to handle snow load.  I haven't had much snow to test it against but so far I'm very confident it can handle any snow it will encounter.  I was also going with beefy trusses to handle the weight of all the insulation, siding and roofing on the north side without bulging out the south side.  If I were to build another one of these greenhouses, I'd be very tempted to attempt an A frame with straight trusses.  The curves probably added 1/3 to the timeline of the project and 60% to the brain power needed.

With your question about cubic feet of battery to glazing, what kind of battery do you have in mind?  Are you thinking of a GHAT or climate battery with air pipes underground?  I decided against that type of system due to our cloudy winter climate (My first Permies post asking about climate batteries in cloudy cold places).  The systems seem to work well in sunny cold places (Colorado, Nebraska, great plains, etc).  This year, I think we had about 15-20 sunny days between Nov 30 and today.  A battery system couldn't gain enough on those days to give back heat on the other 50 (in my climate).

There is a Sunny John calculator for climate batteries that has been posted and lost and reposted.  I think you can get info on sizing through this link: ecosystems-design.com

Regarding if a greenhouse heats up enough to charge the battery, my greenhouse on a frigid sunny day will heat up to 100+ in the middle of the day.  That lasts from about noon till 3pm.  So that's three hours of hot air to put into the battery.  And 21 hours where that heat is needed to be drawn back out.

I think I'll do a poor man's climate battery by digging shallow trenches in the greenhouse (18" deep) to circulate hot air on sunny days.  The main goals of that would be to store that heat when it happens (avoid opening the vents) and maybe heat up the roots of the plants by a degree or two.  I wouldn't use it to return warm air to the greenhouse.  We'll see if I actually do that...

Regarding the phase change, I haven't decided if I'm really going to do that or not.  I think the 6 water barrels I had in there did help moderate the temps until they froze.  I think until I know the temperature swing of the greenhouse when it's "done" I won't be able to pick a good phase change material.  For instance, if the greenhouse swings from 30 to 70 degrees, a phase change material that melts around 50-60 would probably be ideal.  It should melt most days and freeze most nights and hold the temp nicely.  Using water as the phase change would only really kick into action at 32 degrees (too late to protect your tomatoes).   Water, or any phase change material, or a stack of bricks, all act as thermal mass regardless of the temperature.  That just slows down the temperature swing and takes away the peaks.  So they're good too.  I think between the footings and the cement blocks I have about 20,000 lbs of thermal mass.  Add in the top 4" of topsoil and it's a bunch more.  So if I add 30 barrels of water it will help and it will distribute the effect, but I don't know if it's worth the space it takes up.  So that's a long way of saying, I don't know what you should do.  

I managed to avoid the blower on my two layers.  A 1.5" spacer keeps them apart except for one spot in the middle.  But Solawrap or twinwall polycarbonate would be slicker than my installation.

I'm not sure the perfect answer for your endwall question.  I think it depends on your goals for the greenhouse.  If you're going to try to keep it warm through the winter at our latitudes, I think they have to be insulated.  I'd only get a bit of light (and solar heat) through them for an hour a day.  Then I'd bleed heat out through them for 23 hours a day.  If you are just going for a much longer growing season, glazing part of them might start to make more sense.  Maybe glaze the south half of each and insulate the north half.  Another way to think of it is that at 10am the sun is hitting the outside of the E wall and not entering the greenhouse.  But the sun that goes into the greenhouse and hits the solid W wall is reflected back towards the plants.  If those endwalls were clear, that 10am sun would enter the E wall but the sun going through the greenhouse and hitting the W wall would escape and light up the snow outside.  So am I gaining any sun if they were clear?  And keep in mind the tremendous heat loss through those walls 24/7.  

Regarding the compost heat, I haven't got it figured out yet.  I hope to so that we can all heat our stuff in a wonderful way.  But I fully understand your concern.  My current mix is too slow of a "burn".  I'm going to pull some out and change the mix and see if that fixes it for the second half of winter.  

If you have enough ventilation for the summer (meaning a lot), then it's hard to have a really well sealed greenhouse.  Mine has the equivalent of 13 doors on it.  All but one are homemade and sealed with weatherstripping.  I'll fix more leaks but it will always breath more than I want.  So I wouldn't be too worried about wood heat for cold nights sucking up all the oxygen.  Maybe if you're burning a face cord every three days...  Plus the plants should be giving off oxygen.

As you get your plans together feel free to start a build thread like this one.  You'll get lots of good info and we'll all get to watch your progress

Actually, I meant one single 20’ pipe bent to an arch- the side walls would be achieved by 2.5-3 foot straight pipes. But due to the advice I’m seeing here, I could very well scratch that idea in favor of insulating the snot out of my entire north wall instead of glazing it, and possibly doing the same for the east and west gable ends. It’s almost like a chimerical design- one exact half being well insulated, possibly stick built, but with moisture resilient materials, and the other half being a plastic greenhouse.

Due to snow considerations, and wanting to be able to leave on vacation with no worries of snow clearing chores, I’m def thinking a 12/12 pitch.

A side note for others to think about, and something I’m leaning towards, is making the construction such that it could be converted to a more regular outbuilding if the need ever arose. I’m thinking of using PT stickbuild for everything and if I ever had to, I could remove plastic and put up board and bang-presto, have a barn. Just a thought.

I actually had never looked into the air pipes idea, though that seems interesting. I guess I have to look at real climate data for my area versus my own memory...I feel like we have an often-sunny winter (definitely January and February) but I don’t have numbers on it. All I had come up with for thermal batteries was to make a long thin wall of bricks on the north side of the greenhouse, not touching the outside wall (to avoid thermal bridging) but just there to capture sunlight before it streaks out the north side. If not bricks, I’d also thought of wide thing jugs of water, like those military type 5 gallon gas cans that are mostly rectangular. I'm not as good at physics/engineering as the folks I see here, but I do know most brick/concrete/rock has one quarter the thermal capacity of water but has a higher capacitance before it starts to shed that heat? So depending on climate a mix of rock's higher temp capabilities versus water's volume to heat advantage is what we're looking for?

If the $$ made sense, I could also get beeswax from someone, because its phase change temp is closer to the number I’d be theoretically aiming for. I’ve worked for a veggie farm for years that did winter greens in high tunnels via rowcover, etc, so I know the whole “keep it close to 32 and keep the plants alive but not growing much” game- I’m more interested in winter production at 50-70 degrees or more. If that goal is unrealistic, then I change more to a simple goal of a thermally efficient greenhouse that is good for allium and tomato starts by Feb 23rd or so.

I have no idea how to solve the ventilation question. I have very low goals for using it in the summer, actually. Some people in the Northeast don’t realize that 70% of the benefit of a greenhouse for tomatoes is just getting the darn rain off the foliage, which causes disease. You also get an earlier harvest by several weeks and a later harvest, but I can accomplish some of that with field tricks like row cover and careful timing of plantings (brave, and early, with hardened-off starts). Anyways, that’s all to say...I don’t even know my ventilation plan, haha. I’ve been thinking of making modular walls (like for the gable ends) and having dedicated wall builds for winter versus the other seasons. If I could design removable walls that weigh less than 100lbs each, I could just swap em twice a year. I don’t know exactly how I’d do it but I feel like it’s doable. Alternates are to use plastic and wiggle wire to mitigate any drafty parts of the venting system that are extraneous during winter.

So you'd take a 20' piece of conduit and bend it into an arch or an L?  You said arch at one point but also a 12/12 pitch at another.  Not that it matters for the discussion but the peaked roof at a 12 pitch would shed much better.

Sorry about the climate battery confusion.  The phrase "climate battery" is often used to mean underground heat storage so I thought that's what you were talking about.

It's good to have back up plans in case it doesn't work.  My goal is bananas and tropicals.  If that fails I'll go for citrus.  If that fails I'll go for Mediterranean stuff.  If that fails, I'll have a highly extended growing season for annuals.  If that fails I'll turn it into a wedding chapel or barn.

With beeswax or other phase change materials, it's good to look into their suitability for the process.  Many materials have been tested for their phase change reliability.  Some peter out and stop phase changing after a while.  Glycerin is only "ok" as a phase change material.  A bunch of waxes are really good but they're not natural waxes like beeswax.

Hi Mike
I have read many of the screens detailing the evolution of your greenhouse design. Many of your "steps" or ideas aren't much different than mine or a hundred others. I am wondering if the thinking stopped, a strong line was drawn and construction completed. Somewhere, you have to stop thinking and build so, if for no other reason, you can see what should have been build differently. So, just as I did after building my first small greenhouse I wonder if you have discovered what you would do differently with the second greenhouse.

My location is southwest Nova Scotia, Canada at approximately 44.6 degrees north. You, in Wisconsin, would be around 43.8 - closer to the equator than I but we both know our daily average temperatures annually are not similar though this Climate Change thing s causing our temperatures to slide closer to yours. I lived in Calgary, Alberta for almost 50 years before returning home and returning to the land.

Part of my research the past year and a half has been to go back in history and see how greenhouses used to be built. Ever since fossil fuels became easier to ignite, we have forced energy to heat our greenhouses and, as a consequence, we can now grow less variety of fruit and veggies than the mid to late 1800's. Now we complain bitterly of the cost seemingly unaware of the loss of so much food. China was ahead of Europe for centuries. England grew pineapples for the dining room table twelve months of the year without electricity or burning fuel.  

The lessons learned from the first construct and more studying are being applied to the second greenhouse.

Of the texts, abstracts, documentaries and listened to those who have built - your written effort would have to be the most complete, practical, detailed, simple and workable effort to date. And, the only one I have posted a request to learn what would be different, what was "one step" short and other thoughts you would like to share.

Thank you for your efforts so many have benefited from!

Dave

Hi David, welcome to the journey.  Yes, many of the things I've incorporated have been thought of by others but I hope I've brought some originality to the overall greenhouse.

I don't have a clear delineation between when the design ended and the construction began.  I got as much design done as I could last winter and drew the line at the point where I could start to dig the foundation.  Nothing like the weather dictating when you get to start.  Several elements were figured out on the fly and the design evolved a bit.  But I don't think I back tracked on anything major, other than not pursuing some ideas.  Or at least not pursuing them yet.

I haven't put together my full thoughts yet on what a second greenhouse would look like.  Some of my greenhouse's compromises were due to the space and terrain in my back yard.  My initial thoughts on how to do a second one would be:

Build into a South facing hill a bit

Make the south cement block stem/pony wall about 8' high

Have an A frame (not curved) N and S roof faces

Dig a dry pond on the south side to allow snow to slide off into

Luckily, I think you're in a much warmer and more southerly location than me.  I'm half a degree north of you and my winter temps are about 10F lower (both highs and lows).  Or at least that's compared to Halifax, I'm not sure where in SW Nova Scotia you actually are.  I think my design is suited to frigid and often cloudy areas.  If it's cloudy all the time I'm not sure it would work as well.  If it was sunny 95% of the time in winter it would be a slam dunk.  When I get the compost heat working it will be awesome.  If I totally gave up on avoiding fossil fuel heat I think it would be quite affordable to keep at 50 at night.

Last night (March 3rd) we had our second coldest night of the year.  -24F!!!   I trudged out there and the temp inside before the sun hit the building was +26F.  50 degree F delta T without the moveable insulation engaged.  It's been full sun all day and I was working in there with shorts on.  It was 95 in the shade.  Our latest snow has covered the south wall about a foot over the patio door vents so I'm missing out on about 3'x40' of solar gain.  But maybe that helped insulate it overnight a bit...

Thanks for the kind comments on the thoroughness of this journal, that's kind of what I was going for.  Some people might want to build something quietly and only show off if it works.  Here I wanted to get outside input and share the process and the success (or failure).  Plus I like reading other people's build journals so I figured I'd do the same.

Edited to add the temp charts for Halifax (first) and my area (second)

@Mike, do you have any of the temp probes up and plotible?  I forget your background, but if you need help setting up some code to generate plots (and maybe also display details from local weather forecast, etc.) let me know and I will try to break away some time.  Actually I have plans for doing the same for myself...

Hi Ebo, I have a couple temp probes in the ground and in the compost bin and I have an Arduino but they aren't connected.  

I can work on putting siding on the West walls, start on electrical service wiring and the panel, digging and burying a "poor man's GHAT" or setting up the Arduino.  I'm least confident about the Arduino so it keeps getting put off

Well... looks like you have your priorities about right ;-) meaning do what you need and you know first...  I have the embedded electronics and similar stuff sitting in my room to poke at when I wake up and have a moment to play.  BTW, it looks like the house part of my renovation will *finally* get done in a week or three...

Spring is coming and the greenhouse is poking along.  In the winter, I only felt like working in there on sunny days.  Now that it's a bit warmer out (40F) the sunny days are too hot in there so I'm seeking out the overcast days.  

Since the last update I finished most of the siding on the west wall.  The catwalk is now complete except for the handrail.  The missus stained it white so it disappears into the ceiling.  

I'm figuring out the electrical service since I want to do that next.  I'm planning on running 2-2-4 aluminum URD wire from my barn to the greenhouse via a 1.5" pvc conduit the missus trenched in last summer.  I'll feed it with a 50A breaker even though the line could carry more.  I'll do surface mounted EMT conduit for the circuits in the greenhouse.  I'd prefer working with pvc but the EMF blocking of conduit is a deal maker for the boss.  She'll paint it to protect it further from the humidity/condensation.  I'm thinking I'll need 5 circuits for: outlets, water pump, climate battery fan, lights/ceiling fans, and the moveable insulation motor.  I may need more circuits for grow lights but I'm hoping I don't have to use them.

Once that's done, I'll start digging up the floor for the "poor man's climate battery".  I'm thinking I'll dig trenches every 2' from the north wall to about 3' from the south grow bed.  They'll connect at the south end.  The trunk line will be along the north wall.  So air will be sucked off the ceiling and sent down this trunk line (at or near ground level).  Every four feet a 4" drain tile line will leave the trunk line heading south.  When it gets to the south end of the run, it will do a u turn and come back 2' over.  Back at the north end it will turn and blow up into the room.  I'll try to trench 18" deep, we'll see how that goes.  My theory is that when I have sunny winter days (every third to eighth day) I can take hot air off the ceiling and send it through these cold earth tubes.  Condensation will be removed from the air, causing a further heat transfer.  The air should exit the pipes (having gone 25') at around 60 degrees.  The heat will bleed back up into the room slowly.  If anyone is good at climate battery math, let me know if I'm way off-base with my assumptions.

Anyone have good ideas for a trunk line material?  Or ducting to reach up to the roof?  I'm leaning towards black plastic culvert material for the trunk line (smooth ID).  And maybe standard galvanized ducting for the line up to the ceiling.  When the hot humid air travels down into the trunk line, it will condense.  I want to limit rust/rot.

After all that's done, I think I can start planting stuff and mulching the floor.  It should be summer and I can mail order plants without them freezing on their journey north.

I started the first batch of seeds this week, some in flats and some in the planting bed.  In a day or two I'll move the pineapples and citrus from the house out there.  Yay

Lately it's been getting spring-like outside (despite the snow in the last picture).  Highs in the low 40s and lows in the 20s.  The morning temp in the greenhouse for the last four days was 36, 39, 42 and 50.  I think the thermal mass of the building is not hurting the warm-up any more.  Today it was sunny and it got up to 116F in the shade at 4' off the ground.  A bit too hot but I don't have the vents working (or the climate battery).

Oh, one other problem became apparent.  Early on in this thread we debated if I needed a blower for the double poly or if I could just space the two layers apart.  When I first installed the poly, the two layers were just barely touching at one point at the top middle of the greenhouse.  After a long winter with some snow at times, and huge temperature swings, now the layers are touching in many places.  So I think I need to consider adding an inflation fan  See the fourth picture below.

@Mike, if you know of any good engineering books/materials going over the earth battery, please post here.  I have not seen any.  All I have seen is very rough numbers from the Citrus in the Snow guy, and soil temperature profile normals.  The Citrus in the Snow guy uses something like 4 to 8 pipes running something like 200' to get the temp to stabilize.  I would use plastic underground, and try to use stainless above.  I have read people using perforated pipe underground so that any condensation will leak out.

Derating the estimated 100A @90C capacity of 2-2-4 aluminum SER wire is a very good idea.  Also use niloc (or whatever it is called -- which keeps the connections from oxidizing).  Your electrician shoud do that, but know that if you are in a place that will allow you to do your own wiring to read through the code books and comply with at least the residential standards, if not the commercial ones.  Like I tell people "every sentence of the code book represents someone being injured, maimed, or killed".  Following the code is not just the law, it is a VERY good idea.  Also, run another separate ground wire (unless the 2-2-4 is shielded).   Also, go ahead and wire up the an extra outlet circuit (or a special outlet near the door for 240V and 120V).  You never know when you need to run an extra fan, emergency heater, water pumps, welder, etc.  It is easy to wire up when you are starting, and a pain later.  Also, make sure that the ground and commons are *not* tied together in the breakout panel, but *are* in the main panel where you took the power from -- tying both can create a ground-loop.  Oh yea, and this is likely very important also, use GFI's where it makes sense, but know you should not use them on circuits with GFI's...

Before putting in a inflation fan (that will const constantly), try just installing a wax-filled vent piston (see: https://www.amazon.com/Univent-Automatic-Solar-Vent-Opener/dp/B0083IZG0A for a good one that would work close to the ground, but I would look for one that can be set to open near 90 or so for a vent near the apex).  Once you know what can be done with passive means, you know what you have to operate actively.

I probably forgot a dozen things off the top of my head, but this should be a decent start.  Hope this is a good start.

Also forgot to say, this is one cool build Mike.  I wish you the best of success with it!

Thanks Ebo!  I have an electrical engineer (with power experience) helping me with this from afar.  My plan is to not run a ground from the greenhouse back to the barn but to just use a ground rod(s) out at the greenhouse.  The QO panel I got from the restore is in good shape but has the bonded ground so I'll be putting in a separate ground bar.  And I'll use the anti-corrosion paste, thanks for mentioning it!  Great idea about an extra outlet for 220V.  

The one thing I've seen for air tubes is this calculator that I think is the hallowed Sunny John calculator.  https://web.archive.org/web/20120103180312/http://numsum.com/spreadsheet/show_plain/4681

I ran my numbers through it and found I needed 77 pipes.  I'll only be able to fit about 8 at this point in the construction.  No biggie since I'm not trying to store months of heat, just two hours of heat every couple of days.  The calculator figures out ideal air speed which will be cool.  I guess I'm mainly curious now if my pipes are long enough to let the heat fully transfer to the cool soil before the air returns to the greenhouse.  I think I read somewhere that 20' or 40' is the max you need for this before you're just pushing air much further than you need.  Citrus in the Snow could be different since he's using the ground outside to just transfer earth heat to the tubes, not store 100+ degree air.  I think.

I also dreamed last night about using chimney cinder block as the trunk line.  I could bury them so the top side is flush with the surface and hammer drill 4" holes in the side for the corrugated tubing.  If I can get some cheap...  I haven't heard of SS ducting, do you know of an affordable way to source that?

The inflation blower would be to keep the two layers of poly glazing separate, not to ventilate the greenhouse.  I plan to do ventilation with wax cylinders.  I found a Gigavent Opener than can lift 65 lbs.  My upper vents are much heavier than "standard".  I might need two of these to reliably lift and hold one vent.  I'd love to rework them so the wax cylinder is at head level instead of at the peak.  It's ok if it's a bit too hot way up high.

Mike I like your design. Many years ago I played around with the idea of trusses like that with a foot of cellulose blown in them.

Sure is a lot to read, that's a big thread. Better get to reading.

I'm interested to see how your composting works out. Tom has free goat bedding delivered from next door. I had a hard time getting any solid information about potential heat. Tom's not so thrilled about compost, he thinks it's harder than you think! He's a farmer/science teacher it got to work and not take to much time. I don't know enough about keeping it working. I just thought the physical build bins, insulation, heat exchangers, could be fairly robust, load it once in the fall with a tractor? I think you would need some gigantic pile but I really don't know.
 
Mike

@Mike, Here is an updated (version 2.0) of the calculator http://www.ecosystems-design.com/uploads/2/5/1/9/25191018/climatebatterycalculator2.0.xlsx  Apparently they did not take into account the displacement of the hoses and some other things.  I am not sure what the difference is between 1.2 and 2.0, but maybe since you have the numbers handy you can rerun them.  Yes you are correct with the Citrus in the Snow using air outside.  For some reason I thought that it also circulated air and brought it back in, but you might be right.  Also to think of, and probably not experimentalable is something I was taught back in New Mexico working with adobe -- the thickness of the walls are not random, but chosen because of the temperature lag as it migrates through the material.  It has been 40+ years since I was told this and I could have the information wrong, but... at 9" thick walls, the heat will migrate through the adobe in 12 hours.  So the max heat of the day will actually migrate through into the interior by the middle of the night, and the cool of the night will might through to the heat of the day.  The thick walls (I forget if they were 24" or 26", but that would migrate through in 1.5 days.  All that said, the head does not travel in one direction, but all, so you would get this attenuated fluctuation due to the thermal mass.  I always loved living in adobe homes, but you *must* make sure you have a good roof and a good foundation -- everything in between is negotiable.

punched send to quick...

re: SS vents.  Take a look at stove pipe and I have seen commercial SS ducting advertised around.  

Hi Mike, Tom may be right.  I don't have the compost figured out yet.  It started heating up in the fall when I first put it in, but it cooled off and has just sat there all winter.  I've turned most of the "knobs" I have available without clear effect.  Unless I do some summer trials, I think next year I'll run the city wood chips through my wood chipper to greatly increase their surface area to volume ratio.  And I'll mix in a few bales of organic hay, a bunch (40+ gallons) of coffee grounds and a lot more water.  I think with smaller wood chunks, more nitrogen and more room for air passages, the compost will heat up better.  

With large amounts of manure, I'm afraid that it will be too hot for too short a period.  I need 5+ months of heat.  Also it could give off a lot of ammonia which would be a problem with my pile being in the greenhouse.

That's right Ebo, I think I saw a geothermal greenhouse in the prairie of Canada that stored summer heat a ways under the greenhouse and had a layer of insulation between the heat and the floor to deliberately give the right amount of lag.  From what little I know of thermodynamics, that must have been a hell of a gamble.

I may have been unclear.  I think the Citrus in the Snow system sends greenhouse air out, through the long duct run and then back into the greenhouse.  I think since the heat transfer is happening out in the yard, the earth temp is lower than in a climate battery so that could be why it needs more ducting to get the circulating air up to temp.

I think I need something a bit larger than SS stove pipe (I could be wrong though).  And I think SS ductwork for industrial applications would be way out of my price range.

Mike Jay wrote:If anyone is good at climate battery math, let me know

If you wanted a professional with actual climate battery/greenhouse experience, you could reach out to Rob Avis of https://vergepermaculture.ca/  I think he could likely consult with you at whatever level of involvement you wanted, say, a little experience-sharing, up to a full engineered design.  Great guy.

Thanks Kerry, I'll give him a shout!

Ok, it's been a little while, time for an update.  The dandelions are blooming in the greenhouse!  And a winter storm is raging outside

I started the electrical work by adding conduit across the greenhouse (1-2' deep) and up to the panel location.  Then I fed the supply wires through the conduit to the greenhouse which was a pretty easy push (80' straight).  The hard part was figuring out the conduit in the basement of the barn to get around beams and up through the floor to the panel there.  Just the barn part took a full day.

Then I got to learn how to install conduit.  I did a run across the north side of the greenhouse to handle all the outlets, fans and water pumps.  I'll do a run for lights and ceiling fans later.  I still need to pull wires through it and  I also have to get a ground wire outside and put in a grounding rod.  I sure wish I did the ground wire when I was laying the block.  Oh well.

When it's sunny out, the temp can climb to 125 at ground level.  I discovered that my upper vents are glued shut.  The foam weatherstripping I used was adhesive on one side.  But the weight of the vent and the heat must have made both sides sticky.  I got one open and it makes a world of difference.  On a 50 degree sunny day, when it should be 125F inside, if I open one person door at ground level and open one upper vent by 12", it drops the temp at ground level to 85.  That astonishes me.  I might only need to have a vent opener on one or two vents, not all five.  Woo Hoo!

I was going to get a Gigavent opener but they're $130 and can only lift 60 lbs (not shabby but borderline for my vents).  Instead I found a Vent-L for under $40 that can lift 130 lbs!  It's made in Russia.  The only problem is that the instructions aren't in Russian or English.  Well, they're technically in English but are total gibberish.  With the pictures I think I can figure it out.  If they just had Russian instructions I bet someone here on Permies could translate for me.  I'll hopefully get it installed in the next week and then I won't worry about cooking my seedlings.  If it does work, I'll get more and use them on the lower vents as well.

Now I'm to the climate battery phase.  I'm rethinking the "poor man's climate battery" idea.  The idea of burying 300' of plastic a foot underground is starting to seem iffy.  Both from a labor point of view and a plastic ick underground perspective.  But if I'm ever going to do it, now is the time.  

An alternate idea popped into mind.  It would be to harvest heat off the ceiling on sunny cold days by ducting it down to ground level.  Then blowing it through a radiator to transfer the heat into water.  Then either store that water in barrels or use it to heat up phase change materials in barrels.  The things I like about this system would be that I could turn the fan on during cold nights to draw heat out of the barrels.  Or just let the heat bleed out of the barrels slowly.  And if the system is undersized on the collection or storage side, I can just add more radiators or barrels.  Or add a series of barrels with different phase change materials in them.  IE first the hot water goes through a 100F phase change barrel, then to an 80F phase change barrel, then to a 60F IBC water tote.  I don't relish the idea of a loud fan running all the time so I'd want to muffle that somehow.  Any thoughts on this as a good/bad option?

I have a bunch of seedlings started and many are up already.  I moved the pineapples and citrus from the house out to the greenhouse.  And a bunch of peas are 2" high in the planting bed.

First pic is of the panel.  The plastic conduit is crooked
Second pic is of the pineapples and planting bed
Third pic is of the seedlings (dandelions at the upper left)
Fourth pic is of the citrus collection (and a few other plants)

Here's a crazy thought if you wanted to play with it.

You'd need to dig a trench over a foot deep anyway to bury the weeping tile or whatever you'd be using, right?

Why not dig the trench to a foot, then dig a slightly narrower trench to the depth desired for an air passage, and pipe it directly through. You can, and probably should think about, putting grates in strategic places, but you could span the top of the smaller trench with, well, anything that sits on the shoulders formed by the slight widening. Then put your supply piping, whatever you're using to put the air into the underground duct, in place, backfill the trench overtop of the spanning material (I would use bricks or pavers that were wide enough), and bam, an underground heat exchange duct without plastic.

-CK

Ahh, so make an earthen tunnel with a paver/tile/brick top that is all covered with a foot of soil.  I wonder if the sides of the tunnel would hold up or start to slump into the air passage?  I could do bricks on the sides as well but then the cost is starting to climb...  Good idea, I'll noodle on it!

Just the blue barrels siting in the sun in my greenhouse get up to 85.  I have one black barrel but it doesn't seem to make that much difference.  I also have my larger plants in 35 gallon barrels full of soil with a water reservoir in the bottom to wick up into the soil. These also warm up from the direct sun exposure.  
My suggestion for a passive system with your house is to cap black ewer pipe, fill them with water and stand it along the north wall for a minimal loss of space and maximum absorbed area.  You can start with a few and observe the effect before committing to the whole wall.

Glee Skals wrote:Thanks for the reply mike. I've been working on all kinds of methods to cover the glazing at night and I'm finding out why there isn't any real info about how to do it, because it's not an easy thing to have something moveable with a high r value.  When you think about insulating the north, east, west walls to an average r value of say 24  then have half the structure (the glazing) at r2 the high r walls are not saving all that much. Increasing there r value is not cost effective above a minimum without also addressing the glazing heat loss. Now if we could get that glazing to r24  at night then  storing solar heat in the floor, or water ,or even heating the greenhouse become a real asset for cold winter growing in our zone.

I haven't come up with any way to do that yet, at least not if I want a conventional looking greenhouse but I'll continue  thinking it thru.

I Wasn't suggesting you put polycarbonate on your greenhouse just that I had thought of a similar idea but had thought about the polycarbonate because I live where its windy all the time and plastic just wont hold up. I do think though it might help to allow your insulation to endure the rigors of repeated opening and closings. Maybe one day when you have to change it for some other reason

Ill keep following this thread and see how it turns out for you and if I come up with a way to get that r24 glazing covered at night ill share it.

So insulate.  Here is the one that looks like the best bet.  At an R per inch it looks like even R30 or are R40 might be readily doable.



Or more info on another one.

http://organic.yukonfood.com/bubblehouse.htm

Thanks Hans, I had 8 blue barrels of water in the greenhouse over this winter.  They spent December-January frozen solid.  For my space I think I'd need many barrels to store enough heat and once my perennials were full size, they'd shade them.  That's kind of why I like the idea of collecting heat off the ceiling and pumping it into tanks/barrels that can be hidden behind bananas.  And that can be heated up much more than they could via direct solar radiation alone.

C Letellier, the soap bubble systems sound awesome!  I hadn't seen much solid info about them when I designed this greenhouse so I think I missed out on an opportunity.  Oh well, next time

@C Letellier, the soap bubble system looks interesting but there are a number of things that I would want to see worked though before I would consider it, and also cautionary tales I would suggest --

* the type of soap is crucial.  May soaps contain anti-bacterial additives, and that could really mess up the soil organisms.  So could just regular soap itself if it gets on the soil at all.  I do not know if you know, but one anti-mosquito trick if you have open non-potable water sources like a smithy quench tub, is to put a couple of drops of soap on it -- it changes the surface tension on the water and the mosquitoes drown.  I would be seriously concerned about all the beneficial insects, detritivores, and bacteria.  This would completely mess up the soil organisms unless you could recapture basically all of the soap, and you have to plan for dealing with the consequences of the inevitable tear or leak.

* working out how it behaves after the temperature drops below freezing.  Do you know at what temperatures the materials in the bubbles freeze and become a frozen shell?  How sharp would those shells be in a storm when the wind pushes against the exterior surface of the glazing and they break and rub against the plastic.  It is possible that they might remain flexible throughout, but this would have to be tested.  That said, if this was set up as an emergency measure to save a winter crop, it might be worth the cost to re-glaze if you saved enough produce to cover the cost of re-glazing.  This would be a cost benefit analysis.

Hmmm... I just realized that I might have come down as a nay-sayer/downer.  Not my intent.  If you could work through the issues of recapture, potential toxicity to soil and pollinators, and mechanical strength, this could be a simple solution to a really nasty problem.  If you could find a way that would pass organic certification I would definitely go for it.  Maybe there is someone at one of the ag extension research universities that could help you work through these issues.

There are likely other issues as well, but I bumped into this at 2:45 in the morning after waking up, and I have not had my first cup of tea and not all of the 8 cylinders are firing -- feels more like the old single cylinder hit-and-miss <https://www.youtube.com/watch?v=euIMiSaYPX0>...

ok... a bit more awake now...  It looks like there are working examples been running for 17+ years now, so the low temp behavior is not an issue.  They build a trench that recaptures the bubble solution.  What little I have read does not look into the soil/tox issue at all.  Have you seen any discussion on what soaps work in this application and have been tested to not harm soil organisms or pollinators?

Looking into this a little more, "R-value per ASHRAE 90.1-2016 Section A9.4.2. Airspaces less than ½” thick shall have no R-value. The Rvalue for airspaces between 3.5” and 12” thick shall use 3.5” thickness as basis."  So a 30" air gap would give you something around R-8.5 if you can trap the air.  Anyway, this is an interesting idea.  I am just concerned about its effects on the soil in case of a leek.

I think the R value math for the foam isn't the same as it is for a singular air gap.  I'd say it's closer to open cell foam or fiberglass.  It has so many individual air gaps and thermal boundaries that it takes a long time for heat to transfer through it.

Mike Jay wrote:Hi Mike, Tom may be right.  I don't have the compost figured out yet.  It started heating up in the fall when I first put it in, but it cooled off and has just sat there all winter.  I've turned most of the "knobs" I have available without clear effect.  Unless I do some summer trials, I think next year I'll run the city wood chips through my wood chipper to greatly increase their surface area to volume ratio.  And I'll mix in a few bales of organic hay, a bunch (40+ gallons) of coffee grounds and a lot more water.  I think with smaller wood chunks, more nitrogen and more room for air passages, the compost will heat up better.  

With large amounts of manure, I'm afraid that it will be too hot for too short a period.  I need 5+ months of heat.  Also it could give off a lot of ammonia which would be a problem with my pile being in the greenhouse.

Mike, do consider adding biochar to your compost pile. It will cause it to heat up better and it will absorb up to 90x it's volume of ammonia gas.  My little 3x3x3' pile got to 160F.  Only down side might be a faster overall process.  I add about 20% of the volume of the pile throughout it.  Bonus at the end is super nice compost with higher nutrient content that will last for a 1000 years :)

Good point Greg, I'll add that to the recipe.  I can see how it might suck up ammonia gas (carbon filter effect), but how does it contribute to the pile heating up?

That is a great question.  My speculation is that it has to do with being a granular sponge.  I don't crush mine, I leave it at the full size it's made at....something like 1/2 - 1", but lots of other sizes too.  Then I lay 2" on the ground to sop up any compost drippings while creating an air permeable base.  The rest of the pile has it throughout and it may help open up air channels there too, albeit not as much as the base.  Since the biochar can fill up with water, but also space things open a bit for air and drainage I figure it does that in the pile like it does it in the soil.  Also, all the wet surface area in the biochar is a home for soil microbes, so that likely helps in the pile as well.  I should really try and examine my biochar more throughout this process.  Would be fascinating to see exactly what's happening in that microcosm.  I wonder if I can get a university soil scientist interested in my compost piles :)  Hmmm, any of you guys a university soil scientist?

One thing we've learned about biochar is that it's able to efficiently shuttle electrons around, allowing microbes to use it as an electron sink and an electron source, something that the humates in compost can also do.  This really helps make soil microbes' lives easier and leads to higher critter populations.  I assume ultimately that these properties supporting higher populations leads to the heat up and faster turn over times.  Would be very interesting to see how biochar from one batch added to the next effects the situation.  Also, if you could dry this activated biochar and send all the critters into dormancy, then just wake them up with water and a pile of organics...would think that would be a great inoculation process, but???

I just planted a flowering quince in some biochar compost to see how it does compared to a commercial seed starting mix.  I'm expecting it to be interesting :)  At least holding the materials in my hands I can tell you that one of them is MUCH more interesting to me.  Can't wait to see what they look like in a month.

I would ask Dr. Redhawk.

I suspect it's a combination of holding air or water and housing thermophilic bacteria. It's the bacteria that get things hot, so naturally if you fix it so there can be more bacteria in a smaller space, you get a hotter pile than you otherwise would for the size.

-CK

Ebo David wrote:@C Letellier, the soap bubble system looks interesting but there are a number of things that I would want to see worked though before I would consider it, and also cautionary tales I would suggest --

* the type of soap is crucial.  May soaps contain anti-bacterial additives, and that could really mess up the soil organisms.  So could just regular soap itself if it gets on the soil at all.  I do not know if you know, but one anti-mosquito trick if you have open non-potable water sources like a smithy quench tub, is to put a couple of drops of soap on it -- it changes the surface tension on the water and the mosquitoes drown.  I would be seriously concerned about all the beneficial insects, detritivores, and bacteria.  This would completely mess up the soil organisms unless you could recapture basically all of the soap, and you have to plan for dealing with the consequences of the inevitable tear or leak.

* working out how it behaves after the temperature drops below freezing.  Do you know at what temperatures the materials in the bubbles freeze and become a frozen shell?  How sharp would those shells be in a storm when the wind pushes against the exterior surface of the glazing and they break and rub against the plastic.  It is possible that they might remain flexible throughout, but this would have to be tested.  That said, if this was set up as an emergency measure to save a winter crop, it might be worth the cost to re-glaze if you saved enough produce to cover the cost of re-glazing.  This would be a cost benefit analysis.

Hmmm... I just realized that I might have come down as a nay-sayer/downer.  Not my intent.  If you could work through the issues of recapture, potential toxicity to soil and pollinators, and mechanical strength, this could be a simple solution to a really nasty problem.  If you could find a way that would pass organic certification I would definitely go for it.  Maybe there is someone at one of the ag extension research universities that could help you work through these issues.

There are likely other issues as well, but I bumped into this at 2:45 in the morning after waking up, and I have not had my first cup of tea and not all of the 8 cylinders are firing -- feels more like the old single cylinder hit-and-miss <https://www.youtube.com/watch?v=euIMiSaYPX0>...

All of those were on my list of questions.

As for additives in the foaming agent that one solves by buying pure foaming agent.  This is one that isn't listed anywhere I have looked so far.  Guessing they are using a sodium laurel sulfate type product.  In which case the Drexel foam they are using for aircrete and for foam spray makers in the field would work.  It is approved for use on food crops.(still doesn't mean it is safe)  The MSD sheets for it lists it as biodegradable and the hazard warnings are really small.  I am also aware that one of the fire fighting foams is protein based so there again it should biodegrade.

As for bacterial growth in the solution I have been thinking the thing to try there would be copper which would be harmless to beneficial in most soils for spills as most areas have a bit of trace copper shortage anyway.  Probably added as copper sulfate.  That would also stop algae growth in the foam up in the sun.

As for organic debris and bugs in the solution that is a filtration and tank sealing problem.  Should be solvable.

As for frozen material damage I had seriously questioned that too.  I have found no written or video answers so this is my own thinking.  The bubbles should freeze at or just below freezing.  But we are making a light weight very fragile form of ice as it is nearly all air.  As the foam settles out this will happen slowly leaving the outer layers of frozen foam unsupported.  Most likely is for it to break off longer pieces so the foam under it squeezes up and lets it down slowly.  But even if the worst case happens and it breaks quickly will it hit the inside wall quickly or hard?  Remember it is light weight and it still has to push the air out of the way to fall.  Breaking pieces should be basically set down on an air cushion
shouldn't they?