Hey chris, is the site you are thinking of this?
http://www.sunnyjohn.com/indexpages/shcs.htm

Poppa

Nope!

The one I can't find is a university project where they built a greenhouse using brick or stone on the north wall and steel beams and tempered glass on a south facing roof. They had the 6" drainage tubes dug in a few feet and 100' long in a fan shape which they used for fresh air inlet.

The site you posted has great ideas on sucking hot and humid air from the top of the greenhouse and passing it through the raised beds (or water storage) where it gives up heat and returns to the greenhouse drier and cooler. That means the captured heat is not just blown out of an exhaust vent but the heat is retained inside the structure.

Poppa! That's the one I was thinking of. SB

Can't say i have ever seen that one.

I know UMass has something in Amherst that used a deep gravel (Stones actually) bed that they pass the warmed air through. They have been running for a while and seem to be quite happy with it, but it does take a lot of stone.

I liked the SHCS concept, but i could never get a reply either from the website contact nor any of the clients listed as to whether they were happy with their results.

The guys at solaroof didn't put much stock in it for a couple of reasons, mainly the low rate of thermal transfer for earth, low thermal capacity and mold issues. Rick at solaroof has had a few discussions with them and there are a bunch of old discussions archived at the yahoo solaroof forum that are interesting to read.

My goal (Cold Massachusetts winters) is to keep my (Unconstucted yet) 26x 52 greenhouse warm enough to grow some crops all winter (more than cool weather crops) with with little or no supplemental heating.

Current plans: Double wall 26 x 52 GH - poly covered, I would like to use ETFE but can't find any in the USA. GH is really a GH inside a GH, both fully framed with a minimum 20 inches between the two.

Solaroof insulated roof - to R30 roof and R20+ sides. Basically fills the gap between the two frames with bubbles/foam at night and cloudy days.

Heating none: I would like to run the GH as is for two seasons to get an idea of how efficient the solaroof concept is. Eventually i owuld like to use some renewable heat source - biomass/Methane generation/Oil from algae -lots to look at.

Thermal mass: Haven't really decided yet.

I like the SHCS but with the above reservations.

I also like the Solaroof concept but not sure how good it would be at heat removal in the summer. Means constructing a storage tank.

Have a third option (my own) that i am only starting to develop but i have some basic leg work to do to determine if it is feasable.

I don't like the idea of paying for some phase change material.

Poppa

Chris... this is the one in Amherst (UMass) that i know of.
http://www-unix.oit.umass.edu/~caffery/greenhouse/index.html

Poppa

poppa,

Oh boy did I remember it all wrong!

Yep that is the one I was thinking of, I saw it years ago when I was just deciding on building something then I lost the link. I am surprised the website is not updated as it was partially funded by a grant.

I've found a wonderful collection of thoughts, experiments and results:

A sample post

Click the thread link at the bottom to see all the messages. Here is someone that not only has practical experience, but excellent physics background too.

(linked from wikipedia, of course :)

I emailed Colleen/Glen Caffery and asked if they would have the time to repsond to some questions about their experiences with the greenhouse, but I haven't received a response yet. If I do, I'll share the information.

This is the response i got from Glen when i asked a few Q back in October...

Poppa

You're right that excavation and the mass are expensive, prohibitively so for agric. operations that are marginally profitable to start with, and the payback would be too long. However, many other features of our greenhouse are cheap and sensible, such as building with airtight construction methods and being thoughtful about winter ventilation (i.e., separating the ventilation for fresh air from efforts to control temp), and passive summer ventilation. Design's like ours just are not going to compete with hoop greenhouses on cost. But I think commercially available greenhouses could go a long way toward energy efficient design if they were pushed to do so, and if they used a little creativity.

We are very happy with how are greenhouse is performing. The longer term results: we've moderated the temps so that we the greenhouse doesn't get so hot (mostly because we added hens, and they don't like it hot). We still haven't lost any plants--including tomatoes--due to low temps. Our climate is zone 5a/4b, so that's pretty good. Beside the fan that circulates the air, this is without any dditional energy input.

I have found John at SunnyJohn.com very good to answer questions. I have coresponded with several people who have built SHCS greenhouses as well. I hope to take a field trip in March and visit some of these greenhouses.

Here is a comment from John about his first house.

I noticed the SHCS dynamic in my first house done this way, and it was the
36x24 shed roof straw bale arrangement toured on my web site. That system
had 1.3 ft of tube per sqft of house in a three layer matrix - I was getting
a 30 F deg temp differential between inputs and outputs with 90 deg F inputs
and 40 foot 4" tubing sections. The gross response was such that we could
have a 90 deg house when it was 95 outside and a 28 degree house when it
was 30 deg below outside with the wind howling away.

Looking at real world examples it seems that the main problem (apart from the difficulties in construction) is the large swing in day/night temps.

http://www-unix.oit.umass.edu/~caffery/greenhouse/performance.html
They modified the structure and now ""We are very happy with how are greenhouse is performing. The longer term results: we've moderated the temps so that we the greenhouse doesn't get so hot (mostly because we added hens, and they don't like it hot). We still haven't lost any plants--including tomatoes--due to low temps.""

http://www.ibiblio.org/london/renewable-energy/solar/Nick.Pine/msg00002.html
A very good article on the progression from passive to active to agressive solar heating. Note again the problem with excessive temperature swings.

http://www.ibiblio.org/london/renewable-energy/solar/Nick.Pine/msg00028.html
""I've rethought the problem you mentioned, that there may be a daily air
temperature variation (delta T) larger than most growers can tolerate,
in this solar-heated greenhouse design.""

As for SHCS then that system is using the thermal mass of wet dirt. It could just as easily be pipes through water. However, if the SHCS greenhouse also used above ground water storage as well, a hybrid system would have kept the structure at 32F on the times when ""The gross response was such that we could have a 90 deg house when it was 95 outside and a 28 degree house when it was 30 deg below outside with the wind howling away."" That magical 32F. In a "phase change" type of system you would think they would have spotted that important point. The SHCS system emphasises latent heat of vaporisation, not solidification.

And, from the world's expert in raising plants in an unheated greenhouse a realisation of the problems that have to be faced I present!

http://forums2.gardenweb.com/forums/load/strucs/msg1108354418631.html

"" * Posted by: Chris_in_Iowa 4b (My Page) on Thu, Nov 10, 05 at 21:43

I am all for starting seeds and growing them on to transplant size in a minimally heated structure in the spring. If you have minimal or no supplimental heating the biggest problem is it is TOO hot in there during the DAY.

I say that because the temptation is to run the greenhouse as hot as you can during the day so as to store up enough energy in there to make it through the sub freezing night. This causes me to have major problems with "leggy" plants, too hot but not the corresponding intensity of light ""

The "world's expert" comment was a joke....

:)

"Looking at real world examples it seems that the main problem (apart from the difficulties in construction) is the large swing in day/night temps."

Agreed.

"As for SHCS then that system is using the thermal mass of wet dirt. It could just as easily be pipes through water."

Chris, i also thought of that but the issues there would be condensation within the pipe and the amount of ducting needed. I am not sure if the duct would ever actually fill with water from condensation, but i think it would be possible. I thought some sort of drain system would work but then it starts to get complicated.

"If you have minimal or no supplimental heating the biggest problem is it is TOO hot in there during the DAY."

The solaroof system could be used to generate partial shade if needed, though that probably isn't desireable this time of year. I built a small (8 x 12) lean -to once upon a time and during the winter i could see temps as high as 105F in the daytime even when the outside temp was in the 30s. That is really the concern for me. What ever I come up with will have to be able to absorb that much heat. I am leaning towards a hybrid. Something akin to the SHCS design (but better!) and a secondary system the uses the Solaroof heat capture design.

The drawbacks that i see?

In the SHCS system, there seems to be a lot of concern for molds and bacteria. I have visions of legionaire's disease festering under my GH. I have no clue how to tackle that. Since i also plan to have an aquaculture system in the gh, i suspect that it will be a tad on the humid side anyway so maybe it shouldn't be a concern as much as it is a fact that i need to make sure i have a good medical insurance policy. ACK!

The solaroof design, i just don't like the idea of a huge storage tank, never mind the cost of one. I could bury the tank but unless i can find something like a 5,000 gal sap collection tank at auction.... soon.... *sigh* (I still need to do the calcs and figure out how big a tank i would need.)

"The "world's expert" comment was a joke.... "
You sound more reasonable than many. :-)

Poppa

I noticed that the flow of this thread bounced around the idea of SHCS for Solar Heated Greenhouses. It looks to me that there is an opportunity now here to expand some more on that particular design practice. If any one cares to talk about SHCS particularily about theory, concerns and direct experiences, I am on the forum now. It looks like this thread is alive with good solid understanding of SGH ideas. I'd love to contribute any input possible from my 25 years of building dozens of SHG projects in any way I can. BTW, I've already prepared a small FAQ recently that answers some questions already raised in the thread.

Sorry to have ignored you MrHobbit.... things got busy.
I guess the one question i would ask at the moment is... do you have a list of email contacts who would be willing to share some experiences/comments?

I went through your site about 4 months ago and tried to contact any of the sites that you had links to that were still active and i got no responses.

Thanks!
Poppa

Poppa,

Sorry for the time delay, I've yet to set this forum's auto-notification flag (there is one, isn't there)

Sorry for the lack of clickable live links to private homes and folks. I hope you understand.

Someday soon, we will have a fully network accessible online page of a fully decked out and sensed SHCS out in Utah. A Boeing engineer is doing it I believe.

I caught the reference to heat of solidification... only useful if the space is full of tropicals. Otherwise, 28 is plenty for meditteranean perenniels and food stuffs. I've used a barrel of water in my root cellar's over the years, works like a charm.

And because you aren't shooting to 32, the anxiety level drops to zero, 'cause when you can manage 28, it is way too hard to go any lower (like leave a door open or something!) Like Eliot Coleman says, pick the plants to meet the environment that can be done with little or no inputs other than covers. It's working and worked marvelousy in Europe for millions for centuries now.

I hope you aren't still concerned about legionnaire's disease... it is almost impossible for it to develop in soil that is already alive and fully populated with "normal" microbes and molds - and because the tubing in so heavily perforated, there is no isolated conditions for that kind of episode to develop. I've never heard of LD happening in caves - ONLY man-made ducting with NO natural background of microbes and fungi. At least that is my explanation for why it has never happened in anything I've seen or done for the last 20 years. But I could be entirely and foolishly wrong here... each to his own I suppose.