I tried the water barrels last year and seen no real change in temperature. The shade cloth is the best investment I made along with a misting system. I think the key to this posting is most of us have traditional GH not a shed with a partial glazed roof. I think this makes a huge difference in temperatures.

Tom, I wonder if you could check your inside/outside temps at dusk, at 2am, and first thing in the morning? It would be even more instructive if you could check the water temps at all of those times.

I tried the water in my little 10X12 GH it don't really help much. In the fall the ground is still warm and had TOM not had the water the GH would have been warmer than outside temperature.
The wife started complaining about not enough room for the plants because of all the water and I told her she was right we built the GH to grow plants not store water and if I can't afford the very small difference it cost to heat it I had no business buying it in the first place.
The water is gone and on a hot day I depend on shade cloth and a large exhaust fan and it works much better than your water will and since it is thermostat controlled I can maintain a much more steady temp than depending on the water that will only work until it heats up and then it has NO cooling

My goodness. I didn't realize there was an ongoing debate on the use of water barrels as thermal mass. I hope my thread is not angering anyone. First off, Belleville is correct in that this is apples to oranges. I have a sun shed, not a greenhouse. And Wyndy is right in that I have excellent insulation covering everywhere that the polycarbonate twin wall is not. I have one West window and its bubblewrapped. And Greenhouser, yes the sun hits the water containers and heats them up. that is why I have them :) Stressbaby, you give good advice. I will keep records with outside and inside temps and water temp 2 times a day, dusk and dawn. I don't have an automated way to get a 2 a.m. temperature though.

I have read in many places on this forum, as well as several books and websites about using water as thermal mass. It works and works well acording to these references. Even a small amount will reduce your fuel bills. I already know this by the reduction of heat in the summer. On days less than 100, it was downright pleasant inside my shed. My 30 gallon containers will not freeze solid until the coldest part of my winter so I know they will fight hard to keep my shed at 33 or better. No, I don't expect miracles nor do I expect it to last the winter. I do expect it to extend my season and my choice of vegetables after harvesting tomotoes soon, will turn to lettuces and choi's and cilantro and spinach etc which are big enough now to be placed in the shed. I use homemade self watering containers to add even more stored water!

The debate seems to be, if you can't sacrifice the room for enough water to matter, then use fuel. I'm not in that debate. I have enough room.
~tom

I was referring to the water cooling your GH shed. Once the water got warm it wasn't going to cool the air.

When I filled the bins and barrel in my GH the temp stayed the same and the water was pretty darn cool. I don't have the water to hold heat or to cool the GH but to winter over tropical pond plants. The barrel is for dipping the water cans in to save me trips to the hose outlet. :)

I don't think the thread is angering anyone. I benefit a lot from the open exchange of ideas here, and frankly I often learn the most from threads when people share differing experiences.

In the hopes of continuing the conversation with good will towards all...and, admitting I am a newbie to greenhouses...I can't understand how large black containers of water (being warmed by the sun) can lower summer inside temperatures by 30...?

I'm not arguing with what you're seeing, Tom (you know what's happening in your greenhouse.) It's just that I would have thought the sun warming the barrels in the summertime (August) would raise the temperatures in the summer greenhouse, not lower them. (That might be why Greenhouser asked you if the sun hitting the tanks didn't heat up the water.)

There must be something basic I'm not understanding here. How do the barrels have a cooling effect?

Oh no, I don't think anyone is angry at all.
I just think most of us wish we had bigger GH's or more room and resent anything that takes up precious space. :)

We've just discovered there are other ways to effectively and inexpensively cool or heat our GH's (like insulation, pool covers and shade cloth) without having to devote any space to water containers so that's the way we've gone.

I think everybody is OK here, I don't sense this thread going south. Just a good exchange of thoughts and ideas. ;-)

The idea behind the barrels is that they moderate the temps...the barrels absorb light and change that energy to heat and store that heat in the water. The "cooling" would occur because the light energy transferred to the barrels and the water would otherwise heat the air, the plants, or something else in the GH.

The other idea behind the barrels is that they take advantage of the latent heat of water. When water freezes, it releases a large amount of heat. This can serve to keep a greenhouse right at the freezing mark at night. Of course, the next day, when everything thaws out, that same amount of heat is absorbed back into the water. This whole phase change property is useless, of course, if you have tropical plants and desire a GH in the 50's or 60's.

Mudhouse, I, too, have a hard time believing that 220 gallons of water is responsible for 30F drop in daytime temps. I added 130 gallons of water this year and I didn't notice any real difference in temps.

I personally have some doubts about the ability of stored water to have a major, practical impact on moderating temps (outside of the phase change/latent heat property mentioned above). I will give my rationale based on my GH and my water temperature observations. The water will clearly gain heat during the day. However, the heat will be released just as soon as the temp differential is reversed. That is to say, as soon as the GH starts to cool late afternoon, the temps of the water start to drop. This release of heat begins long before that heat is really needed. In order to save any energy, the heat is needed in the middle of the night, but yet the heat release begins by 3:30 or 4pm, long before the temp drops to the minimum at which the heater would kick on. My observations lead me to believe that by the time the GH temp drops to the minimum, when the heaters would kick on, much, maybe most of the stored heat is gone.

Now, one could argue that the drop in GH temps is delayed by the release of heat stored in the water...one could argue that this all depends on the amount of stored water, the material from which the containers are made, the color of the containers, their position in the GH, and countless other factors...and I would agree with all of these points. And I am ready and willing to change my mind. It sounds to me as if you, Tom, you might have an ideal setup for testing these ideas. That is why I asked about taking some temperature measurements.

Thanks for listening!

SB

Thanks Stressbaby for the good explanation! My ears perk up when anyone talks about creative ways to cool...since my small GH is destined to be a challenge in that area.

It does sound to me like Tom has a great set up for experimenting with this (I'm jealous of the great insulation too.) My small space will never allow me to devote that much room to water, but I really do appreciate discussions like this so I can learn.

The real world observations noted here are very useful regarding using water for temperature moderation in greenhouses. Tying together the science and the practicalities noted, here are my conclusions. First the science: one pound of water raised one degree = 1 BTU. A 60 deg.F to 80 deg.F solar heat gain = 20 btu per lb. water. 250 gallons of water solar heated from 60 to 80 deg. = 40,000 btu. This would give somewhat of a cooling effect during the day. But, as stress baby notes, when the water starts to cool in the afternoon, the heat is released. This effect would start at 79 deg. By the time the heaters would come on in the night, at say 60 F., probably a significant part of the heat has already been released from the water. This heat release would delay the need for the heaters, but maybe not by as much as hoped. Just trying to tie all this together for my understanding. CR

The other part of your original question, regarding how much temp. differential can you expect later in the year. Since you have a very well insulated structure, the answer depends on the amount of sunlight. Comparing your 100% sunlight days to what may become 50% sunlight days, I think that you should expect a 50% decrease in the temps.and the differential. The whole solar heat gain equation is dependent on the hours of sun or the percent thereof. If you are fortunate enough to have full sun, but with even very cold temps., your structure should serve you very well.

I think the exchange here was good. It gives other people ideas to try with their GH. I placed rigid insulation along the sides of my GH, hoping it will stay warmer for the winter. I do have a solar pool cover(which is blue) but it will allow light to pass through so I may place this on the roof. I know though I will have to add a heater for the winter if I choose to keep my plants in their over the winter.When the nightime temps get in single digits I will have a heater on

To make sure that everyone knows that I have a shed and not a greenhouse, here is a picture of a very similar shed.

Another reason that my shed's ability to store heat does not apply to most greenhouses: I have a dull black foam floor covering my wooden floor. The shed sits on concrete pillars leaving six inches on average of clearance from the ground. On the ground I placed thick black plastic as a vapor barrier and then skirted the bottom of the shed with rigid insulation that goes downward 9 inches into the ground. The summer sun does not directly hit the floor, but the fall/spring sun does and it will really cover the floor in winter. I am guessing that under the shed is a good build up of heat during the day and it has nowhere to go except slowly upwards. Covering my R-19 insulation is reflective material everywhere that the sun can hit.

I also did not keep accurate records in the summer, but I know by the thermometer that the uninsulated shed with no water storage was hitting near 120 on the worst days with the window open and a small exhause fan. I can't say for sure that there was a 30 degree difference after insulation and the addition of water in August, but it never got over 90 degress inside the shed after that. And yes, August was cooler than July. It was a pleasure to be inside it during the day and in the night it was noticably, but not uncomfortably warmer than outside.

This morning at dawn it was 30 F and my bucket of water outside had a thin layer of ice on top. Inside the shed it was 49 F and the water temp down 6 inches deep was 55 F. No, I've added no external heat nor do I plan to unless the cold hardy vegetables demand it (or if I have any tomatoes left by then!!)

~tom

That's some good info!

Interesting that this morning your barrels still had some stored heat (based on the fact that the water temp had not yet dropped to ambient air temp).

It will be interesting to hear what the temp of the water is around dusk. This will tell us how many BTUs you are getting from the barrels overnight.

Nice work, Tom. We're all learning something.

Nov 02 07 5:22 p.m. 51 F outside, 76 F inside shed, 85 degree water temperature

~tom

30F*220gal*8.33lbs/gal = 54978 BTU. Not bad at all!

Your initial results are good, as SB points out. By my calculations, your structure needs about a 3500 BTU heater to keep the inside at 50 while it is 29 deg. F. outside. Based on SB's calculations, your 55,000 btu in the water should last quite a while during the night. The morning temps. just before the sun hits the shed- inside the shed,the outside temp. and the water storage temp.- will be very interesting. Keep us informed please.

Nov 3, 6:30 a.m. predawn temperatues. clear night and Full sun all last 7 days. 35 F outside, 51 F inside shed. water temp taken from 3 different sized containers and all 60 F.

It seems that I have BTU's to spare for the moment. Can I sell them as carbon offset credits! (just kidding :))

Thank you Stressbaby and Cuestaroble!
The big test I'm waiting for is when its cloudy most or all of the day... and what's it going to be as the temperatures get lower and lower as the winter progresses.
~tom

Tom,
Thanks for your numbers. Your results are impressive. You inspired me to do a little check on my own system. Double polycarb, free standing, 10x14, 75 gal. water storage, under a bench, electric heater turned off.

11/2 - GH - Outside - stored water
6 pm - 76 - 66 - 78
10 pm - 62 - 56 - 62
11/3 7 am - 55 - 51 - 55 (daily min.)
3 pm - 88 - 78 - 80 (daily max.)
6 pm - 79 - 68 - 78

With only 75 gallons for 140 sq. ft. of floor area, the results show at least a few degrees of help from the water during the dead of night. Since the recommended water storage for solar greenhouses is 4 gallons/ sq. ft. floor area (and you have 2.3 vs. my 0.5), I obviously need more water to come close to your results. If I get motivated, I will remove the water in the morning and try to get a comparison with and without. The high and low outside temps. tomorrow are expected to be the same as today, and again not a cloud in the sky. CR

CR, those results look to me to be far more typical. You have a 25 degree differential between 3pm and 7am water temps. Of that, 18 degrees are given back before 10pm, at which time your water has dropped to ambient GH temp. Thanks for posting. It makes Tom's results all the more impressive. SB

Posted by cuestaroble 8 CA Mtn (My Page) on Sat, Nov 3, 07 at 21:31

Tom,
Thanks for your numbers. Your results are impressive. You inspired me to do a little check on my own system. Double polycarb, free standing, 10x14, 75 gal. water storage, under a bench, electric heater turned off.
11/2 - GH - Outside - stored water
6 pm - 76 - 66 - 78
10 pm - 62 - 56 - 62
11/3 7 am - 55 - 51 - 55 (daily min.)
3 pm - 88 - 78 - 80 (daily max.)
6 pm - 79 - 68 - 78

With only 75 gallons for 140 sq. ft. of floor area, the results show at least a few degrees of help from the water during the dead of night. Since the recommended water storage for solar greenhouses is 4 gallons/ sq. ft. floor area (and you have 2.3 vs. my 0.5), I obviously need more water to come close to your results. If I get motivated, I will remove the water in the morning and try to get a comparison with and without. The high and low outside temps. tomorrow are expected to be the same as today, and again not a cloud in the sky. CR
============================================================
In the spring I use my GH to start plants from seed so the temps that you are showing are to cool for my needs.

Since most days are cloudy here in FEB how much extra would it cost me to keep the water at 65 degrees all day and all night,

Even on the days that the sun shines the water Will stop providing any heat after early evening and the rest of the night I would be paying to not only keep the GH warm but pay for keeping the water warm also.

I never tried to figure it I just saw it was not working for my needs and ditched the water

If I could figure out a way to make seeds germinate st 35 degrees then maybe the water would be a little benefit but at the temp required it just don't help.

sizes of containers make a difference also, in that smaller ones get hotter quicker and release the temperature quicker. I've stacked mine on the north wall with larger on the bottom and smaller containers on top of them. The larger containers stubornly hold on to their 60's in the night while the smaller ones which gave up a blast of heat earlier, seem to benefit from setting on the larger ones and become the same temperature(60's). Also, its fun to note that the top half of the larger containers are warmer than the bottom halves. On my reflective 3 ft x 12 ft long bench in front of the glazed area, sits a line of one gallon black containers on the sides and in the rest of the areas of the bench, sits diy earth box clones. These are spray painted dark green and all my gallon containers are spray painted dull black. Under my long bench is a lot of wood that I've stored there, so I have thermal mass there as well.
~tom

The more I read the more thoroughly confused I'm am about the topic of water and it's heating/cooling ability. I thought in my mind I had my entire greenhouse worked out that I would be able to save some energy costs by adding a pond. My summers are so short that I would like to cost effectively use my greenhouse all winter. Please forgive all my questions, but I am new to greenhouses and want to ensure I am building the most efficient greenhouse.

To better help me with my questions let me tell you a little about my greenhouse. I have double paned sliding glass doors on East, South and West sides of my greenhouse, the North side has only one sliding glass door. In between the glass doors, the North wall and the roof have the following layers from outside to inside:
Cedar siding/or shingles for the roof
1/2" sheeting
R-19 insulation
1/2" sheeting
In addition the roof has twin wall polycarbonate panels framed in with 2X6's (all construction was with 2X6's)and the roof inbetween the twinwall panels has been shingled.

With that picture in mind, I had assumed (I know what that word means) if I had a pond in one corner that it would assist with the heat and add humidity in my greenhouse. ND is very dry and I will need assistance with obtaining humidity. My greenhouse is approximately 18' X 22'. My pond has been dug but no water has been put into it yet, as I need to finish the interior sheeting and insulation before I start on the pond. The pond will have anywhere from 1500 gallons to 2000 gallons of water in it.

From reading the above posts and several older threads I think what I understand is 4 gallons of water is needed to heat 1 square foot space. In no way do I believe my pond will solve my heating problems. I am merely looking for a way to assist lowering my heating costs. In some of the posts it appears as though this pond will be a waste of space showing no effective results and then reading Tom's notes in this thread and Stoneunhenged and Chris in Iowa's notes in several others posts the water is working for them to heat and cool (I had not even considered the cooling factor).

My questions are as follows.

1. Will my pond serve in any fashion to assist with the heating? Remember, I will have quite a bit of insulation in my gh and I will be adding bubble wrap and perhaps one day a solar pool cover. These items will be purchased in the future....NOT this year.

2. Will it provide decent humitidy or will I still need something?? else to assist?

3. How will the cooling aspect work? I can't get an understanding of that based on all your posts. I will have a rather large body of water and basing it on my outdoor 4000 gallon pond the water temps get very warm during the summer. I can't imagine it cooling much as the temps will remain warm. I will need the cooling during the day and in my pee brain I can't see how that would happen when the water is heating up during the day. Could it be that the water is pulling the heat from the greenhouse to heat up? Then releasing that heat in the evenings IF they are cooler than the water temperature itself? What happens if the evenings don't really cool down?

4. Since this is a large body of water (with a black rubber liner) will it hold the heat longer into the evening that the barrels of water?

Please help me understand before I proceed with this additional cost. ha ha.

Also, I'm sorry to be so full of questions. This project is really starting adding up in cost even with all my scavenged materials and I don't want to make a big mistake by adding something that is virtually taking up space and useless.

Tj

ladylotus

Unless you're really into pond plants I would never give up precious GH space for a pond. My GH is only 8X16' and the water tanks under the benches don't do anything for humidity or heat. They warm and cool as the sun goes up and down. They're there to overwinter some tropical pond plants. A 2000g pond is quite large. I have a 2000g pond and it's something like 10X14' and several feet deep. How deep do you plan to make your GH pond?

Greenhouser,

I've already dug out the pond prior to even putting up the sides. I have it dug out 4' and in one end 5' deep. I was thinking I could put my tropical waterlilies, my lotus and any other tropical plants in the pond over winter along with a few of my Koi. That way I won't have to bring all the tropicals into my house and garage.

But, I had also hoped it would add additional benefits such as heat and humidity. I may still go ahead with this rather than fill in my hole. But I still have time to decide since I still have to close up the interior of my gh before I get to these frivilous items.

With the depth being 4 to 5', I thought being below the frost line, with insulated (I used 2" blue board down the side of the cement footings)4' cement footings it would stay warm much longer.

I guess, if I ever run out of gh room I could always fill the pond in and add more shelving. VBG.

So far this thread has remained focused on heating and cooling and no mention of ALGAE OR FUNGUS or other water related problems.

People in the business of manufacturing GH products test them and while they would like to claim fabulous results they will tell you that with a good shade cloth and a exhaust fan of sufficient size you will still see GH temps a few degrees higher than outside temp.

Their is no way that you will see the temperature inside the GH lower than outside temp on a sunny day.

I would use the money that you are going to spend on material to install the pond and buy a Magni-Clear 14mm thermal blanket.

The temperature that people report water making a difference is way to cold to keep a GH it may keep it from freezing when it is 20 degrees out but will it keep it warm enough for seed to germinate.

If the bottom of your pond is not insulated it will have a tendency to stay at ground temp 55 degrees so if you heat it to 65 degrees at night the water will absorb the heat and pass it into the ground.

That is why I have insulation under my flooring

Maybe instead of a GH 18x20 and using half the space up with water you should go with half as big a GH you will have the same room for plants and it will cost much less to heat than what you are planing

Hi Folks,

Have been a long time follower of hfgh threads and own a 10x12 for the second year. When I built the green house I put in a 2x12 wooden base like a poster whose name is lawson or larson it was insulated with 1 " foam. This thread is really interesting to me because I have 8-30 gallon barrels filled with water and treated with swimming pool chems at setup, so far no algae! I'm starting temp readings here to night, will post results in a couple of days.
The primary use of this GH is to house incomming daylilies in the early spring (April). Most of the plants are comming in from the southern states and it is quite cold here yet. This allows me to get early bloom, seed set, and great rebloom on most of these daylilies. I use a 1500 watt heater to keep things above freezing in the spring. The GH also serves as a quartine for rust that might hitch a ride in on the new plants.
I just purchased foil faced insulation for the north wall and ceiling, over the next week bubblewrap will also be added. I would like to leave the water in the barrels and not heat this winter in the hope of moderating our zone 5 winter! My concern is the freezing of the water in these plastic 30 gallon barrels and possible splitting.
Last winter I made a bubble wrap tent as an experiment over a bed of daylilies in the middle of the GH. These plants were a full month ahead of stuff in the open yard. This might be due to just earlier warm temps in March and April. So this year I thought to expand the capability of the GH. Trying to promote more root growth over the winter by more insulation and the 240 gallons of water to raise the general temps.
Any input or ideas? - Thanks

Don, have you read Eliot Coleman's "A Winter Harvest Manual"? He does exactly what you did my putting row covers over beds inside his hoop houses. In his words, he moved his maine zone 5 500 hundred miles south by houses within houses.
I don't have a winter's experience with my barrels but I left several inches from being full for the exact fear that you have stated: freezing solid and splitting.

And Gardenerwantabe brings up a good point on fungus and algae. Without any reference to do so, I added pool chemicals to my water storage and they are closed containers.

For LadyLotus, I envy your built in pool. It will certainly add humidity during the summer! It will also cool the greenhouse during the day and release the heat in the evening, but at a slow enough rate. Have you ever dived into a swimming pool in the summer evening after the sunset? It's delightfully warm.
At the end of this great web page is a list of valuable references on greenhouses.
~tom

Tom,
What was your purpose of adding pool chemicals to your closed, water storage containers? If anything actually started to grow, that should just make the water a little darker and if exposed to direct light, could actually absorb even more heat. I am assuming you are not planning to use the water for other purposes such as irrigation.

Tom,

Thanks for the link to ATTRA. I've thought about pumping warm/hot air from the ceiling of the GH thru tubes underneath the soil. Not sure where I saw a diagram of a system that used a attic fan mounted in the end of a barrel that is used like a plenum, the tubes comming out of the sides of the barrel are laid under the soil of the GH. During the sunny afternoons a thermostatically controlled fan pushes air thru the tubes and heats the soil.

Hi Cuestar, it was simply because we had a pool that needed to be empty. But I also liked the idea since I don't know what would happen regarding old water nor did I think it would hurt!
~tom

I normally agree with Gardenerwantabe, but s/he is incorrect when stating, "Their is no way that you will see the temperature inside the GH lower than outside temp on a sunny day." Ask Orchiddude. Evap cooling will get you there.

Ladylotus, the thing to remember about your pond is that water will evaporate out...a key difference between your system and stored water in barrels. This evaporation results in a great loss of energy (think back to the latent heat of vaporization of water). This is good in summer, bad in winter. This is the "cooling effect." Evaporative losses may balance out any heat storage effect in the winter, resulting in little if any "assist in heating." If you are keeping the water at 65F, you will loose some heat to the ground, but if keeping at 55F, there won't be much of a differential there.

Don, I believe I have the link you speak of at home. I will try to post it when I get back. They require hundreds of feet of tubing to gain the effect, and I think the idea was to remove the stored geothermal heat from the soil to heat the GH at night. I don't remember if the system was design to build up heat in the soil during the day.

Stressbaby, couldn't Lotuslady put a canopy or a clear plastic covering over the pond in the winter? Wouldn't this not only prevent much evaporation, but heat the water by the sun even more? Those Koi would settle to the cooler bottom!

She has possibilities with that pond. It is a geothermal system in itself within the greenhouse. She will always have heat rising in the winter when the greenhouse temps are lower than 55F.
~tom

Results of a simple water storage observation.

Comparison of 0.5 gal. per sq. ft.(70 gal/140 sq.ft. greenhouse) vs. no water storage.

With Water-
----------- GH -- Outside -- diff
6 p.m. ---- 76 -- 66 -- +10
10 p.m. ---- 62 -- 56 -- +6
7 a.m. ---- 55 -- 51 -- +4

Without water-

6 p.m. ---- 69 -- 58 -- +11
10 p.m. ---- 62 -- 57 -- +5
7 a.m. ---- 57 -- 55 -- +2

Conclusions for my situation 0.5 gal makes only a slight (1-2 deg.) difference in fall season daytime cooling and night warming. Much more water storage is needed in my greenhouse.

I think that the reason some posters here are so anti water containers for thermal mass is because of 3 main reasons:

1) Thermal mass is not a substitute for insulation. Thermal mass stores and re-radiates heat. Insulation stops heat flowing into or out of the building. A high thermal mass material is not generally a good thermal insulator. Greenhouses with 4 walls and a roof of plastic is not good insulation.
2) Thermal mass takes up valuable space.
3) Some need their greenhouses very warm (over 50), and that requires heaters whether or not thermal mass is used.

For those who have their structures insulated well and have the space for sufficient amount of thermal mass..2.5 to 4 gallons to sq. ft. area (the colder zones need 4), you can use barrels as legs for benches for example, it should work well to moderate temperatures and keep the greenhouse from freezing with only some additional external fossil burning heat for the coldest days.

There shouldn't be just one way is right and there isn't. Some grow tropicals, some grow cold hardy and some are in between. Some are hobby growers and some are commercial so space becomes more of an issue.

I had a partly-mostly hazy cloudy day yesterday so outside it was a high of 54 and my water temps only got up to 59. Last night it was 30 F and inside the shed it was 47 F. which has been my coldest temperature inside so far.
~tom

Posted by stressbaby z6 MO (My Page) on Mon, Nov 5, 07 at 9:16

I normally agree with Gardenerwantabe, but s/he is incorrect when stating, "Their is no way that you will see the temperature inside the GH lower than outside temp on a sunny day." Ask Orchiddude. Evap cooling will get you there.

STRESSBABY
We are not in disagreement their.
I was talking about her GH with the pond in it.

I almost posted about the evaporative cooling because I knew if I didn't someone would bring it up.

I have read all the experiment by university's and how you can bury rocks and run pipe under all your property and I'm sure these will help.
I'm spending about 60 bucks per year to heat my GH so not going to spend 30 thousand to save half of my heating bill.

My wife fills our little 10x12 full of plants I have drums under the down spouts and I made a small hose on a wand and when she pushes the button on The wand a electric pump waters the plants.

That is the only water I have room for is what is in the hose

A little off topic but anyone who is using chlorinated city water would be surprised at how much better the plants do with water out of the rain barrels.

I have made a decision to keep my pond plans and give it a try. Gardenerwantabe, it does not take up half of my greenhouse because of the depth. However, my thoughts are to have plants hanging above the pond, some smaller ornamental Japanese Maples around the pond, and my borderline hardy water plants inside the pond. I still believe this will help my humidity. I can't see how it would not.

I will play around with your ideas Tom. I appreciate your optomistic outlook on my idea. It may or may not work, only time will tell.

As far as space, I have some big plans for my greenhouse, I want to graft conifers, start annuals, and propogate many plants. Who knows what more I will find to add or do with my greenhouse. Right now all the tropicals I have are in my house until the gh is completed. I have the greenhouse already built and am just finishing up the inside. Which I will slowly work on all Winter.

Since I will not have my pond filled with water this Winter, I am going to keep a journal of temps outside and inside my greenhouse. Next Winter I will have it filled and will keep a journal to see what the difference in temps will be. I will make sure to post them whether they are positive or negative. ;)

Tj

My idea for thermal mass is simple. I used some old bricks on the ground and covered them with sand. On one side of the GH I will have a 50 Gal water tank from a RV, underneath that will be a waterbed heater. The idea is the have the heater heat the water in the tank and I will have pumps on the tank to pump water thorough a 3' X 8' Earthbox.

Hopefully this will keep the plants happy and warm enough.

Amigatec,
What is the advantage of your system, which uses an electrically heated waterbed source, over just using an electric heater in the greenhouse?

Whoopie! Yesterday it was partly cloudy and the high temperature was 45 F. Inside the shed with my min/max new thermometer, the high was 84 F.

At dusk the temperatures had fallen to 40 and continued to drop thru the night to 23 F this morning just prior to dawn. The inside shed was 53 F at dusk yesterday with water temp of 59 F. This morning predawn with that cold 23 F outside, the shed is 40 F and the water temps are 45 F. No external heat is used! Excuse my enthusiasm for all of you tropical and tender growers out there, but I'm only growing cold tolerant so this is exciting to me!

~tom

Ladylotus and all.

I think your pond will be beutiful when you are finished. I am also thinking I might get in on this water idea. Thanks for all the posts everyone. I have been following them. Barb

Congratulations Tom, 40-45° is my target minimum for my plants, so those temps sound good to me! I'm very glad you started this thread to share your experiences, and I appreciate the work you're doing to post your results.
Sheri

The idea is the heat the water in the tank and use some of that heat to heat the air in the GH. I will also be using Propane and Electric. Also I can pump heated water to my plants inside.

A small update on my 'solar' shed. I'll post a new msg with more details when I finally freeze inside. The lowest temperature I've had outside in Nov so far, was 20 degrees F. The low inside at dawn was 39 F while 20 F outside. It was all sun that day and the previous day. In the afternoon the high reached 39 F. and the inside shed high was 85 F. At dusk, it fell to 33 F. outside and my inside temperature was 65 F. and that fell thru the night to 43 F.

Water temps at dawn (20 F.) was 50 F. and at dusk (33 F.) was 80 and water temps fell thru the night to 50 F again. Please note that I had lots of sun for 3 days. In Nov. I have had lots of cloudy weather and the inside night has been as low as 39 F. I can see where if I had full clouds for several days and temperatures in the low 20's, I would likely come closer to freezing.

I had beautiful northern delight tomatoes for Thanksgiving from containers that I placed in the shed on Oct 28th just before my first freeze. Those plants are about spent though. Lettuce, cilantro, bok choi, arugula and mizuna are growing great. I am still harvesting kale and bulls blood beets from the raised beds. I failed to sow carrots in time for fall.
~tom

Great thread!

Tom,

Nice to see someone posting actual data to show a large thermal mass can extend a growing season without using supplimental heat.

Hundreds of gallons of water cannot "heat" a greenhouse, the sun does that. However the water can moderate the temperatures in there and extend your growing season by about six to eight weeks.

Great thread, I agree, and it is good to hear from you, Chris.

November's results for my solar, south roof glazed shed:

Outside temps: Ave cold was 37.7F. Coldest night was 20F. Warmest night was 58F. It was below freezing 7 times.

The inside temps average 47.4F. The difference between the outside and inside ave 10.1F warmer inside than outside at dawn for the month. The biggest difference of 19 degrees was on the coldest night of 20F. where the inside temp was 39F. The smallest difference of 2 degrees was on the warmest night of 51F where the inside was 53F.

The coldest inside temperature (dawn) was 37F on a 26F night but the previous day had been cloudy all day. The warmest inside temp was 58F while the outside was 44F. I had plenty of sun for several days for that one.

From my first frost on Oct 29th of 29F, I have extended my growing season by 5 weeks thus far without a nickel of fuel.

~Tom

Again, great stuff, Tom. My opinions are revised every time you post numbers.

I would be very interested to see pictures of your shed.

I think you have answered your original question, yes? Cloudy days drop the differential from as high as 19 degrees to 11 degrees.

SB

ok SB, I'll get around to taking some pics. busy with relatives so it'll be a few days.
~tom