# Rainsing my greenhouse



## Shiva (Mar 24, 2011)

This is my greenhouse in back of the house as it is still looking a few years after construction. It's built on cinder blocks raised three feet high. It's 16 feet or so in lenght and width. Double polycarbonate glazing.







My problem is despite everything I've done to save energy, it stills cost a fortune to heat. Since the price of heating keeps going up, every improvement I make is consumed by the higher prices.
My idea is to raise the g/h four more feet with cinder blocks. That would allow me to install two sliding windows on each sides for ventilation in summer. I could also replace the flimsy aluminium door with a stronger double glass door, which I have already. Raising the g/h would also allow me to get sunlight inside everyday of the year. Right now, the g/h doesn't get any sun for part of the day for about eight weeks in winter. Finally, raising it another four feet would allow me to install a thermal barrier over my head that would keep most of the heat where I grow my plants. In summer, the thermal barrier could be removed creating a chimney effect for the heat that would then be dispersed outside by a fan (I have) a couple of feet over the door.

I would first detach the g/h from it's sill and raise it alternatively in the back and in the front in small increments then fill the void by cinder blocks and the new windows until I get it up to four feet high. I could also rent a small crane to raise it completely and lay it on the ground while the work is done.

I'd like to know what you think of this project? And if you have any suggestions to help in its completion. And also, what would you recommend for a thermal barrier. Of course it would have to let the light through.


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## etex (Mar 24, 2011)

So this is where you grow your beautiful plants and blooms. Very nice greenhouse. I've wondered how folks in the north handle the heating costs with all the snow and cold weather you get.


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## Bob in Albany N.Y. (Mar 24, 2011)

I hate to admit this but the way I handle the cost of the heat in the greenhouse is to just take it. It costs as much to heat my greenhouse as it does to heat my home. I look at it this way. Everyone has so much spendable income. Some people like to gamble, others like women and I just stay at home and play with my plants. Donna, agrees, that this is the way to go.


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## NYEric (Mar 24, 2011)

Do you add bubble insulation sheets inside during the winter? The added R value should help.


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## Shiva (Mar 24, 2011)

NYEric said:


> Do you add bubble insulation sheets inside during the winter? The added R value should help.



I tried it all but the problem remains the same with the ever rising cost of energy. Putting bubble sheets is difficult with all the structural parts in the way and the top of the roof is already 11 feet high. To make a reasonnable job, I'd have to take all the plants out and dismantle all the benches to allow for stepladders movement. That's a lot of hassle and I'm not getting any younger. Raising the whole g/h four feet would simplify everything. I could put a thermal barrier on top of my head at about eight feet level, which would make a significant air space between the roof and the thermal barrier. Four sliding windows would cost me about $800 including taxes. The rest would be cinder blocks, mortar and manpower. My brother has already offered to put the blocks if I mix the mortar.  One more thing, with good crossed ventilation and the thermal barrier removed in late spring plus a lot of paint shading outside, I may keep most of the plants inside instead of moving them out for the summer. 
The cost of heating that greenhouse this last winter is well over $3000.


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## NYEric (Mar 24, 2011)

Shiva said:


> The cost of heating that greenhouse this last winter is well over $3000.



In Florida they only have to heat for one month! oke:
BTW, don't you live in _Southern_ Canada!?


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## Erythrone (Mar 24, 2011)

Wonderful greenhouse...

I would be concern too about energy saving!! That is why we don't have one yet... 

We were looking for a solar passive gh many years ago.


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## Shiva (Mar 24, 2011)

NYEric said:


> In Florida they only have to heat for one month! oke:
> BTW, don't you live in _Southern_ Canada!?



Southern Canada is in Ontario, around Niagara Falls or Hamilton, where JohnM lives. It doesn't look like it, but the more you go south, the more sun you have in winter and that makes a lot of difference. JohnM is in Zone 6-7 while I'm in Zone 4-5, if I remember my zones well.


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## Shiva (Mar 24, 2011)

Erythrone said:


> Wonderful greenhouse...
> 
> I would be concern too about energy saving!! That is why we don't have one yet...
> 
> We were looking for a solar passive gh many years ago.



If I were to start over, I would build a ''greenhouse'' with a solid, well insulated roof and large double glass insulated windows exposed to the sun South and East. The North and West walls would be fully insulated with vapour barriers. I'd also have HID lamps on the ceiling to help light the plants in winter. The sun being low in winter, you'd have good light inside and when the sun is high and spends a lot of time in the South and West, in summer, the roof would help prevent overheating. My conclusion about greenhouses like the one I have is that they're not made for my climate. I've even thought of removing the greenhouse and selling it and use what money I get to build the kind of structure I mentioned above. I just don't think I would get enough money to pay for the new structure. :wink:


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## ohio-guy (Mar 24, 2011)

wouldn't rising the green house just give you more interior space in need of holding heat? The heat would rise to the top and you would be stuck with a cool underneath area. And if you raise the walls 4 feet, will you need to raise the plants too? if so, all your work space will be over head. 
Finally I am not sure it would look aestetically pleasing to my eye. 
I am not sue what the solution is. Is your idea a common configuration for green houses in your area?


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## tim (Mar 24, 2011)

a double-poly, winter-only hoop house costs less than your window idea and is much less work than raising the entire thing...put it up over your existing gh...


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## Marc (Mar 24, 2011)

If and when I build a greenhouse I'm going to make the floor below ground level. But seeing that your house is allready standing I don't think it's an option to lower it.


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## Shiva (Mar 24, 2011)

ohio-guy said:


> wouldn't rising the green house just give you more interior space in need of holding heat? The heat would rise to the top and you would be stuck with a cool underneath area. And if you rais the walls 4 feet, will you need to raise the plants too? if so, all your work space will be over head.
> Finally I am not sure it would look aestetically pleasing to my eye.
> I am not sue what the solution is. Is your idea a common configuration for green houses in your area?



Yes, but the upper part of the greenhouse would be separated in the winter from the lower level by a thick sheet of transparent plastic. The plants would stay where they are since a lot of light would still ge coming from the clear roof and sides. The large volume of air between the roof and the plastic shield would tend to remain at the same temperature, which should help the lower portion to stay warm. The principle is the same as a double pane insulated window but with a lot more air in between. In summer, removing the plastic sheet would allow hot air to rise to the top, making the lower part cooler.

As for the idea, it's totally original as far as I know. I live in a farming area and the neighbours have lots of other things to do then build greenhouses for orchids.

Thanks for your comments Ohio-Guy. I don't want to make mistakes this time and that's why the contributions of ST members are helpful. If my reasonning is wrong or if someone has a better idea, now is the time to talk.  I might even scrap this project and modify the structure for something on the line of what I explained in my response to Erythrone.


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## Shiva (Mar 24, 2011)

Marc said:


> If and when I build a greenhouse I'm going to make the floor below ground level. But seeing that your house is allready standing I don't think it's an option to lower it.



Unfortunately, I'm located in a spring flood area.


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## Shiva (Mar 24, 2011)

tim said:


> a double-poly, winter-only hoop house costs less than your window idea and is much less work than raising the entire thing...put it up over your existing gh...



I have one of those and it nearly crashed under the weight of snow one winter. I actually had to puncture the poly with a shovel to prevent this outcome. Now I use it as a shade house in summer.


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## tim (Mar 24, 2011)

others i know in snowy areas deflate the bubble and increase the heat during snow, which decreases the insulative value and allows the snow to melt. 

what do other greenhouse owners (commercial especially) do to deal with snow and cold?


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## Shiva (Mar 24, 2011)

tim said:


> others i know in snowy areas deflate the bubble and increase the heat during snow, which decreases the insulative value and allows the snow to melt.
> 
> what do other greenhouse owners (commercial especially) do to deal with snow and cold?



They close shop for the winter and remove the poly sheets until early spring. (That's also an option for me. I could bring all the plants inside the house.)


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## Clark (Mar 24, 2011)

Perhaps you could drill a mile and go geothermal. oke:

Must be the paint fumes. :crazy:


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## Shiva (Mar 24, 2011)

Clark said:


> Perhaps you could drill a mile and go geothermal. oke:
> 
> Must be the paint fumes. :crazy:



Or I could use some of these spent nuclear fuel rods from Japan and build my own covered water pool to put them in. The steam could go into pipes warm the greenhouse and go back to the pool. I bet my municipality doesn't have any bylaw against that kind of system. :rollhappy:


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## Erythrone (Mar 24, 2011)

With solar passive GH, you can use heat storage from water or rock to heat the GH. 


http://www.attra.org/attra-pub/solar-gh.html


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## Shiva (Mar 24, 2011)

Erythrone said:


> With solar passive GH, you can use heat storage from water or rock to heat the GH.
> 
> I suppose you can, but I'm not sure it's good enough for our climate. We have long spells of cloudy weather in fall and winter and very cold temps. You'd have to have a standby heating system.
> In the 1980s, one of the Montreal club members had a passive solar greenhouse south of Quebec City. I don't know how well it performed but I do remember the g/h burned down to the ground less than three years after construction. My guess is she had to rig some extra heating set up and the polycarbonate caught fire.
> I don't know and never heard of anyone else using passive solar power to heat a greenhouse in Quebec.


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## Rick (Mar 24, 2011)

Shiva said:


> Erythrone said:
> 
> 
> > With solar passive GH, you can use heat storage from water or rock to heat the GH.
> ...


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## rob (Mar 24, 2011)

I run a hoop house with inflated double poly year round in western Mass( zone 4b 5a). It is only 600 sq ft and houses @ 3000 orchids and it does cost @$2500- $3000 a year to heat (a dollar or so a plant). I have the shade cloth on the outside so I have to rake off the snow in a heavy storm to keep the snow load in check as it sticks more to the cloth than the poly. As it is heated to a minimum of 58, snow rapidly melts and is seldom a problem. It's been up for 12 years and ,knock on wood , no major issues with winter weather.
Rob


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## Shiva (Mar 24, 2011)

Rick said:


> Shiva
> I think you are setting your logic up as a catch 22. You want to capture more sun by getting taller, but you say that passive solar to store more heat won't work.
> I think insulation is just as important. I was amazed by how much I saved just by throwing a tarp over my old GH at night during the winter.



Thanks for your suggestions Rick. I'm beginning to think my project is not the best. That's why I asked for feedback on this forum. :clap:


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## SlipperFan (Mar 24, 2011)

Rather than scrapping this greenhouse and building a new one, since you already have a good foundation, could you place a triple-pane structure on top of your existing foundation? The vents and windows would probably have to be double-pane, but the fixed panels can be triple.

If I understand your idea, I don't think adding height will solve the heating problem since you'd still have your basic structure.


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## Shiva (Mar 24, 2011)

SlipperFan said:


> Rather than scrapping this greenhouse and building a new one, since you already have a good foundation, could you place a triple-pane structure on top of your existing foundation? The vents and windows would probably have to be double-pane, but the fixed panels can be triple.
> 
> If I understand your idea, I don't think adding height will solve the heating problem since you'd still have your basic structure.



I don't have the money for a new structure. I live on a pension and although it's a good one, a triple pane structure is way out of my league. Maybe I should get all the plants inside the house under lights for the three coldest months, december, january and february. That seems to be the least expansive solution. However I'd have to get rid of some very big plants.


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## Rick (Mar 24, 2011)

Another way to look at it, is to determine how much it actually costs to heat now, and what is your dollar goal for what you can live with. Then you can make a better decision as to how much you can feasible afford by increasing energy production efficiency, insulation, or manual labor.

For instance if your present energy cost is $300 a month in the winter, and you are shooting for $30 a month then you probably are looking at consolidating into the house. But I think you could fairly cheaply knock about 20% off your bills.

http://www.attra.org/attra-pub/solar-gh.html#in

Lots of ideas on this site (if someone else didn't already post it).

I see Erythrone already did. Anyway the basic principles are all there.


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## NYEric (Mar 25, 2011)

Shiva said:


> Or I could use some of these spent nuclear fuel rods from Japan and build my own covered water pool to put them in. The steam could go into pipes warm the greenhouse and go back to the pool. I bet my municipality doesn't have any bylaw against that kind of system. :rollhappy:



And my what nice monster plants you would have also!!


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## Shiva (Mar 25, 2011)

Thanks everyone for your comments. Now it's back to the drawing board for me. I wasn't thinking of a passive type solar greenhouse but one that would be in the sun all year long instead of 9-10 months of the year. Maybe Bob in Albany is right: just pay the bills.


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## hchan (Mar 25, 2011)

Bob in Albany said:


> I hate to admit this but the way I handle the cost of the heat in the greenhouse is to just take it. It costs as much to heat my greenhouse as it does to heat my home. I look at it this way. Everyone has so much spendable income. Some people like to gamble, others like women and I just stay at home and play with my plants. Donna, agrees, that this is the way to go.



What, you mean I can't have it all?! Gamble, booze, women, drugs, rock & roll and orchids?!


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## ohio-guy (Mar 25, 2011)

What is the orientation of the present green house? Since you were thinking of doing a solid roof and wall on the north half, could you do that with the present structure? Just dismantle the north side ( I am assuming it is on a East /West axis, with the entry door at the north or south end) then take the North side windows you have and double them up to their South side counterparts, so you have "4 ply", or double, insulation from the plastic windows? I am not sure if this would work, if you have a set thickness on the tracks the windows go into, but it may be a way to use the structure you already have.Also , do you have a lot of heat loss with the door opening and closing? Would building in a small ante chaber be helpful to minimize heat loss?


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## hchan (Mar 25, 2011)

Maybe you could add some cheap solar solutions to supplement the heating? I think at the end of the day you just want to reduce your bills, not eliminate them altogether.

You might as well paint your cinder blocks black, that will help and is quick and cheap to do. What kind of flooring do you have at the moment? Maybe you could optimize it to retain heat better? I know you said that you have a lot of cloudy days, but it might still be enough to help take the edge off your heating costs.


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## Shiva (Mar 25, 2011)

The door is on the South side and the greenhouse is square. So orientation is not really an issue. I've thought of doubling the polycarbonate but from the inside, since there is a through on either side in the metal where the glazing is fixed. It would have to be thin enough to work though. I would simply insert it on the groove on each side and push it up to the top. I also tried at one time to put a transparent insulating ''bubble coat'' on the outside of the greenhouse, but the whole thing was ripped apart by wind. I thought duct tape and self adhesive velcro would hold but after three months of weathering the velcro gave out and the rain and snow made the duct tape useless. But it almost worked. I may try again but this time I would remove the metal strips on both ends of the greenhouse, put the bubble on the roof then screw back the metal strips on their original grooves, thus holding the bubble wrap firmly in place at both ends. I only wonder if it would be worth it. One thing I will certainly do is remove the poly on the north wall and build a new insulated wall. There is very little light coming from that direction anyway.


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## Shiva (Mar 25, 2011)

hchan said:


> You might as well paint your cinder blocks black, that will help and is quick and cheap to do. What kind of flooring do you have at the moment? Maybe you could optimize it to retain heat better? I know you said that you have a lot of cloudy days, but it might still be enough to help take the edge off your heating costs.



I also have to contend with summer. We have long hot days for two months. It's already hard enough to blow out the heat when it's 30°C + outside.


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## hchan (Mar 25, 2011)

Doh, then winter insulation might be the only answer. You could try the water heat storage idea and see whether it makes a difference, it wouldn't cost very much to place some dark containers of water inside your gh during the winter. Then it'd be easy to get rid off during summer when you don't want it. Though I suspect space is at a premium inside your gh


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## goldenrose (Mar 25, 2011)

This year I made sure practically every square inch had bubblewrap on the inside of mine, some might consider too tight. On the north wall & west lower walls I used the foil bubble wrap, one has the insulating values but gets more light reflecting, could also be used on the floor. I agree, can't see where raising the roof would help. I also have 2 dark colored barrels that store rainwater so I'm sure that's helping with passive solar. I love ohio-guy's suggestion, we have a friend who's a brick layer & if & when I can redo/enlarge mine that was a requirement - could I double the space & maintain my same heating cost by using passive? He recommended a double block north wall, allowing an air space so the heat is not leached out thru the back wall. I would go from 2 rain barrels to 4 - one in each corner, small price to pay for space & actually you could use the space above the barrel so how much is lost?
I would also change the orientation of mine, in these northern areas if you orient E-W we have more sun exposure in the winter so the longest length should face south to get the most out of passive solar. Also consider, in summer which direction is the wind most of the time? For me it's west, so that should help with summer cooling.
Gas bills for heating my house & free standing GH (8' x 12'), Dec was $144, Jan. $149 & Feb. $167. I could get a surprise as they usually estimate ever other month but with the deep snows this year, I could have 3 estimated bills. Normally during the coldest months my bills would be $200-250, I'd say that's a noticable savings!


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## Rick (Mar 25, 2011)

Shiva said:


> The door is on the South side and the greenhouse is square. So orientation is not really an issue. I've thought of doubling the polycarbonate but from the inside, since there is a through on either side in the metal where the glazing is fixed. It would have to be thin enough to work though. I would simply insert it on the groove on each side and push it up to the top. I also tried at one time to put a transparent insulating ''bubble coat'' on the outside of the greenhouse, but the whole thing was ripped apart by wind. I thought duct tape and self adhesive velcro would hold but after three months of weathering the velcro gave out and the rain and snow made the duct tape useless. But it almost worked. I may try again but this time I would remove the metal strips on both ends of the greenhouse, put the bubble on the roof then screw back the metal strips on their original grooves, thus holding the bubble wrap firmly in place at both ends. I only wonder if it would be worth it. One thing I will certainly do is remove the poly on the north wall and build a new insulated wall. There is very little light coming from that direction anyway.



Charlies Greenhouse supply sells a bubble wrap system for inside the GH. Its heavier than normal shipping BW, and you apply it with spay adhesive so it fits tight and stays in place easier.


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## Rick (Mar 25, 2011)

goldenrose said:


> This year I made sure practically every square inch had bubblewrap on the inside of mine, some might consider too tight. On the north wall & west lower walls I used the foil bubble wrap, one has the insulating values but gets more light reflecting, could also be used on the floor. I agree, can't see where raising the roof would help. I also have 2 dark colored barrels that store rainwater so I'm sure that's helping with passive solar. !



Ed M replaced all his bench supports with 55 barrel drums (blue plastic) full of water. They were used barrels that he got for $15 I think. I think he said he paid about $300 so that would be about 20 barrels. I think his GH is about 1000 sf. He said he cut his gas heating bill down dramatically. He says by next winter he wants to add a solar hot water heater to get more heat into the barrels during the day.

The space under benches is usually wasted space, but you can use anything that fits from barrels to stock tanks to add a thermal mass. 

I don't know how insulating your flooring is, but a lot of heat is lost to ground, so adding a insulation barrier to your flooring, and covering in pavers can help a lot with adding thermal mass to your GH even if you don't put in a floor heating system.


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## Shiva (Mar 25, 2011)

Forget the passive solar heat sink concept. My greenhouse is too small and orchids are everywhere. The sun doesn’t shine inside for part of the day when there is sunlight available in the dead of winter. I’ve barely got enough space for a barrel of RO water. No houses nearby that could block the wind. In fact, there is really nothing between me and the polar bears in the Arctic except cold north or west wind. The foundations are five feet deep and insulated and the hole is filled with sand and gravel with pavers on top. I’ve planted rows of evergreen trees around the outside perimeter at some distance for a windbreak, but these trees need time to grow. Now I’m thinking of bringing all the plants inside the house for the coldest three months of the year. Of course that means high intensity lighting, but at least it contributes in heating the house. I would save thousands of dollars if I did that for three years. Then I could as Dot says put the money into a new and better insulated structure. No raising the greenhouse anymore. You convinced me now it wouldn’t be worth it. I seriously understimated the cost of heating this place but since I built it, it has nearly doubled.


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## SlipperFan (Mar 25, 2011)

Unfortunately, I don't think that is going to get any better.


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## W. Beetus (Mar 25, 2011)

Shiva said:


> Or I could use some of these spent nuclear fuel rods from Japan and build my own covered water pool to put them in. The steam could go into pipes warm the greenhouse and go back to the pool. I bet my municipality doesn't have any bylaw against that kind of system. :rollhappy:


 
That sounds like a great idea!!  As long as you don't have very many power outages, it would work wonders... oke:


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## Shiva (Mar 26, 2011)

Here's a new idea!

Although a solar heat sink could never get warm enough in my greenhouse to be effective, why not put it outside? Here's what I'm thinking: buy the largest possible used swimming pool with winter cover and paint everything black to absorb the sun's heat. Then I would fill it with water from the small river beside my property in spring and let it warm up over the summer. Meanwhile, i would dig up part of the floor inside the greenhouse and line the hole with panels of stainless steel soldered up together, large enough to accomodate the water in the swimming pool. As the temps get cooler outside, I could pump the hot water inside the large tub built in the g/h. The tub would be closed on top and come up three feet above ground. The top would then be perfect to put those orchids on who like more heat while the rest of the g/h would remain cooler for the cooler loving orchids. I would't bother running pipes in the ground to fill the tub. I could do that from outside before it gets too cold. Any thought on that? 

The question is: how long would the stored heat last?


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## likespaphs (Mar 26, 2011)

hours?


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## mormodes (Mar 26, 2011)

There's an old book written by James C. McCullagh called 'Solar Greenhouse Book'. See if you can get a copy via interlibrary loan. Or Amazon has copies available for $0.79 US. It's an old book, my copy was printed in 1978, but the basic information hasn't changed much. Lots of information. He discusses everything we've suggested here but in-depth. Including your pool idea.


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## Rick (Mar 26, 2011)

There are sites with calculators to figure out this problem Shiva.

One thing you need to know is how many BTU/hour you use during a typical night.

You would need a pretty impressive tank to store enough water to make it through the night hooked up to an efficient solar heating panel to do this. Other wise I guess you are looking at a small lake for a total passive system.


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## hchan (Mar 26, 2011)

If you're considering passive solar as supplementary heating (I think it's clear total passive solar probably won't work for you) situated outside the gh, how about a trombe or water wall? You could build one up against one of your existing walls, just cut some vents into the cinderblocks for the air circulation principle to work. In summer when it's hot, close the vents to minimize the heating effect, in winter open the vents up to get the heat. The construction costs should be reasonable. I think the challenge could be that your gh is square so the surface area of the wall wouldn't be very big relative to your gh volume. I wonder whether it's possible to slope the wall to maxmimise the solar collection area?


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## goldenrose (Mar 27, 2011)

Rick said:


> Charlies Greenhouse supply sells a bubble wrap system for inside the GH. Its heavier than normal shipping BW, and you apply it with spay adhesive so it fits tight and stays in place easier.


I've tried it, in fact Menard's & Home Depot have spray adhesives, they all seem to work to a point but have to be reapplied, my guess is the high humidity.



Rick said:


> Ed M replaced all his bench supports with 55 barrel drums (blue plastic) full of water. They were used barrels that he got for $15 I think. I think he said he paid about $300 so that would be about 20 barrels. I think his GH is about 1000 sf. He said he cut his gas heating bill down dramatically. He says by next winter he wants to add a solar hot water heater to get more heat into the barrels during the day.
> 
> The space under benches is usually wasted space, but you can use anything that fits from barrels to stock tanks to add a thermal mass.
> 
> I don't know how insulating your flooring is, but a lot of heat is lost to ground, so adding a insulation barrier to your flooring, and covering in pavers can help a lot with adding thermal mass to your GH even if you don't put in a floor heating system.


I tries insulating the floor one year, did notice much difference & with all the water draining on it, it wiped it out in no time!
I have use about 3/4's of the bench space below, have plexiglass shields.
People seem to overlook the fact that even though there might not be sun shining, the water is heating up during the day & that heat is being released hopefully at night. My 2 rainbarrels are in the middle of my GH on the west side so they don't get much direct sun but they do sit about a foot from the furnace & help channel the heat when the fan is on.
I've been using all these techniques over the years but this year I replaced any older bubblewrap, resealed everything & sealed my vents. There is the 2" PVc pipe vent for outside air for the furnace & yes I have to manually open/close vents but it's worth the $50-100 I saved each month & I would think we had a pretty average season for temps.


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