Rainsing my greenhouse

[Shiva]

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.

 

[Rick]

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.

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.

The newer solar hot water heating systems are much more efficient than they were a few years ago, and the only way to do anything with solar that will trully help your energy consumption is to figure out how to store the solar energy for use at night (when there is no sun). Simply increasing the height of your GH to collect more sun energy (putting it into increased air mass) will not help you much as air is a poor sink for energy. But if you can store that energy in a solid or liquid mass, you can get some significant savings.

If you get a solar collector (could be mounted at a distance from your GH) you could heat a bunch of water and use it in a radiant floor heating system like Ross put into his GH (although his hot water source is on demand boiler).

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.

I understand your GH is not that small, but maybe you could find a swimming pool insulating blanket that you could role up and down each night to conserve energy.

 

[rob]

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

 

[Shiva]

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:

 

[SlipperFan]

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.

 

[Shiva]

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.

 

[Rick]

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.

 

[NYEric]

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!!

 

[Shiva]

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.

 

[hchan]

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?!

 

[ohio-guy]

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?

 

[hchan]

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.

 

[Shiva]

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.

 

[Shiva]

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.

 

[hchan]

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

 

[goldenrose]

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!

 

[Rick]

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.

 

[Rick]

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.

 

[Shiva]

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.

 

[SlipperFan]

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