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Author Topic: Geodesic dome greenhouse build  (Read 2130 times)

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #25 on: May 20, 2019, 02:14:14 PM »
You will have a lot of condensation with all the heating you will have. It will drop cold water on plants and fungus will develop. It seems like you never had a greenhouse before.
If you put double panels on both sides it will be expensive, and the air between the panels will have an inverse effect, because of the large gap in between. Not to mention the light loss.
You need a phisics lesson  ;D. Condensation occurs on cold surfaces ,like on a beer bottle you have just take out from the fridge.The moisture from surrounding air sticks to the cold surface of the bottle.My greenhouse will not have condensation issues because it will be double walled with a thick air gap inside the walls.Air its the best thermal sealant so the inside walls of the greenhouse will not get cold and thats why no condensation will ocur.The only weak spots that might get cold are the structure of the dome but thats made.of wood wich has a low thermal transfer and will not get too cold like metal would and will also be sealed by a thin policarbonate layer.And the policarbonate its quite cheap,to cover the exterior it costs me ( only the policarbonate) just 350 dollars and the interior probably 250.To that cost i add the special tapes il use,one from plastic and one from aluminum,screws ,etc.For a 50 square meters greenhouse its not that expensive.

lebmung

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Re: Geodesic dome greenhouse build
« Reply #26 on: May 20, 2019, 02:56:14 PM »
Well... You need a phisics lesson, not me. Google the air between two glass panels then we can talk. 5cm gap between panels is a bad idea.
You speak from theory I tell you from practice.
Anyway do as you wish you seem the kid of person who knows everything.

NateTheGreat

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Re: Geodesic dome greenhouse build
« Reply #27 on: May 20, 2019, 07:15:25 PM »
Air its the best thermal sealant so the inside walls of the greenhouse will not get cold and thats why no condensation will ocur.

Air is a terrible insulator. Look at R-values of expensive double or tripple-wall glass, compared to wall materials. I have a double-wall window in my room, and it gets condensation if I have plants in my room (due to the added indoor humidity). Since the glazing will be of plastic rather than glass, you may have less condensation. When I've slept in tents outdoors though, the (plastic) tents do have condensation on the inside in the morning.

The wood sections will almost surely have a much higher R-value than the double-walled polycarbonate.

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #28 on: May 20, 2019, 08:03:36 PM »
Air is the best known thermal insulator and its scientifical prooved.A cold bottle of beer out of the fridge gets condensation on it but the whoole fridge wich is insulated by air between 2 walls ,doesnt gets condensation on the exterior surface because it doesnt gets cold. The bigger the air gap is,the better its insulated.My greenhouse with 5-7 cm thick air layer will be a few times more insulated than a glass window with 1,5 centimeters air gap .

NateTheGreat

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Re: Geodesic dome greenhouse build
« Reply #29 on: May 20, 2019, 08:49:13 PM »
Air is the best known thermal insulator and its scientifical prooved.

Then why do they use insulation instead of just air in walls? I'm not trying to get into an argument, it's a cool project, but these things you're saying just aren't true. The lack of condensation on the beer in the fridge is because it's the same temperature as the surrounding air. The polycarbonate will be some temperature between the outside air and the inside air (if it's -20 out and it's 30 in, the polycarbonate probably is somewhere around 0), so it will be colder than the inside air. Just like the beer bottle once it's out of the fridge. When the warmer air hits a colder surface, condensation.

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #30 on: May 20, 2019, 09:06:29 PM »
Air is the best known thermal insulator and its scientifical prooved.

Then why do they use insulation instead of just air in walls? I'm not trying to get into an argument, it's a cool project, but these things you're saying just aren't true. The lack of condensation on the beer in the fridge is because it's the same temperature as the surrounding air. The polycarbonate will be some temperature between the outside air and the inside air (if it's -20 out and it's 30 in, the polycarbonate probably is somewhere around 0), so it will be colder than the inside air. Just like the beer bottle once it's out of the fridge. When the warmer air hits a colder surface, condensation.
The insulations are insulating because they contain air.A blanket keeps you warm because it contains air,stirofoam insulates because it contains air,,the foan from between the walls of a fridge insulates because it contains air .Insulation material its only a way to keep that air contained into a space.You need material to create a blanket but the air in the material keeps you warm not the material itself.Stirofoam and glasswool are used for constructions thermal insulations just because they provide suport for cement or otther material to be layed over air contained into a space.Somme also prevent the flow of currents so that the air remains stagnant.

NateTheGreat

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Re: Geodesic dome greenhouse build
« Reply #31 on: May 20, 2019, 09:29:10 PM »
That's true, but air convects heat.

"Gases possess poor thermal conduction properties compared to liquids and solids, and thus makes a good insulation material if they can be trapped. In order to further augment the effectiveness of a gas (such as air) it may be disrupted into small cells which cannot effectively transfer heat by natural convection. Convection involves a larger bulk flow of gas driven by buoyancy and temperature differences, and it does not work well in small cells where there is little density difference to drive it, and the high surface-to-volume ratios of the small cells retards gas flow in them by means of viscous drag.

In order to accomplish small gas cell formation in man-made thermal insulation, glass and polymer materials can be used to trap air in a foam-like structure. This principle is used industrially in building and piping insulation such as (glass wool), cellulose, rock wool, polystyrene foam (styrofoam), urethane foam, vermiculite, perlite, and cork. Trapping air is also the principle in all highly insulating clothing materials such as wool, down feathers and fleece.

The air-trapping property is also the insulation principle employed by homeothermic animals to stay warm, for example down feathers, and insulating hair such as natural sheep's wool. In both cases the primary insulating material is air, and the polymer used for trapping the air is natural keratin protein. "

https://en.wikipedia.org/wiki/Thermal_insulation#Applications

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #32 on: May 20, 2019, 09:38:41 PM »
That wouldnt happen on my greenhouse walls because the air will be trapped between the policarbonate with 2 type of sticky tape.So the air can not escape from between the walls.The double walls will be just like as if my greenhouse its covered in stirofoam or glass wool( actually it would be even better because simple air its less conductive than stirofoam or glasswool but to an insignificant level).

Orkine

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Re: Geodesic dome greenhouse build
« Reply #33 on: May 20, 2019, 09:49:16 PM »
You are going to build this and you will share your experience.  So though the conversation has been good, perhaps the results of the real world experiment will resolve this.

NateTheGreat

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Re: Geodesic dome greenhouse build
« Reply #34 on: May 20, 2019, 09:50:39 PM »
I'm sorry, I didn't read your last reply as well as I should have. The thing is, if you have two sheets of polycarbonate, two different temperatures, with air between them, the air will convect heat. Natural convection. If you had something like down filling that gap, it would keep the air from flowing. There would be a steady gradient of warmer to cooler air. Once the down is removed, the warm and cool air can mix, and transfer heat through convection. The conduction through down is minimal.

This may be helpful https://www.commercialwindows.org/ufactor.php

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #35 on: May 20, 2019, 10:15:57 PM »
@Orkine,ies i will build this and put it to the test and if it will be a failure i will post it like i did posted a week ago somme failed experiment with my homemade seedling pots that killed most of my pecan trees.Im bad with pot coultures but with condensation i have big experience as i have build a cold water aquarium thats like an open fridge chilled by a titanium condeser(titanium because its saltwater) through an air conditioned.And off course ,the aquarium has double walls of glass and its thermo insulated.
@Nate the great, the discussion finally led you to my words and because of that i will reward you with an advice on why your big glass wall gets condensation on it.Its because the glass has somme thermal transfer power and if you keep the window open while its cold outside,then the glass on the interior gets cold and it gets condensation.Or in case you have air condioner and inside the house its cold,the interior window gets cold and if you open the window,the exterior hot air that enters your house will condensate on your window.

Mark in Texas

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Re: Geodesic dome greenhouse build
« Reply #36 on: May 21, 2019, 08:28:21 AM »
Ever thought of just going with 8 mm twin walled polycarb and be done with it?  Kicker is the loss of light transmission, L.T. with layer you apply.  https://www.palram.com/us/product/sunlite-diy-polycarbonate-multi-wall/

I have never lost any plants or trees in root tip pruning systems like RootMaker.

I've used these treepots with great success mainly for young seedlings like oaks or pecan that have long tap roots.  On some I applied a copper hydroxide root pruning paint at the bottom to terminate the tap root and prevent root spin out. 
https://www.stuewe.com/products/treepots.php 

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #37 on: May 21, 2019, 02:59:04 PM »
8 mm insulation its too little.I bought 4 mm double walled polycarbonate for exterior and for the interior il buy 3 mm sheets.

Mark in Texas

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Re: Geodesic dome greenhouse build
« Reply #38 on: May 22, 2019, 08:29:58 AM »
8 mm insulation its too little.I bought 4 mm double walled polycarbonate for exterior and for the interior il buy 3 mm sheets.

Understand that with such "glazings" your L.T. is probably down to about 50%.  What are you planning to grow?

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #39 on: May 22, 2019, 02:58:52 PM »
8 mm insulation its too little.I bought 4 mm double walled polycarbonate for exterior and for the interior il buy 3 mm sheets.

Understand that with such "glazings" your L.T. is probably down to about 50%.  What are you planning to grow?
I will measure light and i have tools to measure even the UV.Im planning to grow cherimoyas,Inga in the center,Uvaria grandiflora a few tomatoes and a few red peppers and an annona squamosa.Red guamuchil also and probably somme guava types.

Mark in Texas

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Re: Geodesic dome greenhouse build
« Reply #40 on: May 23, 2019, 07:20:33 AM »
I will measure light and i have tools to measure even the UV.Im planning to grow cherimoyas,Inga in the center,Uvaria grandiflora a few tomatoes and a few red peppers and an annona squamosa.Red guamuchil also and probably somme guava types.

Good luck with that, sounds good.  Should be no UV when you get thru.  I use a meter that measures up to 10K foot candles.

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #41 on: May 23, 2019, 02:50:53 PM »
I will measure light and i have tools to measure even the UV.Im planning to grow cherimoyas,Inga in the center,Uvaria grandiflora a few tomatoes and a few red peppers and an annona squamosa.Red guamuchil also and probably somme guava types.

Good luck with that, sounds good.  Should be no UV when you get thru.  I use a meter that measures up to 10K foot candles.
I will use a lux meter and the UV meter.In theory and ideally there should be no UV but i think somme will pass through and i have a really sensitive UV meter wich i used to measure UV from light sources,bulbs,neon tubes ,etc.My meter measures only the harmfull UVB , UVC and ignores the colored light UVA wich its safe for plastics and there are even plastic LEDs that emit UVA. A PAR meter its a better tool for measuring light for plants but its expensive and i dont have one.I had a PAR meter build in progess with a camera and a difraction grating wich would have measured all the colors in the spectrum of the light source not just the blue and red like the PAR meter.I see no reason to use such a advanced tool for the greenhouse thogh.

lebmung

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Re: Geodesic dome greenhouse build
« Reply #42 on: May 23, 2019, 06:13:12 PM »
Plants will be leggy, internode length high. Tested. Especially tropical guava will not fruit well under 2 polycarbonate sheets.
You will get condensation and a lot of it. I tested before. After you fail with condensation, I might give you a good solution. Get some experience first.

brian

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Re: Geodesic dome greenhouse build
« Reply #43 on: May 23, 2019, 09:52:04 PM »
My experience with polycarbonate, wood, and tape/sealants is that water will find a way and you will have leaks you cannot avoid.  Even manufactured double-pane vacuum-sealed windows leak sometimes. 

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #44 on: May 23, 2019, 10:39:48 PM »
For insylation,each polycarbonate triangle will be sealead on the edges with heavy duty,UV resistant tape thats special for greenhouses.After that the plastic triangles will be fized with screws on the wood frame(manny screws). And over the joints between the plastic sheets il add again that special tape for greenhouses and over that plastic tape il add another adhesive tape,this time aluminum sticky tape,made of real metal not just colored silver.10 years or so il not be expecting problems.

Mark in Texas

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Re: Geodesic dome greenhouse build
« Reply #45 on: May 24, 2019, 10:24:28 AM »
My experience with polycarbonate, wood, and tape/sealants is that water will find a way and you will have leaks you cannot avoid.  Even manufactured double-pane vacuum-sealed windows leak sometimes.

Yep.  Only way to do this is double walled polycarbonate resulting in less light and plants that tend to be leggy and may not fruit well.

Otherwise he needs to go with single and cough up the bucks to heat it.  I would assume that gas heating would be the cheapest with controllers.     

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #46 on: May 24, 2019, 04:29:56 PM »
My experience with polycarbonate, wood, and tape/sealants is that water will find a way and you will have leaks you cannot avoid.  Even manufactured double-pane vacuum-sealed windows leak sometimes.

Yep.  Only way to do this is double walled polycarbonate resulting in less light and plants that tend to be leggy and may not fruit well.

Otherwise he needs to go with single and cough up the bucks to heat it.  I would assume that gas heating would be the cheapest with controllers.   
I have the dome on top of a hill in full sun all day long .And probably right under my greenhouse you could find oil and natural gas ,because i live in an area thats surrounded by oil rigs and extraction heads.Even if the gas is cheap and i could buy a nice and cheap ,second hand heating boiler wich i can install myself for free,i will have the heating going on wood branches because thats not cheap,its free fuel for me.I will spend a bit more monney to build the rocket stove on wood than i would have spend on a nice  second hand ,gas heating central ,but il build it because i want to invent something usefull and interesting even if it makes me to look like the antichrist.

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #47 on: August 14, 2019, 03:23:05 AM »
For sealing the double polycarbonate pannels i decided that the aluminum sticky tape its the best.Sticks well,and its UV resistant,water resistant .Each pannel of polycarbonate ( double walls polycarbonate) will be sealed with 2 layers of aluminum tape on the edges and in between pannels on the dome ,there will be also 2 layers if aluminum tape.
Initially i wanted to use one layer of plastic tape and last layer of aluminum tape for both,the pannels and inbetween the pannels,but now il use only aluminum tape because i found to buy it for cheap (4 dollars per 50 meters x 5 cm).

 You get weak light from double polycarbonate in case water gets inside it and then algae start to grow between the layers.When sealed well,water doesnt gets in and algae doesnt grow = the polycarbonate stays clear.

Forester

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Re: Geodesic dome greenhouse build
« Reply #48 on: August 14, 2019, 03:41:24 AM »
Dude, I canít imagine how much effort and money you have already spent on this! Once I also thought about building a geodesic dome, but after making calculations I realized that it was very expensive for me. I hope you succeed! Good luck

SeaWalnut

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Re: Geodesic dome greenhouse build
« Reply #49 on: August 14, 2019, 04:41:11 AM »
Dude, I canít imagine how much effort and money you have already spent on this! Once I also thought about building a geodesic dome, but after making calculations I realized that it was very expensive for me. I hope you succeed! Good luck
Its actually quite cheap since ive used raw wood boards(cheapest wood) that i cut myself on length to make the struts.
The wood costed @ 400-500 dollars because i had a lot of losses( bad wood with knots,somme curled after they dryed,etc).
Cement for the foundations ,just a few bags.The foundations dont have metal reinforcements in them but i mixed the cement to be on the harder side with slightly more cement than normal.@ 30 dollars
The exterior policarbonate ,4 mm thick and double walled costs @ 400 dollars and the interior polycarbonate another 300 dollars or so.
On screws and anchors i spend probably 200 dollars or slightly more and on aluminum tape another 200 probably.
Total cost @ 1500 dollars for 50 square meters and 4 meters tall .But i didnt calculated the labour.
If you like geodesic domes and want to have one thats even cheaper than mein,then ZipTieDomes has somme kits lately made with pvc plastic pipes and a special connector on them where you can attach greenhouse foil on exterior and on interior and that seals it well from cold( better cold sealed than my dome actually).https://youtu.be/CMsRCiYZl0A
My dome is hubless wich is a lot harder to build than one with hubs ( visible joints).But domes with hubs and with plastic foil are just as beautifull as mein ,just make it bigger to look good and 3v or 4v frequency.
Warning: do not install the dome right next to a busy road because it will cause accidents from drivers looking at the dome instead of the road ;D.

 

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