Author Topic: Greenhouse building questions  (Read 2084 times)

TomekK

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Greenhouse building questions
« on: March 04, 2021, 04:45:15 PM »
Iíve basically decided on the size/shape of the greenhouse I hope to build this year-it will be small, about 16x7 feet, but with two cutouts in the corners (to make it fit in the space I have), making the floor area about 102 feet square. The height will be either 9 feet sloping to 6 feet, or 10 feet sloping to 7 feet. Still havenít decided, it will depend on my budget. There will be a concrete foundation, and possibly a concrete floor with a small cutout for a raised bed (to grow tomatoes, and only about 7.5ft^2), though the floor may change. It will be a zone 13 greenhouse, with electric heating (canít use propane/gas). The polycarbonate will be 8mm thick, probably from this source: https://www.advancegreenhouses.com/made-in-america-polycarbonate/

My questions:

For the frame, I will use either galvanized steel or aluminum. I am leaning more towards the aluminum, as it is probably easier to work with, but havenít decided. Please share your opinion as to which is better. Most importantly, can someone please give a source for the beams/extrusion/frame materials? It needs to be a sturdy greenhouse (able to support a few feet of snow), and I want to know what my options are and where I can buy them.

Regarding the heater, will either of these two following heaters work? If so, should they be mounted on the ceiling, the floor, or somewhere in between? With these heaters (which both seem to have fans), will I need more fans for airflow? Thinking of having two heaters for redundancy, and also a generator in case the power goes out.

https://www.growerssupply.com/farm/supplies/prod1;gs_greenhouse_heaters-gs_wall_ceiling_heaters;pg105811.html

https://www.acfgreenhouses.com/240v-electric-heater-24v-thermostat

Four more things. Insulation: should I insulate the the floor/foundation with the foam boards? Also, I will insulate the back wall-should I build it out of polycarbonate and add the foam boards over that on the inside (like Millet recommended in a different thread), or build a wall out of another material (what would that be?) for even better insulation. The north facing wall will be almost against a brick wall of the garage (not connected).

Attaching the polycarbonate to the aluminum/steel frame: is there anything I need to know/any tips/anything I have to buy in addition to the polycarbonate profiles (from the same source as the frame) and screws/bolts to secure them to the beams?

As this is my cacao house, there will need to be a constant 80/90 percent plus humidity inside. How do I do this? I think some sort of fogging system, any suggestions? On a similar note, how do I manage water? What filters do I need to filter tap water to water/spray/cool/etc. the plants? Do I store the water in a big barrel, or can I just pull water directly from the tap? Do I need a pump?

Finally (for now), cooling. How would you recommend me to cool the greenhouse? Especially during the winter, do I need a good air exchange with the outside, even during the night? That would waste a lot of heat. The max temp should ideally be around 90F, but it might be able to get up to 95F for a few days of the summer.

And of course, if you have any other ideas/suggestions I welcome them all!



Elopez2027@aol.com

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Re: Greenhouse building questions
« Reply #1 on: March 04, 2021, 05:07:36 PM »
On water;
Be careful using tap water. It is treated and chemicals added to satisfy EPA requirements.
Use rainwater you collect into a barrel or tank and maybe you can drip it into the plants with a timer.
You can mist and fog with this water also. These cacaoís love humidity. Donít forget in venting or a little air exchange.

You have a project ahead. A lot of small technicalities. Good Luck

brian

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Re: Greenhouse building questions
« Reply #2 on: March 04, 2021, 05:16:25 PM »
Can do you a quick overhead drawing of your planned greenhouse layout and placement in terms of other buildings and compass direction?

If you are using electric heat the heating cost is going to be a significant part of your planning.  I would try to arrange things so that you can insulate the north facing wall and possibly north roof slope depending on how it is laid out.   I think my old greenhouse was similarly sized and it cost me like $150/mo in extra power (was also electric, two 1500btu heaters set to ~35F).  There is no need for the north wall to be polycarbonate at all.  Use wood, foam panels, whatever.  Maybe a foam board sandwiched between two poly panels. 

Galvanized steel is fine, my new greenhouse is galvanized steel frame and is constantly wet and has no rust so far in years.  Make sure you are getting steel from a reputable supplier, though, I don't know much about it but if "bad galvinization" exists you could have rust issues.

Aluminum frame sounds worse than galvanized to me, but I dunno. 

My frame is from Conley's in california.  It is super high quality, I'm really happy with it.  If you want to go cheap could probably get galvanized fence posts and bend them to size with a pipe bender like Spaugh suggested in some other thread.  Pressure treated wood should be fine too.

If your roof is peaked snow isn't too big of an issue, it just slides off as the bottom layer melts.  I bet you could go with 6ft purlin spacing even though 4ft is recommended for our area.

8mm dual-wall poly doesn't bend much, I had to use 6mm.  If you go A-frame you either need a joint at the corners or 6mm.  If you do a quonset style roof you might be able to bend 8mm.

If you use those polycarbonate "h-channels" and "A-channels" for the glazing joints make sure they are UV rated.  I used non-uv rated ones by accident in my first greenhouse and they distintegrated after a year or two.  I suggest using the aluminum channels instead as they plastic ones ended up looking like crap for me, they accumulated dirt and algae.  The panels themselves always stay nice and clean from rain and snow, but the clear joints got ugly.

I assume you are planning on using drill-screws ("tek screws") and those foam-backed washers to affix the glazing to the frame?  This is what I've always used.  It works fine but is tedious as it takes a bit of effort to get the screws to penetrate the frame steel.   Get a good impact driver.

That heater you specified looks fine.  How are you going to power it?  I think building code likely requires a sub-panel in the greenhouse and grounding rods if you require inspection/permit/otherwise care about code.  I did mine to code and it wasn't too bad, but certainly more work than just running a wire spool across the yard or something.

I strongly recommend insulating your foundation if you are going to plant into the dirt!  I built a concrete perimtered wall as my foundation and insulated it to 2-3ft underground using 2" foam board.

You might want some kind of circulation fan unless your heater stirs things up enough.  I use ceiling fans.

My greenhouse is super humid in the cooler months and I haven't really had mold issues.  I wipe off some alge from the walls every few months.

I used foggers and a high pressure pump to cool it in the summer, when the ventilation fans aren't enough.  If you go this route you need low-hardness water or you will get terrible scale.  A cheap sprinkler running inside the greenhouse works too but isn't as elegant.  I did this for a summer before I put the fog system in.

I have my greenhouse totally enclosed in winter.  Despite everything I've read, it works just fine.  Supposedly you still need ventilation, but that has not been my experience at all.  Maybe it leaks "just enough" ?   

I have ventiliation that turns on when it gets warm enough, louvered vents and exhaust fans on a thermostat.  I still ventilates on sunny winter days sometimes.

I ran a dedicated water line to my greenhouse.  You could use a hose but you gotta keep it from freezing somehow between the water source and the greenhouse.  I had to bury mine 3ft down which sucked.  I guess you could run a hose out every time you need water but that's a pain.  If you let your hose freeze full of water you're screwed, I had that happen once long ago and had to haul buckets of water for a month.

Good luck, having a greenhouse is awesome!




TomekK

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Re: Greenhouse building questions
« Reply #3 on: March 04, 2021, 06:06:15 PM »
Brian, thanks for that detailed response!

I do think galvanized steel will be best, but do you know of a supplier who will custom cut the pieces I need? I would go with a greenhouse manufacturer, but what I need is something very custom and I think getting a company like Conleyís to make a custom frame would be cost prohibitive, at least for me. Aluminum extrusions seem easier to source, and to drill through. But Iím really not sure.

Wow, $150 extra a month in heating! Based on the online heating calculators, I thought it would be around $1000 a year to keep the temps at over 70F. How expensive is electricity where you live? Maybe itís cheaper here. Or the online calculators suck. Iím thinking the latter unfortunately...

To insulate a polycarbonate back wall, do you think I would need to sandwich the insulation between two layers of poly, or will it be fine to keep the insulation boards exposed inside the greenhouse? Donít want to use any wood in the construction, otherwise it would be too easy.

I wonít be bending any polycarbonate, so will need joins. Iím thinking just end pieces on the polycarbonate attached to the frame, no joint between the polycarbonate sheets where the roof meets the sides.

Interesting that your profiles got ugly, while the sheets were fine. Thanks for the tip! Will try to find some aluminum channels.

When affixing the glazing to the frame, do you have to go through the sheets, or do you attach the profiles only (and they keep the sheets in place)?

Will figure out building codes eventually, putting it off as long as I can! The greenhouse is right by the house, so any electrics should be relatively easy. Itís right next to the electric meter even.

I donít think Iíll plant much into the dirt, save for a few tomatoes, but I will definitely insulate around the foundation. Do you think that I should also insulate the floor itself (if not growing in ground), or will just insulating the perimeter 2-3 feet into the ground be enough/almost as good?

For the water, do you use regular tap water, or do you filter/use a rain barrel? I think Iíll need to filter the water, as spraying the leaves in my indoor grow tent leaves some white powder (salt? calcium carbonate?) buildup on the leaves after a few months.

Iíve attached a few photos of some quick plans/drawings/a cardboard model I made because I had nothing else to do. Let me know what you think!













swincher

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Re: Greenhouse building questions
« Reply #4 on: March 04, 2021, 06:10:54 PM »
If you use those polycarbonate "h-channels" and "A-channels" for the glazing joints make sure they are UV rated.  I used non-uv rated ones by accident in my first greenhouse and they distintegrated after a year or two.  I suggest using the aluminum channels instead as they plastic ones ended up looking like crap for me, they accumulated dirt and algae.  The panels themselves always stay nice and clean from rain and snow, but the clear joints got ugly.

I wish I'd received this advice before ordering all my greenhouse materials last week! I think they are UV rated at least, but I definitely went with the poly connectors without thinking about them getting nasty.

Did you seal them with silicon or anything like that? I was thinking it might help to keep it airtight for other reasons, but maybe also would keep out algae/etc...

brian

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Re: Greenhouse building questions
« Reply #5 on: March 04, 2021, 08:06:51 PM »
I tried sealing them with silicone when they started cracking apart, but it only kind of helped. 

brian

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Re: Greenhouse building questions
« Reply #6 on: March 04, 2021, 08:32:54 PM »
TomekK your "greenhouse diorama" is awesome, love it.  And it happens to be the perfect shape for a northern greenhouse.  If I were building a new one I would build a shape much like yours.

So, if you look at the various guides you will see suggestions to cover the back wall with water jugs/barrels to retain heat.  This is probably a very good idea if you have the space.  I was looking into exotic phase change materials like "glauber's salt" that retain even more heat than water but it didn't look reliable to me, and it turned out for me that I have piped gas heat now that is so cheap it is laughable. 

Getting any builder to do any custom anything is gonna cost a fortune, don't bother.  I would just build the frame from treated wood honestly if I were you, or from ~2in diameeter galvanized pipes and either bend them with a jig/mandrel or get those structural steel pipe joints they use for things like jungle gyms.  Or fashion your own joints by bending heavy rebar or something. 

You can cut steel surprisingly easily with a large chop/mitre saw and a metal cutting wheel.  It's loud and sparky but it works fine.  Aluminum cuts way easier, but it is quite expensive.  You have to balance the cost vs effort depending on how much cutting and bending you might be doing.  If you can find affordable aluminum structural pieces go for it. 

Insulation boards will not be harmed whatsoever if exposed inside the greenhouse, but you might want to paint them white for reflected sunlight.  Externally, you should cover them with something as they damage easily and sunlight slowly damages them. 

You don't HAVE to pierce the sheets when attaching them.  This is the most common way, though.  It was unavoidable for me because of the design of my greenhouse, but you could likely fashion a tight joint on the seams and maybe a non-affixed-but-touching inside and outside frame in the center to keep them rigid if they wobble.  8mm poly is fairly stiff, but a 4-6ft span will wobble for sure if it isn't supported by more than the edges.  You could do 10mm 2-wall poly for extra stiffness if you want to limit the purlin-type support

If electric is close you could do an overhead line.  Or to bury it to code is like 18-24in deep depending on type. 

Figure out how you're going to get water in, too.  I use my tap water which is city water that happens to be relatively low dissolved solids.  I tested it with a TDS meter.  I get minor scale on the plants nearest my fogger but no so much it is killing them.

If you have well water or piped water that is hard, you can't spray it around or you'll get scale bad as you've seen.  Plants don't like salty scale on their leaves.  And containerized plants might need flushing occasionally if you water a with really hard water.  A big rain water reserve container and a pump is prob your best bet if you have hard water.  You could do reverse osmosis if you want but I hear it is high maintenance and also electric intensive ($).  I never tried it. 

If you aren't planting in the dirt, instead of insulating the perimeter just put insulation on the floor.  WAY easier.  Those 2" foam panels are pretty much perfect for this.  put whatever base flooring you want first (concrete? dirt? flag stone/tiles?), then the foam, then something abrasion resistant on top.  Cheap vinyl floor or something like that that you can sweep.  White for sure.  Make every surface white if possible it really helps.

Don't forget hanging containers, too.  I have a ton of 1-5gal size containers hanging from my greenhouse roof, it definitely helps keep the floor clear.

Remember that any joint can leak water.  If the only meaningful joint is where the leading edge of the roof (poly panel I assume?) meets the front poly panels that should be okay.  A little water leak doesn't really matter if it just slides down the wall.  You just don't want constant drips onto your actual plants. 

BTW if you are using containers and electric heat, it probably makes more sense to try to heat the soil/containers rather than the air.  The "waste" heat will heat the air anyway.  If you're stuck with paying a fortune for electric you might as well take advantage of its ability to be placed specifically.  Heating mats, heated tables, "christmas lights" around pots, something like that.  You can get cheap electric heating mats on amazon intended for seedling trays.  Plants love warm roots, you could prob heat the soil to 70-80f while the air is at 40F for the same cost as heating just the air.


Oh and I saved the worst for last:  It cost me ~$150 a month to keep it at 35F minimum, not 70F!  You wouldn't want over 55F anyway.  It'll get warm during the day time, you only heat at night.   I think I pay like 9-12c/kwatt-hr?  I forget, but I think it is fairly average.

The biggest thing you could to save money is find some kind of insulation blanket you could affix every night.  I had dreams of setting up some kind of roll-on/roll-off insulation mat like heated pools have, but I forgot all that when I realized I could just burn cheap natural gas from the fracking surplus :-/

oh and small footnote - stopping air infiltration is much more important than insulation R-value.  Feel around the walls on a cold day for any slight drafts and seal them.  A well sealed greenhouse made of saran wrap is probably better than a well insulated one with leaks. 

EDIT - I misread your dimensions, I thought you had 16x17ft. 

16x7 should be cheap enough to heat... but I think you will wish you built a bigger one.  Mine is nearly ~400sqft and I wish it was 4x.


« Last Edit: March 04, 2021, 10:04:39 PM by brian »

brian

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Re: Greenhouse building questions
« Reply #7 on: March 04, 2021, 09:06:05 PM »
costco sells milk in square gallon jugs.  Get a costco membership and start drinking a lot of milk, and you can fill your rear wall with great density!

TomekK

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Re: Greenhouse building questions
« Reply #8 on: March 05, 2021, 12:52:45 PM »
Thanks again for all the tips! I believe that I will give up on a metal frame, after seeing the costs, ha. Pressure treated wood should be fine hopefully, and itíll give better insulation than steel anyway (and much much easier to work with/source).

Iím thinking of making the back wall with insulated walling, basically foam insulation between two galvanized plates. If I can find it is cheaper than the same with poly/foam, then I will use that.

Will the humidity between foam insulation and whatever else (floor, walls, etc.) cause any problems? Also, did you seal anything with silicone/similar (other than the profiles when they fell apart)? What do you use to seal any holes/leaks?

Yes, itís much smaller than I want, at only 100sqft. But I donít have any more space there, nor do I have money to build anything much bigger. This greenhouse is really only for the purpose of giving the plants I currently have a good environment, until I can build something bigger. Iíll probably be going to college next year, and my parents donít really appreciate the indoor grow tent, so I need somewhere better to keep the plants alive while Iím in college. The size should be enough for all of my ultra tropicals (and actually many more), and the plants that need less humidity (actually the biggest plants-avocado, oranges/citrus, passionfruit, dragon fruit, etc.) will stay indoors over the winter as they currently are. I have a good area for the subtropical plants indoors, with a nice big door/window facing south. With the ultra tropicals out of the house, there will be enough room for the sub tropicals to have plenty of sun and space.

swincher

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Re: Greenhouse building questions
« Reply #9 on: March 05, 2021, 01:30:49 PM »
Thanks again for all the tips! I believe that I will give up on a metal frame, after seeing the costs, ha. Pressure treated wood should be fine hopefully, and itíll give better insulation than steel anyway (and much much easier to work with/source).

You could also paint the wooden frame before attaching the panels to increase the longevity of the wood in that environment. That's my plan for my upcoming greenhouse build.

brian

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Re: Greenhouse building questions
« Reply #10 on: March 05, 2021, 01:51:38 PM »
I was worried I'd have mold issues with insulation against/close-to my north wall but there has been zero.  You shuold be fine.

TomekK

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Re: Greenhouse building questions
« Reply #11 on: March 05, 2021, 07:46:36 PM »
Thanks again for all the tips! I believe that I will give up on a metal frame, after seeing the costs, ha. Pressure treated wood should be fine hopefully, and itíll give better insulation than steel anyway (and much much easier to work with/source).

You could also paint the wooden frame before attaching the panels to increase the longevity of the wood in that environment. That's my plan for my upcoming greenhouse build.
Iíll definitely paint the pressure treated frame. What are you doing about the foundation? Also interested in how youíll manage the electrics. Iím still not sure whether to put an actual foundation in, or just bury the posts. Iíll be insulating the floor, so would have to somehow waterproof the insulation/build a floor beneath the insulation, and connect/seal with the walls.

swincher

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Re: Greenhouse building questions
« Reply #12 on: March 06, 2021, 12:21:55 PM »
Iíll definitely paint the pressure treated frame. What are you doing about the foundation? Also interested in how youíll manage the electrics. Iím still not sure whether to put an actual foundation in, or just bury the posts. Iíll be insulating the floor, so would have to somehow waterproof the insulation/build a floor beneath the insulation, and connect/seal with the walls.

I'm in a slightly different situation -- I'm stripping down an existing dirt-floor garage to its wooden framing (old untreated pine/fir), removing every other rafter from the roof, weatherproofing the frame as best as I can, then mounting 8mm twin wall poly panels over the frame.

The garage has a concrete foundation wall that seems solid enough that it hasn't shifted or cracked in 70ish years, and it already has an electrical subpanel with power. No running water, but I'm planning to put a couple rain barrels in the greenhouse to collect water from the roof.

TomekK

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Re: Greenhouse building questions
« Reply #13 on: March 06, 2021, 10:52:01 PM »
I was worried I'd have mold issues with insulation against/close-to my north wall but there has been zero.  You shuold be fine.

That sounds good, Iíll try that! For cooling/ventilation, do you have any vents in the top of the greenhouse, or only the 2 side vent/fan combos? Iím thinking of totally skipping any top vents in my plant, it would be much easier to build as I want fans anyway, and I want to know if adding vents will be unnecessary. Looking at a single 20 inch fan/16 inch exhaust system.

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Re: Greenhouse building questions
« Reply #14 on: March 07, 2021, 01:08:28 AM »
I'm currently building my wife's greenhouse out of Solexx instead of polycarbonate for an 8'x12' with 1 3/8" galvanized top rail for hoops on 2' centers. The Solexx hasn't arrived from order yet but from the look of it seems much more flexible and easier than polycarbonate. After doing quite a bit of research into what was available and price points, I found what I believe to be the best solution if you can build it yourself. It will also be pretty tough and should hold up well to snow.

There are a few companies that make benders for hoop houses which are easy to use and multiple instructional videos online. Just do a search for hoop house arch bender.
You could use this sharper radius to make the bend since you wouldn't be making a full hoop.

I was able to source used 1 3/8" 21' galvanized rails from a fencing company for $10 a piece. That means I was able to get all the galvanized rail I needed for $100. The galvanized cross connectors work perfect of cross support rails at only $1.71 a piece. Call a fence company and ask if they have any used stock for sale.

The Solexx material comes in 3.5mm or 5mm thick and can be purchased in precut sheets or rolls 49.5" wide. There's an extra 1.5" for seam overlap. Whether it's Solexx or polycarbonate, you'll want to seal the ends to prevent air flow and increase the R value. Most calking you would get from the hardware store will get eaten up by the sun. A contractor roofers caulk should last much longer. If I can remember the one that was recommended to me when my chimney was fixed I'll let you know. The material isn't completely clear but allows most light through in a diffused pattern. If you want to see through it this won't work.

As for the heater, I've been looking into solar alternatives since they are free and renewable after the initial investment. The direction I've looked most towards is using solar water heater through a heat exchanger and fan running off a solar panel during the day, electrical cost $0. Water can be stored inside a reservoir that is heated during the day and stays warm during the night. Heated soap stones can be excellent at retaining heat for the night after using the sun during the day. A hybrid system could have soapstone in the heated reservoir helping the water stay warm but I haven't tested to see if it actually works better together. There's also solar air heaters that can be easily made out of a clear box with black painted gutter down spouts. Just look up solar air heater on YouTube.

the solar water heater can be made from a professional collector using vacuum tubes and will be the most efficient, but more expensive. You can find the cheapest easiest version of a solar water heater on YouTube under "Copper Coil Solar Water Heater".

Let me know if something was confusing or you have any questions on anything. My Goal is to have the best solution built for the lowest price with a high price value.





forumfool

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Re: Greenhouse building questions
« Reply #15 on: March 07, 2021, 08:44:17 AM »
Farmtek says a product similar to solexx but a little cheaper

https://www.farmtek.com/farm/supplies/prod1;ft_roofing_wall_coverings-ft_greenhouse_film_covering-ft_greenhouse_polycarbs;pg102948.html

If you want a custom metal kit you can try here
https://www.versatube.com/

Daintree

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Re: Greenhouse building questions
« Reply #16 on: March 07, 2021, 10:21:29 AM »
Hi TomekK,

I have had hundreds of people tramp through my greenhouse because they had exactly your questions.  My setup is 700 square feet.  It is actually two greenhouses butted end to end with a door between.  This is because when I built the first greenhouse it wasn't big enough!
The tropical house is a kit with tubular steel frames and the poly H channels that Brian was grumbling about. 
The orangerie is stick built by me out of 2x4 lumber.
So I have personally made almost EVERY mistake in the book!

First - the H channels - if you got them from a greenhouse supply place they should be UV treated.  Yes, they get gross and slimy.  I solved the problem by not looking at them  ;D That greenhouse is 12 years old.  Two years past the polycarbonate warranty and going strong.

Using lumber - don't spend money on pressure treated except where it comes in contact with the foundation.  Lay down foam strips under the wood of the sill plate.  The foam comes in rolls at Home Depot.  It keeps the moisture from wicking up through the concrete (my foundation is cinder blocks.  In my area, that equals "temporary" which equals "no building permit", but ALWAYS check your area.  They CAN make you rip it out.).
For the frame, PAINT THE HELL OUT OF IT.  I have at least four coats of "porch and patio" paint on mine.  The oldest part of the frame (I have enlarged it a couple of times) is good as new at 10 years old.  Paint the lumber before nailing it together.  Get paint on EVERYTHING. Ends, etc.  I used gray paint because I felt it "sort of" matched the steel tube frame in the tropical house. Don't let any wood come in direct contact with concrete or earth.

Humidity - I made my own fogger out of a Home Depot tub and an ultrasonic mister.  You can buy fogger parts here - https://thehouseofhydro.com
There are way cheaper places, but this stuff is industrial and is holding up REALLY well for me.  Since running the fogger, my cacao have never looked so good!!  They LOVE it.  I am going to make a second fogger for the orangerie.  I also have misters I run in the summer.  But the tap water here is 55 degrees, so I don't use it in the winter!

Water - I water all my plants and fill the ultrasonic fogger with tap water.  Our water here is very good.  HOWEVER, I have a descaler to prevent mineral buildup.  This makes the minerals in the water "slippery", so they don't leave a residue on plant leaves, clog up the misters, etc. I pump water into the pond in the greenhouse and let it circulate to remove chlorine.  I have a big aquarium heater in the pond that warms it to 75-80 degrees (I have orchids also...).  We get 13 inches of rain each year and I have no room for a storage tank so I do not collect rain water.  I have thought about capturing it from the roof of the greenhouse, but I go through 100 gallons of water a week, and like I said, no room for a tank...

Ventilation - Airflow has major impact on cooling.  I have little parrots loose in my greenhouse, so I have shuttered vents, plus a big sliding window on one end that has screen covering the opening part.  For your size of greenhouse, just one intake vent and one exhaust vent fan should be plenty.  Mine are not in the roof.  They are at the very peak of the end walls.  I also have an intake fan.  The intake and exhaust are 40 ft apart and I couldn't move the air enough without an intake fan.  They are wired together and on a thermostat. Along the ridge I have five cheap metal 9 inch fans.  In the summer, they point towards the exhaust vent and blow hot air horizontally along the roof peak.  In the winter, I rotate them so they point down, and they gently blow the hot air back down onto the plants.  Super cheap fans that I got at Big Lots for $10 each, and they last years and years.  Weirdly, my birds love to sit on them.  Don't know if it is the vibration or downdraft or both.

Happy building!!!
Carolynn


TomekK

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Re: Greenhouse building questions
« Reply #17 on: March 07, 2021, 11:51:43 AM »
Thanks for all the info Daintree! Is pressure treated wood just not necessary if I paint it? What wood did you use, just regular pine? How did you connect the polycarbonate panels to the wood? Did you use the h channels for the wood greenhouse?

Iím still thinking about my foundation, not sure what I should do. Pretty much anything here requires a building permit, so thatís great. Iím currently thinking either the cinder blocks like you did, or concrete piers connected with wood. Did you put insulation around the foundation, below the frost line?

Thanks,
Tomek

brian

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Re: Greenhouse building questions
« Reply #18 on: March 07, 2021, 01:01:10 PM »
oh, I was thinking about this more...

because your greenhouse looks like it will have a flat (sloped) roof, and it isn't that large, I would just set the roof on a hinge so you can open it for ventilation.  Evarporative cooling is probably way overboard for you.   They even make automatic vent openers that require no power, they use wax that melts around 80F to push the piston.  You could probably use a few of these to automatically open your roof, and have some way to disable/tie it down on very windy days.

Yeah pressure treated wood is probably only needed near the ground, but I figured it would help with rot resistance on the rest.  Not sure, I never tried it.  Daintree is probably right if untreated works for her.

check your local codes regarding building.  My town anything under 400sq ft has lax building codes, anything over is much stricter.  I built mine 380ft :)

You could probably just do 6x6 treated wood or cinderblocks for the foundation base as you don't need perimeter insulation.  Whatever is enough to keep it from blowing away.  Look at what your neighbor's shed foundations look like to get an idea of what the local gov't requires.  My next door neighbor's new shed is just sitting on a large bed of crushed stone, and it was township inspected. 
« Last Edit: March 07, 2021, 01:05:22 PM by brian »

Kevin Jones

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Re: Greenhouse building questions
« Reply #19 on: March 07, 2021, 01:15:15 PM »
Pressure treated lumber is a fairly easy DIY option. I build this one a couple of years ago... 20 X 12...PT lumber and screws. Extra large doors for summer ventilation. Covered it with greenhouse poly which rolls up in the front for more ventilation. I will be adding gable vents soon for additional ventilation:



No foundation... just earth:










Kevin

Daintree

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Re: Greenhouse building questions
« Reply #20 on: March 07, 2021, 03:41:47 PM »
Thanks for all the info Daintree! Is pressure treated wood just not necessary if I paint it? What wood did you use, just regular pine? How did you connect the polycarbonate panels to the wood? Did you use the h channels for the wood greenhouse?

Iím still thinking about my foundation, not sure what I should do. Pretty much anything here requires a building permit, so thatís great. Iím currently thinking either the cinder blocks like you did, or concrete piers connected with wood. Did you put insulation around the foundation, below the frost line?

Thanks,
Tomek

I just went with the cheapest 2x4s available at Home Depot. The poly is screwed straight to the 2x4s with those little screws that have a rubber washer on them. Not really thick ones like the Tek screws that came with the greenhouse kit.  They were also from Home Depot, located near the fiberglass roofing materials. The cinder blocks are sitting at ground level, in a little trench about 6 inches deep filled with gravel.  Insulated on the inside of the greenhouse with closed cell foam board glued to the cinder blocks. Because our huge maple tree roots take up all of the back yard, I was not able to dig down at all for any foundation. 

TomekK

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Re: Greenhouse building questions
« Reply #21 on: March 07, 2021, 05:00:54 PM »
Thanks for all the info Daintree! Is pressure treated wood just not necessary if I paint it? What wood did you use, just regular pine? How did you connect the polycarbonate panels to the wood? Did you use the h channels for the wood greenhouse?

Iím still thinking about my foundation, not sure what I should do. Pretty much anything here requires a building permit, so thatís great. Iím currently thinking either the cinder blocks like you did, or concrete piers connected with wood. Did you put insulation around the foundation, below the frost line?

Thanks,
Tomek

I just went with the cheapest 2x4s available at Home Depot. The poly is screwed straight to the 2x4s with those little screws that have a rubber washer on them. Not really thick ones like the Tek screws that came with the greenhouse kit.  They were also from Home Depot, located near the fiberglass roofing materials. The cinder blocks are sitting at ground level, in a little trench about 6 inches deep filled with gravel.  Insulated on the inside of the greenhouse with closed cell foam board glued to the cinder blocks. Because our huge maple tree roots take up all of the back yard, I was not able to dig down at all for any foundation.

Did you overlap the polycarbonate, or put the sheets next to each other? If so, did you seal the ends in any way? Also, how thick was the wood where you screwed the sheets in?

I took a look at some of your greenhouse photos, and it seems to me that you doubled up on the 2x4s when the polycarbonate sheets meet (on the sidewalls). Is that correct?

Love how that greenhouse looks!

Thanks,
Tomek
« Last Edit: March 07, 2021, 05:05:26 PM by TomekK »

Daintree

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Re: Greenhouse building questions
« Reply #22 on: March 07, 2021, 05:51:55 PM »
So, my stick-built greenhouse is a hodge-podge.  It started out as 10x10 ft, bolted to the end of the existing greenhouse. Then I widened it to 18 ft.


Then I added another 10 ft onto the front of it.
I paid as I went, so the first winter, the whole 10x10 ft thing was just covered in bubble wrap!
Also, the original roof was corrugated single layer polycarbonate.  So when I had enough $, years later, to put on a doublewall poly roof, the rafters did not line up with the seams of the very expensive new poly.  For a second, I thought of just trimming the poly to fit the rafters, but since I built the thing, the rafters were just a hair tilted.  And when they are only 1 Ĺ inches wide, it was pretty much hopeless to fit the poly on without ripping the whole roof off.  With the summer sun beating down, cooking my plants alive, and my little birds locked up, I ditched the whole ďline it upĒ plan, and just let the seams fall where they may.  No H channels.  No overlap.  Just butted them up against each other and taped them together with that fancy rubberized (Flex) tape.  Worked PERFECTLY.  No leaks at all.  Ok, that Flex tape does NOT COME OFF.  Ever.  No matter what.  So donít make a mistake!  There are a couple of places where I really wanted a screw and there was no 2x4, so I would just scab a piece of 2x4 on to the rafter at that spot.

Come on over!  I'll give you a tour!!!

Cheers,
Carolyn


Poly attached to orangerie wall


Oooh!  Aaahh! Magical Flex tape! You can only tell its there because of a little condensation behind it.


The stuff Brian was talking about with the H Channels.  Just avert your gaze...


Insulation on the cinder block foundation. This is in the tropical house, steel frame. I only scrub the walls once a year, so there is a lot of algae in there right now.  I wait until the weather is hot, because the hose water is so cold.


How I insulate my North wall. 


Water descaler, fogger, and theobroma cacao.
« Last Edit: March 07, 2021, 05:55:12 PM by Daintree »

brian

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Re: Greenhouse building questions
« Reply #23 on: March 07, 2021, 06:32:25 PM »
What is the brand of this flex tape you used?  I have a need for some really good adhesive tape

Daintree

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Re: Greenhouse building questions
« Reply #24 on: March 07, 2021, 07:08:34 PM »
Hi Brian,
You have several choices - If you need CLEAR rubberized tape, then Flex Seal brand is perfect, but very expensive.  Gorilla makes a rubberized tape that is just as good but it only comes in black and white.  I have also used the Crystal Clear Gorilla Tape.  I started with the clear Flex Seal brand on the roof, but it was so expensive I switched to the Gorilla Crystal Clear for the side walls.  They both are holding up very well, no yellowing, no leaking etc.  Just don't EVER try to remove it.

Cheers,
Carolyn

 

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