Help planning my new solar greenhouse

[timnz]

Hi everyone, I'm new here. I searched around for gardening forums with friendly sounding people and the community here looks great

I'm completely new to gardening and greenhouses, but I have a small parcel of land out the back of my shed that I want to grow veges in. I figure rather than growing in the ground I'd be better off building a nice solar greenhouse to increase the space available, extend my growing season, make the most of the space I have. I figure if I'm going to do it, I'll do it properly. I'd love some opinions from people more experienced about whether this is worthwhile, and how my plan sounds.

The spot I have available is behind my shed, facing west. It won't get much morning sun in winter, but it should start getting some sun from 11am or so, right through to sunset. I've attached some photos below. I'll be removing the tree and some bushes to let more sun in, and I may make some kind of modification to let more sun through that gate. I may also consider reflectors to throw more light into the greenhouse. I'm a little worried that it won't get enough sun to be worthwhile. The climate in Wellington, New Zealand can be found below. Basically it gets quite cold in winter but very rarely snows, it's quite windy, in summer it gets up to 25-28 degrees on a good day.

http://en.wikipedia.org/wiki/Wellington#Climate

Here's the basic plan:
- Build a wooden frame, with the south end solid insulated wood painted white. I figure standard 4"x2" frame or maybe slightly less heavy wood, I want it strong enough to stand the wind in an exposed place but I don't want to block the light
- Cover it in a transparent plastic material that insulates well, something double skinned with an air pocket. I'd make sure it sealed well.
- I'm not sure yet if it should just attach to the shed and slope downward, or if it should go up a little to a peak then down. I'm mostly thinking about vents, for summer, so heat can escape.
- A door, and some opening windows for ventilation and to let good insects in. I don't know where to put the windows/vents though, or quite how to do them, but my builder is quite resourceful.
- Right now I'm thinking I'd dig down, insulate the ground, then put a concrete slab down. I'd have it dark concrete so it absorbs heat during the day and releases it at night.
- I'm considering some kind of heating in the concrete, either electric (not connected initially) or just some pipes to allow me to circulate a hot fluid if I decide to later. Any thoughts? Is this overkill? If it's cheap to be prepared I'd do it, and if it's electric I'd wire it in later.
- I'd want to use the brick wall as thermal storage too. I'd probably paint it part black to absorb heat, part white to reflect light to the plants.
- I'd put in shelves along most of the length, though leaving some tall space for tomatoes and corn.
- All the growing would be done in planters or pots, partly because that's easier than bending right down to the ground, partly as I want to use a growing compound like the one recommended in the "square foot gardening" book I've read.
- I'd collect rain water to water it with. I have no plans for electricity, a watering system, or automation, but these could be added later
- Some kind of shield up top so that in summer the plants aren't cooked

I want to grow:
- Brocolli and cauliflower
- A few tomatoes
- Strawberries! I love strawberries and that was my original motivation to build a greenhouse
- Spinach
- Capsicum, onion
- Potato and carrot
- Corn maybe

Thoughts, opinions, and suggestions would all be gratefully received

Tim

My back yard, photo taken facing west.

The gate to where the greenhouse will be. Sun to my back, facing south

The space available. It's about 1.8m wide and about 4m long (that's about 5.2ft x 12ft)

This is a view standing where it will be build, back to the south, facing north. The tree and bushes will be removed as they'll create too much shade

Here's a view looking west at 1.30pm. That tree will have to go I think.

 

[rebbetzin]

Oh NEW ZEALAND!!! How wonderful to have you here! I have dear friends that spent a month
camping and just enjoying the countryside there. They LOVED it!!

I will be no help at all! But wanted to welcome you!

Here in Tucson, Arizona, we don't have many green houses.
They need to be cooled here in the Summer, or your plants
will COOK!!

Here where I live, we would be looking to keep the trees just because they give
good shade in the Summertime. If we want to grow things in the summer here,
we plant so things will be in the shade for the afternoon heat.

I know you will find people here to give you great insights and ideas.

Again.. Welcome!!!

 

[timnz]

Thanks for the welcome In summer I expect I'd have to leave the windows open, and maybe provide some shade, but it only gets up to say 25 degrees on the hottest days, the average high is 20C (70F). I guess it may take me a few years to experiment and get things right, no great hurry though

Oh and water is free here, at least for now. They may start charging by volume one day, but for now it's part of our rates and isn't metered.

 

[rebbetzin]

Thanks for the welcome In summer I expect I'd have to leave the windows open, and maybe provide some shade, but it only gets up to say 25 degrees on the hottest days, the average high is 20C (70F). I guess it may take me a few years to experiment and get things right, no great hurry though

Oh and water is free here, at least for now. They may start charging by volume one day, but for now it's part of our rates and isn't metered.

OH MY GOODNESS!! FREE WATER!!! I would go crazy growing things!! I try to keep the water bill under $100.00 a month in the summer... the water bill runs about $50.00 to $65.00 in the winter. But only about $20 of that is actually the water usage. Most the bill is sewer and trash pick up.

About four years ago my husband had a "spaze attack" when our water bill was over $400.00!! It went from $86.00 one month to over $400.00 the next month. I said that there must be a water leak, or the meter was broken. But, checked the meter and it was fine..

My husband said "I know where the leak is, Heidi... OUT THE END OF YOUR HOSE!".... he is funny!!

Well off to bed for me, I have to get up in 4 hours!!

 

[digitS']

, Tim. And, Welcome!

I had a lean-to greenhouse at my former home that was about the size you are thinking about. I found it real useful for plant starts .

There is quite a lot to think of here with your project. I can start off with a few ideas: First of all, your climate.

Forty-nine inches of rain a year!! That is a lovely blue sky in the picture but for us folks here in the US - that's more rain than Portland, Oregon or Seattle receive and nearly as much as Vancouver . . . I think tho', your temperatures and weather may be more similar to Portland, if that is a help to folks on TEG. The rain clouds will make more of difference to to your growing than winter temperature, I'm thinking.

A couple of cautions: good retaining wall. You don't want the floor to be dropping out from under you! And, I don't think "field crops" would be a good choice for your protected growing. You know, salad crops are really the most valuable of what you can grow, generally, but you haven't mentioned them. Herbs aren't mentioned either but many of them don't really like a greenhouse environment and all the humidity. Fresh tomatoes and peppers are wonderful to have!

Western exposure means - heat . . . usually. You are right to be concerned about ventilation and, unless you want to be there every hour opening and closing vents, some automation is called for - for example, a fan on a thermostat OR an automatic roof vent, right across the top. Other greenhouse folks use a vent opener that doesn't require electricity and report that it works fairly well. I rely mostly on a "window" high on one wall and an exhaust fan on the opposite wall. In my lean-to greenhouse, I had LARGE windows in both walls that opened out. I could really get a lot of air movement thru them since the greenhouse was so small.

The concrete block wall will have a real influence on indoor temperatures. In some ways, you are faced with a trade off: paint it black to absorb the sunlight for heat or leave it white for reflected light back onto your plants. Am I correct that the building has no windows on that side? A window into an interior room, even for an unheated building, would have a moderating affect on temperatures in the greenhouse. It would help with the extremes. (Also, that room might come in handy for storing greenhouse things .)

I'll try to think of some more ideas thru the day. That's just "off the top of my head" this morning. I hope you stay with us, Tim.

Steve

 

[NwMtGardener]

Hi, welcome! I started greenhouse gardening last year, and i love it. I'm wondering if you've had a garden before, and grown all these things without a greenhouse? I kind of think, if you havent done any gardening, that you might want to start small and just do some container gardening there in your spot, without a greenhouse. Just to get a feel for how the microclimate is right there.

About 5 years ago we built our raised bed garden, 12' x 24', and i just planted in there for a few years. Then last year we covered half of the space with plastic, just cheap construction grade plastic, for a few months. That helped me get my plants started much earlier in the spring, here in montana we have a short growing season so any little bit extra helps. This year we covered the whole garden area in plastic.

So my recomendation is to start out simple, see how you like it and what works for you...and then when you know exactly what you want then build somethhing elaborate. You could have a container garden located there this season, maybe next year build a temporary greenhouse by draping some plastic from your garage, and then the following year build the greenhouse of your dreams! But that's just my thoughts i'm sure you'll get lots of good informationby reading some of the older threads here on greenhouses.

 

[Collector]

Sounds like you have put alot of thought into this project already. If what steve says is about your weather being like Prtland is true, have you thought of moving LOL just joking (sorta). There are plenty of learned greenhousemen and women on here to help with your Questions (Im not one though). Welcome and good luck with your endeaver.

 

[timnz]

Thanks everyone, I appreciate the welcome and all the suggestions so far. I've found forums great ways to learn about new subjects, and the communities are great too I'll try to give more information, and address what people have said.'

First up, whether to do it at all. There are a few drivers. One is that I have a builder available who does good work quite cheaply. The second is that area can get a bit of wind as it's very exposed, so I'd like to protect it. Third is that it's not a big area and I can put up shelves to give me probably double the growing room. Fourth I'm not good at moderation, I know I'm going to end up with one eventually so I might as well do it now and save messing around!

The weather's really variable. We can have cold wet days where we use heaters in the middle of summer, though usually it's warm, often cloudy, and quite sunny. Right now it's autumn heading for winter, it's quite chilly outside but it's really sunny, and it's getting nice and warm inside my house. We do pay for water, it's just not metered, everyone pays the same.

Yes there's a great retaining wall there, it goes down more than a meter and has concrete anchors. The same guy who would build the greenhouse made it, it's probably overengineered but that's the way I prefer things!

I think after cutting down one tree and trimming another it should get enough sun to be a lot warmer in there even in winter. In summer I suspect keeping the sun out would be more important. That rainfall is averaged over the whole area, we get less where I live.

The wall it's built against is my shed, I'm unlikely to cut a hole in it for venting. Automated vents sound ok, but do they need mains power or can they run off batteries? I think I'll have to experiment with what color to paint the wall too.

Regarding what I want to grow, do many of those not grow well in a greenhouse? I don't even know what season to grow things in, so I'm (if you'll excuse the pun) very green! I was hoping with a greenhouse that I could grow anything, all year around. I don't have a lot of land, so the area where the greenhouse will be is about it. If I put a garden out back I'd lose my grassy area, which would be great for kids if I ever have any. I could put one out front behind the fence, but that might not be great for appearance or resale value - though I'm not hugely concerned about that because the fence will hide it mostly, and it'd still get a decent amount of sun.

Sorry that's a bit long! Thoughts are very welcome, both on the greenhouse and especially on whether what I want to grow will do well in there.

Tim

 

[Collector]

Sounds like you have thought about it and you may be right, greenhouse might be what you need to have a place to garden. A greenhouse will give you a more controled environment to garden in. There is a learning curve to all types of gardening, starting in a greenhouse shouldnt be any harder than learning to garden outside on bare ground. I do not have any experience with them, but my brother used to grow tomatos in a small greenhouse. he was able to grow tomatoes earlier and faster than normal outdoor planting. I say if thats what you want to do, go for it!

 

[timnz]

Controlling the climate here would definitely be a big advantage

Will potatoes, carrots, and brocolli grow ok in a greenhouse alongside tomato, strawberries, capsicum, etc? Or are some really not suitable for a greenhouse?