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bennelson 03-03-09 10:49 AM

Cheap-o Greenhouse
I built a greenhouse this morning....From scratch....In about ten minutes.

Ok, ok. So it's not what you would call "Big" or "Permanent" or even "Sturdy".

It is however, made completely from free/used/reusable materials, and a good little experiment.

If you live the the daylight-starved great white North like I do, any solar building in the winter is a good one.

I got the idea about this after visiting the Michael Fields Agricultural Institute a few weeks back.

They had a BEAUTIFUL greenhouse there made from patio doors, greenhouse glazing, sheet metal, and insulation. The beams were natural round wood poles. It looked like all materials in the building were recycled.

Now here's the thing. It was an A-frame. The easiest building in the world, because the walls and the roof are the same thing. Imagine the capital letter A. That's what it looks like.

The south wall was all glass and the north wall was all insulation - simple.

For a while, I have thought it would be great to have a greenhouse on my property, but they get complicated and expensive fast.

I already had a couple of sheets of salvaged 4-foot by 9-foot polycarbonate greenhouse glazing. I also have a few sheets of 1/2 and 3/4 EPS (pink foam insulation.

All I did was lean two pieces of the glazing together, with the insulation against the north sheet. I held the two corners together with spring clamps, and then threw a packing blanket over either end. It actually took me longer to write this message than to build it!

No, this is not a permanent greenhouse, and no there is nothing growing in it. In fact, it will be lucky if it doesn't just blow over.

I put a thermometer in there when I built it (30 degrees F.) It's partly cloudy today. I'm going to let the greenhouse sit for a while, and then I will crawl in it this afternoon to see what the temperature is.

This is just a simple proof-of-concept shelter. Obviously, it would have to be built more solid, larger, and have permanent materials to be an actually useful building.

For me though, it's often easier to actually DO something than just dream or sketch on paper.


See more of my projects at

Daox 03-03-09 11:00 AM

A test for ideas on the new garage??? :)

bennelson 03-03-09 12:50 PM

I would SO LOVE to have a passive solar garage!

Too bad about the orientation and that great big pine tree! The only way to get some good solar heat to the garage might be with some hot air collectors, although I really don't like the looks of them.

I know the old style of lift garage door was rigid, it just moved a little different on the track than the multi-part garage doors everyone has now.

Maybe I could have a giant solar hot air collector IN PLACE of a garage door? Not sure how it would be designed to still look nice and blend in with the architecture of my house, but it could be possible?

Experimental buildings are fun.

Higgy 03-03-09 01:17 PM

Hey're not allowed to call yourself part of the Great White North unless you A) Live in Canada, or B) have more then 5 inches of snow on the ground and can't see any grass at this time of the year. :D

That's pretty cool though. I would love to have some kind of green house but my yard is smallish, and my kids are too, which means if I built one they wouldn't have much room to run. So I will probably have to hold off until they're older. So until then I'll have to reside to reading what you and other people do. Keep the ideas coming.

...preferably something that won't get knocked down tomatoes couldn't handle the squashing. :D

Daox 03-03-09 01:19 PM

As long as you don't mind your garage door being flat black I think its totally possible. Maybe you just have to trim your trees a little bit. :) All you really need is good sunlight from about 10AM to 2PM when it is the most direct.

bennelson 03-03-09 01:58 PM

If anyone has more ideas for greening up a garage, head on over to:

SVOboy 03-03-09 02:35 PM

Looks pretty neat. Any plans for putting in something more permanent?

bennelson 03-03-09 02:59 PM

Well, I just crawled inside the cheap-o doghouse, er...greenhouse.

It's warmer in there than outside, but not by a ton. I did throw in a scrap of foam insulation which is black on the one side. I put the black side up.

Crawling inside and laying on the black foam, it was slightly warm. It was warmer than the air.

It appears that there is a bit of a draft going through.

I would actually see a few blades of grass moving from the breeze. I think this was carrying away any heat I was building up.

OK, so maybe blankets are NOT the best construction material...

It DOES make me want to improve this slightly. If I make the ends out of a rigid material, and airtight, I think it should work pretty well.

bennelson 03-03-09 06:46 PM

Version 2 is done.

I don't think the wind is going to blow it away.

I replaced the blanket ends with another (partial) piece of the scrap greenhouse glazing, and some more pink foam.

I sealed up all the ends of the dual-wall polycarbonate with packaging tape, so it will have better insulation value.

The base of the walls are held in place by metal stakes driven into the ground.

The wall end made from the short piece of glazing didn't line up well, do I drilled and ran baling wire through to connect it to the walls.

All seams were caulked with silicone.

(er - gotta go. I have a City Council Meeting to attend to promote Neighborhood Electric Vehicles!!!)

bennelson 03-03-09 09:11 PM

Yea! I just helped pass Neighborhood Electric Vehicle ordinance in my city!

OK, where was I?

er, um, Photos.

I used a stake to hold up an end wall.

I used packaging tape to attach the insulation to the north wall/roof. I used packaging tape to seal up the open ends of the panels and seal seams

I used stakes to keep the bottoms of the walls from slipping out, and eco-clamps (green, reusable, spring clamps) to temp. hold the other end.

I caulked the top seam, and used bailing wire to pin down the one end.
Wire was tightened with my eco-pliers. (They're green too!)

I cut some foam to make the other end.

What's that you say? "No Door?" No problem, that's why God invented the Sawzall.
Yes, it's overkill, but it cuts like butter!

I attached the cut-out to another hunk of foam, and attached a handle. For bonus points, what part of an electric car is the handle made from?

Here's the finished door closed.
And the view from the inside.

And here's the finished product.

It does look kinda like some crazy emergency shelter, doesn't it? Inside, I put down a black packing blanket and a thermometer.

The next sunny day I am not working, I will be out there!

Daox 03-04-09 07:38 AM

Just to clarify, what is the purpose of doing this?

bennelson 03-04-09 06:56 PM

Mostly, it's just a little experiment.

I saw a pretty cool-looking A-Frame greenhouse, and I though, "hey, I could build one of those!"

I already had all these materials just sitting around, so this is really a scale model of what could later be a full-scale greenhouse for my backyard.

As it is, I might just go sit out there on a sunny, cold day. (It's still winter here! Don't be deceived, it snowed 11 inches, within 30 miles of my house the day before I was working on this!)

I am also planning on using it as a "cold-frame" for getting some garden plants started early.

Besides that, it is also giving me some ideas about what I might want to do for solar space heating for my garage or house.


bennelson 03-06-09 10:51 AM

Holy Crap! I built a Sauna!
I am home today, it's sunny, and time to test out the cheap-o greenhouse!

It's 42℉ and sunny. A beautiful, unseasonably warm day.

I finished building ver 2 of the mini-solar-greenhouse at the end of the day 3 days ago.

For the last two days plus just this morning, it has been soaking up solar energy, although it's been fairly cloudy until this morning.

When I pulled off the hatch of the greenhouse, the first thing that happened was that I got hit in the face with a blast of hot air and my glasses steamed up!

I crawled inside and pulled the door shut behind me.

The thermometer I had left in there was reading off the chart, but it was laying flat on the black blanket in the sun, so I know that's not accurate.

It was WARM in there though. No, I take that back. HOT. It felt like the high 80's℉ in there.

That's over a 40℉ difference in air temperature!

I think leaving the black blanket in there made a big difference as well. While all surfaces inside the greenhouse were warm (except the wet ground) the blanket itself was HOT and radiating heat!

I could tell that the greenhouse was still not perfectly sealed up. There was a small gap on at least the one end, and a few little spots where the the ground wasn't level and there was a little space to the ground.

The next thing I noticed amazed me. Green grass. The exposed grass had sucked up enough heat and light to start turning green again! Outside the greenhouse, it's all still brown and dormant.

It was hot and steamy in there. All the snow was completely melted off, although there was still a couple very small bits of ice left in there. The ice was actually bubbling as it melted away!

I SO want a bigger version of this greenhouse now!

Daox 03-06-09 11:23 AM

So, what the next step Ben? :D

bennelson 03-06-09 12:21 PM


Originally Posted by Daox (Post 2343)
So, what the next step Ben? :D

Um, finish upgrading my electric car, help you with the EcoRider, convert my truck to bio-diesel, make bio-diesel, rebuild my garage.......

RobbieWT 03-11-09 12:02 AM

Have you checked to see how well it holds heat over night?

bennelson 03-11-09 07:22 PM

I haven't checked for overnight heat holding yet, but I can tell you that it can't be good right this second. All the crazy weather we have been having lately (snow, rain, thunder-snow, wind.....) has split the seams on both ends of the greenhouse.

I will repair it and seal it up real good. I think we should then be able to use it as a "coldframe" for starting up seeds in trays.

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