Garbage greenhouse: What's the plan, Stan?

Why a greenhouse?

As I mentioned in my last post, I've been making plans and gathering materials for the last six months with the goal of building a greenhouse out of mostly repurposed materials.  The project was motivated primarily by poor yields of ripe tomatoes and peppers, given the short growing season in the Keweenaw.  Granted, my green tomatoes were edible, and found their way into pasta sauces, salsas, and the like.  However, there was something incredibly gratifying about pulling off the few juicy, red tomatoes off the vine.

Why garbage?

Now, about repurposing.  While in my life I've gotten to the point where I feel it needs neither explanation nor justification, that wasn't always the case.  I recognize that transition is a process, not an event, and there are those are yet struggling to free themselves of old ways of thinking that encourage scrapping the old and buying brand new.  If you, dear reader, embrace frugal and freegan practices, bear with me while I develop this point a bit, or just skip down to the planning phase.  In my lifetime . . . I'm 33 now . . . I expect energy shortages to be a pressing challenge.  We're currently riding the jagged plateau of peak oil, with no end of increasing energy demand in sight as the planet's population rises along with standards of living in developing nations.  While solar and wind are making headway in providing electricity, alternative transportation fuels are proving to be a tougher nut to crack.  Corn ethanol's a demonstrated loser.  Algal biodiesel holds promise, in that it makes use of non-arable land, but continues to be found lacking with regard to viability as a net energy positive resource (see here and here).  That is, more energy is currently required to produce algal biodiesel than can be produced by its burning.

To me, the question is whether or not advancing technology will bring us the solution to fossil fuel shortages before fossil fuel shortages begin wreaking havoc on the gears the global economic and political systems.  Honestly, I'm hopeful, but not optimistic about that prospect.  Tavis Smiley distinguished the two during a panel discussion I caught a while back on PBS.

Optimism suggests there's a set of facts or circumstances or conditions, something you can see, feel or touch, that gives you reason to feel good about the future. Hope is a different thing. It's having faith in the substance of your future even when there's no evidence that it will be better. Even if you don't have reason to be optimistic, you can always be hopeful.

Granted, Smiley was discussing the plight of the poor in our current economic crisis, but I think we can apply the thinking to any crisis of the times, including the impending energy crisis.  So, what's one to do in the face of ominous facts on the ground?  Well, one can hope that academia, the market, the state, in other words, someone that is not me, will come up with a solution to the energy problem.  That's an attractive mode of thinking in that it doesn't require me to alter my lifestyle by, for instance, driving less, wearing my clothes until they are worn, growing my own food, shopping second-hand, reusing garbage as a construction material, etc.  Someone-else-will-solve-it-ism requires no exertion of personal responsibility for either the energy problem or its solution.  Next, we have the despair so prevalent in Mayan calendar and other prophetic end of the world scenarios.  While I'd agree that the world as we know it will look drastically different in another decade or century, I think we're going to make it as a species.  Yes, the economy will have to contract.  Yes, people will have to learn to live with fewer of the luxuries to which we've grown accustomed in the developed world.  There will probably have to be fewer of us.  However, people will live.  That leads me to what I'd consider the healthiest and most meaningful response to peak oil and the end of abundant energy.  We alter our lifestyles.  We use less.  We waste less.  We produce more.  We reuse materials.  We make them last.  We mend and repair.  This isn't news.  Our ancestors did it as a matter of necessity.  I think our descendants shall, as well.

Getting back to the greenhouse, it takes more energy to make a new window than to pick one up out of a friend's basement or garage.  It takes less energy to put that window to use growing food than it does to put it in a diesel-burning garbage truck and ship it to the dump.  It takes less energy to pick a tomato out of my greenhouse or garden than it does to have one shipped to the Keweenaw from Mexico.  I've focused primarily on energy in this discussion thus far.  I'll save the food security issues for another post.  Of course, it's all related.

Let's get down to brass tacks, here

I hadn't intended to spend that many words on the rationale, but so it goes.  Let's jump into the design phase of the greenhouse, some of the challenges faced, and how I met those challenges.  First, I'll note that this post is not going to leave you with a cookie cutter recipe for your own garbage greenhouse.  On this project, the nature of using repurposed materials places constraints on the design.  Specifically, the design came to meet the requirements laid out by the dimensions of windows available in Keweenaw basements and garages, as opposed to buying the proper materials to fit a preconceived design.  However, following a similar patient planning process, which in my case took about six months at a leisurely pace, you should be able to apply the principles to your own project.

Greenhouse foundation, 2011, Jeremy Sandrik

First, I should mention that I've already got a 12'x12' concrete pad foundation that's already plumbed.  A former homeowner here had a sauna out back.  In fact, a neighbor to one side erected a privacy fence to block the view of all the naked people running between the sauna and the house.  True story!  Unfortunately, it was torn down long before I bought the place, but the plumbing remains and in good condition.  In the picture at right, you're looking at the west side of the foundation.  In the center sits a fiberglass shell of an outdoor fireplace I picked up at Goodwill.  It's going to have to move.  Also, you'll notice some small trees on the southeast corner, which would effectively block quite a bit of light from entering any finished greenhouse.  Fortunately, my neighbor on that side plows the snow from his driveway into the space behind the foundation, and was happy help (do the bulk of the work) remove it.  Win, win.

Inspiration, collaboration & collection

Nobody wants to reinvent the wheel.  My search for inspiration began on Youtube, checking out greenhouses other people have built (here, here, and here).  I'd tinkered with the idea of making walls out of plastic two liter bottles, but Michigan's carbonated beverage bottle recycling program means I'd likely have to buy them off people at 10 cents a piece.  Some rough calculations told me I'd need thousands of bottles, or hundreds of dollars worth.  Nuts to that.  I reasoned that if I had 2-3 windows in the basement, I'd be able to gather a boat load for free pretty quickly.  Further, I'd save myself the labor of rinsing, removing labels, cutting, and gluing those thousands of bottles together.  Wanting a fairly well insulated north-facing wall, I decided on a glass bottle wall, held together with concrete, mortar, or some other binding material.  I didn't worry too much about it being sturdy enough to withstand our winters, as the Kaleva Bottle House was built near Manistee, MI in 1941 using similar methods, and still stands.

It was at this time that I brought some more brains into the mix, for a number of reasons.  First, I knew I'd need help actually assembling the greenhouse.  Second, I know that more brains working on a problem, especially in the planning stages, would help generate ideas I wouldn't find alone.  Third, I want this project to be both a learning and teaching experience.  I want to set an example.  Finally, talking about your project to people outside of your immediate social circle is a way to commit to it.  They'll ask about your progress and keep you motivated.  To these ends, I contacted Michigan Tech's Students for Environmental Sustainability (SfES), and shortly thereafter presented my plans, limited as they were at the time.  Our shared enthusiasm about the project was enough to light a fire under my ass and start collecting materials.

The Keweenaw Freecycle Network, and its members, have been invaluable in rounding up windows and bottles for the sunny and shady walls, respectively.  Two ads netted about 55 windows (about 350 sq. ft.) and about 300 glass bottles in under a week.  I'd already been saving all my glass for about 2 years, so at that point, I had enough materials to plan around.

Planning

I've never taken a drafting course, architectural or otherwise.  When I was a kid, I'd look through the Sunday paper each week and look at the featured floor plan.  I'd play a bit, designing fantastical houses that made no practical sense.  Nobody would have wanted to plumb my designs.

SW corner

Fast forward to fall 2011.  In this day and age, I wanted to be able to work the design up with inexpensive digital tools (CAD's out of my price range), rotate around the structure, zoom, and alter it without erasing or scrapping sketches.  While it may be rudimentary for the professional architect or engineer, Google SketchUp is a dream come true for the DIY tinkerer.  The price is right (free), there's a wealth of training tutorials, and an online 3D Warehouse where you can download models of everything from stud walls to skyscrapers.  I downloaded an outdoor water spigot to match the one on my existing foundation.  If you want to share your creations with the world, you can upload your SketchUp creations to Google Earth.  All around, it's a cool tool.

SE corner

As mentioned above, the design has to fit the windows I've got on hand, and the foundation that exists on the ground.  So, I started by measuring and rendering the foundation.  I measured the outer dimensions and rendered each window.  I have a door in the garage that'll work, and I rendered that.  I'll note here that the foundation doesn't sit square with the cardinal directions, so understand that when I refer to the east wall, it's actually facing somewhat south of due east.  Anywho, it then became a 3D jigsaw puzzle.  I started by piecing together the skin of windows, then rendered a 2x4 lumber frame to support the skin.  The final pieces to be added were the bottles, sheets of plywood to cover some of the triangular gaps in the gables, and some corrugated roofing material on the north-facing roof.  I assumed a 4 inch diameter bottle (many I've got are larger) in the model, which allowed a liberal estimate for the number of required bottles.

NE corner

Along the way, I discovered there were things I didn't know how to do, like frame a door, attach a wood frame to a cured concrete foundation, frame and attach a gabled roof, etc.  Houghton's Goodwill store happened to have a copy of Carpentry and Building Construction by Feirer and Hutchings (1981), which is a 1000 page tome that runs the gamut from reading blueprints to painting, and has been and will be quite useful for the self-taught builder.  I'm sure it's no substitute for a proper apprenticeship, but it's helped me solve a few problems.  Beyond that, the interwebs are crawling with tips and forums, particularly if you're looking for very specific information, like anchoring the frame to a concrete foundation, which will be accomplished in my case with lag shields, lag screws, and washers.

NW corner

For the sake of brevity (clearly a high priority), I've just included isometric views of the complete model and the frame without windows or bottles.  I'll admit I'm a novice builder.  I don't have 16" studs, mostly because I'm not living in the thing and I'll save a few bucks.  The studs are spaced to fit the window frames, 27 1/2" on center.  I'm counting on the window frames screwed to the studs adding some rigidity to the walls.  That said, if you see something that leads you to believe this thing will fall down in 6 months, please speak up in the comments.  Unclear from the sketches is that the roof rafters will rest on the double top plate of the walls with a bird's mouth joint.

SW corner

SE corner

NE corner

NW corner

With a fairly detailed design in hand, I was off the the library to see what tips and tricks I could pick up.  I read through their copy of Building Your Own Greenhouse by Mark Freeman (1997), which was useful.  He spends the first few chapters describing framing, glazing, and ventilation generally; then goes on to detail several DIY greenhouses belonging to friends and acquaintances.  I learned within those pages that I should provide a waterproof barrier between the foundation and the bottom plate of my frame, I should ventilate the greenhouse in some manner, and put some aluminum flashing or other waterproof material over the roof ridge to keep water from collecting.  The web's wonderful if you know exactly what you're looking for, but I find I still love a book when I want a broader knowledge base on a topic.

From the completed design, I was able to make some estimates for the number of bottles , and quantity of binding material to fill the bottle walls.  I assumed a 6" depth of concrete, calculated the volume of the rectangular wall at that depth, and subtracted the volume of the bottles in the wall, again assuming a 4" diameter bottle.  I ended up with a requirement of 12 cubic feet of binder, and picked up 20, 80-pound bags of concrete.  Further, I was able to use the framing plan to carefully estimate the lumber requirements, always rounding up for each board to give me some wiggle room.  All told, I picked up 10, 8-foot 2x4s; 20, 10-foot 2x4s; and 1, 10-foot 2x6 for the roof ridge; all pressure-treated lumber as this is an outside job.  The top plate of the bottle wall (north) will be anchored into the concrete binder with "L" concrete bolts, nuts, and washers.

Unsolved mysteries

I've still got a number of concerns that I haven't quite addressed to my satisfaction.  If you've got tips or suggestions, do tell.  Primary among those concerns is whether or not the south-facing roof face, composed mostly of glass, will support the snow loads common to Keweenaw winters.  As drawn, the south face makes a roughly 50 degree angle with the horizontal.  My hope is that's a steep enough pitch that the snow will slide off, but there's a hitch.  The windows are wood framed, and the panes are recessed in those frames by about 1/2", which could prevent the snow from sliding smoothly off.  I'm also worried about damage during freeze/thaw cycles in spring and fall resulting from ice and water that collect in the same recesses.  Further, rainwater will collect there and rot the wood frames quicker than I'd like.  For the time being, the best solution I've read (in Freeman's book) is to cover the entire southern roof face with 7 mil plastic, creating a smooth plane over the windows for snow and rain to slide off.  I've also considered removing the glass roof altogether in the winter months, in which case I won't be growing or overwintering anything during that time.  I'm hopeful that diligent use of the roof rake will alleviate these concerns, but I'm not so sure.  Ultimately, I'm an experimentalist, not a theorist, and will simply replace any broken windows next spring with acrylic or corrugated polycarbonate sheets.

Also, my design shows corrugated roof panels on the north-facing roof face, but I don't have them yet.  Freecycle's come up empty on that request.  Ed's Iron Salvage is just down the street from me, and I thought I'd give them a whirl if I don't come up with any better options.  A good friend gave me a roll of tar paper, which I'll be using as a barrier between the foundation and frame, and may also find a use over some sheets of plywood on the roof.  For the time being, I'm moving forward and counting on scrounging or buying what I need for the roof when the time comes to install it.

Ventilation is also going to be key, and I don't have a good answer for that, yet.  Examples in Freeman's book employed solutions as simple as screen-covered holes in the gables on opposing ends to allow a cross breeze, and as complicated as a thermostat-controlled exhaust fan .  I read on a discussion forum that I should plan to be able to exchange the entire volume (roughly 600 cubic ft.) of the greenhouse in a minute if I expect interior temperatures over 90 degrees F.  If I truly need an exhaust fan to avoid burning up my precious tomatoes, I've got another challenge in that I'll need to run power underground to the foundation, which sits about 30 feet from my house.  More than likely, I'd want it on its own circuit, and I'll be back to the books to bone up on electrical work.  I think this year I'll cut holes that will accommodate a fan, but just screen them for now and monitor the temperature inside.  If I find it getting much above 90 degrees F, I may just prop open the door, or I'll install the fan and appropriate wiring.

Closing some loops

Now, I recognize there are some components of this project that aren't entirely sustainable.  As of 2009, it was generally held that 5% of the global carbon footprint resulted from the concrete industry.  Had I spent more time in the research phase on this component, I might have purchased a green concrete mix, composed of 50% recycled material, including fly ash, which would have reduced my greenhouse's carbon footprint.  Whether it's carried by the local building supply stores is a moot point now.  Further, I might have harvested readily abundant stamp sand, an ugly remnant of the mining industry in the Keweenaw, if I had a pickup truck or could borrow one.  I'll own up to my shortcuts, though, and hope that the carbon expenditure in the concrete is balanced by the carbon savings in growing my own food vs. having it shipped from the tropics.

Another concern is the use of pressure-treated lumber for the frame.  There are a number of human and environmental health concerns associated with its use, primarily regarding leaching of arsenic either directly from the structure to soil, air, etc. while the structure stands, but particularly when the lumber is discarded.  The previous link provides a green alternative treated lumber, in Denver.  Again, I'm not terribly excited about having lumber shipped halfway across the country.  There's the option of reused or locally harvested lumber, specifically cedar, which is naturally rot resistant.  I'll be frank that I simply went to the lumber yard and paid for convenience.  I'm also not exactly wealthy, and cedar's a bit pricey compared to pressure-treated pine.  Again, now that I have the material, I'm doing the research for better options.  On my next project, I'll be making greater efforts to find more local and ecologically sustainable lumber and concrete options.

What's the score here?  What's next?

It's now time for action.  It seems we've seen the last of the cold weather, though I should know better than to say that out loud or put it in writing.  Regardless, the forecast calls for 50s this week, and it's time to start cutting and hammering a frame together.  As the construction begins and progresses, look for posts (shorter ones, I promise) detailing the steps along the way in words and photos.  A good buddy's got a framing nailer that will save me a lot of work and time.  Once I've got the walls framed, I'll be inviting SfES out to the house to anchor the walls, attach windows, and start laying in the bottle walls.

My next post will be more about the garden itself.  I've learned quite a bit in the last 2 years of planting, and I'll be sharing a diagram of the garden plan, along with an approximate timeline for indoor planting, transplanting outside, and planting from seed outside.  Thanks for reading.