Green Roof on a Root Cellar

Reader Contribution by Kyle Chandler-Isacksen
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In 2014 we built an earthbag and balecob/strawbale root cellar on our off-grid urban homestead.  

We’ve been using it since then and last year decided to put a green roof on it as well.  This “Part II” will describe our green roof process and about how the cellar has performed overall.

Root Cellar Use

Our root cellar is right next to our existing home and under twenty feet from our mudroom door – “Zone 1” in Permaculture parlance.  This close proximity is crucial because as things get even marginally more distant use and utility decline exponentially.  On winter mornings it’s still a stretch for me to put on shoes and go farther than the mudroom for our staples.  I find I often bargain with my wife: “If you get the potatoes from the root cellar, I’ll clean them and set them on the stove.” Or, I’ll interrupt my kids at play and remind them this is a small way they can contribute to our family’s continued survival…and that we’ve fed, protected, and sheltered them…and we cleaned diapers, lost a lot of sleep…they get the picture eventually.  

After the earth bags I switched to strawbales and the Balecob technique (recent blog article here).  The strawbales provide great above ground insulation and allowed us to plaster over them.  As is normal for us and our process, we’ve given the bales a good rough coat but have yet to give them a true finish coat.

Our food production and homestead knowledge have increased over the years so our root cellar has filled more, too.  With improved shelving we store crates of potatoes and onions, carrots in crates of sand, apples wrapped in paper and keep our jars of lard down there as well.  The temps inside the cellar stay consistently cool in the summer and never go below freezing in the winter.  In short, it works great!  

I should also reiterate in this Part II that our homestead is electricity and fossil-fuel-free (no solar, either) so food preservation is a bigger challenge for us.  Old and “Appropriate Technology” using the coolth of the earth has been essential to our increased sustainability.  Importantly, projects like this are also just plain fun; to build, tinker, experiment, fail sometimes, and ultimately connect more deeply with our land, our climate, our food and the direct role we take with our sustenance.  

The Green Roof

Originally, I roofed the cellar with some salvaged metal roofing and insulated it with salvaged R-30 fiberglass attic insulation.  This functioned fine but the low (4’ to 6’ above grade) metal roof, in a busy “pass-through” space from our house to our back gardens, felt too hard, harsh, and glaring.  In an effort to soften and beautify this Zone 1 area we decided to transform it into a green, or living, roof.  

Over the metal I cut in and placed two layers of inch-thick Thermasheath-3 insulation (acquired from some Burners who used it for a hexayurt shelter).  This served two purposes:  more insulative value while raising the surface above the metal fins of the metal roof so my next layer of vinyl would not rub on them.  

I built up the edges of the roof with 2 x 10’s to make a basin, essentially, into which we could place the soil.  Next, I laid out an old vinyl billboard sign on top of the insulation and tacked it to the sidewalls and to a ramshackle part of our house.  Billboard signs are a great urban resource – contact your local ad company for leftover signs and expect to pay about $20 for a 14’ x 48 ’sign. Finally, over this we put a mix of soil, compost and a few woodchips about 6-8 inches thick.  Thicker is better on top of a roof as they dry quickly but we’re only ever planning for sedums, some flowers, and weeds to grow there.  We were lucky to get a crew from Patagonia for a volunteer work day to do the heavy lifting and initial planting.  Many hands…

Along the bottom, low-side of the roof I placed a wad of rolled-up Agribon row cover against a section of hardware cloth to serve as a filter and catch to prevent soil and debris from leaving the roof.  I added a gutter after that which drains into a perennial bed full of Goji berries and protects the balecob section from drips.  

During our first growing season the green roof met our expectations of softening the environment while also growing some plants.  I didn’t notice a marked improvement inside the root cellar but, then again, I don’t keep very close track of temperatures.  Our biggest challenge was keeping the roof moist through hand-watering but this year we plan to irrigate it with a couple drip lines for consistency.  More flowers, more life, more beauty.  Amen!


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