Growing Food on Roofs - Rooftop Permaculture Can Help Feed the Urban Core

Green Roof Mat with Swale Pads For Food Growing - Roof Permaculture

Growing food on the roof makes sense.  With hundreds of thousands of acres of otherwise wasted space available for planting in the Urban Core, city dwellers are now more than ever planting their rooftop spaces to help offset high food prices.

The rooftop permaculture systems we work with generally employ some type of three dimensional weave to allow plant roofs the chance for anchoring.  These are the same systems we just successfully tested in the hurricane simulators - where, once installed the plants and soils stay embedded in the mats under 120 mph winds.

Soil embedded three dimensional netting, though not essential, is important in sub tropical climates influenced each summer by cyclones and hurricanes, helping hold both soil and plants in place.  The weave also allows for steeply sloped rooftop areas to be taken advantage of for agricultural purposes.

Green Roof Mat & Soil Added For Food Growing - Roof Permaculture

Low cost and organic alternatives to the polypropylene weave include hemp and burlap fabric, fowl or hail netting, twine weave and any other system allowing inter-connectivity of plant roots to underlying roofing systems.

Importantly, growing food on the roof creates economic opportunity.  Many small cafes and restaurants will purchase locally grown organic produce.  Moreover, rooftop gardens  reduce heat island effect, produce oxygen and sequester carbon, provide habitat and offer many other benefits.

One of the first suggestions a friend offered was to take the multi-dimensional mat and fold it under in certain areas, creating a swale-like structure - a technique successfully used in permaculture practices, one with a focus on water efficiency maximization.

Judy's Spring Mix Ready for Green Roof Planting

The folds were added after the fact because the mat had already been installed.

A lightweight roof soil mix was added to the mat and seedlings Judy had grown - a spring mix - were planted.

Growing food on roofs and walls in the Urban Core opens many economic, ecological and social doors.  Elimination of food transportation costs can even help reduce our dependence on foreign oil.

Green Roof Food Garden - Roof Permaculture

Green 'Green Roof' with Fertilizer from the Air - Floating Wetland Secrets & Companion Fertilizer Legumes

Science has shown us the most common component of air is Nitrogen, typically making up about 80-82% of the earth's atmosphere.

Green Roof plants, as well as every other living organism on the face of the earth must take this nitrogen and build protein, amino acids, nucleic acids, DNA and other life-giving substances.

Green Roof Legumes companion planted

However most of the atmospheric nitrogen exists in a form that cannot be used unless converted into ammonia.  Ammonia is formed from one nitrogen and four hydrogen atoms.  Ammonia is the substance living organisms use to process nitrogen into life.

On a rooftop or in a garden, available ammonia nitrogen amounts are usually discernible by shades of green across leaves.  Darker green typically represents strong availability of ammonia nitrogen whereas light green or yellow leaves may indicate a serious lack of available ammonia nitrogen.

One school of thought concerning ammonia nitrogen availability focuses on use of industrially processed ammonia compounds in the form of liquid or more commonly, pelletized fertilizers.  However with the world's waterbodies, lakes, rivers and springs quickly eutrophying with runoff carrying excess ammonia and phosphorous, industrial fertilizers are coming under frequent criticism.

Adding industrial fertilizers to green roofs may compound existing pollution problems.

Another perspective for providing green roof with adequate supplies of ammonia fertilizers is an approach incorporating nitrogen fixing plants into green roof plantings.

Nitrogen fixing plants are commonly represented by the well-know legume families such as clover, beans and other 'green manure' plants where the nitrogen in the form of nitrogen gas, N2, is converted to ammonia, NH4, by bacterial processes.  The NH4 is then released to the soil and plants when either the bacteria die or the bacteria live in close association with plants.

Planting nitrogen fixing plants on a green roof can reduce or eliminate all together the necessity of additional industrial fertilizers.

The opportunity to use nitrogen fixing plants to provide ammonia really caught my attention over the last year as we worked with floating wetland technology.

Hoping floating wetland plants would clean stormwater through uptake of nutrients, the research conducted ultimately pointed towards a very interesting conclusion with green roof fertilizer implications.

In waterbodies with low nitrogen concentrations (very clean lakes, streams and rivers) the water under and around the floating wetlands had higher than normal nitrogen concentrations.

At first these findings were a big surprise yet as we looked at the systems from a more global perspective and noticed the presence of certain nitrogen fixing plant and bacteria species the results began to make sense.

Nature knows when ammonia fertilizers are needed and provides the biological process to accomplish such.

In a time of severe water pollution and excess nutrients we should be looking to nitrogen fixing plants for green roof fertilizers.

Especially in Urban Core areas where NOx and SOx smog is bad, plants not only make fertilizers available but clean the air in the process.

Many of the plants in the Fabaceae family fix nitrogen.  Wikipedia offers some interesting perspectives on the topic also.

Studies have shown nitrogen fixing plants can add up to seventy five pounds of nitrogen to the soil per acre in natural ecosystems and up to several hundred pounds per acre in cropping systems.

Nature can teach us (biomimicry) about important agricultural and green roof considerations.  There are many web resources available for more information on nitrogen fixing plant types and their biological processes.

Next time you consider applying industrial fertilizers, try using nitrogen fixing plants .  You'll be helping keep our waterbodies free from algae blooms, cleaning the air, providing your plants with needed nitrogen and much more.

DIY Solar Hot Water Heater we Built & Use for Under $200 with a Green Roof twist

Sits right next to the small Cubanelle pepper Green Roof on a southerly exposure sloped roof and the DIY solar hot water panel works very well.  Photos below but first a photo of the Green Roof Cherry Tomatoes growing adjacent to the Rooftop Solar hot Water Heater :)

Rooftop Permaculture - Cherry Tomatoes

I will be clear up front I have alot to do before It is truly complete.  I know there are many unorthodox approaches here and I am sure a mechanical designer could list many reasons why this is an inefficient design and why a much more expensive system would be capture and retain with higher efficiencies.  Importantly, I didn't want to use CPVC or Copper in the collection coils because of photodegradation.

But the point here is simple.  I have disconnected the circuit breaker to the electric hot water heater and we still have plenty of hot water for a family of four, including two shower loving teenagers.

So I understand that the system is inefficient.

But I am not paying for hot water now.  And I am not using coal or petroleum generated electrical power.  What I am doing is using the sun's energy, reducing my electrical bill and affording us here on the Jax Urban Farm another step towards true independence.  Once we get our electric bill I'll do a follow up post.

DIY Solar Hot Water Directions.

1. Find your most sun exposed roof surface.
2. I used a old tin planter boxes for the frames however 3" edging could be used to create the side walls.  You really dont need a bottom to the box.
3. Once you decide the length and width you want - I used 1 meter x 2 meters, cut a piece of used plastic, preferably a EDPM or PVC material - something like a Coy Pond Liner (you can find these on Craigslist for almost nothing).
4. Make sure the roof is clean and spot adhere the waterproofing liner to the asphalt shingles using a tube of roofing adhesive from your home improvement store.
5. Attach the box or frame (I'd recommend a 1 M x 2 M rectangular frame made from 3" edging without a bottom) to the roof above the liner.  Use 1 1/4 or 1 1/2" metal roofing screws with sealant washers.
6. Uncoil a roll of 1" PPE 150PSI Black Irrigation Tubing (see photo below) and place inside frame/box)
7. Drill entry/exit holes in frame or box for tubing.
8. Run 3/4 CPVC pipe from existing hot water heater inlet to tubing in solar box and attach with standard adapter and band.
9. Add drain valve to system for draining during very cold weather.
10. Cover all pipe with standard pipe insulation.
11. Let glue dry.
12. Enjoy free hot water.

I am going to add a piece of clear fiberglass or plexiglass over the box as a top at some point but haven't yet.

The system heats the water going into my hot water heater.  Once in the hot water heater the water stays warm because the tank is insulated.

We've noticed of course the water is hotter during the afternoon than it is in the morning yet there is still plenty of hot water to go around.

What I do plan to do is add another coil of 1" insulation tubing to increase capacity, add a clear cover.

We are considering adding a green roof soil media around the coils and plant some small plants as an experiment.  We have found on our many green roofs that our speciality soil media serves as a heat sink, allowing for the storage of heat.  Will update the post as we implement the green roof component.

There have been no leaks.  The systems has experienced 150-170F , 65C to 75C during the day dropping to 70F,  20C at night so there has been plenty of thermal expansion going on.

Yes, many different ways to cost-effectively (the key here is inexpensive) improve this system and I'd love to hear your comments.  We have worked for years in designing living wall and green roof systems for low cost applications in slums and intense Urban Core permaculture situations and what I cannot incorporate are expensive, custom components.

Disclaimers important, I will say your should check with all the appropriate regulatory authorities for code, permit and blah, blah, blah requirements.  Insurance companies also have their own blah, blah, blah requirements.

However, if you want free hot water you can have free hot water and for less than US $200 and a weekend of your time.

Please leave your thoughts on fine tuning and I'll consider incorporating them!

MATERIALS

1. Tube of adhesive $4
2. Pond Liner or plastic $5
3. Roofing Screws $7
4.  6 M ( 20') 3" vinyl or aluminum edging (for sidewall frame) $15
5.  50' roll black 1" 150 PSI irrigation tubing $60
6.  3/4 CPVC to 1" tubing adapters (2) $4
7. Misc 90's ells and couplings 3/4" CPVC & CPVC Glue $15
8. 3/4" CPVC pipe $24
9. 3/4" drain valve $4
10. Standard pipe insulation $10

Total Approximate Cost $ 138

Installed $200 Solar Hot Water Heater

Tubing to CPVC Connection

1" 150 PSI Irrigation Tubing serves as Coils

CPVC supply lines to Hot Water Heater