Greenhouses

Greenhouses can be small, portable units like those sold in many garden centers, or they can be custom built, walk in setups.  The actual greenhouse itself is pretty cheap and easy to construct.  Many greenhouse kits exist that range from $15 to $1000 and anywhere in between.  The real expense in building a greenhouse though is the humidifier, depending on scale.  Humidifiers can range from a $25 ultrasonic teamed up with a $25 impeller coolmist, to a custom bulk humidifier made from a 55 gallon food grade plastic barrel and a pair of pond foggers for around $100 to $200 depending how savvy of a shopper you are.  I have 2 separate setup suggests, based on scale.

CONSTRUCTION

Small Scale:  For the individual or small family, a small scale greenhouse can be made cheaply with a portable mini greenhouse kit.  These kits are usually 3 or 4 shelf, have a gabled roof, and usually retail between $15 and $50 at local garden centers.  I suggest setting the unit up with a drip tray since it is easy to spill water while refilling your humidifiers.  I also recommend putting a coolmist impeller type humidifier on the bottom shelf (keep it on 24/7) with an ultrasonic humidifier on the shelf directly above it (this will need to be on a timer or on 24/7 based on the species you are cultivating).  The ultrasonic helps bump your humidity back up after a computer fan performs your fresh air exchange cycle, and the coolmist helps keep the air inside the greenhouse moving, ensuring even distribution of humidity, and making it a less hospitable environment for contaminates.  I like to use a 120mm computer fan on a timer for fresh air exchange.  You will need to splice the wires with a wall wort (12v DC cell phone charger) so the fan will have power.  For small setups, a timer set to run the fan for 1 minute at a time should be just about perfect.  You will need to light these units externally.

Some people opt to place their coolmist humidifiers on the outside of the greenhouse, and pipe them in.  I advise against this because it accelerates wear and tear on the device, and you will end up replacing it regularly.  If you want your humidifier on the outside so you can combine fresh air exchange and humidity into the same device, I suggest scaling down the bulk humidifier described in the the Large Scale setup.  Simply replace the barrel with a plastic bin, and you will only need 1 small pond fogger instead of 2 medium sized foggers, you can also use a computer fan instead of the duct fan.  Pipe the unit in so that the fresh air enters at the top.  If your greenhouse does not have an open bottom, cut a few slits in the plastic at the bottom, on the opposite side of where you piped in the humidifier, so that the old air can be pushed out.



Large Scale:  For large scale, the greenhouse is usually made with pvc pipe and sheet plastic (I like 6mil sheet plastic).  The greenhouse itself can usually be constructed for around $75 with supplies from Lowes or Home Depot.  You can also find greenhouse door zippers for less than $10 each on ebay.  Gorilla Tape is a great water resistant adhesive to secure the plastic sheeting with.  Cut 1 slit on the side of the greenhouse opposite from where you pipe in your bulk humidifier so that old air can be pushed out.

Lighting for this unit can be achieved by using waterproof LED light ropes in the 6500k color spectrum, or by making bottle lights with 1 quart canning jars, and the make your own lamp kits sold at Walmart and Radioshack.  Just drill a hole in the lid of the jar so that the wires can be run through, and place the bulb and fixture on the inside.  Tighten the lid down on the jar, and seal the hole with silicone.  Hang the light in the most effective location.

The most effective way to achieve proper humidity and fresh air exchange with this unit is to use a bulk humidifier, piped in from the outside.  The bulk humidifier build starts with a plastic, food grade 55 gallon barrel with a removable lid.  When you get your barrel, fill it half way with water, and test the PH of the water the next day.  Some barrels used to store acidic or base foods, such as citrus juices, will require PH balancing to 7.0 for a while until the acid has been neutralized.  You will also need a duct fan with enough power to cycle out all the air in your greenhouse in a short amount of time (within 10 minutes), a 4 inch fan with a 65cfm power rating does nicely for most applications.  On the lid of the barrel, drill a 4inch hole to one side to attach your fan (make sure the fan blows IN to the barrel).  On the opposite side of the lid, drill 2 holes to insert 2 inch pvc pipes.  Use pipes between 24" and 36" long so that the bottom of the pipes will be a few inches above the surface of the water, and still give you 12" to 18" above the lid.  On the top side of the pipes, use a elbow so that you can pipe them into the greenhouse.  Ensure all connections are water tight.  Use 2 3 disk pond foggers inside the barrel.  I say to use 2 because it is often cheaper to get 2 3 disk foggers than it is to get 1 5 disk fogger, and it also gives you a little redundancy if one of the foggers goes out.  The foggers will need to be run on timers, and adjusted as necessary to maintain a 95%+ relative humidity in your greenhouse.  The fan should be running at all times.  When the fan and foggers are on, you should see a large amount of mist billowing in from the pipes.


OPERATION

Once your hardware is running, operation is as simple as setting trays or logs of colonized substrate inside, and keeping the water filled.  As long as your lights and foggers are on timers, and the fan is always on, this setup requires little to no interaction on your part.  Simply harvest your mushrooms as necessary and enjoy!